Volume 45,Issue 9,2016 Table of Contents
2016, 45(9):2201-2207.
Abstract:
In this study, the microstructure, phase assemblages, hardness and wear properties of Al0.5CoCrCuFeNiBx (x=0-1) high-entropy alloys were investigated. The parameters representing simple solid-solution formation ability in Al0.5CoCrCuFeNiBx alloys were estimated. Without boron addition, the alloy was composed of simple FCC solid solution structure. With the addition of boron, the alloys were composed of borides and simple FCC solid solution matrix phase. Boron precipitated as borides instead of entering the crystal structure and thus there is no change in the lattice constant of the matrix FCC phase. Borides precipitation significantly hardens the alloy and the hardness showed a strong correlation to the boron content. There was no distinct difference in the wear resistance of the alloys with x?0.4, but the wear resistance showed a strong relation to the boron content in the alloys with x?0.6. With increasing boron content, the wear mechanism changes from delamination wear to oxidative wear. The great enhancement in the hardness and wear resistance is attributed to the combination of the large hard borides and relatively ductile and tough FCC matrix.
In this study, the microstructure, phase assemblages, hardness and wear properties of Al0.5CoCrCuFeNiBx (x=0-1) high-entropy alloys were investigated. The parameters representing simple solid-solution formation ability in Al0.5CoCrCuFeNiBx alloys were estimated. Without boron addition, the alloy was composed of simple FCC solid solution structure. With the addition of boron, the alloys were composed of borides and simple FCC solid solution matrix phase. Boron precipitated as borides instead of entering the crystal structure and thus there is no change in the lattice constant of the matrix FCC phase. Borides precipitation significantly hardens the alloy and the hardness showed a strong correlation to the boron content. There was no distinct difference in the wear resistance of the alloys with x?0.4, but the wear resistance showed a strong relation to the boron content in the alloys with x?0.6. With increasing boron content, the wear mechanism changes from delamination wear to oxidative wear. The great enhancement in the hardness and wear resistance is attributed to the combination of the large hard borides and relatively ductile and tough FCC matrix.
2016, 45(9):2208-2213.
Abstract:
The effects of heat treatment on microstructure and mechanical properties of the as-extruded Mg-9Sn-1.5Y-0.4Zr (wt%) alloy were investigated experimentally in this study. The results showed that the heat treatment plays an important role on the microstructure and mechanical properties of the as-extruded Mg-9Sn-1.5Y-0.4Zr alloy. The as-extruded alloy is mainly composed of non-uniform Mg2Sn phase. After the solution treated at 495℃for 10h, a majority of the Mg2Sn phases in the alloy were dissolved into the matrix. Aging treatment can highly improve the mechanical properties of the Mg-9Sn-1.5Y-0.4Zr alloy with the optimized experimental condition of aging at 250℃for 60h after solution treated at 495℃for 10h. The corresponding mechanical property parameters are: hardness of 89HV, ultimate tensile strength of 262MPa, yield strength of 218MPa, elongation of 10.4%. Based on the experimental results analysis, it is found that the precipitation strengthening is the main contributor (~51.76%) to the total yield strength in the aged experimental alloy.
The effects of heat treatment on microstructure and mechanical properties of the as-extruded Mg-9Sn-1.5Y-0.4Zr (wt%) alloy were investigated experimentally in this study. The results showed that the heat treatment plays an important role on the microstructure and mechanical properties of the as-extruded Mg-9Sn-1.5Y-0.4Zr alloy. The as-extruded alloy is mainly composed of non-uniform Mg2Sn phase. After the solution treated at 495℃for 10h, a majority of the Mg2Sn phases in the alloy were dissolved into the matrix. Aging treatment can highly improve the mechanical properties of the Mg-9Sn-1.5Y-0.4Zr alloy with the optimized experimental condition of aging at 250℃for 60h after solution treated at 495℃for 10h. The corresponding mechanical property parameters are: hardness of 89HV, ultimate tensile strength of 262MPa, yield strength of 218MPa, elongation of 10.4%. Based on the experimental results analysis, it is found that the precipitation strengthening is the main contributor (~51.76%) to the total yield strength in the aged experimental alloy.
2016, 45(9):2214-2218.
Abstract:
Heterogeneous Cu2O/Cu nanoparticles are synthesized by colloidal chemistry approach using ascorbic acid as a reducing agent and polyvinylpyrrolidone as a surfactant. Morphology and structure of Cu2O/Cu nanoparticles are analyzed by SEM, XRD and N2 sorption technique. The catalytic performances of Cu2O/Cu nanoparticles for the degradation of methyl orange (MO) are investigated and reaction kinetics of MO degradation is also studied. The results show heterogeneous Cu2O/Cu nanoparticles display cobblestone-like morphology with ranging from 20 to 40 nm, which are slightly smaller in particle size and higher in BET surface areas than those of pure Cu2O. The Cu2O/Cu nanoparticles demonstrate good potential on degradation of MO because Cu nanoparticles in the Cu2O/Cu hererostructures promote the interfacial charge-transfer kinetics between Cu and Cu2O. High initial MO concentration not only produces low degree of MO degradation, but also increases the reaction time to reach equilibrium, and the degradation reactions follow the pseudo-first-order kinetics model. The Cu2O/Cu catalyst still demonstrates good catalytic activity after four photodegradation cycles of MO solutions.
Heterogeneous Cu2O/Cu nanoparticles are synthesized by colloidal chemistry approach using ascorbic acid as a reducing agent and polyvinylpyrrolidone as a surfactant. Morphology and structure of Cu2O/Cu nanoparticles are analyzed by SEM, XRD and N2 sorption technique. The catalytic performances of Cu2O/Cu nanoparticles for the degradation of methyl orange (MO) are investigated and reaction kinetics of MO degradation is also studied. The results show heterogeneous Cu2O/Cu nanoparticles display cobblestone-like morphology with ranging from 20 to 40 nm, which are slightly smaller in particle size and higher in BET surface areas than those of pure Cu2O. The Cu2O/Cu nanoparticles demonstrate good potential on degradation of MO because Cu nanoparticles in the Cu2O/Cu hererostructures promote the interfacial charge-transfer kinetics between Cu and Cu2O. High initial MO concentration not only produces low degree of MO degradation, but also increases the reaction time to reach equilibrium, and the degradation reactions follow the pseudo-first-order kinetics model. The Cu2O/Cu catalyst still demonstrates good catalytic activity after four photodegradation cycles of MO solutions.
2016, 45(9):2219-2226.
Abstract:
Based on the central composite rotatable design (CCD), clad beads of Inconel 625 were deposited on the surface of AISI 4130 plates using hot wire pulsed TIG technology. The response surface methodology (RSM) was utilized to establish models between process parameters and geometrical characteristics of the clad beads. Then, multiple-track two-layer weld overlay was successfully deposited using the optimized process parameters. The microstructure of the weld overlay is primarily composed of columnar dendrites, and there are also a few planar crystals and cellular dendrites situated near the fusion zone. Meanwhile, equiaxed grains and steering dendrites are mainly distributed in the upper portion of the weld overlay. Potentiodynamic polarization tests were used to evaluate the corrosion resistance of the weld overlay and substrate. The results show that adding clad layers can enhance the corrosion resistance, which degrades with the increase in Fe dilution. Moreover, the corrosion resistance of the second layer surface is close to that of wrought Inconel 625.
Based on the central composite rotatable design (CCD), clad beads of Inconel 625 were deposited on the surface of AISI 4130 plates using hot wire pulsed TIG technology. The response surface methodology (RSM) was utilized to establish models between process parameters and geometrical characteristics of the clad beads. Then, multiple-track two-layer weld overlay was successfully deposited using the optimized process parameters. The microstructure of the weld overlay is primarily composed of columnar dendrites, and there are also a few planar crystals and cellular dendrites situated near the fusion zone. Meanwhile, equiaxed grains and steering dendrites are mainly distributed in the upper portion of the weld overlay. Potentiodynamic polarization tests were used to evaluate the corrosion resistance of the weld overlay and substrate. The results show that adding clad layers can enhance the corrosion resistance, which degrades with the increase in Fe dilution. Moreover, the corrosion resistance of the second layer surface is close to that of wrought Inconel 625.
2016, 45(9):2227-2231.
Abstract:
Semi-solid Al2Y/AZ91 magnesium matrix composites slurry was prepared by ultrasonic vibration, and the apparent viscosity of semi-solid slurry was measured as well. According to the experimental results, with the increase the of volume fraction of Al2Y the apparent viscosity of semi-solid Al2Y/AZ91 magnesium matrix composites slurry increases, the relationship between apparent viscosity and solid fraction varies according to the exponential law, under the same experimental conditions, the apparent viscosity decreases with the increase of ultrasonic power. Based on the experimental data fitting, the rheological model of semi-solid Al2Y/AZ91 magnesium matrix composites prepared by ultrasonic vibration was established.
Semi-solid Al2Y/AZ91 magnesium matrix composites slurry was prepared by ultrasonic vibration, and the apparent viscosity of semi-solid slurry was measured as well. According to the experimental results, with the increase the of volume fraction of Al2Y the apparent viscosity of semi-solid Al2Y/AZ91 magnesium matrix composites slurry increases, the relationship between apparent viscosity and solid fraction varies according to the exponential law, under the same experimental conditions, the apparent viscosity decreases with the increase of ultrasonic power. Based on the experimental data fitting, the rheological model of semi-solid Al2Y/AZ91 magnesium matrix composites prepared by ultrasonic vibration was established.
2016, 45(9):2232-2236.
Abstract:
In this work, nitrogen doped titanium oxides (N-doped TiOx) films were deposited by sputtering the TiO2 target in N2/Ar gas mixture to control the doping amount of nitrogen accurately. In order to modify the resultant films, the samples were annealed in air where the temperature ranged from 300 to 600℃, then they were irradiated under visible-light (VIS) after being placed in dark. X-ray photoelectron spectroscopy (XPS) spectra results showed that chemical composition of the films underwent the formation of N-Ti-O (β-N) and hydroxyl due to nitrogen doped into TiOx lattice. And the content of hydroxyl increased with annealing temperatures increasing, which led to the better hydrophilicity. X-ray diffraction (XRD) was used to investigate the crystallinity of the films annealed at different temperature and the results showed that the amorphous films transformed into crystalline phase as a consequence of annealing. Scanning electron microscopy (SEM) results showed that the particle size became bigger with the higher temperature. Hydrophilicity was tested by contact angle meter. The results showed that water contact angle decreased with the raising heat treatment temperature due to the change of particle size and the content of –OH. Hydrophilicity was also influenced by storing process, and the water contact angles increased with time. Furthermore, the hydrophilicity of N-doped TiOx films increased under visible light (VIS) irradiation.
In this work, nitrogen doped titanium oxides (N-doped TiOx) films were deposited by sputtering the TiO2 target in N2/Ar gas mixture to control the doping amount of nitrogen accurately. In order to modify the resultant films, the samples were annealed in air where the temperature ranged from 300 to 600℃, then they were irradiated under visible-light (VIS) after being placed in dark. X-ray photoelectron spectroscopy (XPS) spectra results showed that chemical composition of the films underwent the formation of N-Ti-O (β-N) and hydroxyl due to nitrogen doped into TiOx lattice. And the content of hydroxyl increased with annealing temperatures increasing, which led to the better hydrophilicity. X-ray diffraction (XRD) was used to investigate the crystallinity of the films annealed at different temperature and the results showed that the amorphous films transformed into crystalline phase as a consequence of annealing. Scanning electron microscopy (SEM) results showed that the particle size became bigger with the higher temperature. Hydrophilicity was tested by contact angle meter. The results showed that water contact angle decreased with the raising heat treatment temperature due to the change of particle size and the content of –OH. Hydrophilicity was also influenced by storing process, and the water contact angles increased with time. Furthermore, the hydrophilicity of N-doped TiOx films increased under visible light (VIS) irradiation.
2016, 45(9):2237-2241.
Abstract:
In this paper, Al-12Zn-2.4Mg-1.2Cu (wt%) alloy billets as-deposited were extruded to be Ф100mm bar, Ф100mmxФ80mm seamless pipe and 160mmx15mm stripper plate under different deformation ways., respectively. The microstructures and mechanical properties of the products as-heat-treated were studied by optical metallographic, measurement of mechanical performance and scanning electron microscope examination. Metallographic testing results show that the grains in the initial billets are almost equiaxed with diameter about 20μm. There are some second phase precipitated distributing in the grains and the grain boundary. The deposited ventages around the grain as-deposited were welded together by welding metallurgy way during extrusion process. The flow lines were clearly observed in the extrusion direction in the different extrusion products. Properties of the products as-heat-treated including tensile strengths, yield strengths and elongations tests results show that the value of bars are 688 MPa, 654 MPa and12% in the cross direction(CD )and 698 MPa,674 MPa and10.5% in the longitude direction(LD). The value of the plates are 783MPa, 748 MPa and 7% in the CD and 751MPa, 719 MPa, 8%. in the LD. The seamless pipes also have excellent properties which are 781 MPa, 735 MPa and 9% in the LD. Scanning electron microscope examination shows the fracture characteristics of the fractured specimens revealed three different fracture models which are ductile fracture, mixed fracture and brittle fracture corresponding to bars, pipes and plates, respectively.
In this paper, Al-12Zn-2.4Mg-1.2Cu (wt%) alloy billets as-deposited were extruded to be Ф100mm bar, Ф100mmxФ80mm seamless pipe and 160mmx15mm stripper plate under different deformation ways., respectively. The microstructures and mechanical properties of the products as-heat-treated were studied by optical metallographic, measurement of mechanical performance and scanning electron microscope examination. Metallographic testing results show that the grains in the initial billets are almost equiaxed with diameter about 20μm. There are some second phase precipitated distributing in the grains and the grain boundary. The deposited ventages around the grain as-deposited were welded together by welding metallurgy way during extrusion process. The flow lines were clearly observed in the extrusion direction in the different extrusion products. Properties of the products as-heat-treated including tensile strengths, yield strengths and elongations tests results show that the value of bars are 688 MPa, 654 MPa and12% in the cross direction(CD )and 698 MPa,674 MPa and10.5% in the longitude direction(LD). The value of the plates are 783MPa, 748 MPa and 7% in the CD and 751MPa, 719 MPa, 8%. in the LD. The seamless pipes also have excellent properties which are 781 MPa, 735 MPa and 9% in the LD. Scanning electron microscope examination shows the fracture characteristics of the fractured specimens revealed three different fracture models which are ductile fracture, mixed fracture and brittle fracture corresponding to bars, pipes and plates, respectively.
2016, 45(9):2242-2245.
Abstract:
Large amounts of massive cracked intermetallic compounds were observed at the interface of the laminated Mg/Al composite fabricated by accumulative roll bonding. Scanning electron microscopy revealed that the effect of these cracked intermetallic compounds dominated the fracture behavior of the accumulative roll bonded Mg/Al composite during uniaxial tensile testing. The results indicated that (i) obvious Mg/Al interface delamination was promoted by the cracked the intermetallic compounds, and (ii) the crack propagated into the softer Mg layer and leading to the rupture of Mg layer. These two factors led to premature failure of the laminated Mg/Al composite.
Large amounts of massive cracked intermetallic compounds were observed at the interface of the laminated Mg/Al composite fabricated by accumulative roll bonding. Scanning electron microscopy revealed that the effect of these cracked intermetallic compounds dominated the fracture behavior of the accumulative roll bonded Mg/Al composite during uniaxial tensile testing. The results indicated that (i) obvious Mg/Al interface delamination was promoted by the cracked the intermetallic compounds, and (ii) the crack propagated into the softer Mg layer and leading to the rupture of Mg layer. These two factors led to premature failure of the laminated Mg/Al composite.
9 Effect of Y addition on the isothermal oxidation behaviour of a Ti50Ni50 shape memory alloy at 700℃
2016, 45(9):2246-2252.
Abstract:
The effect of Y addition on the microstructure and isothermal oxidation behaviour of an equal-atomic Ti-Ni shape memory alloy at 700 ℃ in air was investigated. The results showed that the microstructure of Ti50Ni50 alloy was changed obviously with Y addition and the grains of Ti-Ni alloy was evidently refined. The oxidation rate was significantly reduced by the addition of 0.5 at. %Y and 1.0 at. %Y due to the inhibition of the fast outward diffusion of Ti by the segregated Y ions. However, the oxidation rate was increased by 5 at.%Y addition since the formation of oxide along the Y-rich phase broke the continuity of the TiO2 scale.
The effect of Y addition on the microstructure and isothermal oxidation behaviour of an equal-atomic Ti-Ni shape memory alloy at 700 ℃ in air was investigated. The results showed that the microstructure of Ti50Ni50 alloy was changed obviously with Y addition and the grains of Ti-Ni alloy was evidently refined. The oxidation rate was significantly reduced by the addition of 0.5 at. %Y and 1.0 at. %Y due to the inhibition of the fast outward diffusion of Ti by the segregated Y ions. However, the oxidation rate was increased by 5 at.%Y addition since the formation of oxide along the Y-rich phase broke the continuity of the TiO2 scale.
2016, 45(9):2253-2257.
Abstract:
Hastelloy C-276 was subjected to low strain deformation and annealed at 1100°C for different times. The Σ3 and Σ9 boundary percentages and grain boundary plane distributions were characterized by electron back-scatter diffraction (EBSD) and the five-parameter analysis method. The results shown that the Σ3 boundary was evolving towards a more exact coincident-site lattice (CSL) misorientation and the Σ3 boundary plane was more close to low surface energy plane {111} with extended annealing time. This is consistent with fine tuning mechanism. While the population of incoherent Σ3 boundary was increasing, the proportion of Σ9 boundary with larger deviations would be increasing. And the distributions of grain boundary density planes forΣ9 boundary were more intensive on the whole [110] zone.
Hastelloy C-276 was subjected to low strain deformation and annealed at 1100°C for different times. The Σ3 and Σ9 boundary percentages and grain boundary plane distributions were characterized by electron back-scatter diffraction (EBSD) and the five-parameter analysis method. The results shown that the Σ3 boundary was evolving towards a more exact coincident-site lattice (CSL) misorientation and the Σ3 boundary plane was more close to low surface energy plane {111} with extended annealing time. This is consistent with fine tuning mechanism. While the population of incoherent Σ3 boundary was increasing, the proportion of Σ9 boundary with larger deviations would be increasing. And the distributions of grain boundary density planes forΣ9 boundary were more intensive on the whole [110] zone.
2016, 45(9):2258-2262.
Abstract:
Considering the application of WCu alloy at elevated temperature, hot compression was applied on WCu alloy and W skeleton to analyze the microstructure and mechanical behaviors at different temperature and strain rate. The results show that the stress-strain behaviors of WCu alloy is affected mainly by the temperature, the sintering necks disappear mostly after hot compression, and the plastic flow of WCu alloy appear at 300℃ while W particles are mostly homogeneous approximately at 900℃. In addition, the strength of W skeleton is reduced slightly at high strain rate, round grains and cracking appear at the substructure of W particle under different strain rate.
Considering the application of WCu alloy at elevated temperature, hot compression was applied on WCu alloy and W skeleton to analyze the microstructure and mechanical behaviors at different temperature and strain rate. The results show that the stress-strain behaviors of WCu alloy is affected mainly by the temperature, the sintering necks disappear mostly after hot compression, and the plastic flow of WCu alloy appear at 300℃ while W particles are mostly homogeneous approximately at 900℃. In addition, the strength of W skeleton is reduced slightly at high strain rate, round grains and cracking appear at the substructure of W particle under different strain rate.
2016, 45(9):2263-2268.
Abstract:
The evolution of microstructure and texture for the Mg-9Gd-4Y-0.6Zr extruded alloy during static annealing was investigated. The grain growth, precipitation and texture modification were characterized by optical microscopy, scanning electron microscopy, transmission electron microscopy, differential scanning calorimeter, XRD texture instrument and EBSD. The results show that the recrystallization process resulted in the grain refinement at the initial stage of static annealing, and that the intergranular deformation stimulated local precipitating which in turn inhibited the recrystallization process. The texture analysis indicates that the hot extrusion produces the conventional basal fiber with {0001} // ED and the unusual prismatic fiber with c axis // ED. During static recrystallization, the process of grain nucleation weakens the prismatic fiber, while the process of grain growth strengthens it. A large number of plate phases precipitate at grain boundaries along with subgrain boundaries, which significantly inhibits the texture modification.
The evolution of microstructure and texture for the Mg-9Gd-4Y-0.6Zr extruded alloy during static annealing was investigated. The grain growth, precipitation and texture modification were characterized by optical microscopy, scanning electron microscopy, transmission electron microscopy, differential scanning calorimeter, XRD texture instrument and EBSD. The results show that the recrystallization process resulted in the grain refinement at the initial stage of static annealing, and that the intergranular deformation stimulated local precipitating which in turn inhibited the recrystallization process. The texture analysis indicates that the hot extrusion produces the conventional basal fiber with {0001} // ED and the unusual prismatic fiber with c axis // ED. During static recrystallization, the process of grain nucleation weakens the prismatic fiber, while the process of grain growth strengthens it. A large number of plate phases precipitate at grain boundaries along with subgrain boundaries, which significantly inhibits the texture modification.
2016, 45(9):2269-2274.
Abstract:
Magnesium alloys have a significant advantage-low density over other structure metals currently and have been widely used in various fields such as transportation and aerospace. With the development of further research and the enlargement of research scope, more advantages have been developed: high storage capacity, high theoretical volumetric energy density, extraordinarily high damping capacity, good biocompatibility, excellent shielding efficiency as well as impressive thermal conductivity. Therefore Mg alloys have the potential to be various functional materials, such as hydrogen storage material, rechargeable electrochemical batteries, damping material, biodegradable implant material, electromagnetic shielding material, and thermal conductive material. Unfortunately, each kind of functional material has bottlenecks or troubles needing to be broken through, and a lot of researches have been carried out in recent years. This review comprehensively covers the research history, progress and the up-to-date summary of Mg and Mg alloys as functional materials. The six kinds of materials above all will be discussed respectively.
Magnesium alloys have a significant advantage-low density over other structure metals currently and have been widely used in various fields such as transportation and aerospace. With the development of further research and the enlargement of research scope, more advantages have been developed: high storage capacity, high theoretical volumetric energy density, extraordinarily high damping capacity, good biocompatibility, excellent shielding efficiency as well as impressive thermal conductivity. Therefore Mg alloys have the potential to be various functional materials, such as hydrogen storage material, rechargeable electrochemical batteries, damping material, biodegradable implant material, electromagnetic shielding material, and thermal conductive material. Unfortunately, each kind of functional material has bottlenecks or troubles needing to be broken through, and a lot of researches have been carried out in recent years. This review comprehensively covers the research history, progress and the up-to-date summary of Mg and Mg alloys as functional materials. The six kinds of materials above all will be discussed respectively.
2016, 45(9):2275-2281.
Abstract:
The effect of samarium (Sm) adding (0, 0.5, 1, 1.5 and 2 wt.%) on the microstructure and mechanical properties of AZ61 magnesium alloy was investigated by OM, XRD, SEM and EDS. The results indicated that 0.4-2.2 vol.% Al2Sm particles with the average diameter of 1-7μm were found in AZ61 magnesium alloy with different Sm content addition. When rare earth element Sm content increased from 0 to 2.0 wt.%, the size of Al2Sm particles gradually increased and the content of β-Mg17Al12 was decreased. Meanwhile the grain size of AZ61-xSm magnesium alloy with solution treatment at 693K for 24h firstly decreased with Sm content increased to 1.0 wt.%, then gradually increased when Sm content excessed 1.0 wt.%. The maximum values of the ultimate tensile strength and the yield strength of AZ61-xSm magnesium alloys with solution treatment were 215 and 142 MPa, respectively, for the alloy with 1.0 wt.% Sm. And the maximum elongation (4.1%) of AZ61-xSm magnesium alloys was also achieved with 1.0 wt.% Sm addition.
The effect of samarium (Sm) adding (0, 0.5, 1, 1.5 and 2 wt.%) on the microstructure and mechanical properties of AZ61 magnesium alloy was investigated by OM, XRD, SEM and EDS. The results indicated that 0.4-2.2 vol.% Al2Sm particles with the average diameter of 1-7μm were found in AZ61 magnesium alloy with different Sm content addition. When rare earth element Sm content increased from 0 to 2.0 wt.%, the size of Al2Sm particles gradually increased and the content of β-Mg17Al12 was decreased. Meanwhile the grain size of AZ61-xSm magnesium alloy with solution treatment at 693K for 24h firstly decreased with Sm content increased to 1.0 wt.%, then gradually increased when Sm content excessed 1.0 wt.%. The maximum values of the ultimate tensile strength and the yield strength of AZ61-xSm magnesium alloys with solution treatment were 215 and 142 MPa, respectively, for the alloy with 1.0 wt.% Sm. And the maximum elongation (4.1%) of AZ61-xSm magnesium alloys was also achieved with 1.0 wt.% Sm addition.
15 The formation and influence mechanism as well as experimental characterization of composite porosity
2016, 45(9):2282-2286.
Abstract:
In view of the common issue of composite porosity, the formation and influence mechanism of composite porosity are elucidated from the aspects of mechanical mixed nucleation theory and classic nucleation theory. The characterization of porosity morphology, distribution and size are conducted through specific test. The results show that: poor wettability of fibers, retention of vapor molecules and molecular volatilization generated during the crosslinking reaction are the main reasons of porosity formation. The lower cure pressures have a little effect on eliminating the porosity. With the increase of cure pressure, the porosity factor and porosity size decrease significantly. With the method of data fitting, the relations of porosity factor, porosity diameter and cure pressure are obtained, and the power function relations of three times are existed among them. This paper provides a theoretical and experimental support for optimizing the design of composites manufacturing process.
In view of the common issue of composite porosity, the formation and influence mechanism of composite porosity are elucidated from the aspects of mechanical mixed nucleation theory and classic nucleation theory. The characterization of porosity morphology, distribution and size are conducted through specific test. The results show that: poor wettability of fibers, retention of vapor molecules and molecular volatilization generated during the crosslinking reaction are the main reasons of porosity formation. The lower cure pressures have a little effect on eliminating the porosity. With the increase of cure pressure, the porosity factor and porosity size decrease significantly. With the method of data fitting, the relations of porosity factor, porosity diameter and cure pressure are obtained, and the power function relations of three times are existed among them. This paper provides a theoretical and experimental support for optimizing the design of composites manufacturing process.
Deng Zhenbo
,
zhouchangchun
,
Fan Yujiang
,
Peng Jingping
,
Zhu Xiangdong
,
Pei Xuan
,
Yin Guofu
,
Zhang Xingdong
2016, 45(9):2287-2292.
Abstract:
In order to fabricate bone tissue engineering scaffold accurately, a novel method that combines parametric modeling and 3D printing was proposed. In this method, the scaffold structures were designed using cloud data of molded surface. Firstly, the cloud data containing the surface information of Cube structure, Diamond structure and Gryriod structure were obtained. Then the scaffold structures with different parameters were expressed by mathematical functions. After that, finite element analysis was done to the scaffolds. The mechanical properties of porous scaffolds were calculated based on finite element analysis. Bone tissue engineering scaffolds with differentSporous structures were manufactured by 3D printing. Finally, characterizations of printed titanium scaffolds were done to detect the porosity and mechanical properties. The results show that the parameterized model and rapid prototyping manufacturing can design and fabricate titanium alloy scaffolds with specific pore structure characteristics effectively. And the scaffold"s mechanical properties can be also designed. It realized porous titanium alloy scaffolds with optimized biological functions from the perspective of bionics.
In order to fabricate bone tissue engineering scaffold accurately, a novel method that combines parametric modeling and 3D printing was proposed. In this method, the scaffold structures were designed using cloud data of molded surface. Firstly, the cloud data containing the surface information of Cube structure, Diamond structure and Gryriod structure were obtained. Then the scaffold structures with different parameters were expressed by mathematical functions. After that, finite element analysis was done to the scaffolds. The mechanical properties of porous scaffolds were calculated based on finite element analysis. Bone tissue engineering scaffolds with differentSporous structures were manufactured by 3D printing. Finally, characterizations of printed titanium scaffolds were done to detect the porosity and mechanical properties. The results show that the parameterized model and rapid prototyping manufacturing can design and fabricate titanium alloy scaffolds with specific pore structure characteristics effectively. And the scaffold"s mechanical properties can be also designed. It realized porous titanium alloy scaffolds with optimized biological functions from the perspective of bionics.
Gao Xuanqiao
,
Bai Haiyang
,
Guo Linjiang
,
Ren Guangpeng
,
Xue Jianrong
,
Yin Tao
,
Hu Zhongwu
,
Li Laiping
2016, 45(9):2293-2296.
Abstract:
The β-relaxation is the principal source of the dynamics in glassy state, but the structural origin of β-relaxation is still not well understood. Here, the correlation between the β-relaxation and mixing enthalpy was studied, and the chemical effect is interpreted from the aspect of local structure. The dynamic mechanical measurements and molecular dynamics simulation of local structure were performed for Zr-Cu and Zr-Ni metallic glasses, which indicates the smaller negative mixing enthalpy facilitates the formation of the icosahedral clusters, and atom motion related to the β-relaxation is hindered by icosahedral clusters with high dynamic stability.
The β-relaxation is the principal source of the dynamics in glassy state, but the structural origin of β-relaxation is still not well understood. Here, the correlation between the β-relaxation and mixing enthalpy was studied, and the chemical effect is interpreted from the aspect of local structure. The dynamic mechanical measurements and molecular dynamics simulation of local structure were performed for Zr-Cu and Zr-Ni metallic glasses, which indicates the smaller negative mixing enthalpy facilitates the formation of the icosahedral clusters, and atom motion related to the β-relaxation is hindered by icosahedral clusters with high dynamic stability.
2016, 45(9):2297-2302.
Abstract:
To enhance the fracture toughness of TiB2 ceramic film, Ti/TiB2 bionic multilayers was formed by intervention of period Ti layer which was abstracted into a soft layer according to the structural characteristics of nacre. The improved indentation method was proposed to characterize the fracture toughness (KIC) of the Ti/TiB2 bionic multilayers. The results show that the KIC of the multilayers strongly depends on the modulation ratios (Λ, the ratio of TiB2 to Ti thickness, is denoted tTiB2:tTi) and modulation period (T). With the increase of modulation ratio, the KIC of the multilayers increases first and gets a maximum of2.68 MPa
To enhance the fracture toughness of TiB2 ceramic film, Ti/TiB2 bionic multilayers was formed by intervention of period Ti layer which was abstracted into a soft layer according to the structural characteristics of nacre. The improved indentation method was proposed to characterize the fracture toughness (KIC) of the Ti/TiB2 bionic multilayers. The results show that the KIC of the multilayers strongly depends on the modulation ratios (Λ, the ratio of TiB2 to Ti thickness, is denoted tTiB2:tTi) and modulation period (T). With the increase of modulation ratio, the KIC of the multilayers increases first and gets a maximum of2.68 MPa
2016, 45(9):2303-2306.
Abstract:
In order to explore the possibility of determining crystallographic creep exponent using indentation method, extensive finite element simulations were carried out on differently oriented nickel based single crystal superalloys by incorporating crystal plasticity theory. The results showed that the crystallographic symmetry led to a certain symmetric distribution pattern of stress, and the crystallographic orientation had a remarkable influence on the indentation depth and its propagation rate. The steady state indentation depth propagation rates under different indentation loads were extracted by extrapolation approach, and the crystallographic creep stress exponent was then obtained by linear regression method. The creep stress exponents determined by this approach were independent of crystallographic orientation, which shed some light on the evaluation of creep properties of anistropic high temperature alloy using indentation method.
In order to explore the possibility of determining crystallographic creep exponent using indentation method, extensive finite element simulations were carried out on differently oriented nickel based single crystal superalloys by incorporating crystal plasticity theory. The results showed that the crystallographic symmetry led to a certain symmetric distribution pattern of stress, and the crystallographic orientation had a remarkable influence on the indentation depth and its propagation rate. The steady state indentation depth propagation rates under different indentation loads were extracted by extrapolation approach, and the crystallographic creep stress exponent was then obtained by linear regression method. The creep stress exponents determined by this approach were independent of crystallographic orientation, which shed some light on the evaluation of creep properties of anistropic high temperature alloy using indentation method.
2016, 45(9):2307-2312.
Abstract:
TC4 titanium alloy plates were impacted by projectile at a high speed. The microstructure changes inside and nearby the adiabatic shear bands (ASBs) were observed by transmission electron microscope (TEM). The microstructure nearby the ASBs indicated that the boundaries of the ASBs might be the sources for the crack initiation. High stress was concentrated nearby the ASBs, making it easy to form high density dislocation configurations (such as tangled dislocations, banded dislocation cells and so on) and stress induced martensite. The microstructure inside the ASBs indicated that they were mainly induced by high stress. Along the direction vertical to the ASBs, the closer to the center of the ASBs, the more serious the grain fragmentation is. The typical characteristics of dynamic recrystallization (DRX) were not found in the ASBs, thus the present observations did not support the traditional viewpoints that DRX occurred in the ASBs and the origin and dissemination of the ASBs were related to the DRX. Besides, amorphous was also found in the center of the ASBs.
TC4 titanium alloy plates were impacted by projectile at a high speed. The microstructure changes inside and nearby the adiabatic shear bands (ASBs) were observed by transmission electron microscope (TEM). The microstructure nearby the ASBs indicated that the boundaries of the ASBs might be the sources for the crack initiation. High stress was concentrated nearby the ASBs, making it easy to form high density dislocation configurations (such as tangled dislocations, banded dislocation cells and so on) and stress induced martensite. The microstructure inside the ASBs indicated that they were mainly induced by high stress. Along the direction vertical to the ASBs, the closer to the center of the ASBs, the more serious the grain fragmentation is. The typical characteristics of dynamic recrystallization (DRX) were not found in the ASBs, thus the present observations did not support the traditional viewpoints that DRX occurred in the ASBs and the origin and dissemination of the ASBs were related to the DRX. Besides, amorphous was also found in the center of the ASBs.
2016, 45(9):2313-2316.
Abstract:
The hardness and grain refinement mechanism of V-5Cr-5Ti alloy by equal channel angular pressing (ECAP) and annealing treatment were studied. ECAP was tested using pressing die using universal material testing machine. The annealing was done in vacuum heat treatment furnace. The hardness was tested using Vickers hardness tester. The phase structure was identified using X-ray diffraction (XRD). The microstructure was observed using optical microscope (OM). The results indicated that the grain size of V-5Cr-5Ti alloy can be refined from ~100μm to ~30μm after ECAP two times and annealed above 950℃. Different from the traditional grain refinement mechanism of B.C.C alloy, the grains of V-5Cr-5Ti alloy are rotated on itself at ECAP process, and a lot of shearing glide bands are formed in coarse grains. With the annealing temperature increasing, fine grains are formed gradually at shearing glide bands and the initial grain boundaries are still clear. Finally, the fine grains are formed completely above 950℃, and the initial grain boundaries become blurred gradually.
The hardness and grain refinement mechanism of V-5Cr-5Ti alloy by equal channel angular pressing (ECAP) and annealing treatment were studied. ECAP was tested using pressing die using universal material testing machine. The annealing was done in vacuum heat treatment furnace. The hardness was tested using Vickers hardness tester. The phase structure was identified using X-ray diffraction (XRD). The microstructure was observed using optical microscope (OM). The results indicated that the grain size of V-5Cr-5Ti alloy can be refined from ~100μm to ~30μm after ECAP two times and annealed above 950℃. Different from the traditional grain refinement mechanism of B.C.C alloy, the grains of V-5Cr-5Ti alloy are rotated on itself at ECAP process, and a lot of shearing glide bands are formed in coarse grains. With the annealing temperature increasing, fine grains are formed gradually at shearing glide bands and the initial grain boundaries are still clear. Finally, the fine grains are formed completely above 950℃, and the initial grain boundaries become blurred gradually.
2016, 45(9):2317-2321.
Abstract:
Abstract: Adopt the method of numerical simulation and experiment to study the metal flowing law in dual equal channel extrusion process ,dual equal channel extrusion technology can cause severe shear deformation within the material, lead to grain refinement and deformation strengthening effect, and the deformation process should be control by adjusting the coefficient of friction. By four passes extrusion 6061 Alloy within A, B path respective, dual equal channel extrusion has strong effetive strain, and at the same passes, path B have great strain strengthening ability than path A.
Abstract: Adopt the method of numerical simulation and experiment to study the metal flowing law in dual equal channel extrusion process ,dual equal channel extrusion technology can cause severe shear deformation within the material, lead to grain refinement and deformation strengthening effect, and the deformation process should be control by adjusting the coefficient of friction. By four passes extrusion 6061 Alloy within A, B path respective, dual equal channel extrusion has strong effetive strain, and at the same passes, path B have great strain strengthening ability than path A.
2016, 45(9):2322-2326.
Abstract:
The corrosion resistance of Fe24 xCo24-xCr15Mo14C15B6Y2 (X=0, 2, 4, 6, 17) bulk amorphous alloy was investigated by electrochemical test methods and neutral salt spray experiment, respectively. The alloy formed wide passivation zone in 1mol/L HCl, its EIS spectra was composed of a single capacitive loop, which showing a good corrosion resistance. Combined with the results of polarization curves and AC impedance analysis, it can be obtained that the corrosion resistance of the alloy increases first and then decreases with the increasing of Co content. It gets the best corrosion resistance when the Co content of 20%. Using spectroscopy (EDS) and atomic force microscopy (AFM) to analyze the salt spray result, it can be known that the corrosion products mainly composed of iron and cobalt oxides and their chlorides. Meanwhile, FeCo-based bulk amorphous alloy corrosion degree was changed with Co content varied, and its salt spray corrosion resistance rule is consistent with electrochemical corrosion resistance rule.
The corrosion resistance of Fe24 xCo24-xCr15Mo14C15B6Y2 (X=0, 2, 4, 6, 17) bulk amorphous alloy was investigated by electrochemical test methods and neutral salt spray experiment, respectively. The alloy formed wide passivation zone in 1mol/L HCl, its EIS spectra was composed of a single capacitive loop, which showing a good corrosion resistance. Combined with the results of polarization curves and AC impedance analysis, it can be obtained that the corrosion resistance of the alloy increases first and then decreases with the increasing of Co content. It gets the best corrosion resistance when the Co content of 20%. Using spectroscopy (EDS) and atomic force microscopy (AFM) to analyze the salt spray result, it can be known that the corrosion products mainly composed of iron and cobalt oxides and their chlorides. Meanwhile, FeCo-based bulk amorphous alloy corrosion degree was changed with Co content varied, and its salt spray corrosion resistance rule is consistent with electrochemical corrosion resistance rule.
2016, 45(9):2327-2331.
Abstract:
It is of great value for the control and optimation of titanium alloy''s properties by establishing its microstructure-tensile property relationship. Based on quantitative metallography and Stereology, the quantitative relationship between microstructure and tensile property for Ti-6Al-4V alloy with basket-weave structure is establised using multielement non-linear regression in present paper. In this model, the independent variables including lamellar α phase’s thickness and lamellar α phase’s aspect ratio, and the dependent variables are Ti-6Al-4V alloy’s tensile properties. Results show that the multiple regression model built in present paper can precisely describe the microstructure-tensile property relationship of Ti-6Al-4V alloy with basket-weave structure, which indicates that the mehod of establishing model used in present paper is applicable.
It is of great value for the control and optimation of titanium alloy''s properties by establishing its microstructure-tensile property relationship. Based on quantitative metallography and Stereology, the quantitative relationship between microstructure and tensile property for Ti-6Al-4V alloy with basket-weave structure is establised using multielement non-linear regression in present paper. In this model, the independent variables including lamellar α phase’s thickness and lamellar α phase’s aspect ratio, and the dependent variables are Ti-6Al-4V alloy’s tensile properties. Results show that the multiple regression model built in present paper can precisely describe the microstructure-tensile property relationship of Ti-6Al-4V alloy with basket-weave structure, which indicates that the mehod of establishing model used in present paper is applicable.
2016, 45(9):2332-2336.
Abstract:
In order to research the effect of boron additions on precipitation phases of New Co base superalloy. to save cost and to short period. The precipitation phases of Co-8.8Al-9.8W alloy with different B content have been studied by Thermodynamic Simulation Calculation of JMatPro software. The result shows that the precipitation temperature and precipitation quantity of γ phase and μ-Co7W6 phase becomes lower while the content of B increases. whereas the precipitation temperature and precipitation quantity of η-Co3Al phase becomes higher. Finally, the result has been explained from the factors of boride phases and the effect of B on composition of precipitation. Interpretation indicates that with the increase of B content，content of each element of Solid-liquid equilibrium phase has a growing difference when γ phase precipitates ,lowering the temperature increases, increasing the degree of super cooling, can make phase γ nucleation and growth. Thus with the increase of B content, the content of γ phase gets less and the precipitation temperature gets lower. The precipitation of borides leads a lot Co, W solid solution, which made a growth of Al in the solid-liquid equilibrium phase and promotes the precipitation of Co3Al.
In order to research the effect of boron additions on precipitation phases of New Co base superalloy. to save cost and to short period. The precipitation phases of Co-8.8Al-9.8W alloy with different B content have been studied by Thermodynamic Simulation Calculation of JMatPro software. The result shows that the precipitation temperature and precipitation quantity of γ phase and μ-Co7W6 phase becomes lower while the content of B increases. whereas the precipitation temperature and precipitation quantity of η-Co3Al phase becomes higher. Finally, the result has been explained from the factors of boride phases and the effect of B on composition of precipitation. Interpretation indicates that with the increase of B content，content of each element of Solid-liquid equilibrium phase has a growing difference when γ phase precipitates ,lowering the temperature increases, increasing the degree of super cooling, can make phase γ nucleation and growth. Thus with the increase of B content, the content of γ phase gets less and the precipitation temperature gets lower. The precipitation of borides leads a lot Co, W solid solution, which made a growth of Al in the solid-liquid equilibrium phase and promotes the precipitation of Co3Al.
2016, 45(9):2337-2341.
Abstract:
Abstract:The influences of strain rates on mechanical properties and serrated flow behaviors of Zr67.76Cu11.94Ni8.30Al12 metallic glass composite have been investigated in this paper with statistical methods. The results demonstrate that both the plastic strain and the compressive strength decreased with the increasing of strain rates;Meanwhile, the serrated distribution of stress drop (Δσs) changed from a monotonical decreasing into a peak-like shape, the absolute frequency of it ranged from small to large interval. The serrated number of units of plastic strain (M) continuously declined. Moreover, the number of the shear bands of sample reduced and the interaction among them significantly weakened. According to the changes all above, the energy dissipation mechanism deteriorates and the increasing of the temperature and the shear expansion effects due to the energy accumulation within the material resulting the specimen fracture catastrophically occur.
Abstract:The influences of strain rates on mechanical properties and serrated flow behaviors of Zr67.76Cu11.94Ni8.30Al12 metallic glass composite have been investigated in this paper with statistical methods. The results demonstrate that both the plastic strain and the compressive strength decreased with the increasing of strain rates;Meanwhile, the serrated distribution of stress drop (Δσs) changed from a monotonical decreasing into a peak-like shape, the absolute frequency of it ranged from small to large interval. The serrated number of units of plastic strain (M) continuously declined. Moreover, the number of the shear bands of sample reduced and the interaction among them significantly weakened. According to the changes all above, the energy dissipation mechanism deteriorates and the increasing of the temperature and the shear expansion effects due to the energy accumulation within the material resulting the specimen fracture catastrophically occur.
2016, 45(9):2342-2346.
Abstract:
The Fe-based alloy coatings reinforced with in situ synthesized ceramic phases containing titanium were prepared on Q235 steel by reactive plasma cladding process using Fe901, Ti, B4C and h-BN powders as raw materials. The results show that Fe is apt to react with h-BN to produce FeB comparing with B4C. If both of B4C and BN are added as reactants, the content of FeB will increase and the Ti2N and TiB intermediates can be found in the coatings when B4C/h-BN ratio decreases to a certain value. However, it can depress the growth of ceramic phases. The microstructure of the clad coatings exhibits an obvious gradient distribution along the depth direction. The size and morphology of TiB2 change with the temperature and composition of the molten pool. Increasing h-BN amount will result in the decrease of microhardness of the coatings. The high microhardness value 1126HV0.2 can be achieved at the near surface layer for the coating at Ti : B4C : h-BN=3 : 1 : 0.
The Fe-based alloy coatings reinforced with in situ synthesized ceramic phases containing titanium were prepared on Q235 steel by reactive plasma cladding process using Fe901, Ti, B4C and h-BN powders as raw materials. The results show that Fe is apt to react with h-BN to produce FeB comparing with B4C. If both of B4C and BN are added as reactants, the content of FeB will increase and the Ti2N and TiB intermediates can be found in the coatings when B4C/h-BN ratio decreases to a certain value. However, it can depress the growth of ceramic phases. The microstructure of the clad coatings exhibits an obvious gradient distribution along the depth direction. The size and morphology of TiB2 change with the temperature and composition of the molten pool. Increasing h-BN amount will result in the decrease of microhardness of the coatings. The high microhardness value 1126HV0.2 can be achieved at the near surface layer for the coating at Ti : B4C : h-BN=3 : 1 : 0.
2016, 45(9):2347-2351.
Abstract:
Effects of laser peening and shot peening on residual stress fields performance of a GH742 superalloy were investigated. Compressive residual stresses in the surface layer were analyzed by the X-ray diffraction stress analyse tester. The characteristics of compressive residual stresses induce by these two kinds of surface enhancement processes were compared and the surface residual stress evlution was investigated under different high temperatures. The results show that both laser peening and shot peening can induce compressive residual stresses in surface layer, while the compressive residual stress layer is deeper for laser-peened specimens and the maximum residual compressive locate at surface; while for shot-peened specimens, the depth of compressive residual stress layer in thinner. Moreover, the maximum compressive residual stress moves from surface to subsurface with the increase of shot peening intensity.
Effects of laser peening and shot peening on residual stress fields performance of a GH742 superalloy were investigated. Compressive residual stresses in the surface layer were analyzed by the X-ray diffraction stress analyse tester. The characteristics of compressive residual stresses induce by these two kinds of surface enhancement processes were compared and the surface residual stress evlution was investigated under different high temperatures. The results show that both laser peening and shot peening can induce compressive residual stresses in surface layer, while the compressive residual stress layer is deeper for laser-peened specimens and the maximum residual compressive locate at surface; while for shot-peened specimens, the depth of compressive residual stress layer in thinner. Moreover, the maximum compressive residual stress moves from surface to subsurface with the increase of shot peening intensity.
2016, 45(9):2352-2358.
Abstract:
In this paper, Ti/Ni composites material with Multi-layered structure was produced by accumulative roll bonding (ARB) process. The micro-structure and interface structure of composites material were analyzed by scanning electron microscope, energySdisperseSspectroscopy, and transmissionSelectronSmicroscope. The mechanical propertiesSof composite material in different ARB cycles were tested by universal material testing machine and micro-hardness tester. The results show that the micro-structure of Ti layer and Ni layer of composites material was obviously refined. Ultrafine grains with the size of 200 um ~ 300 um is acquired in both Ti and Ni layer. And the micro-structureShomogeneity, the tensile strength, micro-harded and interfacial bonding strength were improved with the increasing of ARB cycles. After ARB 5 cycles, the tensile strength was 810 MPa, the elongation was 24.4%, and the average micro-hardness of Ti layer and Ni Layer is 233 HV and 229 HV. There is no obvious diffusion at the interface of Ti/Ni composites material with multi-layered structure during ARB 1-5 cycles.
In this paper, Ti/Ni composites material with Multi-layered structure was produced by accumulative roll bonding (ARB) process. The micro-structure and interface structure of composites material were analyzed by scanning electron microscope, energySdisperseSspectroscopy, and transmissionSelectronSmicroscope. The mechanical propertiesSof composite material in different ARB cycles were tested by universal material testing machine and micro-hardness tester. The results show that the micro-structure of Ti layer and Ni layer of composites material was obviously refined. Ultrafine grains with the size of 200 um ~ 300 um is acquired in both Ti and Ni layer. And the micro-structureShomogeneity, the tensile strength, micro-harded and interfacial bonding strength were improved with the increasing of ARB cycles. After ARB 5 cycles, the tensile strength was 810 MPa, the elongation was 24.4%, and the average micro-hardness of Ti layer and Ni Layer is 233 HV and 229 HV. There is no obvious diffusion at the interface of Ti/Ni composites material with multi-layered structure during ARB 1-5 cycles.
2016, 45(9):2359-2365.
Abstract:
of velocity from 1450 m/s to 2100m/s. Zr-based metallic glass composites with 80% Volume fraction and 0.3mm diameter of tungsten fiber were used to perforate 30CrMnMo steel plates. According to the result, we find: firstly, the penetration efficiency is influenced by properties and structure of the material, which is helpful to design the rod penetrator of composite material. Secondly, for the different structures of the penetrator, curves of penetration depth with velocity are different. The curves of two segments and three segments are convex, and at 1750m/s~1800m/s and 1850m/s they arrive at the maximums which are both 1.7L, respectively. And for the monolithic penetrator, the curve is asymptote, but after 1850m/s, the penetration depth arrive to the hydrodynamic limit which is L*(rp/rt)1/2, and it is about 1.5L. Finally, according to the dynamic damage characteristic of the unidirectional fiber reinforced composite materials, the characteristic of dynamic crack propagation and penetration velocity of impact, optimal segmentation is defined, and analysis the problem from (2), provide the reference for structure design of segment penetrator.
of velocity from 1450 m/s to 2100m/s. Zr-based metallic glass composites with 80% Volume fraction and 0.3mm diameter of tungsten fiber were used to perforate 30CrMnMo steel plates. According to the result, we find: firstly, the penetration efficiency is influenced by properties and structure of the material, which is helpful to design the rod penetrator of composite material. Secondly, for the different structures of the penetrator, curves of penetration depth with velocity are different. The curves of two segments and three segments are convex, and at 1750m/s~1800m/s and 1850m/s they arrive at the maximums which are both 1.7L, respectively. And for the monolithic penetrator, the curve is asymptote, but after 1850m/s, the penetration depth arrive to the hydrodynamic limit which is L*(rp/rt)1/2, and it is about 1.5L. Finally, according to the dynamic damage characteristic of the unidirectional fiber reinforced composite materials, the characteristic of dynamic crack propagation and penetration velocity of impact, optimal segmentation is defined, and analysis the problem from (2), provide the reference for structure design of segment penetrator.
2016, 45(9):2366-2372.
Abstract:
Since the copper could not be nitrided, the conventional surface hardening method can not be used to improve the surface hardness of the copper. In this paper, the stability and hardness of N-containing Cu alloy films were studied by adding Ti which could stabilize N to Cu alloy films, and the effective method of improving the surface hardness of the copper was further explored. The Cu alloy films containing different content of Ti, N were deposited onto the Si (100) substrates by magnetron sputtering and their microstructure, hardness and resistivities were analyzed. The result suggests that the addition of Ti could make N exist in Cu alloys films in the form of Ti-N compounds, and the hardness of the alloy films was improved compared with that of pure Cu film (~3.5 GPa). Especially, the hardness of Cu80.2Ti9.8N10.0 film was still up to 5.4 GPa even after annealing at 400 ℃ for 1 h. The resistivity of the Cu81.2Ti9.9N8.9 film (~660 μΩ?cm) with large contents of Ti and N was much higher than that of Cu88.5Ti4.3N7.2 film (~123 μΩ?cm), but the two films were about the same hardness (~5.2 GPa). Therefore, the Ti, N contents should be controlled properly when preparing Cu(Ti, N) films.
Since the copper could not be nitrided, the conventional surface hardening method can not be used to improve the surface hardness of the copper. In this paper, the stability and hardness of N-containing Cu alloy films were studied by adding Ti which could stabilize N to Cu alloy films, and the effective method of improving the surface hardness of the copper was further explored. The Cu alloy films containing different content of Ti, N were deposited onto the Si (100) substrates by magnetron sputtering and their microstructure, hardness and resistivities were analyzed. The result suggests that the addition of Ti could make N exist in Cu alloys films in the form of Ti-N compounds, and the hardness of the alloy films was improved compared with that of pure Cu film (~3.5 GPa). Especially, the hardness of Cu80.2Ti9.8N10.0 film was still up to 5.4 GPa even after annealing at 400 ℃ for 1 h. The resistivity of the Cu81.2Ti9.9N8.9 film (~660 μΩ?cm) with large contents of Ti and N was much higher than that of Cu88.5Ti4.3N7.2 film (~123 μΩ?cm), but the two films were about the same hardness (~5.2 GPa). Therefore, the Ti, N contents should be controlled properly when preparing Cu(Ti, N) films.
32 Influences of Melt Temperature on Microstructures and Properties of in-situ Al-18%Mg2Si composites
2016, 45(9):2373-2378.
Abstract:
The effects of the melt temperature on the microstructures and properties of in-situ Al-18%Mg2Si composites were investigated. The results show that the coarse dendrite primary Mg2Si phases transformed to the polygons and lumps and some transformed to small particles with the rising of the melt temperature. The primary Mg2Si is the smallest with the average grain size of 7μm when the melt temperature is 870℃.The grain size of the primary Mg2Si increased slightly when the temperature is over 870℃.The lamellar eutectic Mg2Si transformed to small particles, then changed into the mixed microstructure with small and rodlike particles with increasing the melt temperature. The size of the eutectic group decreased first and then increased. The tensile strength, the elongation rate and the hardness increased first and then decreased with the rising of the melt temperature. The mechanical properties achieved the best value when the temperature is 870℃.The result and analysis of DTA show that the microstructure and mechanical properties of in-situ Al-18%Mg2Si composites are the best, which results from the comprehensive function of multiple factors including large nucleation undercooling and the change of growth pattern.
The effects of the melt temperature on the microstructures and properties of in-situ Al-18%Mg2Si composites were investigated. The results show that the coarse dendrite primary Mg2Si phases transformed to the polygons and lumps and some transformed to small particles with the rising of the melt temperature. The primary Mg2Si is the smallest with the average grain size of 7μm when the melt temperature is 870℃.The grain size of the primary Mg2Si increased slightly when the temperature is over 870℃.The lamellar eutectic Mg2Si transformed to small particles, then changed into the mixed microstructure with small and rodlike particles with increasing the melt temperature. The size of the eutectic group decreased first and then increased. The tensile strength, the elongation rate and the hardness increased first and then decreased with the rising of the melt temperature. The mechanical properties achieved the best value when the temperature is 870℃.The result and analysis of DTA show that the microstructure and mechanical properties of in-situ Al-18%Mg2Si composites are the best, which results from the comprehensive function of multiple factors including large nucleation undercooling and the change of growth pattern.
2016, 45(9):2379-2384.
Abstract:
A novel preparation process has been developed to fabricate TiAl intermetallic compound porous materials based on the combination effect of making pores arising from the chemical reaction and physical space occupation. The technique is mainly consisted of four stages describled as mixing, compacting, dissolution and sintering. The typical double pore structures of the TiAl porous materials were successfully achieved, where the micron pore is associated with the Kirkendall effect and the millimeter pore comes from the space holders. The TiAl porous materials exhibit a thorough open-cellular structure and a perfect homogeneous distribution. Moreover, the porosity, pore size, pore shape, pore structure can be tailored as designed, and the maximum of porosity even reaches 90%. The results of quasi-state compression tests indicate that the TiAl porous materials are typical brittle porous materials with corresponding brittle fracture failure mechanism. The relationship between yield strength and relative density can be understood in terms of the cube cell modle.
A novel preparation process has been developed to fabricate TiAl intermetallic compound porous materials based on the combination effect of making pores arising from the chemical reaction and physical space occupation. The technique is mainly consisted of four stages describled as mixing, compacting, dissolution and sintering. The typical double pore structures of the TiAl porous materials were successfully achieved, where the micron pore is associated with the Kirkendall effect and the millimeter pore comes from the space holders. The TiAl porous materials exhibit a thorough open-cellular structure and a perfect homogeneous distribution. Moreover, the porosity, pore size, pore shape, pore structure can be tailored as designed, and the maximum of porosity even reaches 90%. The results of quasi-state compression tests indicate that the TiAl porous materials are typical brittle porous materials with corresponding brittle fracture failure mechanism. The relationship between yield strength and relative density can be understood in terms of the cube cell modle.
2016, 45(9):2385-2390.
Abstract:
Using different external fields application ways, AZ61 magnesium alloy was semi-continuously cast into billets with diameter of 165mm. The effects of the different external fields application ways on the grain size and hardness of AZ61 billets were investigated. The results show that compared with the conventional direct-chill semi-continuous cast billets, the grain size of the AZ61 billets cast reduced from 248μm in the edge and 276μm in the centre to 196μm and 259μm respectively(with a reduce of 21% and 6.2% respectively) by low-frequency electromagnetic field (f=30Hz, I=60A)，the structure in edge and centre refining effects are significantly diverse. However, the grain size in the edge and centre from reduced from 248μm in the edge and 276μm in the centre to 185μm and 208μm respectively (with a reduce of 25.4% and 24.6% respectively) by combining ultrasonic and LFEC, and the structure in centre refining effects were significantly improved. Moreover, compared with the conventional DC casting, the compound physical Field can improve the hardness of the ingot and obviously reduce the different hardness from edge to centre. Therefore, the compound physical Field obviously improved the inner qualities of AZ61 magnesium alloy ingot billet, and the microstructure is markedly refined, so the hardness of ingot uniformly improved.
Using different external fields application ways, AZ61 magnesium alloy was semi-continuously cast into billets with diameter of 165mm. The effects of the different external fields application ways on the grain size and hardness of AZ61 billets were investigated. The results show that compared with the conventional direct-chill semi-continuous cast billets, the grain size of the AZ61 billets cast reduced from 248μm in the edge and 276μm in the centre to 196μm and 259μm respectively(with a reduce of 21% and 6.2% respectively) by low-frequency electromagnetic field (f=30Hz, I=60A)，the structure in edge and centre refining effects are significantly diverse. However, the grain size in the edge and centre from reduced from 248μm in the edge and 276μm in the centre to 185μm and 208μm respectively (with a reduce of 25.4% and 24.6% respectively) by combining ultrasonic and LFEC, and the structure in centre refining effects were significantly improved. Moreover, compared with the conventional DC casting, the compound physical Field can improve the hardness of the ingot and obviously reduce the different hardness from edge to centre. Therefore, the compound physical Field obviously improved the inner qualities of AZ61 magnesium alloy ingot billet, and the microstructure is markedly refined, so the hardness of ingot uniformly improved.
2016, 45(9):2391-2396.
Abstract:
Effects of different forging deformation, including amount of 30%, 50%, 70%, on the microstructure and friction and wear behavior of Al3Ti/6063Al composite material microstructure were studied. The results show that Al3Ti in-situ particles were broken and paralleled to the forging direction after deformation. Morphology of matrix grain changed obviously and formed the streamlined texture. Forging also caused a great dislocation in composites. When Amount of forging deformation increases, the friction coefficient decreased and friction coefficient declined under the same load. What’s more 70% forging material had the lowest friction coefficient; the relationship of roughness and deformation had the same function of friction coefficient and deformation., When the deformation amount of material was 30%, the extent of material roughness only can fluctuate in a small range, and change was relatively stable; when the deformation increases, the width and depth of wear scar become wider as well as shallower; abrasiveness and delimitation wear mainly occurred in the process of abrasiveness.
Effects of different forging deformation, including amount of 30%, 50%, 70%, on the microstructure and friction and wear behavior of Al3Ti/6063Al composite material microstructure were studied. The results show that Al3Ti in-situ particles were broken and paralleled to the forging direction after deformation. Morphology of matrix grain changed obviously and formed the streamlined texture. Forging also caused a great dislocation in composites. When Amount of forging deformation increases, the friction coefficient decreased and friction coefficient declined under the same load. What’s more 70% forging material had the lowest friction coefficient; the relationship of roughness and deformation had the same function of friction coefficient and deformation., When the deformation amount of material was 30%, the extent of material roughness only can fluctuate in a small range, and change was relatively stable; when the deformation increases, the width and depth of wear scar become wider as well as shallower; abrasiveness and delimitation wear mainly occurred in the process of abrasiveness.
2016, 45(9):2397-2402.
Abstract:
The Al-5Zr master alloy was fabricated by direct melt reaction technique in the Al-K2ZrF6 system. Three-dimensional morphologies of the primary Al3Zr phase in Al-5Zr master alloy were acquired by the alkali corrosion and their formation mechanisms were analyzed. The effects of pouring temperature (1 250, 1 050, 950, 800 ℃) on the morphology, size and the amount of primary Al3Zr phase in the cooling process were investigated. The theoretical and experimental values of solid fractions were calculated by JMatPro software and area-method, respectively. The results show that the morphologies of Al3Zr phase in the master alloy display thick-plate, thin-flake, petal and cross-bridge shapes; and the formation of these morphologies are resulted from two-dimensional nucleus growth and constitutional supercooling. With the decrease of pouring temperature, the morphologies of Al3Zr phase are changed from thin-flake to thick-plate, the size and the amount for the thin-flake phase decrease, while the size and the amount for the thick-plate phase increase, but the total amount of Al3Zr phase reduces. The theoretical value of solid fraction agrees well with experimental value. With the decrease of pouring temperature, the relative content of thick-plate Al3Zr phase increases in terms of the solid fraction.
The Al-5Zr master alloy was fabricated by direct melt reaction technique in the Al-K2ZrF6 system. Three-dimensional morphologies of the primary Al3Zr phase in Al-5Zr master alloy were acquired by the alkali corrosion and their formation mechanisms were analyzed. The effects of pouring temperature (1 250, 1 050, 950, 800 ℃) on the morphology, size and the amount of primary Al3Zr phase in the cooling process were investigated. The theoretical and experimental values of solid fractions were calculated by JMatPro software and area-method, respectively. The results show that the morphologies of Al3Zr phase in the master alloy display thick-plate, thin-flake, petal and cross-bridge shapes; and the formation of these morphologies are resulted from two-dimensional nucleus growth and constitutional supercooling. With the decrease of pouring temperature, the morphologies of Al3Zr phase are changed from thin-flake to thick-plate, the size and the amount for the thin-flake phase decrease, while the size and the amount for the thick-plate phase increase, but the total amount of Al3Zr phase reduces. The theoretical value of solid fraction agrees well with experimental value. With the decrease of pouring temperature, the relative content of thick-plate Al3Zr phase increases in terms of the solid fraction.
37 Effect of Carbon Addition on Tungsten Nano-powders Prepared by Hydrogen Reduction of Tungsten Oxide
2016, 45(9):2403-2408.
Abstract:
Spherical tungsten powders with the average grain size of 56.4 nm were prepared by hydrogen reduction assisted by carbon because the volatility of tungsten oxide, which is the fundamental reason of the rapid and abnormal grain growth of tungsten powder during hydrogen reduction, was inhibited by carbon addition. The effect of carbon on the reduction mechanism of tungsten oxide was investigated. It is shown that the C:W molar ratio of precursors has a great influence on the grain size and residual carbon content of tungsten powders, and the optimum molar ratio is 2.6. The grain size increases with the prolongation of reduction time, and the grain growth rate is closely related to the reduction temperature. With the reduction temperature increase from 680 ℃ to 760 ℃, the grain size and residual carbon of tungsten powders decreases and the dispersion is improved, and then the grain size increases slightly when the reduction temperature increase to 800 ℃. The results indicate that the reaction between carbon and H2O steam occurs when the reduction temperature exceeded 710 ℃, which can reduce the partial pressure of H2O steam. Therefore, the volatility of tungsten oxides is inhibited, and the dominant growth mechanism of tungsten powders transforms from volatility-sedimentation mechanism to atomic diffusion mechanism.
Spherical tungsten powders with the average grain size of 56.4 nm were prepared by hydrogen reduction assisted by carbon because the volatility of tungsten oxide, which is the fundamental reason of the rapid and abnormal grain growth of tungsten powder during hydrogen reduction, was inhibited by carbon addition. The effect of carbon on the reduction mechanism of tungsten oxide was investigated. It is shown that the C:W molar ratio of precursors has a great influence on the grain size and residual carbon content of tungsten powders, and the optimum molar ratio is 2.6. The grain size increases with the prolongation of reduction time, and the grain growth rate is closely related to the reduction temperature. With the reduction temperature increase from 680 ℃ to 760 ℃, the grain size and residual carbon of tungsten powders decreases and the dispersion is improved, and then the grain size increases slightly when the reduction temperature increase to 800 ℃. The results indicate that the reaction between carbon and H2O steam occurs when the reduction temperature exceeded 710 ℃, which can reduce the partial pressure of H2O steam. Therefore, the volatility of tungsten oxides is inhibited, and the dominant growth mechanism of tungsten powders transforms from volatility-sedimentation mechanism to atomic diffusion mechanism.
2016, 45(9):2409-2413.
Abstract:
An ultra-fine Nb-Silicide in situ composite whose nominal composition is Nb-16Si-10Ti-10Mo-5Hf was fabricated by mechanical alloying followed by spark plasma sintering. The microstructure consists of an Nb solid solution, Nb5Si3 and a small amount of Nb3Si with all three phases being in the sub-micro range. This in-situ composite exhibits good balance of strength between ambient temperature and high temperature; the ultimate tensile strength is 413 and 496 MPa at room temperature and 1200oC, respectively. The tensile fracture behavior is dominated by cleavage of the Nb5Si3 phase at 1200oC and lower temperatures. However, the fracture behavior is governed by ductile rupture of Nbss at 1300oC and higher temperature, which would be ascribed to both the increased ductility of Nbss and the decreased interface strength. At 1400oC and higher temperature, the material exhibits extensive plasticity or superplasticity; the dominant deformation mechanism is grain boundary at 1400oC and higher temperature.
An ultra-fine Nb-Silicide in situ composite whose nominal composition is Nb-16Si-10Ti-10Mo-5Hf was fabricated by mechanical alloying followed by spark plasma sintering. The microstructure consists of an Nb solid solution, Nb5Si3 and a small amount of Nb3Si with all three phases being in the sub-micro range. This in-situ composite exhibits good balance of strength between ambient temperature and high temperature; the ultimate tensile strength is 413 and 496 MPa at room temperature and 1200oC, respectively. The tensile fracture behavior is dominated by cleavage of the Nb5Si3 phase at 1200oC and lower temperatures. However, the fracture behavior is governed by ductile rupture of Nbss at 1300oC and higher temperature, which would be ascribed to both the increased ductility of Nbss and the decreased interface strength. At 1400oC and higher temperature, the material exhibits extensive plasticity or superplasticity; the dominant deformation mechanism is grain boundary at 1400oC and higher temperature.
2016, 45(9):2414-2418.
Abstract:
A series of Al/Ni composites were fabrication with friction stir processing to investigate the effect of PTFE on the homogeneity of Ni distribution in the composites. The microstructures of the surface composites were analyzed by SEM and EDS, the phase composition was examined by XRD. Results show that the uniformity of composites can significantly improved by adding PTFE; the interface between Ni and Al will be increase after adding PTFE, because the PTFE can Blocking Ni powder together. Then , the reaction degree between Al and Ni will be increase, so the number of Al3Ni intermetallic compound will be increase.
A series of Al/Ni composites were fabrication with friction stir processing to investigate the effect of PTFE on the homogeneity of Ni distribution in the composites. The microstructures of the surface composites were analyzed by SEM and EDS, the phase composition was examined by XRD. Results show that the uniformity of composites can significantly improved by adding PTFE; the interface between Ni and Al will be increase after adding PTFE, because the PTFE can Blocking Ni powder together. Then , the reaction degree between Al and Ni will be increase, so the number of Al3Ni intermetallic compound will be increase.
2016, 45(9):2419-2423.
Abstract:
Al Cu and Al Si powders were prepared on the surface of AZ31B magnesium alloy by a method of combining Laser cladding and friction stir processing. The microstructure and phase analyses of the modified layer were studied by scanning electron microscopy and X-ray diffraction measurement. Meanwhile, The microhardness and corrosion resistance of the modified layer were investigated in detail. The composite modified layers with Al Cu and Al Si powders are compose of β-Al12Mg17, AlCu4, AlMg and Mg2Si, AlMg, β-Al12Mg17, respectively. Both modified layer showed very good bonding with the magnesium alloy substrate. The microhardness and corrosion resistance of the modified layer are higher than that of substrate. Compared with the matrix, the maximum microhardness (296 HV) of the modified layer with Al Si powders increased by 385.3%, and the maximum self-corrosion potential (-0.975 V) with Al Cu powders increased by 37.4%.
Al Cu and Al Si powders were prepared on the surface of AZ31B magnesium alloy by a method of combining Laser cladding and friction stir processing. The microstructure and phase analyses of the modified layer were studied by scanning electron microscopy and X-ray diffraction measurement. Meanwhile, The microhardness and corrosion resistance of the modified layer were investigated in detail. The composite modified layers with Al Cu and Al Si powders are compose of β-Al12Mg17, AlCu4, AlMg and Mg2Si, AlMg, β-Al12Mg17, respectively. Both modified layer showed very good bonding with the magnesium alloy substrate. The microhardness and corrosion resistance of the modified layer are higher than that of substrate. Compared with the matrix, the maximum microhardness (296 HV) of the modified layer with Al Si powders increased by 385.3%, and the maximum self-corrosion potential (-0.975 V) with Al Cu powders increased by 37.4%.
2016, 45(9):2424-2428.
Abstract:
high entropy alloy (HEA) SiFeCoCrTi coating is prepared on Q235 steel by laser cladding. effect of WC Particles on the Microstructure and Properties of High Entropy Alloy SiFeCoCrTi coating is researched.in this paper, the organization,phase, microhardness and wear resistance are investigated by means of OM，XRD，SEM, hardness testing and wear testing. the experimental result shows that he microstructure of the HEA SiFeCoCrTi coating is dendrite consisting of BCC phase and intermetallics. the coating form grain dendrite after adding WC particle, and large amounts of intermetallics are found in the coating, such as TiCo3、Co1.07Fe18.93. the substrate’s dilution rate decrease and the properties of coating increase with adding WC particle. comparing to the HEA FeSiCrCoMo coating, the average hardness of the HEA FeSiCrCoMo coating increased by 23% and both of wear rate and friction coefficient decreased with adding WC, the wear-resisting property is improved obviously.
high entropy alloy (HEA) SiFeCoCrTi coating is prepared on Q235 steel by laser cladding. effect of WC Particles on the Microstructure and Properties of High Entropy Alloy SiFeCoCrTi coating is researched.in this paper, the organization,phase, microhardness and wear resistance are investigated by means of OM，XRD，SEM, hardness testing and wear testing. the experimental result shows that he microstructure of the HEA SiFeCoCrTi coating is dendrite consisting of BCC phase and intermetallics. the coating form grain dendrite after adding WC particle, and large amounts of intermetallics are found in the coating, such as TiCo3、Co1.07Fe18.93. the substrate’s dilution rate decrease and the properties of coating increase with adding WC particle. comparing to the HEA FeSiCrCoMo coating, the average hardness of the HEA FeSiCrCoMo coating increased by 23% and both of wear rate and friction coefficient decreased with adding WC, the wear-resisting property is improved obviously.
2016, 45(9):2429-2433.
Abstract:
The Ti3Al/TC11 dual alloy specimen were prepared by laser solid forming, and then deformed by near isothermal forging with various deformation amounts. Afterwards, the effect of deformation amount on the microhardness and element diffusion of the transition zone and its two sides for Ti3Al/TC11 dual alloy specimen were investigated. The results show that after deformation, whatever the deformation amount is, the microhardness value of the transition zone and its two sides are decreased obviously, the differences in microhardness value along the same specimen are reduced significantly and the distribution is relatively homogeneously. In addition, the deformation amount has an obvious effect on the microhardness and element diffusion in the transition zone and its two sides. With the increase of deformation amount, all the value of the microhardness and its distribution homogeneity along the same specimen are increased; the concentration gradients of the alloying elements including Ti, Al and Nb on both sides of the transition zone are decreased, and they diffuse relatively sufficiently along the joining interface. The reason for that is because of larger deformation, the coarse columnar grains formed in laser solid forming are broken sufficiently, the grain boundaries of βphases are disappear, and the αand α2 phases show the fine and equiaxed shape.
The Ti3Al/TC11 dual alloy specimen were prepared by laser solid forming, and then deformed by near isothermal forging with various deformation amounts. Afterwards, the effect of deformation amount on the microhardness and element diffusion of the transition zone and its two sides for Ti3Al/TC11 dual alloy specimen were investigated. The results show that after deformation, whatever the deformation amount is, the microhardness value of the transition zone and its two sides are decreased obviously, the differences in microhardness value along the same specimen are reduced significantly and the distribution is relatively homogeneously. In addition, the deformation amount has an obvious effect on the microhardness and element diffusion in the transition zone and its two sides. With the increase of deformation amount, all the value of the microhardness and its distribution homogeneity along the same specimen are increased; the concentration gradients of the alloying elements including Ti, Al and Nb on both sides of the transition zone are decreased, and they diffuse relatively sufficiently along the joining interface. The reason for that is because of larger deformation, the coarse columnar grains formed in laser solid forming are broken sufficiently, the grain boundaries of βphases are disappear, and the αand α2 phases show the fine and equiaxed shape.
2016, 45(9):2434-2438.
Abstract:
The low frequency electromagnetic casting(LFEC) process was used in casting the large scale AZ31 magnesium slab with the cross section of 300mm×800mm, and its macrostructure and macrosegregation were investigated at different casting velocities. The result shows that the segregation was slight in the centre and become serious in region about 20mm~30mm near the slab surface, There exist three zone in AZ31 magnesium alloy slab, surface chill zone, columnar crystal zone, internal equiaxed crystal zone. With the casting velocity increasing, the size of grain increases first and then decreases, the width of columnar crystal zone decreases drastically as well as the macrosegregation. At high casting velocity, the grain size is finer, but more uneven. Thus, the appropriate casting velocity in this process is 32mm/min.
The low frequency electromagnetic casting(LFEC) process was used in casting the large scale AZ31 magnesium slab with the cross section of 300mm×800mm, and its macrostructure and macrosegregation were investigated at different casting velocities. The result shows that the segregation was slight in the centre and become serious in region about 20mm~30mm near the slab surface, There exist three zone in AZ31 magnesium alloy slab, surface chill zone, columnar crystal zone, internal equiaxed crystal zone. With the casting velocity increasing, the size of grain increases first and then decreases, the width of columnar crystal zone decreases drastically as well as the macrosegregation. At high casting velocity, the grain size is finer, but more uneven. Thus, the appropriate casting velocity in this process is 32mm/min.
2016, 45(9):2439-2443.
Abstract:
The volt-ampere characteristics of gas discharge was introduced form positive-Ohm of magnetron sputtering ion plating into anti-Ohm section using pulse mode and deposited TiN films under different target current density. The influences of positive-Ohm and anti-Ohm sections on the microstructure and properties of the films were studied. The results indicated that in the anti-Ohm section with target current density (Itd) is more than 0.2A?cm-2, the films have good surface quality and density degree, and the hardness and membrane-binding strength were upgraded from 18.9GPa、4.5N in positive-Ohm section (Itd=0.11A?cm-2) to 25.8GPa、18N in anti-Ohm section (Itd=0.38 A?cm-2) respectively.
The volt-ampere characteristics of gas discharge was introduced form positive-Ohm of magnetron sputtering ion plating into anti-Ohm section using pulse mode and deposited TiN films under different target current density. The influences of positive-Ohm and anti-Ohm sections on the microstructure and properties of the films were studied. The results indicated that in the anti-Ohm section with target current density (Itd) is more than 0.2A?cm-2, the films have good surface quality and density degree, and the hardness and membrane-binding strength were upgraded from 18.9GPa、4.5N in positive-Ohm section (Itd=0.11A?cm-2) to 25.8GPa、18N in anti-Ohm section (Itd=0.38 A?cm-2) respectively.
2016, 45(9):2444-2448.
Abstract:
In this paper, graphene oxide was prepared as raw material by the improved Hummers method. Then graphene-Fe3O4 magnetic carrier was obtained by co-precipitation method, finally TiO2/graphene-Fe3O4 magnetic ternary complex photocatalyst was synthesized by hydrothermal method. The properties of products were characterized by XRD, SEM, and UV-Vis DRS. Photocatalytic activity and stability of the resulting catalyst was evaluated by the degradation of methylene blue solution under visible and UV light. It was found that the degradation reaction accorded with first-order kinetic model. The composite catalyst had better photocatalytic activity than pure TiO2 in the UV and visible light. As a support and electron acceptor, graphene extended and enhanced the band edge absorption of TiO2 into the visible light region, so it could effectively enhance the photocatalytic activity of TiO2. At the same time magnetic Fe3O4 was added to improve its recyclability.
In this paper, graphene oxide was prepared as raw material by the improved Hummers method. Then graphene-Fe3O4 magnetic carrier was obtained by co-precipitation method, finally TiO2/graphene-Fe3O4 magnetic ternary complex photocatalyst was synthesized by hydrothermal method. The properties of products were characterized by XRD, SEM, and UV-Vis DRS. Photocatalytic activity and stability of the resulting catalyst was evaluated by the degradation of methylene blue solution under visible and UV light. It was found that the degradation reaction accorded with first-order kinetic model. The composite catalyst had better photocatalytic activity than pure TiO2 in the UV and visible light. As a support and electron acceptor, graphene extended and enhanced the band edge absorption of TiO2 into the visible light region, so it could effectively enhance the photocatalytic activity of TiO2. At the same time magnetic Fe3O4 was added to improve its recyclability.
2016, 45(9):2449-2453.
Abstract:
Continuous SiC fibre reinforced SiC matrix composites (SiC/SiC) have been studied as materials for heat resistant and nuclear applications. Thermal stability is one of the key issues for SiC/SiC composites. In this study, 3D SiC/SiC composites are fabricated via the polymer impregnation and pyrolysis (PIP) process, and then heat treated at 1400~1800癈 in an inert atmosphere. The effect of heat treatment on microstructure and mechanical properties of the composites is investigated. The results indicate that the mechanical properties of the SiC/SiC composites are improved after heat treatment at 1400癈 mainly because the mechanical properties of the matrix are greatly improved due to crystallisation. With the increasing of heat treatment temperature, the properties of the composites are conversely decreased because of severe damage of the fibres and the matrix.
Continuous SiC fibre reinforced SiC matrix composites (SiC/SiC) have been studied as materials for heat resistant and nuclear applications. Thermal stability is one of the key issues for SiC/SiC composites. In this study, 3D SiC/SiC composites are fabricated via the polymer impregnation and pyrolysis (PIP) process, and then heat treated at 1400~1800癈 in an inert atmosphere. The effect of heat treatment on microstructure and mechanical properties of the composites is investigated. The results indicate that the mechanical properties of the SiC/SiC composites are improved after heat treatment at 1400癈 mainly because the mechanical properties of the matrix are greatly improved due to crystallisation. With the increasing of heat treatment temperature, the properties of the composites are conversely decreased because of severe damage of the fibres and the matrix.
2016, 45(9):2454-2457.
Abstract:
In this article, it studies the effect of TC4 - DT titanium alloy''s triple heat treatment on microstructur-e after thermal deformational at high temperature. It shows that the first temperature and the second temper-ature which in the triple heat treatment influenced the amount of alpha phase in alloy microstructure, m-oreover ,with the increasing of the first temperature and the second temperature, equiaxed alpha phase w-ould gradually decease. The tri-modal structure which results from 940℃?h WQ 920℃?h WQ 820℃?.5h AC, which consists of about 20% equiaxed alpha, 50%~60% basketweave formed by striature alpha and transformed beta matrix.Further more, there are smaller secondary strip alpha among first strip alpha in the basketweave which formed by striped alpha, the microstructure has a smaller aspect ratio and the alpha staggered cluster that refined the microstructure.
In this article, it studies the effect of TC4 - DT titanium alloy''s triple heat treatment on microstructur-e after thermal deformational at high temperature. It shows that the first temperature and the second temper-ature which in the triple heat treatment influenced the amount of alpha phase in alloy microstructure, m-oreover ,with the increasing of the first temperature and the second temperature, equiaxed alpha phase w-ould gradually decease. The tri-modal structure which results from 940℃?h WQ 920℃?h WQ 820℃?.5h AC, which consists of about 20% equiaxed alpha, 50%~60% basketweave formed by striature alpha and transformed beta matrix.Further more, there are smaller secondary strip alpha among first strip alpha in the basketweave which formed by striped alpha, the microstructure has a smaller aspect ratio and the alpha staggered cluster that refined the microstructure.
2016, 45(9):2458-2461.
Abstract:
This work was to introduce the voltage characteristics between the target and the vacuum chamber into positive-Ohm and anti-ohm and to study the influence rule on the uniformity of the coating and the membrane-binding intensity caused by the different target current controlled by impulse model. It was found that the target voltage increased with increasing target current density linearly when the target current density(Id) increased from 0.083A/cm2 to 0.175A/cm2. Meanwhile, the difference of coating thickness increased from 7.984μm to 14.011μm. However, the targer volttage decreased linearly with increasing target current density when the target current density increases from 0.175A/cm2 to 0.25A/cm2, and the difference of coating thickness decreased from 14.011μm to 10.077μm. The decreasing rate of film thickness changed from 97.38% (Id=0.083A/cm2) to 89.491% (Id=0.25 A/cm2). In addition, the film adhesion intensity rapidly increased with increasing target current density in the anti-ohm section. The above results show that the anti-ohm environment is conducive to improving the uniformity of the coating and the film adhesion intensity.
This work was to introduce the voltage characteristics between the target and the vacuum chamber into positive-Ohm and anti-ohm and to study the influence rule on the uniformity of the coating and the membrane-binding intensity caused by the different target current controlled by impulse model. It was found that the target voltage increased with increasing target current density linearly when the target current density(Id) increased from 0.083A/cm2 to 0.175A/cm2. Meanwhile, the difference of coating thickness increased from 7.984μm to 14.011μm. However, the targer volttage decreased linearly with increasing target current density when the target current density increases from 0.175A/cm2 to 0.25A/cm2, and the difference of coating thickness decreased from 14.011μm to 10.077μm. The decreasing rate of film thickness changed from 97.38% (Id=0.083A/cm2) to 89.491% (Id=0.25 A/cm2). In addition, the film adhesion intensity rapidly increased with increasing target current density in the anti-ohm section. The above results show that the anti-ohm environment is conducive to improving the uniformity of the coating and the film adhesion intensity.
2016, 45(9):2462-2465.
Abstract:
The nanocrystalline powders of Tb4O7-18%TiO2 (mass%)were prepared by high energy ball milling. Systematical investigations were carried out on microstructure、grain size、lattice distortion and morphology of the Tb4O7-18%TiO2 milled powders using Laser Particle Analyzer, X-ray diffraction, transmission electron microscopy and scanning electron microscopy. The experiment results showed that the nanocrystalline and nanoparticle powders were synthesized and microstructure was homogeneous.With the increase of ball milling time, the diffraction peaks of Tb4O7 phase broadened gradually and moved to large angles. Meanwhile, the diffraction peaks of TiO2 phase weakened gradually and disappeared after 4h milling. At the initial stage of ball milling, both particle size and crystalline size reduced significantly, then the size reduced slowly and tended to a stable value on the late stage of ball milling. After 96h milling, the average of particle size and crystalline size was 200nm and 95nm respectively. The lattice distortion was up to 1.35%. The reason of solid solution and nanocrystalline formation and the mechanism of microstructure evolution were also discussed in the present work.
The nanocrystalline powders of Tb4O7-18%TiO2 (mass%)were prepared by high energy ball milling. Systematical investigations were carried out on microstructure、grain size、lattice distortion and morphology of the Tb4O7-18%TiO2 milled powders using Laser Particle Analyzer, X-ray diffraction, transmission electron microscopy and scanning electron microscopy. The experiment results showed that the nanocrystalline and nanoparticle powders were synthesized and microstructure was homogeneous.With the increase of ball milling time, the diffraction peaks of Tb4O7 phase broadened gradually and moved to large angles. Meanwhile, the diffraction peaks of TiO2 phase weakened gradually and disappeared after 4h milling. At the initial stage of ball milling, both particle size and crystalline size reduced significantly, then the size reduced slowly and tended to a stable value on the late stage of ball milling. After 96h milling, the average of particle size and crystalline size was 200nm and 95nm respectively. The lattice distortion was up to 1.35%. The reason of solid solution and nanocrystalline formation and the mechanism of microstructure evolution were also discussed in the present work.
2016, 45(9):2466-2472.
Abstract:
Many of the problems associated with ingot metallurgy (IM), such as macrogregation, dendritic segregation, chemical inhomogeneity, and regions of varying microstructure can be solved by powder metallurgy, which is an important method to fabricate TiAl alloy. The research states of TiAl alloy in powder metallurgy at home and abroad were reviewed and the fabricatrion processes of TiAl powder were discussed, including prealloyed method, element powder method, mechanical alloying, and their sintering techniques. Their respective advantages and disadvantages, mechanical properties, and some improvement of TiAl powder metallurgy fabrication in future were finally pointed out.
Many of the problems associated with ingot metallurgy (IM), such as macrogregation, dendritic segregation, chemical inhomogeneity, and regions of varying microstructure can be solved by powder metallurgy, which is an important method to fabricate TiAl alloy. The research states of TiAl alloy in powder metallurgy at home and abroad were reviewed and the fabricatrion processes of TiAl powder were discussed, including prealloyed method, element powder method, mechanical alloying, and their sintering techniques. Their respective advantages and disadvantages, mechanical properties, and some improvement of TiAl powder metallurgy fabrication in future were finally pointed out.
