Volume 46,Issue 9,2017 Table of Contents
2017, 46(9):2345-2351.
Abstract:
B4C/Al MMC is one of the most potential neutron-shielding materials. The poor wettability of B4C/Al interface damages the mechanical properties. To understand the alloying (or doping) effects in improving the wettability of Al/B4C interfaces, we investigated the Al(111)/AlB2(0001) and Al(111)/TiB2(0001) interfacial structures via a combined approach of experiment and DFT calculations. We find a larger work of adhesion (Wad) on the Al(111)/TiB2(0001) than the Al(111)/AlB2(0001) interfaces. The subsequently calculated partial density of states (PDOS) of doped-diborides shew fewer anti-bonding states in Al(111)/TiB2(0001) than in Al(111)/AlB2(0001), which contribute to a stronger bonding between Ti-3d and B-2p states and lead to a higher Wad and better wetting. Furthermore, we predict improved wettability of Al/B4C by a V-doping, because of the fewer anti-bonding states in vanadium-boron molecular orbitals. The same approach developed in this study may be applied for general design of alloy elements to improve the interfacial wetting of alloy-semiconductor systems.
B4C/Al MMC is one of the most potential neutron-shielding materials. The poor wettability of B4C/Al interface damages the mechanical properties. To understand the alloying (or doping) effects in improving the wettability of Al/B4C interfaces, we investigated the Al(111)/AlB2(0001) and Al(111)/TiB2(0001) interfacial structures via a combined approach of experiment and DFT calculations. We find a larger work of adhesion (Wad) on the Al(111)/TiB2(0001) than the Al(111)/AlB2(0001) interfaces. The subsequently calculated partial density of states (PDOS) of doped-diborides shew fewer anti-bonding states in Al(111)/TiB2(0001) than in Al(111)/AlB2(0001), which contribute to a stronger bonding between Ti-3d and B-2p states and lead to a higher Wad and better wetting. Furthermore, we predict improved wettability of Al/B4C by a V-doping, because of the fewer anti-bonding states in vanadium-boron molecular orbitals. The same approach developed in this study may be applied for general design of alloy elements to improve the interfacial wetting of alloy-semiconductor systems.
2017, 46(9):2352-2358.
Abstract:
The tensile and compression behavior of hot extruded Mg99.2Ca0.6Mn0.2 (at%) alloy were tested, the cyclic polarization curves and impedance spectroscopy of the alloy soaked in SBF solutions with various pH values were measured by electrochemical method so that the corrosion properties of the alloy can be evaluated and the experimental foundations for preparation of magnesium implant materials is provided. The results show that the tensile failure of the alloy appears to be characteristic of quasi-cleavage fracture, the tensile strength, yield strength, compressive strength and elongation are 279 MPa, 251 MPa, 330 MPa and 11% at room temperature, respectively. The PH value of the solution has prominent effect on corrosion property. As the PH value increases, the arc radius of impedance spectroscopy and corrosion potentials increase remarkably, whereas the corrosion current density decreases, and thus the corrosion resistance of the alloy is strengthened. There is only one time constant which appears in low frequency in phase angle plot. The corrosion rate can be significantly reduced by increasing PH value of the solution. The instantaneous corrosion rates of the alloy immersed in the solutions with PH value of 7.2 and 10.0 are 4.1 mm/a and 0.2 mm/a after, respectively.
The tensile and compression behavior of hot extruded Mg99.2Ca0.6Mn0.2 (at%) alloy were tested, the cyclic polarization curves and impedance spectroscopy of the alloy soaked in SBF solutions with various pH values were measured by electrochemical method so that the corrosion properties of the alloy can be evaluated and the experimental foundations for preparation of magnesium implant materials is provided. The results show that the tensile failure of the alloy appears to be characteristic of quasi-cleavage fracture, the tensile strength, yield strength, compressive strength and elongation are 279 MPa, 251 MPa, 330 MPa and 11% at room temperature, respectively. The PH value of the solution has prominent effect on corrosion property. As the PH value increases, the arc radius of impedance spectroscopy and corrosion potentials increase remarkably, whereas the corrosion current density decreases, and thus the corrosion resistance of the alloy is strengthened. There is only one time constant which appears in low frequency in phase angle plot. The corrosion rate can be significantly reduced by increasing PH value of the solution. The instantaneous corrosion rates of the alloy immersed in the solutions with PH value of 7.2 and 10.0 are 4.1 mm/a and 0.2 mm/a after, respectively.
2017, 46(9):2359-2365.
Abstract:
IN718 alloy exhibits excellent mechanical properties at high-temperature and good workability, it has been widely used in aircraft engine turbine disks, compressor disks, and power turbine shafts (i.e., rotating components). The mechanical properties of IN718 alloy, specifically, its creep and fatigue properties are a key factor determining the safety and reliability of engines. In this study, the effects of solution treatment at temperature ranging from 900 oC to 1050 oC on the microstructure and mechanical properties (including the tensile strength at room temperature and 650 oC, the stress-rupture behavior at 650 oC and 700 MPa, and the low-cycle fatigue behavior at 450 oC) were systematically investigated. The results showed that in specimens subjected to solution treatment at temperature from 900 oC to 990 oC, the mass fraction of the d-phase decreases with increasing temperature,whereas the grain size remains the same. However, in specimens treated at temperatures ranging from 990 oC to 1050oC, the d-phase was dissolved and the grain size increased from 15 to 100 mm. With proper adjustment of the microstructure of IN718 alloy, this material exhibits a wider and superior range of performance to satisfy the requirements for fields that require high-temperature, corrosion-resistant, and radiation-tolerant materials, such as the aviation, petrochemical, and nuclear power industries.
IN718 alloy exhibits excellent mechanical properties at high-temperature and good workability, it has been widely used in aircraft engine turbine disks, compressor disks, and power turbine shafts (i.e., rotating components). The mechanical properties of IN718 alloy, specifically, its creep and fatigue properties are a key factor determining the safety and reliability of engines. In this study, the effects of solution treatment at temperature ranging from 900 oC to 1050 oC on the microstructure and mechanical properties (including the tensile strength at room temperature and 650 oC, the stress-rupture behavior at 650 oC and 700 MPa, and the low-cycle fatigue behavior at 450 oC) were systematically investigated. The results showed that in specimens subjected to solution treatment at temperature from 900 oC to 990 oC, the mass fraction of the d-phase decreases with increasing temperature,whereas the grain size remains the same. However, in specimens treated at temperatures ranging from 990 oC to 1050oC, the d-phase was dissolved and the grain size increased from 15 to 100 mm. With proper adjustment of the microstructure of IN718 alloy, this material exhibits a wider and superior range of performance to satisfy the requirements for fields that require high-temperature, corrosion-resistant, and radiation-tolerant materials, such as the aviation, petrochemical, and nuclear power industries.
Zhao Yanchun
,
Ma Wenlong
,
Zhao Zhiping
,
Huang Mingyuan
,
Kou Shengzhong
,
Li Chunyan
,
Yuan Zizhou
2017, 46(9):2366-2370.
Abstract:
Ti40Ni40Cu20 amorphous matrix composite plate specimens were fabricated in the levitation suspend melting - water cooled Cu mold process. The specimens were by pre-compressed at different degrees with a pressure testing machine and then annealed at 150 ℃ for approx. 30 min. And the effects of the predeformation and annealing processes of the microstructure and mechanical properties of the Ti40Ni40Cu20 alloy system were studied. The results show that the austenite phase into the martensitic phase transformation under external force occurred then. The phase transition induced by the deformation coupled with the annealing release of residual thermal stress plays a role in enhancing both strength and toughness of the amorphous matrix composite. Both martensite phases and austenite phases are increased with the increase in the degrees of pre-deformation, but martensite phases are increased faster. Thus the yield strength of the composite increased, while the ductility reduced .Therefore the controllable yield strength in the pre-compression stage for shaping can be realized.
Ti40Ni40Cu20 amorphous matrix composite plate specimens were fabricated in the levitation suspend melting - water cooled Cu mold process. The specimens were by pre-compressed at different degrees with a pressure testing machine and then annealed at 150 ℃ for approx. 30 min. And the effects of the predeformation and annealing processes of the microstructure and mechanical properties of the Ti40Ni40Cu20 alloy system were studied. The results show that the austenite phase into the martensitic phase transformation under external force occurred then. The phase transition induced by the deformation coupled with the annealing release of residual thermal stress plays a role in enhancing both strength and toughness of the amorphous matrix composite. Both martensite phases and austenite phases are increased with the increase in the degrees of pre-deformation, but martensite phases are increased faster. Thus the yield strength of the composite increased, while the ductility reduced .Therefore the controllable yield strength in the pre-compression stage for shaping can be realized.
2017, 46(9):2371-2374.
Abstract:
Nickel oxalate nano-fibers were controlled synthesized via a restricted self-assembly growth process in liquid phase precipitation system. Nickel nano-fibers were prepared by decomposing nickel oxalate under the guidance of fiber micro-structure, in Ar gas atmosphere. The characteristics were measured by the techniques of X-ray powder diffraction, Scanning Electron Microscope and Transmission Electron Microscopy. As a result, the existence of ammonia changed the growth behavior of nickel oxalate from free self-assembly mode to restricted one. The nickel oxalate crystal nano-fibers with monoclinic geometry were about 100-200nm in diameter, 1-5μm in length. The nickel nano-fibers with face-centered cubic geometry were also about 100-200nm in diameter, 1-5μm in length, which surface was very rough. Nickel nano-fibers formed via a process of nucleation, grain growth and aggregation under the guidance of long and narrow space provided by nickel oxalate nano-fibers.
Nickel oxalate nano-fibers were controlled synthesized via a restricted self-assembly growth process in liquid phase precipitation system. Nickel nano-fibers were prepared by decomposing nickel oxalate under the guidance of fiber micro-structure, in Ar gas atmosphere. The characteristics were measured by the techniques of X-ray powder diffraction, Scanning Electron Microscope and Transmission Electron Microscopy. As a result, the existence of ammonia changed the growth behavior of nickel oxalate from free self-assembly mode to restricted one. The nickel oxalate crystal nano-fibers with monoclinic geometry were about 100-200nm in diameter, 1-5μm in length. The nickel nano-fibers with face-centered cubic geometry were also about 100-200nm in diameter, 1-5μm in length, which surface was very rough. Nickel nano-fibers formed via a process of nucleation, grain growth and aggregation under the guidance of long and narrow space provided by nickel oxalate nano-fibers.
2017, 46(9):2375-2378.
Abstract:
In this paper, the shape memory effect and recovery ratio of dual-phase Ni58Mn25Ga16.9Gd0.1 alloy were investigated by bend test. The results showed that this alloy exhibited goodSshape recovery capability. The recovery ratio of 86% was observed with bend pre-strain of 4.6% after heating, which was larger than that of other reported dual-phase Ni-Mn-Ga alloys. This characteristic was attributed to the critical slip stress increasing of γ phase by small amount of Gd addition, causing the ability improvement of γ phase to resist irreversible deformation.
In this paper, the shape memory effect and recovery ratio of dual-phase Ni58Mn25Ga16.9Gd0.1 alloy were investigated by bend test. The results showed that this alloy exhibited goodSshape recovery capability. The recovery ratio of 86% was observed with bend pre-strain of 4.6% after heating, which was larger than that of other reported dual-phase Ni-Mn-Ga alloys. This characteristic was attributed to the critical slip stress increasing of γ phase by small amount of Gd addition, causing the ability improvement of γ phase to resist irreversible deformation.
2017, 46(9):2379-2383.
Abstract:
Sintered stainless steel fiber felt (SSSFF) is a kind of porous material promising for functional and structural applications such as energy absorption and solid/gas filtration etc. In this work microwave heating was used for sintering of 316L stainless steel fiber felt and the effect of microwave heating on the sintering profile ，microstructure and mechanics performance of the sintered stainless steel fiber felt was investigated by means of μ-CT，SEM and so on. The experiment result showed that in contrast with conventional sintering method, microwave heating can sinter stainless steel fiber felt at lower temperature within shorter time, and the higher mechanic performance of SSSFF can be achieved by this means. The microwave field induced arcing between metal fibers may accelerate the sintering process.
Sintered stainless steel fiber felt (SSSFF) is a kind of porous material promising for functional and structural applications such as energy absorption and solid/gas filtration etc. In this work microwave heating was used for sintering of 316L stainless steel fiber felt and the effect of microwave heating on the sintering profile ，microstructure and mechanics performance of the sintered stainless steel fiber felt was investigated by means of μ-CT，SEM and so on. The experiment result showed that in contrast with conventional sintering method, microwave heating can sinter stainless steel fiber felt at lower temperature within shorter time, and the higher mechanic performance of SSSFF can be achieved by this means. The microwave field induced arcing between metal fibers may accelerate the sintering process.
2017, 46(9):2384-2388.
Abstract:
Abstract: The advanced magnetocaloric composites in active magnetic regenerator (AMR) are required to meet the good mechanical properties, magnetocaloric effect (MCE) and thermal conductivity. However there are challenges in the shape up and heat conduction of most of the magnetocaloric composites currently. In this paper, we reported a LaFe11.6Si1.4Hy magnetocaloric composites which was pressed together with a low melting point metal of indium (In) and the different compaction pressures of 0~800 MPa at 430K. The results show that the MCE of the composite will be deteriorated when compaction pressure exceeds 200 MPa. The In-bonded LaFe11.6Si1.4Hy composites of 0.8mm-thick sheet pressed with 100Mpa has the maximum adiabatic temperature change of 5.88K at the magnetic field change of 0~2 T.
Abstract: The advanced magnetocaloric composites in active magnetic regenerator (AMR) are required to meet the good mechanical properties, magnetocaloric effect (MCE) and thermal conductivity. However there are challenges in the shape up and heat conduction of most of the magnetocaloric composites currently. In this paper, we reported a LaFe11.6Si1.4Hy magnetocaloric composites which was pressed together with a low melting point metal of indium (In) and the different compaction pressures of 0~800 MPa at 430K. The results show that the MCE of the composite will be deteriorated when compaction pressure exceeds 200 MPa. The In-bonded LaFe11.6Si1.4Hy composites of 0.8mm-thick sheet pressed with 100Mpa has the maximum adiabatic temperature change of 5.88K at the magnetic field change of 0~2 T.
2017, 46(9):2389-2394.
Abstract:
Morphology evolution and oxidation behavior of Zr powders milled with and without CNTs for different time were compared. XRD and SEM were used to determine the phase composition and morphology of obtained Zr and Zr/CNTs powders. Thermogravity (TG) analysis was applied to evaluate the thermal oxidation behavior of Zr and Zr/CNTs. Results showed that the phase composition of Zr after milling was not influenced by adding CNTs, but the morphology and oxidation behavior of Zr were influenced. In case of milling without CNTs, particle size of Zr continued to reduce from more than 10 μm to about 2~3 μm when milling time increased from 1 h to 3 h. In case of CNTs-assisted milling, the particle size reduction of Zr was not obvious until milling time prolonged to 3 h. This was because those CNTs adhered on the surface of Zr or CNTs-induced agglomerations among Zr prohibited the mechanical impact and fracturing effects of milling balls on Zr particles. Compared with direct milling of Zr, when the obtained Zr had similar particle size, adding CNTs lowered the onset oxidation temperature and peak exothermic temperature of Zr powders by 11 ℃~37 ℃, depending on milling time. This was ascribed to the high heat conductivity of CNTs which favored heat transfer between Zr particles. At the same time, oxidative weight gain of Zr/CNTs was slightly lower than the corresponding pure Zr when milling time was less than 2 h and then this trend reversed. The initial decrease in weight gain of Zr in Zr/CNTs mixtures under shorter milling time was related to two factors: one was CNTs-induced agglomerations of Zr, which prohibited the contact of Zr with oxygen and thus decreased the degree of oxidation, and the other was the delayed particle size reduction of Zr in Zr/CNTs mixtures. The subsequent reversal in weight gain for pure Zr and Zr/CNTs was because the positive effect of particle size reduction of Zr in Zr/CNTs on its thermal oxidation just began, while the spontaneous oxidation-induced negative effect for well-refined pure Zr has become very obvious.
Morphology evolution and oxidation behavior of Zr powders milled with and without CNTs for different time were compared. XRD and SEM were used to determine the phase composition and morphology of obtained Zr and Zr/CNTs powders. Thermogravity (TG) analysis was applied to evaluate the thermal oxidation behavior of Zr and Zr/CNTs. Results showed that the phase composition of Zr after milling was not influenced by adding CNTs, but the morphology and oxidation behavior of Zr were influenced. In case of milling without CNTs, particle size of Zr continued to reduce from more than 10 μm to about 2~3 μm when milling time increased from 1 h to 3 h. In case of CNTs-assisted milling, the particle size reduction of Zr was not obvious until milling time prolonged to 3 h. This was because those CNTs adhered on the surface of Zr or CNTs-induced agglomerations among Zr prohibited the mechanical impact and fracturing effects of milling balls on Zr particles. Compared with direct milling of Zr, when the obtained Zr had similar particle size, adding CNTs lowered the onset oxidation temperature and peak exothermic temperature of Zr powders by 11 ℃~37 ℃, depending on milling time. This was ascribed to the high heat conductivity of CNTs which favored heat transfer between Zr particles. At the same time, oxidative weight gain of Zr/CNTs was slightly lower than the corresponding pure Zr when milling time was less than 2 h and then this trend reversed. The initial decrease in weight gain of Zr in Zr/CNTs mixtures under shorter milling time was related to two factors: one was CNTs-induced agglomerations of Zr, which prohibited the contact of Zr with oxygen and thus decreased the degree of oxidation, and the other was the delayed particle size reduction of Zr in Zr/CNTs mixtures. The subsequent reversal in weight gain for pure Zr and Zr/CNTs was because the positive effect of particle size reduction of Zr in Zr/CNTs on its thermal oxidation just began, while the spontaneous oxidation-induced negative effect for well-refined pure Zr has become very obvious.
2017, 46(9):2395-2398.
Abstract:
A one-step microwave-assisted method was used for the synthesis of silver nanoparticles, and the corresponding nature and structure of silver nanoparticles were characterized by UV-Vis absorption spectroscopy, transmission electron microscopy (TEM), and atomic force microscopy (AFM). Raman scattering activities of silver nanoparticles with different reaction times were checked by using rhodamine 6G (R6G) as a probe molecule. The results showed that the intensity of surface enhancement Raman scattering (SERS) signals could be increased by silver nanoparticles. And then we made a comparison on SERS spectra of R6G molecules adsorbed on three kinds of silver nanoparticles to investigate the effect of surface enhancement Raman. Meanwhile, we have also performed substantially studying of the mechanism in the process of enhancement by silver nanoparticles.
A one-step microwave-assisted method was used for the synthesis of silver nanoparticles, and the corresponding nature and structure of silver nanoparticles were characterized by UV-Vis absorption spectroscopy, transmission electron microscopy (TEM), and atomic force microscopy (AFM). Raman scattering activities of silver nanoparticles with different reaction times were checked by using rhodamine 6G (R6G) as a probe molecule. The results showed that the intensity of surface enhancement Raman scattering (SERS) signals could be increased by silver nanoparticles. And then we made a comparison on SERS spectra of R6G molecules adsorbed on three kinds of silver nanoparticles to investigate the effect of surface enhancement Raman. Meanwhile, we have also performed substantially studying of the mechanism in the process of enhancement by silver nanoparticles.
2017, 46(9):2399-2404.
Abstract:
AZ91D magnesium alloys were processed by micro-arc oxidation (MAO) in silicate-containing electrolyte. The key factor of this research is a unique experimental design to fabricate coatings with same thickness but by different power voltages which represents different growth rate. The fact, that the coatings with same thickness corresponding to different coating growth rate of 1μm/min, 5μm/min, 15μm/min and 25μm/min respectively, makes the comparison and analysis-targeted microstructure and corrosion resistance of the coatings academic and practical. The coating growth rate demonstrates considerable influence on surface porosity, size and amount of micro-pores, mass and mass to thickness ratio, and anti-corrosion property of the coatings based on both qualitative and quantitative analysis, but it is not the case for the composition and element distribution of the coatings. An industrial application-oriented selection of appropriate coating growth rate, which demands for both productive efficiency and good performance, has to be considered together with anti-corrosion property of the coatings. The case of the coating fabricated with the growth rate of 15μm/min supports this point strongly.
AZ91D magnesium alloys were processed by micro-arc oxidation (MAO) in silicate-containing electrolyte. The key factor of this research is a unique experimental design to fabricate coatings with same thickness but by different power voltages which represents different growth rate. The fact, that the coatings with same thickness corresponding to different coating growth rate of 1μm/min, 5μm/min, 15μm/min and 25μm/min respectively, makes the comparison and analysis-targeted microstructure and corrosion resistance of the coatings academic and practical. The coating growth rate demonstrates considerable influence on surface porosity, size and amount of micro-pores, mass and mass to thickness ratio, and anti-corrosion property of the coatings based on both qualitative and quantitative analysis, but it is not the case for the composition and element distribution of the coatings. An industrial application-oriented selection of appropriate coating growth rate, which demands for both productive efficiency and good performance, has to be considered together with anti-corrosion property of the coatings. The case of the coating fabricated with the growth rate of 15μm/min supports this point strongly.
2017, 46(9):2405-2410.
Abstract:
The microstructure and corrosion resistance of Mg-6Zn-4Si alloy with Sr addition were studied using XRD, OM, SEM, EDS, potentiodynamic polarization and immersion testing. A proper Sr addition observably modifies the morphologies and sizes of primary and eutectic Mg2Si phases in Mg-6Zn-4Si alloy. The grain size of the primary Mg2Si decreased initially and then gradually increased with the increasing of Sr amount. Sr significantly improves the corrosion resistance of Mg-6Zn-4Si alloy. The ternary alloy with 0.5Sr has the optimal corrosion resistance, which exhibits the highest corrosion potential, the lowest corrosion current density and corrosion rate. The homogeneous dispersion of fine Mg2Si particles with Sr element is responsible for the improvement of corrosion resistance. Excessive Sr (≥1.0%) leads to the generation of SrMgSi new phase, which has unfavorable effects on the corrosion resistance of the alloys.
The microstructure and corrosion resistance of Mg-6Zn-4Si alloy with Sr addition were studied using XRD, OM, SEM, EDS, potentiodynamic polarization and immersion testing. A proper Sr addition observably modifies the morphologies and sizes of primary and eutectic Mg2Si phases in Mg-6Zn-4Si alloy. The grain size of the primary Mg2Si decreased initially and then gradually increased with the increasing of Sr amount. Sr significantly improves the corrosion resistance of Mg-6Zn-4Si alloy. The ternary alloy with 0.5Sr has the optimal corrosion resistance, which exhibits the highest corrosion potential, the lowest corrosion current density and corrosion rate. The homogeneous dispersion of fine Mg2Si particles with Sr element is responsible for the improvement of corrosion resistance. Excessive Sr (≥1.0%) leads to the generation of SrMgSi new phase, which has unfavorable effects on the corrosion resistance of the alloys.
2017, 46(9):2411-2416.
Abstract:
The fatigue lifetime of the laser-MIG hybrid welded joint of 7075-T6 aluminum alloy was studied in this paper. The results showed that there existed a strong relationship between the fatigue crack initiation lifetime and fatigue failure lifetime. For the base metal specimens the ratio of fatigue crack initiation lifetime and fatigue failure lifetime was about 64.5%, while for the welded joint specimens it was about 20.2%. The observation of fatigue fracture surface showed that there existed a large number of dimples in the base metal specimens, while there appeared lots of gas porosities in the welded joint specimens instead. These gas porosities were regarded to be the reason of lower fatigue crack initiation lifetime.
The fatigue lifetime of the laser-MIG hybrid welded joint of 7075-T6 aluminum alloy was studied in this paper. The results showed that there existed a strong relationship between the fatigue crack initiation lifetime and fatigue failure lifetime. For the base metal specimens the ratio of fatigue crack initiation lifetime and fatigue failure lifetime was about 64.5%, while for the welded joint specimens it was about 20.2%. The observation of fatigue fracture surface showed that there existed a large number of dimples in the base metal specimens, while there appeared lots of gas porosities in the welded joint specimens instead. These gas porosities were regarded to be the reason of lower fatigue crack initiation lifetime.
14 Influence of multi-beam electron beam welding technique on the deformation of Ti6Al4V alloy sheet
2017, 46(9):2417-2422.
Abstract:
Multi-beam electron beam welding (EBW) is a new technique that allows more than two electron beams running simultaneously for welding and it is considered a promising method to reduce welding stress and deformation. In order to reduce the deformation of Ti6Al4V alloy sheets, a novel multi-beam EBW method is proposed in this study, besides one main electron beam to melt metals, also including two additional electron beams to post-heat the weld. Experiments were conducted on Ti6Al4V alloy sheets using this multi-beam technique. Results show that compared with the conventional EBW, the multi-beam EBW can improve the welding thermal cycle and effectively reduce the welding deformation by adjusting the position and energy distribution of two additional electron beams.
Multi-beam electron beam welding (EBW) is a new technique that allows more than two electron beams running simultaneously for welding and it is considered a promising method to reduce welding stress and deformation. In order to reduce the deformation of Ti6Al4V alloy sheets, a novel multi-beam EBW method is proposed in this study, besides one main electron beam to melt metals, also including two additional electron beams to post-heat the weld. Experiments were conducted on Ti6Al4V alloy sheets using this multi-beam technique. Results show that compared with the conventional EBW, the multi-beam EBW can improve the welding thermal cycle and effectively reduce the welding deformation by adjusting the position and energy distribution of two additional electron beams.
2017, 46(9):2423-2427.
Abstract:
To meet the Chinese GB regulations (Equivalent to Euro V) and to adsorb the excess hydrocarbons emitted during a period of engine cold-start, in addition, Hydrocarbon (HC) adsorption behavior on Pd-based catalyst appeared during a cold-start period of actual driving cycle in the vehicles of, Dragon and Cherry, therefore, we leaded in HCA (Hydrocarbon Absorber) material. Catalytic performance of prepared HCA catalyst and HC adsorption process were tested, and then their applications were studied in the whole vehicle. In this work, Pd /Ce-HZSM-5 was used as the main recipes of HCA materials as well as a combination of zeolite and precious metals. For Dragon and Cherry models, their emission results show Pd/Ce-HZSM-5 catalyst is superior to conventional catalyst for HC trap. Since Pd-based catalyst showed relatively good light-off performance, the combination of HC adsorption and early light-off activity has led to an improvement of overall HC emission reduction to Pd/Ce-HZSM-5. Use of zeolite combined with Pd-based catalyst caused maximize HC adsorption between 20-30 s during the cold-start period at fresh. HCA material has great research potential to meet high standards of HC emissions quality at low temperature.
To meet the Chinese GB regulations (Equivalent to Euro V) and to adsorb the excess hydrocarbons emitted during a period of engine cold-start, in addition, Hydrocarbon (HC) adsorption behavior on Pd-based catalyst appeared during a cold-start period of actual driving cycle in the vehicles of, Dragon and Cherry, therefore, we leaded in HCA (Hydrocarbon Absorber) material. Catalytic performance of prepared HCA catalyst and HC adsorption process were tested, and then their applications were studied in the whole vehicle. In this work, Pd /Ce-HZSM-5 was used as the main recipes of HCA materials as well as a combination of zeolite and precious metals. For Dragon and Cherry models, their emission results show Pd/Ce-HZSM-5 catalyst is superior to conventional catalyst for HC trap. Since Pd-based catalyst showed relatively good light-off performance, the combination of HC adsorption and early light-off activity has led to an improvement of overall HC emission reduction to Pd/Ce-HZSM-5. Use of zeolite combined with Pd-based catalyst caused maximize HC adsorption between 20-30 s during the cold-start period at fresh. HCA material has great research potential to meet high standards of HC emissions quality at low temperature.
2017, 46(9):2428-2432.
Abstract:
Aluminum (Al) alloys with gallium (Ga) and indium (In) were prepared via mechanical alloying technology. The hydrolysis reaction between the Al alloys and pure water was studied to observe the hydrogen yield evolution. The results obtained by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy show that Ga and In elements mainly exist in the alloy in the forms of dissolution and precipitated phases, respectively. The dissolution of Ga and In can improve the hydrogen yield of Al alloy by enhancing the activity of hydrolysis reaction. Moreover, the quantity and distribution of precipitated phase determined by ball milling time directly influence the hydrogen yields, and the Al alloy with appropriate number and uniform-distributed precipitated phase can react with 0 oC pure water to produce 1132.8ml/g hydrogen.
Aluminum (Al) alloys with gallium (Ga) and indium (In) were prepared via mechanical alloying technology. The hydrolysis reaction between the Al alloys and pure water was studied to observe the hydrogen yield evolution. The results obtained by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy show that Ga and In elements mainly exist in the alloy in the forms of dissolution and precipitated phases, respectively. The dissolution of Ga and In can improve the hydrogen yield of Al alloy by enhancing the activity of hydrolysis reaction. Moreover, the quantity and distribution of precipitated phase determined by ball milling time directly influence the hydrogen yields, and the Al alloy with appropriate number and uniform-distributed precipitated phase can react with 0 oC pure water to produce 1132.8ml/g hydrogen.
2017, 46(9):2433-2436.
Abstract:
Zirconium boride reinforced NbMo-matrix composites with a composition of 42.5%Nb+42.5%Mo+15%ZrB2 (Vol.%) and SiC doped with a composition of 42.5%Nb+42.5%Mo+10.5%ZrB2+4.5% SiC (Vol.%) was fabricated by hot-pressing under an uniaxial load of 30 MPa at 1600℃ in Ar atmosphere with two kind of holding time. The microstructure and phase compositions were analyzed by means of scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The mechanical properties were measured by Micro Vickers and hydraulic universal tester. NbMo solid solution was observed with small ZrB particles distributed uniformly in it. No SiC particle was founded. The compressive strength was improved to 1974.17MPa compared to the NbMo solid solution 1380.15MPa. The yield stress was improved to 1664.13MPa and the hardness was 3~5 times higher than NbMo. The increase in strength and hardness of the composites is a consequence of the solid solution strengthening mechanism and the excellent interface bonding between ZrB and Nb-Mo solid solution.
Zirconium boride reinforced NbMo-matrix composites with a composition of 42.5%Nb+42.5%Mo+15%ZrB2 (Vol.%) and SiC doped with a composition of 42.5%Nb+42.5%Mo+10.5%ZrB2+4.5% SiC (Vol.%) was fabricated by hot-pressing under an uniaxial load of 30 MPa at 1600℃ in Ar atmosphere with two kind of holding time. The microstructure and phase compositions were analyzed by means of scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The mechanical properties were measured by Micro Vickers and hydraulic universal tester. NbMo solid solution was observed with small ZrB particles distributed uniformly in it. No SiC particle was founded. The compressive strength was improved to 1974.17MPa compared to the NbMo solid solution 1380.15MPa. The yield stress was improved to 1664.13MPa and the hardness was 3~5 times higher than NbMo. The increase in strength and hardness of the composites is a consequence of the solid solution strengthening mechanism and the excellent interface bonding between ZrB and Nb-Mo solid solution.
2017, 46(9):2437-2444.
Abstract:
The corrosion behavior of friction stir welded Zn-modified Al-Mg alloys are systematically investigated as well as the effects of pre-weld temper conditions on the corrosion behavior of the friction stir welded alloys. Both maximum corrosion depth and dominating corrosion mode in different weld regions after post welding heat treatment show obvious variations with an increase in the Zn content. With Zn additions the dominating corrosion mode changes from intergranular corrosion to pitting corrosion, and the severe galvanic corrosion tendency obviously occurs in the precipitation hardened alloys compared to that of the strain hardened alloy. This would be greatly related with the formation of discontinuously distributed grain boundary precipitates as well as abundant intragranular precipitates (mainly T-AlZnMgCu phase) in the precipitation hardened Al-Mg-Zn alloys while it is in line with the continuously distributed β-AlMg phase along grain boundary in the Zn-free Al-Mg alloys.
The corrosion behavior of friction stir welded Zn-modified Al-Mg alloys are systematically investigated as well as the effects of pre-weld temper conditions on the corrosion behavior of the friction stir welded alloys. Both maximum corrosion depth and dominating corrosion mode in different weld regions after post welding heat treatment show obvious variations with an increase in the Zn content. With Zn additions the dominating corrosion mode changes from intergranular corrosion to pitting corrosion, and the severe galvanic corrosion tendency obviously occurs in the precipitation hardened alloys compared to that of the strain hardened alloy. This would be greatly related with the formation of discontinuously distributed grain boundary precipitates as well as abundant intragranular precipitates (mainly T-AlZnMgCu phase) in the precipitation hardened Al-Mg-Zn alloys while it is in line with the continuously distributed β-AlMg phase along grain boundary in the Zn-free Al-Mg alloys.
2017, 46(9):2445-2448.
Abstract:
The Ti-46Ni alloy ribbons were fabricated by melt-spinning. The microstructure characteristics, the transformation behaviors and shape memory effect of Ti-46Ni alloy ribbon were investigated by SEM, XRD, differential scanning calorimetry and bending test. The results show that the microstructure morphology of as-cast and 400~600℃ annealed state of Ti-46Ni alloy ribbon presents dendritic, the grain is small, and the composition phases are martensite (B19ˊ) and parent phase (B2). The one stage martensite transformation are appeared upon cooling and heating. The as-cast and annealed Ti-46Ni alloy ribbons are all of excellent shape memory effect.
The Ti-46Ni alloy ribbons were fabricated by melt-spinning. The microstructure characteristics, the transformation behaviors and shape memory effect of Ti-46Ni alloy ribbon were investigated by SEM, XRD, differential scanning calorimetry and bending test. The results show that the microstructure morphology of as-cast and 400~600℃ annealed state of Ti-46Ni alloy ribbon presents dendritic, the grain is small, and the composition phases are martensite (B19ˊ) and parent phase (B2). The one stage martensite transformation are appeared upon cooling and heating. The as-cast and annealed Ti-46Ni alloy ribbons are all of excellent shape memory effect.
2017, 46(9):2449-2454.
Abstract:
Wear behavior and characteristic of TC4 alloy in TC4/GCr15 and TC4/ W6Mo5Cr4V2 tribo-systems were studied. The morphologies, element and structure of worn surface and cross-section were observed and analysed with SEM, EDS and XRD. The results show that in two tribo-systems, wear rate of titanium alloy at 25℃ was high and wear performance was poor; at 400℃, wear rate in TC4/ W6Mo5Cr4V2 was much higher than that in TC4/GCr15; wear rate of titanium alloy at 600℃ was very low and wear rate in TC4/GCr15 was lower than that in TC4/ W6Mo5Cr4V2.At 400 and 600℃, counterface materials have different impact on wear rate of alloy. The decrease of wear rate was related with the amount of oxides, titanium alloy presented extremely low wear rate and excellent wear performance when worn surface contained a large amount of oxides which can be existed stably.
Wear behavior and characteristic of TC4 alloy in TC4/GCr15 and TC4/ W6Mo5Cr4V2 tribo-systems were studied. The morphologies, element and structure of worn surface and cross-section were observed and analysed with SEM, EDS and XRD. The results show that in two tribo-systems, wear rate of titanium alloy at 25℃ was high and wear performance was poor; at 400℃, wear rate in TC4/ W6Mo5Cr4V2 was much higher than that in TC4/GCr15; wear rate of titanium alloy at 600℃ was very low and wear rate in TC4/GCr15 was lower than that in TC4/ W6Mo5Cr4V2.At 400 and 600℃, counterface materials have different impact on wear rate of alloy. The decrease of wear rate was related with the amount of oxides, titanium alloy presented extremely low wear rate and excellent wear performance when worn surface contained a large amount of oxides which can be existed stably.
2017, 46(9):2455-2458.
Abstract:
The vaporation dynamics of Fe element in uramium melting during vacuum induction melting bave been studied, the results of experiment and calculation showed that the evaporation rate of Fe was first order with respect to Fe content in the metal. The activation energy of evaporation of Fe form uranium melt was obtained to be 121kJ/mol, and the rate of Fe evaporation is simultaneously controlled by the diffusion through the liquid boundary layer and the evaporation reaction of Fe at the metal/gas interface, in which the mass transfer coefficient was estimated to be from 4.52′10-4cm/s at 1673K to 1.01′10-3cm/s at 1853K.
The vaporation dynamics of Fe element in uramium melting during vacuum induction melting bave been studied, the results of experiment and calculation showed that the evaporation rate of Fe was first order with respect to Fe content in the metal. The activation energy of evaporation of Fe form uranium melt was obtained to be 121kJ/mol, and the rate of Fe evaporation is simultaneously controlled by the diffusion through the liquid boundary layer and the evaporation reaction of Fe at the metal/gas interface, in which the mass transfer coefficient was estimated to be from 4.52′10-4cm/s at 1673K to 1.01′10-3cm/s at 1853K.
2017, 46(9):2459-2464.
Abstract:
With the precipitation strengthening phase of ternary compound γ′-Co3(Al,W), the Co-Al-W superalloy is a novel cobalt-based superalloy. In order to study the phase composition and cracking behavior of Co-8.8Al-9.8W-0.2B cladding layer on the 304 stainless steel with TIG welding. The phase composition and relative content of elements at different positions in cladding layer were studied with thermodynamic simulation calculation of JMatPro software. The results show that the phase composition should be the same in different position of cladding layer, but the content of those phases are difference. Based on the analysis of the phase composition and content of the elements in the cladding layer, the surface cracks of cladding layer are hot cracks, which are the results of thermal stress, the phase transformation stress and Laves phase.
With the precipitation strengthening phase of ternary compound γ′-Co3(Al,W), the Co-Al-W superalloy is a novel cobalt-based superalloy. In order to study the phase composition and cracking behavior of Co-8.8Al-9.8W-0.2B cladding layer on the 304 stainless steel with TIG welding. The phase composition and relative content of elements at different positions in cladding layer were studied with thermodynamic simulation calculation of JMatPro software. The results show that the phase composition should be the same in different position of cladding layer, but the content of those phases are difference. Based on the analysis of the phase composition and content of the elements in the cladding layer, the surface cracks of cladding layer are hot cracks, which are the results of thermal stress, the phase transformation stress and Laves phase.
23 Interface reaction between aluminium and uranium at high temperature using in-situ X-ray diffraction
2017, 46(9):2465-2469.
Abstract:
Aluminum film was prepared using magnetron sputtering deposition process on depleted uranium surface. The interface reaction between aluminium and uranium was investigated using in-situ X-ray diffraction at high temperature. The reaction product and the changes with temperature and time were researched and discussed. The experimental results indicate that there are absent any of intermetallic compounds in the original sample, and the interface reaction occurs and the intermetallic compound UAl3 forms when the temperature is higher than 335 °C. The dynamics of surface reaction is in accord with nucleation-growth mechanism. It is interesting that the diffraction peak’s intensity of UAl3 decreases with the increasing of temperature and disappear at 600°C, which is analyzed and discussed in this paper.
Aluminum film was prepared using magnetron sputtering deposition process on depleted uranium surface. The interface reaction between aluminium and uranium was investigated using in-situ X-ray diffraction at high temperature. The reaction product and the changes with temperature and time were researched and discussed. The experimental results indicate that there are absent any of intermetallic compounds in the original sample, and the interface reaction occurs and the intermetallic compound UAl3 forms when the temperature is higher than 335 °C. The dynamics of surface reaction is in accord with nucleation-growth mechanism. It is interesting that the diffraction peak’s intensity of UAl3 decreases with the increasing of temperature and disappear at 600°C, which is analyzed and discussed in this paper.
2017, 46(9):2470-2475.
Abstract:
By tensile and compressive tests of commercial pure titanium (CP-Ti), the tensile and compressive stress-strain relationships under various deformation tempretures and strain rates are obtained. Then, the influences of deformation tempreatures, tension/compression loading paths and strain rates on the stress-strain relationships are investigated. With Zener-Hollomon model, the influencing rules of the temperatures and strain rates on work hardening are obtained and the compressive deformation processing map is constructed. Based on the EBSD analysis, the grain orientations of CP-Ti are obtained and the plastic deformation mechanisms for tension and compression are clarified: the slipping dominates the tension plastic deformation and the mechanism of compression plastic deformation is dominated by slipping-twinning-slipping.
By tensile and compressive tests of commercial pure titanium (CP-Ti), the tensile and compressive stress-strain relationships under various deformation tempretures and strain rates are obtained. Then, the influences of deformation tempreatures, tension/compression loading paths and strain rates on the stress-strain relationships are investigated. With Zener-Hollomon model, the influencing rules of the temperatures and strain rates on work hardening are obtained and the compressive deformation processing map is constructed. Based on the EBSD analysis, the grain orientations of CP-Ti are obtained and the plastic deformation mechanisms for tension and compression are clarified: the slipping dominates the tension plastic deformation and the mechanism of compression plastic deformation is dominated by slipping-twinning-slipping.
2017, 46(9):2476-2480.
Abstract:
To understand the reason of creep rupture life of superalloy K424 drops sometimes under investment casting process, the defects in the test bars were investigated on the shape, distribution with the help of scanning electron microscope (SEM) and microhardness tester. The causes of the defects and influences on creep rupture were analysed. The results show that there are micro shrinkage porosities in interdendritic regions and intact regular octahedron shaped MC carbides can be founded nearby. The microsegregation of the elements is in different degrees which the most serious element is Cr. The cause of the micro shrinkage porosities is that the adjacent dendrite arms join each other and split liquid alloy into closed parts. The micro shrinkage porosities cause stress concentration in the test bars and thus cause the lower high temperature creep rupture life.
To understand the reason of creep rupture life of superalloy K424 drops sometimes under investment casting process, the defects in the test bars were investigated on the shape, distribution with the help of scanning electron microscope (SEM) and microhardness tester. The causes of the defects and influences on creep rupture were analysed. The results show that there are micro shrinkage porosities in interdendritic regions and intact regular octahedron shaped MC carbides can be founded nearby. The microsegregation of the elements is in different degrees which the most serious element is Cr. The cause of the micro shrinkage porosities is that the adjacent dendrite arms join each other and split liquid alloy into closed parts. The micro shrinkage porosities cause stress concentration in the test bars and thus cause the lower high temperature creep rupture life.
2017, 46(9):2481-2486.
Abstract:
The temperature distribution along the thickness direction of AZ3lB Mg alloy was measured during rolling with heated rolls, basing on the previous study of temperature rise effect during rolling with cold (RT) rolls. The effect of different rolling conditions on temperature distribution and its relation with microstructure were investigated. On this basis, simplified energy-based state equations were established to predict temperature rises. The results show the temperature rises during rolling both increased with either increased reduction or decreased initial rolling temperature. The roll temperature had obvious effects on surface temperature and overall temperature rise. As a result, the amount of twin in surface layer decreased sharply and the overall recrystallization zone increased during rolling with heated roll. The calculated results by energy-based state equations were in good agreement with experimental ones.
The temperature distribution along the thickness direction of AZ3lB Mg alloy was measured during rolling with heated rolls, basing on the previous study of temperature rise effect during rolling with cold (RT) rolls. The effect of different rolling conditions on temperature distribution and its relation with microstructure were investigated. On this basis, simplified energy-based state equations were established to predict temperature rises. The results show the temperature rises during rolling both increased with either increased reduction or decreased initial rolling temperature. The roll temperature had obvious effects on surface temperature and overall temperature rise. As a result, the amount of twin in surface layer decreased sharply and the overall recrystallization zone increased during rolling with heated roll. The calculated results by energy-based state equations were in good agreement with experimental ones.
2017, 46(9):2487-2492.
Abstract:
Aiming at reducing the heat input of the forming course, controlling the distribution of heat-affected zone and the stress distribution of the forming layers, the forming course of laser remanufacture was simulated dynamically in the method of finite element analysis. The temperature field of the laser remanufacture for CW/pulsed laser was compared and analysed, the non-contacting infrared thermometer was taken to validate the result of the analysis. The related CW/pulsed laser process was compared and validate by the experiment of laser remanufacture forming. The result of the analysis and the test shows that, the optimized process parameters of laser remanufacture for pulsed laser are the 1.2kW laser power, the 3mm spot diameter, the 5mm/s scanning speed, the 3.2mm width of the forming layer, the 10ms pulse width, the 1:1 duty ratio. On the same condition of forming and heat dissipation, the temperature maximum of laser remanufacture molten pool is about 1400℃,it is 170 ℃ higher than the pulsed laser. The heat input and heat-affected zone for CW laser remanufacture is bigger than the pulsed laser remanufacture’s. The related process and methods could be taken for reference for the remanufacture of impeller blades.
Aiming at reducing the heat input of the forming course, controlling the distribution of heat-affected zone and the stress distribution of the forming layers, the forming course of laser remanufacture was simulated dynamically in the method of finite element analysis. The temperature field of the laser remanufacture for CW/pulsed laser was compared and analysed, the non-contacting infrared thermometer was taken to validate the result of the analysis. The related CW/pulsed laser process was compared and validate by the experiment of laser remanufacture forming. The result of the analysis and the test shows that, the optimized process parameters of laser remanufacture for pulsed laser are the 1.2kW laser power, the 3mm spot diameter, the 5mm/s scanning speed, the 3.2mm width of the forming layer, the 10ms pulse width, the 1:1 duty ratio. On the same condition of forming and heat dissipation, the temperature maximum of laser remanufacture molten pool is about 1400℃,it is 170 ℃ higher than the pulsed laser. The heat input and heat-affected zone for CW laser remanufacture is bigger than the pulsed laser remanufacture’s. The related process and methods could be taken for reference for the remanufacture of impeller blades.
2017, 46(9):2493-2498.
Abstract:
The isothermal oxidation behaviors of three kinds of experimental third generation single crystal superalloys with different tungsten contents were investigated at 1100℃ in air by X-ray diffraction (XRD), scanning election microscopy (SEM) and energy disperse X-ray analysis (EDX). The experimental results showed that three kinds of alloys approximately obeyed subparabolic rate law during oxidation of 100h at 1100℃. The mass gains of 8wt. % W-containing alloy remained higher than the mass gains of 6 wt.% and 7wt.% W-containing alloys. The oxide scale exposed at 1100℃ was consist of three layers: an outer Ni(Co)O layer, an intermediate layer mainly composed of oxides and spinels, and an inner Al2O3 layer. The γ′-free layer was formed in the base alloy. In the current alloy system, the transition of oxidation mechanism happened with increasing W content at 1100℃, therefore, it was found that the alloys with a W content less 7% exhibited relative balance between oxidation resistance and solution strength.
The isothermal oxidation behaviors of three kinds of experimental third generation single crystal superalloys with different tungsten contents were investigated at 1100℃ in air by X-ray diffraction (XRD), scanning election microscopy (SEM) and energy disperse X-ray analysis (EDX). The experimental results showed that three kinds of alloys approximately obeyed subparabolic rate law during oxidation of 100h at 1100℃. The mass gains of 8wt. % W-containing alloy remained higher than the mass gains of 6 wt.% and 7wt.% W-containing alloys. The oxide scale exposed at 1100℃ was consist of three layers: an outer Ni(Co)O layer, an intermediate layer mainly composed of oxides and spinels, and an inner Al2O3 layer. The γ′-free layer was formed in the base alloy. In the current alloy system, the transition of oxidation mechanism happened with increasing W content at 1100℃, therefore, it was found that the alloys with a W content less 7% exhibited relative balance between oxidation resistance and solution strength.
2017, 46(9):2499-2504.
Abstract:
The tungsten (W) parts and coating with High purity, fully dense are achieved by Chemical Vapor Deposition (CVD）with high efficiency. Based on its application requirements, the changing of surface morphology, grains size and surface roughness of CVD-W with different growth steps were studied and the relations of them were achieved. The behaviors of crystal structure of CVD-W in high temperature were observed.
The tungsten (W) parts and coating with High purity, fully dense are achieved by Chemical Vapor Deposition (CVD）with high efficiency. Based on its application requirements, the changing of surface morphology, grains size and surface roughness of CVD-W with different growth steps were studied and the relations of them were achieved. The behaviors of crystal structure of CVD-W in high temperature were observed.
2017, 46(9):2505-2511.
Abstract:
Molecular dynamics method has been applied to the research on the process of crack propagation of single crystal γ-TiAl. The atomic trajectory figure, energy evolution and the relationship between stress and strain were obtained after the holes size effect had been studied. The results indicate that the initiation stress decreased with holes size increased. After the crack combined with the hole: when R=1?, crack occurred at the center of holes boundary after holes deformation , and it propagated along the direction of [100] until material fracture, mother-child model was found; when R=2?, crack occurred at one corner after holes deformation, and it propagated along the direction of [100] until material fracture; when R=3?, crack occurred at two corners after holes deformation, and it propagated along the direction of [110]and , which mother-child model was found at the direction of [110], and child crack occurred at boundary which combined with crack in this direction and propagate until material fracture. In addition the crack propagate was inhibited by the hole.
Molecular dynamics method has been applied to the research on the process of crack propagation of single crystal γ-TiAl. The atomic trajectory figure, energy evolution and the relationship between stress and strain were obtained after the holes size effect had been studied. The results indicate that the initiation stress decreased with holes size increased. After the crack combined with the hole: when R=1?, crack occurred at the center of holes boundary after holes deformation , and it propagated along the direction of [100] until material fracture, mother-child model was found; when R=2?, crack occurred at one corner after holes deformation, and it propagated along the direction of [100] until material fracture; when R=3?, crack occurred at two corners after holes deformation, and it propagated along the direction of [110]and , which mother-child model was found at the direction of [110], and child crack occurred at boundary which combined with crack in this direction and propagate until material fracture. In addition the crack propagate was inhibited by the hole.
2017, 46(9):2512-2516.
Abstract:
Dynamic recrystallization of IN690 super alloy during tube extrusion had been simulated based on Cellular Automata(CA). It had been determined that model of dislocation density and model of reply and model of nucleation and model of grain growth. It had been obtained that grain morphology and distribution and orientation and size during the process of deformation. The results presented that the grain size of the external wall was smaller than that of the middle under the same extrusion ratio. With the increasing of extrusion ratio, the grain size at the same site of the tube decreased. The relative errors of the grain sizes of simulation and experiment were less than 16.6%.
Dynamic recrystallization of IN690 super alloy during tube extrusion had been simulated based on Cellular Automata(CA). It had been determined that model of dislocation density and model of reply and model of nucleation and model of grain growth. It had been obtained that grain morphology and distribution and orientation and size during the process of deformation. The results presented that the grain size of the external wall was smaller than that of the middle under the same extrusion ratio. With the increasing of extrusion ratio, the grain size at the same site of the tube decreased. The relative errors of the grain sizes of simulation and experiment were less than 16.6%.
2017, 46(9):2517-2522.
Abstract:
Cu-24wt%Ag alloy sheets were prepared by cold rolling and aging to reveal the evolution of microstructures, mechanical properties and electrical conductivity. The connection between the strengthening, conductivity and microstructure refinement of the alloy was discussed. After severe cold rolling, the microstructure develops into nano-layered structure of Cu and Ag arranged alternatively, with numerous Ag nano-fibers embedded in Cu matrix and (Cu+Ag) eutectics distributed in Ag areas. Shear bands occur in longitudinal sections as the strain reaches 94% or so. With increasing the rolling strain, spacing of Cu/Ag interface, Ag fibers and eutectic lamellae decreases gradually to nanoscale, leading to significant enhancement of the strengthening effect, and hence the hardness increases rapidly when the strain exceeds 96%. The relationship between the resistivity increment caused by Cu/Ag interface and rolling reduction was established, reflecting the influence rule of microstructure refinement on electrical conductivity in the rolling process.
Cu-24wt%Ag alloy sheets were prepared by cold rolling and aging to reveal the evolution of microstructures, mechanical properties and electrical conductivity. The connection between the strengthening, conductivity and microstructure refinement of the alloy was discussed. After severe cold rolling, the microstructure develops into nano-layered structure of Cu and Ag arranged alternatively, with numerous Ag nano-fibers embedded in Cu matrix and (Cu+Ag) eutectics distributed in Ag areas. Shear bands occur in longitudinal sections as the strain reaches 94% or so. With increasing the rolling strain, spacing of Cu/Ag interface, Ag fibers and eutectic lamellae decreases gradually to nanoscale, leading to significant enhancement of the strengthening effect, and hence the hardness increases rapidly when the strain exceeds 96%. The relationship between the resistivity increment caused by Cu/Ag interface and rolling reduction was established, reflecting the influence rule of microstructure refinement on electrical conductivity in the rolling process.
2017, 46(9):2523-2527.
Abstract:
The Fe-based amorphous composites reinforced by toughness ZnAl particle were prepared using pressureless sintering methods, and the structure, thermal stability and thermal conductivity of the composite material were investigated by XRD, SEM, DSC and laser indeed thermal conductivity tester, respectively. The results illustrate that compact ZnAl/ Fe-based amorphous composites can be formed by using pressureless sintering technique in the supercooled liquid region. ZnAl has no effect on the nature of Fe-based amorphous matrix. There is no interface reaction phase generated in sintering process, but the thermal stability slightly decreases. Within the scope of the 298 K to 423 K, the heat conduction coefficient of composites is lower than that of the Fe-based amorphous alloy, and the thermal diffusion coefficient slightly change with the raising the temperature, which show that the composite materials has the better thermal insulation property.
The Fe-based amorphous composites reinforced by toughness ZnAl particle were prepared using pressureless sintering methods, and the structure, thermal stability and thermal conductivity of the composite material were investigated by XRD, SEM, DSC and laser indeed thermal conductivity tester, respectively. The results illustrate that compact ZnAl/ Fe-based amorphous composites can be formed by using pressureless sintering technique in the supercooled liquid region. ZnAl has no effect on the nature of Fe-based amorphous matrix. There is no interface reaction phase generated in sintering process, but the thermal stability slightly decreases. Within the scope of the 298 K to 423 K, the heat conduction coefficient of composites is lower than that of the Fe-based amorphous alloy, and the thermal diffusion coefficient slightly change with the raising the temperature, which show that the composite materials has the better thermal insulation property.
2017, 46(9):2528-2532.
Abstract:
The mutual effect of Fe and Sn on the microstructure of Zr alloys was investigated in the present work. It has been found that in Zr-Fe binary alloys (with Fe amount less than 1 wt.%), very few amount of Fe element was dissolved in Zr alloys while most of the Fe was precipitated as Zr3Fe phase. Moreover, the dimension of Zr3Fe increased with the Fe content. However, the Sn element added in the present work (≤5.0 wt.%) has been entirely dissolved in Zr alloys, while no precipitate containing Sn element was found. It also observed that the addition of the Sn element could inhabit the recovery and recrystallization process of Zr alloys. In Zr-Sn-Fe ternary alloys, the addition of Sn element could increase the solubility of Fe in Zr alloys, and inhabit the grain growth of lath crystal and migration of Fe element duing rapid cooling process of β-phase. Moreover, finer and more uniformly distributed Zr3Fe phase were observed after addition of Sn element.
The mutual effect of Fe and Sn on the microstructure of Zr alloys was investigated in the present work. It has been found that in Zr-Fe binary alloys (with Fe amount less than 1 wt.%), very few amount of Fe element was dissolved in Zr alloys while most of the Fe was precipitated as Zr3Fe phase. Moreover, the dimension of Zr3Fe increased with the Fe content. However, the Sn element added in the present work (≤5.0 wt.%) has been entirely dissolved in Zr alloys, while no precipitate containing Sn element was found. It also observed that the addition of the Sn element could inhabit the recovery and recrystallization process of Zr alloys. In Zr-Sn-Fe ternary alloys, the addition of Sn element could increase the solubility of Fe in Zr alloys, and inhabit the grain growth of lath crystal and migration of Fe element duing rapid cooling process of β-phase. Moreover, finer and more uniformly distributed Zr3Fe phase were observed after addition of Sn element.
2017, 46(9):2533-2538.
Abstract:
W-Lu2O3 and W-Nb-C-Lu2O3 composites were fabricated by mechanical milling and spark plasma sintering. The morphology of composite powders, surface and fracture surface morphology of the samples were characterized by field-emission scanning electron microscopy (FE-SEM), energy-dispersive spectroscopy (EDS) and transmission electron microscopy (TEM). The relative density, thermal conductivity, hardness and strength of the samples were also measured. Results revealed that the addition of trace Nb and C on the basis of W-Lu2O3 composite had an obvious effect on grain refinement, densification and strength. The relative density of W-Nb-C-Lu2O3 composite was 5.75% higher than W-Lu2O3 and reached 95.12%. The grain size of W-Nb-C-Lu2O3 composite was refined from 8~13 μm to 2~5 μm, and its microhardness and strength were obvious improved compared with W-Lu2O3 composite.
W-Lu2O3 and W-Nb-C-Lu2O3 composites were fabricated by mechanical milling and spark plasma sintering. The morphology of composite powders, surface and fracture surface morphology of the samples were characterized by field-emission scanning electron microscopy (FE-SEM), energy-dispersive spectroscopy (EDS) and transmission electron microscopy (TEM). The relative density, thermal conductivity, hardness and strength of the samples were also measured. Results revealed that the addition of trace Nb and C on the basis of W-Lu2O3 composite had an obvious effect on grain refinement, densification and strength. The relative density of W-Nb-C-Lu2O3 composite was 5.75% higher than W-Lu2O3 and reached 95.12%. The grain size of W-Nb-C-Lu2O3 composite was refined from 8~13 μm to 2~5 μm, and its microhardness and strength were obvious improved compared with W-Lu2O3 composite.
2017, 46(9):2539-2545.
Abstract:
In this work, the nanocrystalline SmCo8.9Si0.9 alloy with a high stability was first prepared and then a systematic study was carried out on the phase transformation and corresponding magnetic properties of the metastable SmCo8.9Si0.9 phase.The results revealed that the stability of the metastable upersaturated solid solution SmCo9.8 could be greatly improved for the addition of Si. With the increase of the heat-treatment temperature, the nanocrystalline SmCo8.9Si0.9 alloy transformed from the SmCo9.8(H) phase to the Co(FCC) phase and the coercivity was correspondingly improved. The mechanism was that the precipitated fine Co phase enhanced the pinning effect. With a further increase in temperature, the Sm2Co17(H) phase transformed into Sm2Co17(R) accompanied with an evident grain growth and an inhomogeneous grain size distribution, leading to the decrease in the magnetic properties.
In this work, the nanocrystalline SmCo8.9Si0.9 alloy with a high stability was first prepared and then a systematic study was carried out on the phase transformation and corresponding magnetic properties of the metastable SmCo8.9Si0.9 phase.The results revealed that the stability of the metastable upersaturated solid solution SmCo9.8 could be greatly improved for the addition of Si. With the increase of the heat-treatment temperature, the nanocrystalline SmCo8.9Si0.9 alloy transformed from the SmCo9.8(H) phase to the Co(FCC) phase and the coercivity was correspondingly improved. The mechanism was that the precipitated fine Co phase enhanced the pinning effect. With a further increase in temperature, the Sm2Co17(H) phase transformed into Sm2Co17(R) accompanied with an evident grain growth and an inhomogeneous grain size distribution, leading to the decrease in the magnetic properties.
2017, 46(9):2546-2552.
Abstract:
The research of the stress relaxation behavior in superalloys provides the reference of selecting the appropriate working conditions for fasteners and experimental basis for relaxation laws . The effects of the temperature,the initial stress and various heat treatment regime on the stress relaxation in the superalloy GH4738 were investigated. The results indicated that: a threshold stress was found between two stages. Below the threshold stress, the plastic strain rate fell fast. The relaxation stability of the alloy decreased with the increase of temperature, meanwhile, the stress relaxation rate rised and the relaxation limit declined. The stress relaxation rate of the first stage speeded up and the relaxation limit increased when the initial stress was improved. Different heat treatment systems mainly affected the second stage of the stress relaxtion, whereas, no obvious influence was observed on the threshold stress and the relaxation stability.
The research of the stress relaxation behavior in superalloys provides the reference of selecting the appropriate working conditions for fasteners and experimental basis for relaxation laws . The effects of the temperature,the initial stress and various heat treatment regime on the stress relaxation in the superalloy GH4738 were investigated. The results indicated that: a threshold stress was found between two stages. Below the threshold stress, the plastic strain rate fell fast. The relaxation stability of the alloy decreased with the increase of temperature, meanwhile, the stress relaxation rate rised and the relaxation limit declined. The stress relaxation rate of the first stage speeded up and the relaxation limit increased when the initial stress was improved. Different heat treatment systems mainly affected the second stage of the stress relaxtion, whereas, no obvious influence was observed on the threshold stress and the relaxation stability.
2017, 46(9):2553-2557.
Abstract:
The microstructure and quenching characteristics of 6082 aluminum alloy were investigated via end quench test, interrupted quenching method and transmission electron microscopy (TEM). The result shows that the hardenability depth of 6082 aluminum alloy is 15-20 mm, when the cooling rate was 20℃/s, plenty of fine and dispersed β″ and a narrow PFZ were formed after artificial aging. By interrupted quenching method, when the alloys were preserved at high temperature, the precipitation of β-equilibrium phase was not obvious which retained high saturated solid solution and had small effect to aging; while in the isothermal process of medium temperature, β-equilibrium phases were formed and grew up quickly by the consumption of solute atoms nearby which made a great contribution to properties loss; When the alloys were preserved at low temperature, quench induced precipitates formed slowly but grew up with the extension of time. No matter in slow cooling or isothermal process, quench induced precipitates β is prior to nucleate on the (AlFeSi) dispersoids, which is a part reason of alloy’s high quench sensitivity.
The microstructure and quenching characteristics of 6082 aluminum alloy were investigated via end quench test, interrupted quenching method and transmission electron microscopy (TEM). The result shows that the hardenability depth of 6082 aluminum alloy is 15-20 mm, when the cooling rate was 20℃/s, plenty of fine and dispersed β″ and a narrow PFZ were formed after artificial aging. By interrupted quenching method, when the alloys were preserved at high temperature, the precipitation of β-equilibrium phase was not obvious which retained high saturated solid solution and had small effect to aging; while in the isothermal process of medium temperature, β-equilibrium phases were formed and grew up quickly by the consumption of solute atoms nearby which made a great contribution to properties loss; When the alloys were preserved at low temperature, quench induced precipitates formed slowly but grew up with the extension of time. No matter in slow cooling or isothermal process, quench induced precipitates β is prior to nucleate on the (AlFeSi) dispersoids, which is a part reason of alloy’s high quench sensitivity.
2017, 46(9):2558-2564.
Abstract:
In-situ β-Ti toughening of Ti-based bulk metallic glass matrix composites have been synthesized by the Bridgman solidification, and the microstructure, phase composition and chemical composition of this material has been studied by using XRD, SEM, EBSD, TEM, EDS and three-dimensional reconstruction method. Based on these, the deformation process was studied by using in-situ SEM and EBSD. The results showed that the crystal phase is dendritic morphology, which has the very good connectivity and the secondary dendrite arm of 1~3 μm. The chemical composition of dendritic crystal phase is Ti62.4 Zr18.4 Cu2.6 V16.6 (at %) and the amorphous matrix is T45Zr34.8Cu10.6V9.6 respectively.
In-situ β-Ti toughening of Ti-based bulk metallic glass matrix composites have been synthesized by the Bridgman solidification, and the microstructure, phase composition and chemical composition of this material has been studied by using XRD, SEM, EBSD, TEM, EDS and three-dimensional reconstruction method. Based on these, the deformation process was studied by using in-situ SEM and EBSD. The results showed that the crystal phase is dendritic morphology, which has the very good connectivity and the secondary dendrite arm of 1~3 μm. The chemical composition of dendritic crystal phase is Ti62.4 Zr18.4 Cu2.6 V16.6 (at %) and the amorphous matrix is T45Zr34.8Cu10.6V9.6 respectively.
40 Influences of In on the Microstructure and Mechanical Properties of Low Silver Ag-Cu-Zn Filler Metal
Ma Chaoli
,
Xue Songbai
,
Zhang Tao
,
Jiang Junyi
,
Long Weimin
,
Zhang Guanxing
,
Zhang Qingke
,
He Peng
2017, 46(9):2565-2570.
Abstract:
To develop novel low silver based filler metals used for brazing brass and 304 stainless steel. The microstructure morphology and the wettability of low silver based filler metals were observed by using scanning electron microscopy (SEM) and electrical resistance furnace. The results indicate that, the wettability of the low silver based filler metals imporved with increasing indium content. Brass and stainless steel were brazed with flame method, the mechanical properties of lap joint were tested and analyzed at the same time. It is found that the tensile strength of joints increased with the addition of indium due to the solution strength effect. The shear strength of joint brazed with the 17AgCuZn-1In filler metal reached 312.6MPa closes to joint brazed with the B25AgCuZnSn filler metal. The joints part formed via brazing the 304 stainless steel and brass with 17AgCuZn-1In by flame brazing, had no defects at all, which, meanwhile, proved its good performance.
To develop novel low silver based filler metals used for brazing brass and 304 stainless steel. The microstructure morphology and the wettability of low silver based filler metals were observed by using scanning electron microscopy (SEM) and electrical resistance furnace. The results indicate that, the wettability of the low silver based filler metals imporved with increasing indium content. Brass and stainless steel were brazed with flame method, the mechanical properties of lap joint were tested and analyzed at the same time. It is found that the tensile strength of joints increased with the addition of indium due to the solution strength effect. The shear strength of joint brazed with the 17AgCuZn-1In filler metal reached 312.6MPa closes to joint brazed with the B25AgCuZnSn filler metal. The joints part formed via brazing the 304 stainless steel and brass with 17AgCuZn-1In by flame brazing, had no defects at all, which, meanwhile, proved its good performance.
2017, 46(9):2571-2576.
Abstract:
ABSTRACT The effect of V on hot corrosion behavior of cast Ni-base superalloy K417G exposed to 75%Na2SO4+25%NaCl at 900℃ for 100h has been investigated by means of thermogravimetry(TG) and scanning electron microscopy equipped with energy dispersive X-ray spectrum(EDS), corrosion resistance obtained by measuring the polarization curve at 900℃.the results showed that The hot corrosion rate of the alloy with 0.016 v content is almost unchanged, the hot corrosion rate of alloy increased with the increase of V content. but the hot corrosion rate of alloy with 1.19 V content is more 100 times than the low V alloy. The corrosion product on the surface of K417G alloys is found to be composed of oxide and sulfides is still made up of three layer, that is the external oxide layer consists of Al、Cr、Ti and Ni, sulfides formed in different layer of NiS、MoS and NiCrS. With the content of V content, S element diffusion toward to interlayer, and the layer of Al2o3 and Cr2o3 become thinner, hence the inner sulfides layer formed in the alloy with 1.19 V which can decreased the corrosion resistance. Com pared with the alloy with 1.19 V, the results of the polarization curve showed that the corrosion potential shift 0.4V toward positive direction, the corrosion resistance of the alloy with 0.016 V is better than that alloy with high V content.
ABSTRACT The effect of V on hot corrosion behavior of cast Ni-base superalloy K417G exposed to 75%Na2SO4+25%NaCl at 900℃ for 100h has been investigated by means of thermogravimetry(TG) and scanning electron microscopy equipped with energy dispersive X-ray spectrum(EDS), corrosion resistance obtained by measuring the polarization curve at 900℃.the results showed that The hot corrosion rate of the alloy with 0.016 v content is almost unchanged, the hot corrosion rate of alloy increased with the increase of V content. but the hot corrosion rate of alloy with 1.19 V content is more 100 times than the low V alloy. The corrosion product on the surface of K417G alloys is found to be composed of oxide and sulfides is still made up of three layer, that is the external oxide layer consists of Al、Cr、Ti and Ni, sulfides formed in different layer of NiS、MoS and NiCrS. With the content of V content, S element diffusion toward to interlayer, and the layer of Al2o3 and Cr2o3 become thinner, hence the inner sulfides layer formed in the alloy with 1.19 V which can decreased the corrosion resistance. Com pared with the alloy with 1.19 V, the results of the polarization curve showed that the corrosion potential shift 0.4V toward positive direction, the corrosion resistance of the alloy with 0.016 V is better than that alloy with high V content.
2017, 46(9):2577-2582.
Abstract:
The anelasticity behavior was investigated of Zr-based bulk metallic glasses in a geometrically constrained quasi-static cyclic loading–unloading compression tests. The results demonstrated that the dissipative energy during cycle loading was in inverse proportion to the cross-head displacement rate used, and the anelasticity behavior have close correlation with the elastic stress-induced microstructure evolution. The dissipative energy during cycle loading in BMGs could also be used as a parameter to characterize the spatial multiplication ability of shear bands. The larger dissipative energy implies the higher the spatial multiplication ability of shear bands.
The anelasticity behavior was investigated of Zr-based bulk metallic glasses in a geometrically constrained quasi-static cyclic loading–unloading compression tests. The results demonstrated that the dissipative energy during cycle loading was in inverse proportion to the cross-head displacement rate used, and the anelasticity behavior have close correlation with the elastic stress-induced microstructure evolution. The dissipative energy during cycle loading in BMGs could also be used as a parameter to characterize the spatial multiplication ability of shear bands. The larger dissipative energy implies the higher the spatial multiplication ability of shear bands.
43 Thermodynamics Analysis of Melting Characteristics for SilverBrazing Alloys with Electroplating Tin
2017, 46(9):2583-2588.
Abstract:
Silver brazing alloys with electroplating tin were prepared using the combination process of electroplating and heat diffusion based on BAg50CuZn substrate. By revealing the thermodynamic properties of silver brazing alloys with electroplating tin, the melting temperature of silver brazing alloys were observed by differential scanning calorimeter (DSC), the phase transformation thermodynamic characteristic of silver brazing alloys were analyzed with the thermal analysis kinetics of non-isothermal differential and integral methods. The microstructure and phase composition of wetting interface between 304 stainless steel and silver brazing alloys were investigated by optical microscope and XRD, respectively. The results show that the phase transformation temperature range of silver brazing alloys from solid to liquid would be narrower with the increase of Sn content, and the phase transformation activation energy of silver brazing alloys is gradually increased by non-isothermal differential and integral method. When Sn content is 7.2 %, the activation energy and pre exponential factor reach to the maximum, which are 555.56 kJ/mol and 1.41×1032, respectively. The phase transformation rate equation of silver brazing alloys with electroplating tin is deduced as k=1.41×1032exp(-5.56×105/RT). Silver brazing alloys of 7.2 % Sn content is melted on the surfae of 304 stainless steel, the microstructure of wetting interface are composed of Ag phase, Cu phase, CuZnphase, Cu5Zn8 phase, Cu41Sn11 phase and Ag3Sn phase.
Silver brazing alloys with electroplating tin were prepared using the combination process of electroplating and heat diffusion based on BAg50CuZn substrate. By revealing the thermodynamic properties of silver brazing alloys with electroplating tin, the melting temperature of silver brazing alloys were observed by differential scanning calorimeter (DSC), the phase transformation thermodynamic characteristic of silver brazing alloys were analyzed with the thermal analysis kinetics of non-isothermal differential and integral methods. The microstructure and phase composition of wetting interface between 304 stainless steel and silver brazing alloys were investigated by optical microscope and XRD, respectively. The results show that the phase transformation temperature range of silver brazing alloys from solid to liquid would be narrower with the increase of Sn content, and the phase transformation activation energy of silver brazing alloys is gradually increased by non-isothermal differential and integral method. When Sn content is 7.2 %, the activation energy and pre exponential factor reach to the maximum, which are 555.56 kJ/mol and 1.41×1032, respectively. The phase transformation rate equation of silver brazing alloys with electroplating tin is deduced as k=1.41×1032exp(-5.56×105/RT). Silver brazing alloys of 7.2 % Sn content is melted on the surfae of 304 stainless steel, the microstructure of wetting interface are composed of Ag phase, Cu phase, CuZnphase, Cu5Zn8 phase, Cu41Sn11 phase and Ag3Sn phase.
2017, 46(9):2589-2593.
Abstract:
Abstract: Ti/IrO2-Ta2O5 electrodes were prepared by low thermal decomposition method. The influence of Ta contents on the microstructure and capacitive performance of the Ti/IrO2-Ta2O5 electrodes was investigated by XRD, cyclic voltammetry,electrochemical impedance spectroscopy and galvanostatic charge-discharge tests. The results showed that Ta2O5 can inhibit crystallization of the IrO2.With increasing Ta contents, the crystallization degree decreased.When the content of Ta increased to 60%mol, the electrode with a content of 6.4% crystalline structure had a superior capacitive performanceof 239.2 g/F,which was considerably higher than that of IrO2 electrode(54.1 g/F) .
Abstract: Ti/IrO2-Ta2O5 electrodes were prepared by low thermal decomposition method. The influence of Ta contents on the microstructure and capacitive performance of the Ti/IrO2-Ta2O5 electrodes was investigated by XRD, cyclic voltammetry,electrochemical impedance spectroscopy and galvanostatic charge-discharge tests. The results showed that Ta2O5 can inhibit crystallization of the IrO2.With increasing Ta contents, the crystallization degree decreased.When the content of Ta increased to 60%mol, the electrode with a content of 6.4% crystalline structure had a superior capacitive performanceof 239.2 g/F,which was considerably higher than that of IrO2 electrode(54.1 g/F) .
2017, 46(9):2594-2600.
Abstract:
In this paper, laser cladding of Al-Si/Al2O3 powders was applied on a Mg-Nd-Zn-Zr magnesium rare earth alloy, and the microstructure, phase components and properties of the clad layers were carefully characterized. X ray diffraction (XRD) analyses and scanning electron microscope (SEM) observations show that the clad layer is mainly consisted of α-Mg, Mg2Si, Mg12Nd and Al3.21Si0.47 or Mg17Al12 phases. However, Al2O3 particles agglomerate at the bottom of the clad layer close to the melt-substrate interface. The cross section microhardness tests reveal that the maximum hardness of the clad layer ranges from 309HV to 475HV, about 5 to 8 times higher than that of the Mg-Nd-Zn-Zr alloy (55HV) substrate. Such an increased hardness is attributed to the grain refinement, the solution strengthening, the formation of hardening phases and the dispersion strengthening from oxide particles. According to the potentiodynamic polarization measurements carried out in the 3.5wt% NaCl water solution, the corrosion potential of the alloy increased after laser cladding, while the corrosion current density decreased from 1.683×10-4(A/cm2)for the Mg alloy substrate to 0.843×10-5(A/cm2)for the laser clad alloy. Therefore, the corrosion resistance of Mg-Nd-Zn-Zr alloy can also be significantly improved by laser cladding with Al-Si/Al2O3 powders.
In this paper, laser cladding of Al-Si/Al2O3 powders was applied on a Mg-Nd-Zn-Zr magnesium rare earth alloy, and the microstructure, phase components and properties of the clad layers were carefully characterized. X ray diffraction (XRD) analyses and scanning electron microscope (SEM) observations show that the clad layer is mainly consisted of α-Mg, Mg2Si, Mg12Nd and Al3.21Si0.47 or Mg17Al12 phases. However, Al2O3 particles agglomerate at the bottom of the clad layer close to the melt-substrate interface. The cross section microhardness tests reveal that the maximum hardness of the clad layer ranges from 309HV to 475HV, about 5 to 8 times higher than that of the Mg-Nd-Zn-Zr alloy (55HV) substrate. Such an increased hardness is attributed to the grain refinement, the solution strengthening, the formation of hardening phases and the dispersion strengthening from oxide particles. According to the potentiodynamic polarization measurements carried out in the 3.5wt% NaCl water solution, the corrosion potential of the alloy increased after laser cladding, while the corrosion current density decreased from 1.683×10-4(A/cm2)for the Mg alloy substrate to 0.843×10-5(A/cm2)for the laser clad alloy. Therefore, the corrosion resistance of Mg-Nd-Zn-Zr alloy can also be significantly improved by laser cladding with Al-Si/Al2O3 powders.
2017, 46(9):2601-2606.
Abstract:
TNZS, TiO2/TNZS and HA/TNZS bio-medical materials were prepared by powder metallurgy comebining high-energy milling with cold pressed sintering. Histocompatibility in vitro of the three TNZS-based materials were studied. The results show that: three materials have no cytotoxicity, meeting toxicity safety requirements of implant materials; CPIR on the surface of TiO2/TNZS and HA/TNZS for 1 d, 3 d, 5 d and 7 d have significantly lower than that of TNZS group, showing that the addition of TiO2 and HA can improve the speed of cell proliferation on the surface of TNZS material and have better induction of proliferation of osteoblasts in vitro; the distribution of osteoblasts attached to the surface of TiO2/TNZS has more uniform; pseudopodium extension of osteoblasts attached to the surface of three materials are in good condition.
TNZS, TiO2/TNZS and HA/TNZS bio-medical materials were prepared by powder metallurgy comebining high-energy milling with cold pressed sintering. Histocompatibility in vitro of the three TNZS-based materials were studied. The results show that: three materials have no cytotoxicity, meeting toxicity safety requirements of implant materials; CPIR on the surface of TiO2/TNZS and HA/TNZS for 1 d, 3 d, 5 d and 7 d have significantly lower than that of TNZS group, showing that the addition of TiO2 and HA can improve the speed of cell proliferation on the surface of TNZS material and have better induction of proliferation of osteoblasts in vitro; the distribution of osteoblasts attached to the surface of TiO2/TNZS has more uniform; pseudopodium extension of osteoblasts attached to the surface of three materials are in good condition.
2017, 46(9):2607-2612.
Abstract:
:A new type Al-Zn-Mg-Cu alloy Al-Mg alloy was welded using Tungsten Inert Gas welding method. Microstructures and microhardness of the joint were analyzed. The relationship between the temperature and microstructure and microhardness were established based on the simulation result of the temperature fieldthrough the Visual-weld.At last, the residual stress was employing the X-ray diffraction method. The results showed that microstructure in the weldseam shown as corase equiaxed grain zone(EQZ). That zone closed to fusion line was an equiaxed grain zone with small size, whichis ascalled Fine-Grain Layer. For the Fine-Grain layer, microstructure showed epitaxial solidification morphology. However, partial grain boundary re-melt appears outside of fusion line. Residual stress in the weldment is small and has the same distribution in the stable forming segment of weldseam. However, it has an inverse distribution in the front end of weldseam. With the influence of temperature curve of welding and η phase, microhardnesses in the hot affect zone is bigger than that in other zones in the weldment.Keywords:Butt-weld of MIG; Al-Zn-Mg-Cualloy; residual stress; microtopography; microhardness
:A new type Al-Zn-Mg-Cu alloy Al-Mg alloy was welded using Tungsten Inert Gas welding method. Microstructures and microhardness of the joint were analyzed. The relationship between the temperature and microstructure and microhardness were established based on the simulation result of the temperature fieldthrough the Visual-weld.At last, the residual stress was employing the X-ray diffraction method. The results showed that microstructure in the weldseam shown as corase equiaxed grain zone(EQZ). That zone closed to fusion line was an equiaxed grain zone with small size, whichis ascalled Fine-Grain Layer. For the Fine-Grain layer, microstructure showed epitaxial solidification morphology. However, partial grain boundary re-melt appears outside of fusion line. Residual stress in the weldment is small and has the same distribution in the stable forming segment of weldseam. However, it has an inverse distribution in the front end of weldseam. With the influence of temperature curve of welding and η phase, microhardnesses in the hot affect zone is bigger than that in other zones in the weldment.Keywords:Butt-weld of MIG; Al-Zn-Mg-Cualloy; residual stress; microtopography; microhardness
2017, 46(9):2613-2617.
Abstract:
Pure titanium was hydrothermally treated in 0.1 mol/L MgCl2 solutions with different pH at 200°C for 24hr in order to improve its bioactivity. Surface morphology, roughness, wettability and chemical composition were characterized with sophisticated equipment before and after treatment. Simulated body fluid immersion experiment was conducted to examine in vitro osteoconductivity. Hydrothermal treatment preserved the macro topography of polished substrates in spite nano-sized precipitations were observed and these surfaces showed superhydrophilicity. Magnesium titanate was formed on titanium surface after hydrothermal treatment in MgCl2 solution, however, under high pH, Mg(OH)2 precipitated from the solution. Typical apatite spheres were observed on hydrothermally treated samples after immersion in SBF for 2 days. However, the precipitation was depressed with increasing Mg amount incorporated into titanium surface. The hydrothermal treatment was a promising finial treatment for fabricating titanium implants with good bioactivity.
Pure titanium was hydrothermally treated in 0.1 mol/L MgCl2 solutions with different pH at 200°C for 24hr in order to improve its bioactivity. Surface morphology, roughness, wettability and chemical composition were characterized with sophisticated equipment before and after treatment. Simulated body fluid immersion experiment was conducted to examine in vitro osteoconductivity. Hydrothermal treatment preserved the macro topography of polished substrates in spite nano-sized precipitations were observed and these surfaces showed superhydrophilicity. Magnesium titanate was formed on titanium surface after hydrothermal treatment in MgCl2 solution, however, under high pH, Mg(OH)2 precipitated from the solution. Typical apatite spheres were observed on hydrothermally treated samples after immersion in SBF for 2 days. However, the precipitation was depressed with increasing Mg amount incorporated into titanium surface. The hydrothermal treatment was a promising finial treatment for fabricating titanium implants with good bioactivity.
2017, 46(9):2618-2622.
Abstract:
Ultra-fine grain commercial pure (CP) Ti were processed by Equal channel angular pressing(ECAP) at room temperature and ECAP followed by cold rolling (CR).Effect of annealing temperature on microstructure and properties of ultra-fine grain commercial pure Ti were investigated by transmission electron microscopy (TEM),uniaxial tensile test and microhardness test.The results showed that,the average grain size of ultra-fine grain was about 130 nm ,and ultimate tensile strength was over 813 MPa;when annealing temperature was below 400℃,the organization had no obvious change.Ultimate tensile strength and microhardness slightly decreased.At the same time,elonggation increased.when annealing temperature was higher 400℃,grain size of ultra-fine grain CP Ti grew slowly,and dislocation density decreased.Ultimate tensile strength and microhardness decreased obviously when annealing temperature at 500℃, grain size of ultra-fine grain CP Ti grew rapidly,and average grain size was 2 μm.
Ultra-fine grain commercial pure (CP) Ti were processed by Equal channel angular pressing(ECAP) at room temperature and ECAP followed by cold rolling (CR).Effect of annealing temperature on microstructure and properties of ultra-fine grain commercial pure Ti were investigated by transmission electron microscopy (TEM),uniaxial tensile test and microhardness test.The results showed that,the average grain size of ultra-fine grain was about 130 nm ,and ultimate tensile strength was over 813 MPa;when annealing temperature was below 400℃,the organization had no obvious change.Ultimate tensile strength and microhardness slightly decreased.At the same time,elonggation increased.when annealing temperature was higher 400℃,grain size of ultra-fine grain CP Ti grew slowly,and dislocation density decreased.Ultimate tensile strength and microhardness decreased obviously when annealing temperature at 500℃, grain size of ultra-fine grain CP Ti grew rapidly,and average grain size was 2 μm.
2017, 46(9):2623-2627.
Abstract:
Ag-Sn-In alloy powders were prepared by atomization. By investigating the effect of the process parameters (sintering temperature , sintering time , compacting pressure ),we confirm the optimal sintering temperature , sintering time and compacting pressure is 950℃ for 10h and 200MPa. By the comparative study on properties and micro-structures of AgSnO2 electric contact materials prepared by the pure oxygen atmosphere sintering process and the traditional sintering process, The results indicate that a pure oxygen atmosphere is conducive to the high temperature sintering, which improves the efficiency of the sintering and eventually improves the micro-structure and performance of AgSnO2 electric contact materials.
Ag-Sn-In alloy powders were prepared by atomization. By investigating the effect of the process parameters (sintering temperature , sintering time , compacting pressure ),we confirm the optimal sintering temperature , sintering time and compacting pressure is 950℃ for 10h and 200MPa. By the comparative study on properties and micro-structures of AgSnO2 electric contact materials prepared by the pure oxygen atmosphere sintering process and the traditional sintering process, The results indicate that a pure oxygen atmosphere is conducive to the high temperature sintering, which improves the efficiency of the sintering and eventually improves the micro-structure and performance of AgSnO2 electric contact materials.
2017, 46(9):2628-2632.
Abstract:
V-5Cr-5Ti alloy was prepared from vacuum sintering hydrogenation dehydrogenization powder by cold isostatic pressing(CIP). Hot isostatic pressing(HIP), hot forging and heat treatment were subsequently used to improve the microstructure and properties of V-5Cr-5Ti alloy. The phase composition of raw materials and V-5Cr-5Ti alloy was characterized using by XRD．The content of oxygen and nitrogen of V-5Cr-5Ti alloy was tested. Microstructures and mechanical properties of V-5Cr-5Ti alloy were investigated using by OM, SEM and mechanical property tester. The results show that the relative density of the powder metallurgy(PM)V-5Cr-5Ti alloy is as high as 99%. V-5Cr-5Ti alloy consists of single bcc phase vanadium alloy solid solution. The oxygen weight percent of V-5Cr-5Ti alloy annealed after hot forging is less than 600×10-6, the tensile strength is 490 MPa, yield strength is 368 MPa, and the elongation and reduction of area are 28% and 61.5%, respectively. Thefracture morphology is composed of all fine ductile dimples.
V-5Cr-5Ti alloy was prepared from vacuum sintering hydrogenation dehydrogenization powder by cold isostatic pressing(CIP). Hot isostatic pressing(HIP), hot forging and heat treatment were subsequently used to improve the microstructure and properties of V-5Cr-5Ti alloy. The phase composition of raw materials and V-5Cr-5Ti alloy was characterized using by XRD．The content of oxygen and nitrogen of V-5Cr-5Ti alloy was tested. Microstructures and mechanical properties of V-5Cr-5Ti alloy were investigated using by OM, SEM and mechanical property tester. The results show that the relative density of the powder metallurgy(PM)V-5Cr-5Ti alloy is as high as 99%. V-5Cr-5Ti alloy consists of single bcc phase vanadium alloy solid solution. The oxygen weight percent of V-5Cr-5Ti alloy annealed after hot forging is less than 600×10-6, the tensile strength is 490 MPa, yield strength is 368 MPa, and the elongation and reduction of area are 28% and 61.5%, respectively. Thefracture morphology is composed of all fine ductile dimples.
2017, 46(9):2633-2638.
Abstract:
Rare earth/PP shielding fibers filled with different contents of rare-earth have been prepared by melt spinning. The fibers are characterized by the Fourier-transformed infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), X-ray diffraction spectroscopy (XRD), scanning electron micrographs (SEM). Short fibers are compression-molded for the test of lead equivalent. The results show that, when the rare earth content is less than 50 wt%, rare earth can be dispersed in the PP matrix with nano-scale, and x-ray shielding performance of the fibers enhanced with the increase of content of rare-earth.
Rare earth/PP shielding fibers filled with different contents of rare-earth have been prepared by melt spinning. The fibers are characterized by the Fourier-transformed infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), X-ray diffraction spectroscopy (XRD), scanning electron micrographs (SEM). Short fibers are compression-molded for the test of lead equivalent. The results show that, when the rare earth content is less than 50 wt%, rare earth can be dispersed in the PP matrix with nano-scale, and x-ray shielding performance of the fibers enhanced with the increase of content of rare-earth.
53 Microstructure and properties of FeCrNiCoMnBx high-entropy alloy coating prepared by laser cladding
2017, 46(9):2639-2644.
Abstract:
An FeCrNiCoMnBx high-entropy alloy coating was prepared by laser cladding on a low carbon steel substrate. The effect of boron addition on the microstructure, hardness, and wear resistance of FeCrNiCoMnBx was studied. The formation mechanism of stacking faults (SFs) in boride was analyzed. Results showed that the coatings had a simple FCC structure with boride precipitation. Boride precipitation was mainly the (Cr, Fe)2B phase when the boron content x was increased from 0.25 to 0.75. However, as the value of x reached 1.0, many (Fe, Cr)2B phases were found in the boride. The volume fraction of borides increased with the increase in boron content. Hardness and wear resistance of the coating were also enhanced with the increase in boron content. (Fe, Cr)2B borides had high-density SFs on the (10) planes. The generation of SFs in (Fe, Cr)2B occurred probably because of the (Fe, Cr)2B → (Cr, Fe)2B phase transformation generated by a simple shear of (Fe, Cr)2B (10) planes (with shear vectors at nearly 1/4 [111]).
An FeCrNiCoMnBx high-entropy alloy coating was prepared by laser cladding on a low carbon steel substrate. The effect of boron addition on the microstructure, hardness, and wear resistance of FeCrNiCoMnBx was studied. The formation mechanism of stacking faults (SFs) in boride was analyzed. Results showed that the coatings had a simple FCC structure with boride precipitation. Boride precipitation was mainly the (Cr, Fe)2B phase when the boron content x was increased from 0.25 to 0.75. However, as the value of x reached 1.0, many (Fe, Cr)2B phases were found in the boride. The volume fraction of borides increased with the increase in boron content. Hardness and wear resistance of the coating were also enhanced with the increase in boron content. (Fe, Cr)2B borides had high-density SFs on the (10) planes. The generation of SFs in (Fe, Cr)2B occurred probably because of the (Fe, Cr)2B → (Cr, Fe)2B phase transformation generated by a simple shear of (Fe, Cr)2B (10) planes (with shear vectors at nearly 1/4 [111]).
2017, 46(9):2645-2650.
Abstract:
In order to study the effect of thermal accumulation of Laser deposition manufacturing (LDM) process on melt pool geometry. A three-dimensional(3D) multi-layer model for LDMed TA15 titanium alloy was developed to discover thermal cycle characteristics, temperature distribution of melt pool and melt pool geometry. Results showed that melt pools width increase gradually with the increase of deposition layer because of thermal accumulation. The numerical results were validated by experimental-measured values collected by in-situ monitoring techniques. Thermal accumulation is strongly correlated to melt pool width and melt pool inclination, however, melt pool temperature and width gradually become relatively stableSafter a certain number of layers. The experimental data and model prediction show a good agreement.
In order to study the effect of thermal accumulation of Laser deposition manufacturing (LDM) process on melt pool geometry. A three-dimensional(3D) multi-layer model for LDMed TA15 titanium alloy was developed to discover thermal cycle characteristics, temperature distribution of melt pool and melt pool geometry. Results showed that melt pools width increase gradually with the increase of deposition layer because of thermal accumulation. The numerical results were validated by experimental-measured values collected by in-situ monitoring techniques. Thermal accumulation is strongly correlated to melt pool width and melt pool inclination, however, melt pool temperature and width gradually become relatively stableSafter a certain number of layers. The experimental data and model prediction show a good agreement.
55 Influence of heat treatment process on microstructure and mechanical properties of TLM titanium tube
2017, 46(9):2651-2654.
Abstract:
An alloy with the normal composition of Ti-25Nb-3Zr-3Mo-2Sn (TLM) has been prepared using cold-rolling technology for application as a thin tube material with a size of Φ4.0×0.3mm. The heat treatment process has been carried out for TLM in temperature range of 933、993K and follow by aging treatment at 783K. The effects of heat treatment and aging process for TLM on the microstructure and mechanical properties have been investagted by metallogical microscopy, X-ray diffraction and mechanical measurement at room temperature. The column-like crystals can be observed at any heat-treatment temperature. The average grain sizes increase with increasing temperature. The phase transition from β+α' to α occurs in TLM. The analysis reveals that the mechanical property depends on heat treatment temperature, which is due to the phase transition induced by temperature. The phase transition are dynamic, which can be described as β+α'→β+α'+α→β+α. The presention of α phase is benefical for improving the tensile strength and elastic modulus and declining the elongation ratio. The fine property can be otaioined at 993K, 0.5h (ST) +783K, 3h (AT).
An alloy with the normal composition of Ti-25Nb-3Zr-3Mo-2Sn (TLM) has been prepared using cold-rolling technology for application as a thin tube material with a size of Φ4.0×0.3mm. The heat treatment process has been carried out for TLM in temperature range of 933、993K and follow by aging treatment at 783K. The effects of heat treatment and aging process for TLM on the microstructure and mechanical properties have been investagted by metallogical microscopy, X-ray diffraction and mechanical measurement at room temperature. The column-like crystals can be observed at any heat-treatment temperature. The average grain sizes increase with increasing temperature. The phase transition from β+α' to α occurs in TLM. The analysis reveals that the mechanical property depends on heat treatment temperature, which is due to the phase transition induced by temperature. The phase transition are dynamic, which can be described as β+α'→β+α'+α→β+α. The presention of α phase is benefical for improving the tensile strength and elastic modulus and declining the elongation ratio. The fine property can be otaioined at 993K, 0.5h (ST) +783K, 3h (AT).
2017, 46(9):2655-2660.
Abstract:
Through-thickness macrotexture evolution of Ti-6Al-4V hot-rolled and annealed sheet was warm rolled to about 45% reduction at temperatures of 450oC, 600oC and 750oC, and was analyzed using orientation distribution function(ODF) in the study. The results show that the ND// fiber texture and the basal texture (0001)[2-1-10] or (0001)[1-210] , which can improve the mechanical property anisotropy of Ti-6Al-4V alloy, can be obtained by multipass warm rolling successfully. Moreover, the ND// fiber texture is developed in the bulk sheet, and the transverse texture (-12-10)[10-10] in the center layer varies with rolling temperature, whereas the basal texture in the surface layer is formed by accumulated shear strain from dislocation slip and its formation depends on initial orientation.
Through-thickness macrotexture evolution of Ti-6Al-4V hot-rolled and annealed sheet was warm rolled to about 45% reduction at temperatures of 450oC, 600oC and 750oC, and was analyzed using orientation distribution function(ODF) in the study. The results show that the ND//
2017, 46(9):2661-2666.
Abstract:
The traditional CuW alloy prepared by single particle size of tungsten powder has been difficult to meet the requirement of electrical contact of the high-frequency switching capacitor switch.This experimen prepares CuW alloy with three kinds of particle size of tungsten powder (super rice, micron and submicron).The microstructures of CuW alloy were analyzed by field emission scanning electron microscopy and the arc breakdown properties of CuW alloys were investigated.The results show that CuW alloy prepared by grading tungsten powder can form a variety of W-W sintered neck which strengthened tungsten skeleton. This kind of tungsten skeleton makes the Cu phase more uniform and more dispersed.The hardness and electrical conductivity of the CuW alloy is 30~40% higher than the national standard, and the CuW alloy has a higher resistance of voltage strength.In addition,the bonding strength of the CuW/CrCu prepared by grading tungsten powder is 40~60% higher than the national standard.
The traditional CuW alloy prepared by single particle size of tungsten powder has been difficult to meet the requirement of electrical contact of the high-frequency switching capacitor switch.This experimen prepares CuW alloy with three kinds of particle size of tungsten powder (super rice, micron and submicron).The microstructures of CuW alloy were analyzed by field emission scanning electron microscopy and the arc breakdown properties of CuW alloys were investigated.The results show that CuW alloy prepared by grading tungsten powder can form a variety of W-W sintered neck which strengthened tungsten skeleton. This kind of tungsten skeleton makes the Cu phase more uniform and more dispersed.The hardness and electrical conductivity of the CuW alloy is 30~40% higher than the national standard, and the CuW alloy has a higher resistance of voltage strength.In addition,the bonding strength of the CuW/CrCu prepared by grading tungsten powder is 40~60% higher than the national standard.
2017, 46(9):2667-2672.
Abstract:
The morphology, microhardness, microstructure, thermal stability, particle size distribution and phase composition of the gas atomized Al86Ni6Y4.5Co2La1.5 amorphous alloy powder were investigated by scanning electron microscope(SEM), X-ray diffractometry, X-ray Photoelectron Spectroscopy(XPS), particle size analysis, differential scanning calorimetry (DSC), and hardness tester. The result showed that the most size of Al86Ni6Y4.5Co2La1.5 amorphous alloy powder was smaller 45μm(about 80%), and the structure the powder was consisted of amorphous matrix and nano-crystallization phase. Its crystallization process was amorphous→amorphous′+fcc-Al→fcc-Al+AlNiY+Al2Y. There existed layer of Al2O3 oxidation with width of 180.81nm. The hardness of the powder was beyond 300HV0.1.
The morphology, microhardness, microstructure, thermal stability, particle size distribution and phase composition of the gas atomized Al86Ni6Y4.5Co2La1.5 amorphous alloy powder were investigated by scanning electron microscope(SEM), X-ray diffractometry, X-ray Photoelectron Spectroscopy(XPS), particle size analysis, differential scanning calorimetry (DSC), and hardness tester. The result showed that the most size of Al86Ni6Y4.5Co2La1.5 amorphous alloy powder was smaller 45μm(about 80%), and the structure the powder was consisted of amorphous matrix and nano-crystallization phase. Its crystallization process was amorphous→amorphous′+fcc-Al→fcc-Al+AlNiY+Al2Y. There existed layer of Al2O3 oxidation with width of 180.81nm. The hardness of the powder was beyond 300HV0.1.
Yong Zheng
,
Yang Zhou
,
Jiaqi Wang
,
Hongyu Li
,
Shibo Li
,
Zhenying Huang
,
Cuiwei Li
,
Hongxiang Zhai
2017, 46(9):2673-2678.
Abstract:
TiC/Fe composites have been fabricated by planetary ball milling, cold-pressing and pressureless sintering, which used the mixture of TiC powders, reduced iron powders and carbonyl iron powders. The effect of carbonyl iron powder volume contents, sintering temperature and TiC volume contents on microstructure and mechanical properties of the composites was investigated. The results demonstrated that when carbonyl iron powders accounted for 60% volume fraction of Fe matrix powders, it was the optimal proportion for the properties of TiC/Fe compoaites. The relative density, Vickers hardness and bending strength of composites were improved with increasing temperature from 1460 °C to 1500 °C. Further increasing temperature to 1530 °C caused the mechanical properties decreased. The relative density and bending strength of 70 vol. % TiC/Fe were both to be maximized: 99.5% and 437 MPa at the temperature of 1500 °C. The Vickers hardness of 80 vol. % TiC/Fe reached the peak of 12.2 GPa at 1500 °C.
TiC/Fe composites have been fabricated by planetary ball milling, cold-pressing and pressureless sintering, which used the mixture of TiC powders, reduced iron powders and carbonyl iron powders. The effect of carbonyl iron powder volume contents, sintering temperature and TiC volume contents on microstructure and mechanical properties of the composites was investigated. The results demonstrated that when carbonyl iron powders accounted for 60% volume fraction of Fe matrix powders, it was the optimal proportion for the properties of TiC/Fe compoaites. The relative density, Vickers hardness and bending strength of composites were improved with increasing temperature from 1460 °C to 1500 °C. Further increasing temperature to 1530 °C caused the mechanical properties decreased. The relative density and bending strength of 70 vol. % TiC/Fe were both to be maximized: 99.5% and 437 MPa at the temperature of 1500 °C. The Vickers hardness of 80 vol. % TiC/Fe reached the peak of 12.2 GPa at 1500 °C.
2017, 46(9):2679-2683.
Abstract:
Coated conductors are the key practical materials for developing power applications at high temperatures of 77 K and high magnetic fields. The increase of number of buffer layer would result in the increase of the degree of difficulty for controlling growth, microscopy and interface structure. Therefore, simplifying architecture of buffer layer becomes important for the simplification of preparation technics and the reduction of cost for coated conductors. In this paper, we have explored the influence of thermal decomposition and preparation technics of film on the epitaxial growth of SrTiO3 (STO) buffer layers deposited on textured NiW substrates by chemical solution deposition (CSD) method. The results show that STO thin film with good c-axis texture and smooth surface could be obtained by choosing appropriate precursor solution and introducing seed layer before deposting the final oxide film.
Coated conductors are the key practical materials for developing power applications at high temperatures of 77 K and high magnetic fields. The increase of number of buffer layer would result in the increase of the degree of difficulty for controlling growth, microscopy and interface structure. Therefore, simplifying architecture of buffer layer becomes important for the simplification of preparation technics and the reduction of cost for coated conductors. In this paper, we have explored the influence of thermal decomposition and preparation technics of film on the epitaxial growth of SrTiO3 (STO) buffer layers deposited on textured NiW substrates by chemical solution deposition (CSD) method. The results show that STO thin film with good c-axis texture and smooth surface could be obtained by choosing appropriate precursor solution and introducing seed layer before deposting the final oxide film.
2017, 46(9):2684-2687.
Abstract:
The effects of sinter atmosphere and sinter temperature on pore radius and permeability of porous support were investigated in the present paper. Ring tensile resultes show that atmosphere of H2 sintered sample tensile strength is 87.56 MPa and an activation atmosphere of H2 adding 0.2wt% NH4Cl sintered sample tensile strength is 115.20 MPa, the strength of an activationsintered sample is enhanced 30 percent. The effects of sinter temperature on mechanical properties of porous support were also investigated. The relationship between density of porous support and mechanical properties was obtained. The relationship could be used to forecast strength of porous materials by test density of the porous materials.
The effects of sinter atmosphere and sinter temperature on pore radius and permeability of porous support were investigated in the present paper. Ring tensile resultes show that atmosphere of H2 sintered sample tensile strength is 87.56 MPa and an activation atmosphere of H2 adding 0.2wt% NH4Cl sintered sample tensile strength is 115.20 MPa, the strength of an activationsintered sample is enhanced 30 percent. The effects of sinter temperature on mechanical properties of porous support were also investigated. The relationship between density of porous support and mechanical properties was obtained. The relationship could be used to forecast strength of porous materials by test density of the porous materials.
2017, 46(9):2688-2694.
Abstract:
An advanced Cu-Fe-C alloy with dual-phase structure was prepared by combining a vacuum melting and rapid solidification. The microstructure evolution and deformation behaviors of the alloy in the as-cast and rolling states were studied by OM, SEM, TEM and XRD characterization, and mechanical property measurements. The results show that, when the moving speed of freezing interface satisfies the relationship of Vcp, both micro-scale and nano-scale Fe-C particles can uniformly distribute in the alloy matrix, but the range between Vc and Vp for micro-scale particles is much narrower than that of nano-scale particles. Due to the solution of Fe in the Cu matrix and the existence of Fe-C particles with different sizes, the Cu-Fe-C alloy in the as-cast state possesses a much higher work hardening exponent (n=0.5149). The phase transformationSof Fe-C particles from γ-Fe to α-Fe can be induced by cold rolling 80%, which can be greatly used to control and optimize the strength and deformation performance of Cu-Fe-C alloy. Although the deformability of Cu-Fe-C alloy in both the as-cast and rolling states is good, yet, compared with the cold rolling state, the alloy in the as-cast state possesses a much better coordinative deformation performance due to the FCC structure of Fe-C phases in this state. Additionally, according to the microstructure evolution and tensile fracture morphologies of Cu-Fe-C alloy with a dual-phase structure, the coordinative deformation and fracture models were put forward in this paper.
An advanced Cu-Fe-C alloy with dual-phase structure was prepared by combining a vacuum melting and rapid solidification. The microstructure evolution and deformation behaviors of the alloy in the as-cast and rolling states were studied by OM, SEM, TEM and XRD characterization, and mechanical property measurements. The results show that, when the moving speed of freezing interface satisfies the relationship of Vc
Li Beibei
,
Fan Jian feng
,
Zeng Xun
,
Zhang Hua
,
Zhang qiang
,
Wang Xiaodan
,
Dong Hongbiao
,
Xu Bingshe
2017, 46(9):2695-2701.
Abstract:
Electropulsing treatment (EPT) is a new method to refine the microstructure and improve the mechanical properties of metal materials. In the present paper, the microstructure evolution of rolled AZ31 alloy sheets with 10%, 15% and 20% rolling reduction were investigated by VHX-2000 optical microscope and scanning electron microscope equipped with electron backscattered diffraction (EBSD). After EPT with a pluse-width of 30 μs, a current density of 4.16×109 A/m2, a duty ratio of 0.003 and a processing time of 10min, the average grain size of AZ31 alloy is refined from 150 μm to 20 μm, the tensile strength is improved to 265 MPa and the elongation can reach 19.7%. The affect of the thermal and athermal effect on the recrystallization during EPT was analysied. The result shows that the athermal effect plays a major role in recrystallization and the mechanism of the athermal effect is also revealed.
Electropulsing treatment (EPT) is a new method to refine the microstructure and improve the mechanical properties of metal materials. In the present paper, the microstructure evolution of rolled AZ31 alloy sheets with 10%, 15% and 20% rolling reduction were investigated by VHX-2000 optical microscope and scanning electron microscope equipped with electron backscattered diffraction (EBSD). After EPT with a pluse-width of 30 μs, a current density of 4.16×109 A/m2, a duty ratio of 0.003 and a processing time of 10min, the average grain size of AZ31 alloy is refined from 150 μm to 20 μm, the tensile strength is improved to 265 MPa and the elongation can reach 19.7%. The affect of the thermal and athermal effect on the recrystallization during EPT was analysied. The result shows that the athermal effect plays a major role in recrystallization and the mechanism of the athermal effect is also revealed.
2017, 46(9):2702-2707.
Abstract:
Secondary electronic emission on metal is the cause of multipactor effect, which is a limition of the space payload RF power increase. In this paper, micrometer-scale trap structure was constructed through large scale pol-ystyrene array to suppress secondary electron emission. PS microspheres self-assembly method are studied, the trap structure are presented, and the secondary emission characteristics are tested. The results showed that the trap structure silver film were prepared based on self-assemble of PS microspheres.Its structure can decreasing the maximum of SEY from 2.2 to 1.6
Secondary electronic emission on metal is the cause of multipactor effect, which is a limition of the space payload RF power increase. In this paper, micrometer-scale trap structure was constructed through large scale pol-ystyrene array to suppress secondary electron emission. PS microspheres self-assembly method are studied, the trap structure are presented, and the secondary emission characteristics are tested. The results showed that the trap structure silver film were prepared based on self-assemble of PS microspheres.Its structure can decreasing the maximum of SEY from 2.2 to 1.6
2017, 46(9):2708-2713.
Abstract:
Plastic deformation characteristics and hot processing conditions are important bases for the selection of processing parameters of extrusion and rolling of titanium alloy.The compressive deformation behavior and microstructure of TA15 alloy were investigated at temperature range of 850~1050℃ and strain rate range of 0.01~20 s-1.The constitutive equation of TA15 alloy was derived through Arrhenius hyperbolic sine function.Based on dynamic materials modeling(DMM), the processing map of TA15 alloy was established for strain of 0.1~0.7.The results show that α phase in the alloy gradually transforms to β phase with the increase of deformation temperature. The transform extent of α phase to β phase gradually reduces with the increase of the strain rate. According to processing map, the two hot processing safety areas of the alloy were determined: (1) deformation temperature 950~1050℃, strain rate 0.01~0.37 s-1; (2) deformation temperature 875~950℃, strain rate 1.65~13.5 s-1.
Plastic deformation characteristics and hot processing conditions are important bases for the selection of processing parameters of extrusion and rolling of titanium alloy.The compressive deformation behavior and microstructure of TA15 alloy were investigated at temperature range of 850~1050℃ and strain rate range of 0.01~20 s-1.The constitutive equation of TA15 alloy was derived through Arrhenius hyperbolic sine function.Based on dynamic materials modeling(DMM), the processing map of TA15 alloy was established for strain of 0.1~0.7.The results show that α phase in the alloy gradually transforms to β phase with the increase of deformation temperature. The transform extent of α phase to β phase gradually reduces with the increase of the strain rate. According to processing map, the two hot processing safety areas of the alloy were determined: (1) deformation temperature 950~1050℃, strain rate 0.01~0.37 s-1; (2) deformation temperature 875~950℃, strain rate 1.65~13.5 s-1.
2017, 46(9):2714-2719.
Abstract:
For improvement of the safety and compatibility of nuclear engineering systems, Uranium intermetallic compounds are of technological importance for nuclear fuel chemistry and physics, since these compounds are occasionally found to exist as metallic inclusions in irradiated fuel. The predictions of compatibility of metallic uranium with stainless steel, Cu and Al cladding may require the characteristics of the intermetallics. It is therefore useful to understand the physico-chemical properties of the uranium intermetallic compounds. In the present study, UCu, UAl and UFe have been selected as the intermetallic compounds through method of materials genome engineering, the microstructure, phase transformation and mechanical properties such as elastic moduli and hardness of the compounds have been studied by means of nanoindentation, XRD, SEM, EDX. The microstructure of the compounds displayed a new phase with more than 10 μm thickness, which has a ration of U:Cu with 1:4. The nanoindentation testing on sample indicated that hardness of Uranium intermetallic compounds are higher than that of metal U and Cu. Uranium intermetallic compounds has a Young’s moduli with 121GPa,and a thermal expand coefficient with the value of 7.3×10-5K-1.
For improvement of the safety and compatibility of nuclear engineering systems, Uranium intermetallic compounds are of technological importance for nuclear fuel chemistry and physics, since these compounds are occasionally found to exist as metallic inclusions in irradiated fuel. The predictions of compatibility of metallic uranium with stainless steel, Cu and Al cladding may require the characteristics of the intermetallics. It is therefore useful to understand the physico-chemical properties of the uranium intermetallic compounds. In the present study, UCu, UAl and UFe have been selected as the intermetallic compounds through method of materials genome engineering, the microstructure, phase transformation and mechanical properties such as elastic moduli and hardness of the compounds have been studied by means of nanoindentation, XRD, SEM, EDX. The microstructure of the compounds displayed a new phase with more than 10 μm thickness, which has a ration of U:Cu with 1:4. The nanoindentation testing on sample indicated that hardness of Uranium intermetallic compounds are higher than that of metal U and Cu. Uranium intermetallic compounds has a Young’s moduli with 121GPa,and a thermal expand coefficient with the value of 7.3×10-5K-1.
67 Controllable Preparation and Gas Sensing PerformanceOf Nanosized ZnO with Different Micromophology
2017, 46(9):2720-2724.
Abstract:
Zinc oxide (ZnO) is a typical gas sensitive material. Highly oriented zinc oxide (ZnO) nanoparticels with rich micromophology were synthesized by controlling the preparation conditions. The results showed that micromophologies of ZnO were under the influence of degree of supersaturation and pressure. The gas sensing properties were studied systematically. It was found that the sensor fabricated by ZnO rows assembled by ZnO nanorods exhibited better sensing responses to test gases.
Zinc oxide (ZnO) is a typical gas sensitive material. Highly oriented zinc oxide (ZnO) nanoparticels with rich micromophology were synthesized by controlling the preparation conditions. The results showed that micromophologies of ZnO were under the influence of degree of supersaturation and pressure. The gas sensing properties were studied systematically. It was found that the sensor fabricated by ZnO rows assembled by ZnO nanorods exhibited better sensing responses to test gases.
2017, 46(9):2725-2730.
Abstract:
In order to study the effect of different sample diameters on the instability of eutectic structure, directional solidification experiment was carried out on Ni-Ni3Si alloy with sample diameters of 4 mm and 7 mm.The results show that the primary phase of coupled eutectic growth is Ni3Si phase and the instability of lamellar eutectic is more likely to occur on the sample with small diameter. The form of instability is a zigzag instability which leads to curved lamellar structure. The sample with smaller diameter gets higher thermal gradient, leading to the smaller undercooling of the alloy. Further, the instability of lamellar eutectic will happened at larger growth rates, and which can help to reduce the difference of diffusion growth of the eutectic phase, thus narrowing the width gaps between the two phases. In addition, this instability is related to the grain orientation.
In order to study the effect of different sample diameters on the instability of eutectic structure, directional solidification experiment was carried out on Ni-Ni3Si alloy with sample diameters of 4 mm and 7 mm.The results show that the primary phase of coupled eutectic growth is Ni3Si phase and the instability of lamellar eutectic is more likely to occur on the sample with small diameter. The form of instability is a zigzag instability which leads to curved lamellar structure. The sample with smaller diameter gets higher thermal gradient, leading to the smaller undercooling of the alloy. Further, the instability of lamellar eutectic will happened at larger growth rates, and which can help to reduce the difference of diffusion growth of the eutectic phase, thus narrowing the width gaps between the two phases. In addition, this instability is related to the grain orientation.
2017, 46(9):2731-2736.
Abstract:
Mesoporous zirconia microspheres were prepared by sol-gel method using F127 and sodium dodecyl sulfate (SDS) as templates. The effects of calcination temperature and the content of templates on the structure and properties of mesoporous microspheres were studied. The size of microspheres is uniform, with diameter of about 900μm. It is found that with the increase of the calcination temperature, the specific surface area of the sample decreases, while the average pore diameter has increase trend. After calcined at low temperature, the samples are pure tetragonal zirconia, and there begin to appear monoclinic phase after calcined at 600 ℃. With the same calcination temperature, the specific surface area and pore volume of the sample added more templates are larger. The addition amount of templates has no influence on the phase structure of the sample.
Mesoporous zirconia microspheres were prepared by sol-gel method using F127 and sodium dodecyl sulfate (SDS) as templates. The effects of calcination temperature and the content of templates on the structure and properties of mesoporous microspheres were studied. The size of microspheres is uniform, with diameter of about 900μm. It is found that with the increase of the calcination temperature, the specific surface area of the sample decreases, while the average pore diameter has increase trend. After calcined at low temperature, the samples are pure tetragonal zirconia, and there begin to appear monoclinic phase after calcined at 600 ℃. With the same calcination temperature, the specific surface area and pore volume of the sample added more templates are larger. The addition amount of templates has no influence on the phase structure of the sample.
2017, 46(9):2737-2743.
Abstract:
γ-TiAl alloys are potentially used as high-temperature structural materials with a high specific strength and low density. The mechanical properties of γ-TiAl alloys are extremely anisotropic with respect to the lamellar orientation of the microstructures. A balance combination of room-temperature ductility and strength can be achieved when the lamellar orientation are aligned parallel to the growth direction. The lamellar orientation can be alliged by directional solidification technique. However, the orientation of the primary phase have great influence on room temperature lamellar orientation. This paper reviewed the research progress of the primary phase growth direction in directional solidified TiAl alloys, the method for determined the orientation of primary high temperature phase and effects of solidification conditions and interface on the growth direction of primary phase are presented. Finally, the future research direction is summarized.
γ-TiAl alloys are potentially used as high-temperature structural materials with a high specific strength and low density. The mechanical properties of γ-TiAl alloys are extremely anisotropic with respect to the lamellar orientation of the microstructures. A balance combination of room-temperature ductility and strength can be achieved when the lamellar orientation are aligned parallel to the growth direction. The lamellar orientation can be alliged by directional solidification technique. However, the orientation of the primary phase have great influence on room temperature lamellar orientation. This paper reviewed the research progress of the primary phase growth direction in directional solidified TiAl alloys, the method for determined the orientation of primary high temperature phase and effects of solidification conditions and interface on the growth direction of primary phase are presented. Finally, the future research direction is summarized.
2017, 46(9):2744-2752.
Abstract:
Lithium-ion batteries (LIBs) are efficient and clean energy storage devices, which offer widely promising applications for consumer electronic products, energy storage facilities and electric vehicles, and have great significance to optimize the energy structure and relieve the energy crisis and environmental pollution. Olivine-type LiFePO4 is one of most promising positive electrode materials for LIBs. However, the intrinsically low electronic conductivity and lithium-ion diffusion velocity result in poor performance of LiFePO4 and hinder its large-scale application for power type LIBs. Nanocarbon materials, especially the nitrogen-doped amorphous carbon, carbon nanotube and graphene, present many merits such as high electronic conductivity, large specific surface area, superior chemical affinity and good thermal or chemical stability etc, which demonstrate unique advantages to improve the electrochemical performances of LiFePO4. In this review, the research progresses of the nitrogen-doped nanocarbon modified LiFePO4 materials have been summarized from the aspects of doping method, morphology and structure, electrochemical performance, and the future developments of the doped nanocarbon modified LiFePO4 materials are outlooked.
Lithium-ion batteries (LIBs) are efficient and clean energy storage devices, which offer widely promising applications for consumer electronic products, energy storage facilities and electric vehicles, and have great significance to optimize the energy structure and relieve the energy crisis and environmental pollution. Olivine-type LiFePO4 is one of most promising positive electrode materials for LIBs. However, the intrinsically low electronic conductivity and lithium-ion diffusion velocity result in poor performance of LiFePO4 and hinder its large-scale application for power type LIBs. Nanocarbon materials, especially the nitrogen-doped amorphous carbon, carbon nanotube and graphene, present many merits such as high electronic conductivity, large specific surface area, superior chemical affinity and good thermal or chemical stability etc, which demonstrate unique advantages to improve the electrochemical performances of LiFePO4. In this review, the research progresses of the nitrogen-doped nanocarbon modified LiFePO4 materials have been summarized from the aspects of doping method, morphology and structure, electrochemical performance, and the future developments of the doped nanocarbon modified LiFePO4 materials are outlooked.
