Volume 49,Issue 8,2020 Table of Contents
2020, 49(8):2549-2556.
DOI: 10.12442/j.issn.1002-185X.20190378
Abstract:
W/Zr based metallic glass composite is the novel generation of multifunctional energetic structural materials. The quasi-sealed chamber tests are applied in order to investigate the shock-induced reaction characteristics of porous W/Zr-based metallic glass composite at various impact velocities. The influences of the cover plate thickness on the overpressure are also tested. Thermochemical theory of temperature controlled shocked-induced chemical reactions is used to analyze the reaction characteristics of materials, as well as to identify the reaction parameters. The experimental and theoretical results show that the peak value of the quasi-static pressure and impact velocities of the fragments had positive correlation. The critical velocity to initiate the reaction is around 766 m/s. For certain velocity, there would be an optimal thickness of cover plate to maximize the overpressure behind the plate. However, the behind-plate overpressure effect is relatively mild while the cover plate thickness less than 8 mm. The critical shock pressure Pc to initiate the chemical reaction is 18.37 GPa. Relatively, the theoretical critical shock temperature Tc is calculated to be 3736.6 K. The theoretical results show that the reaction efficiency in the chamber are increased with increasing of shock pressure or temperature. The theoretical reaction efficiency reaches 61.5% when the shock pressure is 40 GPa. Therefore, the chemical reactions of the material are uncompleted in the experiments.
W/Zr based metallic glass composite is the novel generation of multifunctional energetic structural materials. The quasi-sealed chamber tests are applied in order to investigate the shock-induced reaction characteristics of porous W/Zr-based metallic glass composite at various impact velocities. The influences of the cover plate thickness on the overpressure are also tested. Thermochemical theory of temperature controlled shocked-induced chemical reactions is used to analyze the reaction characteristics of materials, as well as to identify the reaction parameters. The experimental and theoretical results show that the peak value of the quasi-static pressure and impact velocities of the fragments had positive correlation. The critical velocity to initiate the reaction is around 766 m/s. For certain velocity, there would be an optimal thickness of cover plate to maximize the overpressure behind the plate. However, the behind-plate overpressure effect is relatively mild while the cover plate thickness less than 8 mm. The critical shock pressure Pc to initiate the chemical reaction is 18.37 GPa. Relatively, the theoretical critical shock temperature Tc is calculated to be 3736.6 K. The theoretical results show that the reaction efficiency in the chamber are increased with increasing of shock pressure or temperature. The theoretical reaction efficiency reaches 61.5% when the shock pressure is 40 GPa. Therefore, the chemical reactions of the material are uncompleted in the experiments.
2020, 49(8):2557-2566.
DOI: 10.12442/j.issn.1002-185X.20190437
Abstract:
Microalloying is an important means of strengthening aluminum alloys. Sc has attracted much attention as a refiner for aluminum alloys. Experimental studies have shown that the addition of Zr and Sc in aluminum matrix can achieve better grain refinement, which is due to the formation of Al3(Zr, Sc) refining phase in the aluminum matrix. Based on the first-principles density functional theory, the energy and elastic properties of Al3(Zr, Sc) formed under different ratios of Sc/Zr are systematically studied. Besides these, the interfacial properties of Al3(Zr, Sc) with Al matrix are also investigated. The results show that when Sc/Zr is not higher than 1/3, the refining phase prefers to precipitate as Al3(Zr, Sc) based on its larger absolute value of formation enthalpy. And the addition of Sc element is also beneficial to the formation of the interface and the improvement of the interface bonding strength with better wetting effect, but the excessive increasing of Sc/Zr ratio higher than 1/3 shows no positive effect on the improvement of the interface performance. Additionally, the co-addition of Zr and Sc can improve the elastic properties and weaken the anisotropy of Al3Sc while greatly reducing the cost of the alloy.
Microalloying is an important means of strengthening aluminum alloys. Sc has attracted much attention as a refiner for aluminum alloys. Experimental studies have shown that the addition of Zr and Sc in aluminum matrix can achieve better grain refinement, which is due to the formation of Al3(Zr, Sc) refining phase in the aluminum matrix. Based on the first-principles density functional theory, the energy and elastic properties of Al3(Zr, Sc) formed under different ratios of Sc/Zr are systematically studied. Besides these, the interfacial properties of Al3(Zr, Sc) with Al matrix are also investigated. The results show that when Sc/Zr is not higher than 1/3, the refining phase prefers to precipitate as Al3(Zr, Sc) based on its larger absolute value of formation enthalpy. And the addition of Sc element is also beneficial to the formation of the interface and the improvement of the interface bonding strength with better wetting effect, but the excessive increasing of Sc/Zr ratio higher than 1/3 shows no positive effect on the improvement of the interface performance. Additionally, the co-addition of Zr and Sc can improve the elastic properties and weaken the anisotropy of Al3Sc while greatly reducing the cost of the alloy.
2020, 49(8):2567-2573.
DOI: 10.12442/j.issn.1002-185X.20200090
Abstract:
Discontinuous yielding phenomenon (DYP) and adiabatic temperature rising (ATR) effect have been investigated in this paper for Ti-5553 (Ti-5Al-5Mo-5V-3Cr) alloys manufactured by powder metallurgy (PM) and ingot metallurgy (IM) approaches based on hot compression testing conducted at the temperature range of 700 °C to 1100 °C and the strain rate range of 0.001 s-1 to 10 s-1. The results show that the magnitude of yield drop exhibits a positive correlation to strain rate but nearly a negative correlation to deformation temperature for both PM and IM alloys, and the occurrences of DYP in the alloys are elucidated by the dynamic theory. IM alloy shows a higher degree of yield drop than PM alloy at the same condition because of low initial dislocation density at as-cast state and the subsequently promoted newly-generated mobile dislocation from grain boundary. Strong positive correlation between ATR effect and strain rate but intensive negative correlation when it subjected to deformation temperature are uncovered for the two alloys. PM alloy shows a lower degree of ATR effect at the same processing condition than IM alloy as a result of its lower deformation resistance and higher deformation compatibility.
Discontinuous yielding phenomenon (DYP) and adiabatic temperature rising (ATR) effect have been investigated in this paper for Ti-5553 (Ti-5Al-5Mo-5V-3Cr) alloys manufactured by powder metallurgy (PM) and ingot metallurgy (IM) approaches based on hot compression testing conducted at the temperature range of 700 °C to 1100 °C and the strain rate range of 0.001 s-1 to 10 s-1. The results show that the magnitude of yield drop exhibits a positive correlation to strain rate but nearly a negative correlation to deformation temperature for both PM and IM alloys, and the occurrences of DYP in the alloys are elucidated by the dynamic theory. IM alloy shows a higher degree of yield drop than PM alloy at the same condition because of low initial dislocation density at as-cast state and the subsequently promoted newly-generated mobile dislocation from grain boundary. Strong positive correlation between ATR effect and strain rate but intensive negative correlation when it subjected to deformation temperature are uncovered for the two alloys. PM alloy shows a lower degree of ATR effect at the same processing condition than IM alloy as a result of its lower deformation resistance and higher deformation compatibility.
4 Microstructure and wear properties of Ni-based composite layer on aluminum alloy by laser cladding
2020, 49(8):2574-2582.
DOI: 10.12442/j.issn.1002-185X.20190406
Abstract:
The microstructure and wear properties of Ni-based composite coatings on aluminum alloy by laser cladding were investigated by means of SEM, EDS, a microhardness tester and friction tester. The results showed that the holes and cracks are relatively few in the layer when the scanning speeds of 5 mm/s.Many massive and continuous network Ni-Al intermetallic compounds formed at top of the cladding layer, and (Ni, Cr, Fe) XCy intermetallic compounds were formed at the middle of the cladding layer. The microstructure of the bottom cladding layer consisted of the columnar α-Al dendrite with obvious growth direction. The middle and the top of the cladding layer maintained a high microhardness value. The microhardness of the middle of layer had a maximum value of 820HV, which was more than 5 times that of the bottom of the cladding layer. The microhardness decreased sharply at the end of the middle of layer. The friction coefficients of the layer have a fluctuation with the different of load, and it decreased with the load increasing. The Ni-Al and (Ni, Cr, Fe) XCy intermetallic, forming and distributing on the top and middle of the cladding layer were the primary reason for the improvement of the microhardness and wear of the layer.
The microstructure and wear properties of Ni-based composite coatings on aluminum alloy by laser cladding were investigated by means of SEM, EDS, a microhardness tester and friction tester. The results showed that the holes and cracks are relatively few in the layer when the scanning speeds of 5 mm/s.Many massive and continuous network Ni-Al intermetallic compounds formed at top of the cladding layer, and (Ni, Cr, Fe) XCy intermetallic compounds were formed at the middle of the cladding layer. The microstructure of the bottom cladding layer consisted of the columnar α-Al dendrite with obvious growth direction. The middle and the top of the cladding layer maintained a high microhardness value. The microhardness of the middle of layer had a maximum value of 820HV, which was more than 5 times that of the bottom of the cladding layer. The microhardness decreased sharply at the end of the middle of layer. The friction coefficients of the layer have a fluctuation with the different of load, and it decreased with the load increasing. The Ni-Al and (Ni, Cr, Fe) XCy intermetallic, forming and distributing on the top and middle of the cladding layer were the primary reason for the improvement of the microhardness and wear of the layer.
2020, 49(8):2583-2590.
DOI: 10.12442/j.issn.1002-185X.20190430
Abstract:
In this work, the Chromium Aluminum Nitride (CrAlN) coatings were prepared on TC11 titanium alloy by arc ion plating. The effects of negative bias voltage on the micro-structure and mechanical properties, such as hardness and elastic modulus of the coatings were investigated by X-ray Diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX) and nano-indentation. A series of solid particle erosion experiments were also conducted to study the influence of bias voltages on the solid particle erosion resistance of CrAlN coatings. It has been found out that the preferred growth orientation of CrA1N coatings gradually varied from (200) to (111) crystal plane with the bias voltage changing from 0V to 200V. The hardness increased from 15.1 GPa to nearly 20 GPa. At the same time, the number of macro-particles and pinholes decreased with the surface gradually flattens, which improved the erosion resistance of the CrAlN coating. The CrAlN coating deposited at the bias voltage of 150V obtained minimum erosion rates which were 0.032 μm/g at 30° and 1.869μm/g at 90°, respectively. These results indicate that the CrAlN coating formed at an appropriate bias voltage can achieve an excellent solid particle erosion resistance.
In this work, the Chromium Aluminum Nitride (CrAlN) coatings were prepared on TC11 titanium alloy by arc ion plating. The effects of negative bias voltage on the micro-structure and mechanical properties, such as hardness and elastic modulus of the coatings were investigated by X-ray Diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX) and nano-indentation. A series of solid particle erosion experiments were also conducted to study the influence of bias voltages on the solid particle erosion resistance of CrAlN coatings. It has been found out that the preferred growth orientation of CrA1N coatings gradually varied from (200) to (111) crystal plane with the bias voltage changing from 0V to 200V. The hardness increased from 15.1 GPa to nearly 20 GPa. At the same time, the number of macro-particles and pinholes decreased with the surface gradually flattens, which improved the erosion resistance of the CrAlN coating. The CrAlN coating deposited at the bias voltage of 150V obtained minimum erosion rates which were 0.032 μm/g at 30° and 1.869μm/g at 90°, respectively. These results indicate that the CrAlN coating formed at an appropriate bias voltage can achieve an excellent solid particle erosion resistance.
2020, 49(8):2591-2598.
DOI: 10.12442/j.issn.1002-185X.20190435
Abstract:
The constitutive behavior and hot workability of as-cast Mg-8Y-6Gd-1Nd-0.17Zn magnesium alloy during the hot compression were investigated at elevated temperature (350 °C ~ 450 °C) and different strain rates (0.0001 s?1~0.1 s?1) under the ultimate compression ratio of 50%. The relationship among these deformation parameters of Mg-8Y-6Gd-1Nd-0.17Zn alloy could be adequately characterized by a sine hyperbolic equation. The experimental results show that both temperature and strain rate have important effects on the flow stress behavior of Mg-8Y-6Gd-1Nd-0.17Zn magnesium alloy, and the flow stress increased with lower temperature and higher strain rates. Typical dynamic recrystallization character is found in the true stress-strain curves when samples compressed above the temperature of 400 ℃. The activation energy (Q) and stress exponent (n) during deformation were 359.258 kJ/mol and 5.24, respectively. The average error (ARE) between experimental and calculated values is 3.37%. Then, the processing map was also established and analyzed based on dynamic material model. Considering the processing map and microstructures observation, the optimum hot-working parameters of the alloy were determined to be at a temperature of 400 °C ~ 450 °C and a strain rate of 0.0001 s-1 ~ 0.001 s-1.
The constitutive behavior and hot workability of as-cast Mg-8Y-6Gd-1Nd-0.17Zn magnesium alloy during the hot compression were investigated at elevated temperature (350 °C ~ 450 °C) and different strain rates (0.0001 s?1~0.1 s?1) under the ultimate compression ratio of 50%. The relationship among these deformation parameters of Mg-8Y-6Gd-1Nd-0.17Zn alloy could be adequately characterized by a sine hyperbolic equation. The experimental results show that both temperature and strain rate have important effects on the flow stress behavior of Mg-8Y-6Gd-1Nd-0.17Zn magnesium alloy, and the flow stress increased with lower temperature and higher strain rates. Typical dynamic recrystallization character is found in the true stress-strain curves when samples compressed above the temperature of 400 ℃. The activation energy (Q) and stress exponent (n) during deformation were 359.258 kJ/mol and 5.24, respectively. The average error (ARE) between experimental and calculated values is 3.37%. Then, the processing map was also established and analyzed based on dynamic material model. Considering the processing map and microstructures observation, the optimum hot-working parameters of the alloy were determined to be at a temperature of 400 °C ~ 450 °C and a strain rate of 0.0001 s-1 ~ 0.001 s-1.
2020, 49(8):2599-2606.
DOI: 10.12442/j.issn.1002-185X.E20190077
Abstract:
Magnesium and its alloys have great potential as absorbable biomaterials in clinical medicine, but their rapid corrosion might lead to implant failure. The purpose of this study was to prepare Poly-β-hydroxybutyrate (PHB) coating with drug on the surface of WE magnesium alloys using layer-by-layer self-assembly technique. The corrosion behavior of magnesium alloys with drug coating in simulated body fluid (SBF) was studied. The solution concentration and microstructure change during degradation process were observed. The effects of drug coating on tissue cells were investigated by cell migration, cytotoxicity and apoptosis. The results showed that the bioactive drug coating effectively reduced the corrosion rate of the samples in SBF, cytotoxicity, apoptosis, and promoted the migration of the cells.
Magnesium and its alloys have great potential as absorbable biomaterials in clinical medicine, but their rapid corrosion might lead to implant failure. The purpose of this study was to prepare Poly-β-hydroxybutyrate (PHB) coating with drug on the surface of WE magnesium alloys using layer-by-layer self-assembly technique. The corrosion behavior of magnesium alloys with drug coating in simulated body fluid (SBF) was studied. The solution concentration and microstructure change during degradation process were observed. The effects of drug coating on tissue cells were investigated by cell migration, cytotoxicity and apoptosis. The results showed that the bioactive drug coating effectively reduced the corrosion rate of the samples in SBF, cytotoxicity, apoptosis, and promoted the migration of the cells.
2020, 49(8):2607-2614.
DOI: 10.12442/j.issn.1002-185X.20190369
Abstract:
A study of the Ge substitution for Si in the Co64V16Si20 shape memory alloy was performed in this work. The microstructure, martensitic transformation, thermal cycle stability, microstructural evolution during thermal cycling of the Co64V16Si20-xGex (x = 2, 4, 6, 8, at. %) alloys were studied. When x = 2, the alloy is single D022 martensite. With increasing Ge content to 4 and 6 at. %, two-phase microstructure of (αCo) + D022 martensite was observed. When Ge content is up to 8 at. %, three-phase microstructure of (αCo) + D022 martensite + R phase was observed. The results show that the reversible martensitic transformation temperatures increased by nearly 50°C through adding Ge comparing with that of the Co64V16Si20 matrix alloy. Although the (αCo) or R phases precipitated during thermal cycling process, the reversible martensitic transformation peaks were observed during ten times thermal cycles. It reveals that the Ge addition can improve thermal cycling stability of Co-V-Si high-temperature shape memory alloy.
A study of the Ge substitution for Si in the Co64V16Si20 shape memory alloy was performed in this work. The microstructure, martensitic transformation, thermal cycle stability, microstructural evolution during thermal cycling of the Co64V16Si20-xGex (x = 2, 4, 6, 8, at. %) alloys were studied. When x = 2, the alloy is single D022 martensite. With increasing Ge content to 4 and 6 at. %, two-phase microstructure of (αCo) + D022 martensite was observed. When Ge content is up to 8 at. %, three-phase microstructure of (αCo) + D022 martensite + R phase was observed. The results show that the reversible martensitic transformation temperatures increased by nearly 50°C through adding Ge comparing with that of the Co64V16Si20 matrix alloy. Although the (αCo) or R phases precipitated during thermal cycling process, the reversible martensitic transformation peaks were observed during ten times thermal cycles. It reveals that the Ge addition can improve thermal cycling stability of Co-V-Si high-temperature shape memory alloy.
2020, 49(8):2615-2622.
DOI: 10.12442/j.issn.1002-185X.20190444
Abstract:
In this study, the modification of Al-Cu alloy by adding grain refiner combined with different heat treatments (superheat treatment and thermal rate treatment) is investigated. The phase composition, solidification microstructure and mechanical properties of Al-Cu-Ti alloys are analyzed. Moreover, the melt structure transformation of Al-Cu-Ti alloys after different melt heat treatments was studied by DSC. The experimental results showed that the thermal rate treatment greatly refined the grain of Al-Cu-Ti alloy and improved the mechanical properties. Through the analysis of thermodynamic phase transition, it was found that the latent heat of fusion of Al-Cu-Ti alloy after superheat treatment and thermal rate treatment became smaller due to the increase of interfacial energy, which leads to refine the microstructure of alloy to some extent.
In this study, the modification of Al-Cu alloy by adding grain refiner combined with different heat treatments (superheat treatment and thermal rate treatment) is investigated. The phase composition, solidification microstructure and mechanical properties of Al-Cu-Ti alloys are analyzed. Moreover, the melt structure transformation of Al-Cu-Ti alloys after different melt heat treatments was studied by DSC. The experimental results showed that the thermal rate treatment greatly refined the grain of Al-Cu-Ti alloy and improved the mechanical properties. Through the analysis of thermodynamic phase transition, it was found that the latent heat of fusion of Al-Cu-Ti alloy after superheat treatment and thermal rate treatment became smaller due to the increase of interfacial energy, which leads to refine the microstructure of alloy to some extent.
2020, 49(8):2623-2629.
DOI: 10.12442/j.issn.1002-185X.20190449
Abstract:
In this study, (CrMoTaNbVTi)N multi-element films are deposited by direct current magnetron sputtering CrMoTaNbV mosaic alloy target and pure Ti target. The composition, structure, mechanical properties and wear behavior of the films deposited at RN (N2/(Ar+N2)=0%, 10%, 20%, 30% and 40% are investigated. The (CrMoTaNbVTi)N films deposited at RN=0% and 10 % exhibit a simple BCC solid solution structure, whereas those deposited at RN=20%, 30 % and 40% show a simple FCC solid solution structure. With increasing of RN, the size of the surface particles is decreased and the columnar crystals are become denser. Meanwhile, the compressive stress, adhesive critical load (Lc), hardness and elastic modules are increased and reach a maximum value of -3.3 GPa, 352 mN, 25.6±1.2 GPa and 278.8±11.2 GPa at RN=40%, respectively. The wear rate of film deposited at RN =40% is decreased about ten times that the alloy film (RN=0%), indicated an excellent wear resistance.
In this study, (CrMoTaNbVTi)N multi-element films are deposited by direct current magnetron sputtering CrMoTaNbV mosaic alloy target and pure Ti target. The composition, structure, mechanical properties and wear behavior of the films deposited at RN (N2/(Ar+N2)=0%, 10%, 20%, 30% and 40% are investigated. The (CrMoTaNbVTi)N films deposited at RN=0% and 10 % exhibit a simple BCC solid solution structure, whereas those deposited at RN=20%, 30 % and 40% show a simple FCC solid solution structure. With increasing of RN, the size of the surface particles is decreased and the columnar crystals are become denser. Meanwhile, the compressive stress, adhesive critical load (Lc), hardness and elastic modules are increased and reach a maximum value of -3.3 GPa, 352 mN, 25.6±1.2 GPa and 278.8±11.2 GPa at RN=40%, respectively. The wear rate of film deposited at RN =40% is decreased about ten times that the alloy film (RN=0%), indicated an excellent wear resistance.
2020, 49(8):2630-2635.
DOI: 10.12442/j.issn.1002-185X.20190450
Abstract:
In order to prepare Monel alloy porous filtration material, Monel powder was used as raw material and K2CO3 as a space holder, the porous Monel samples with different porosity were fabricated by a sintering-dissolution process. The influence of space holder, compacting pressure and sintering temperature on the porosity, cell size and permeability of samples were investigated and discussed. The experimental results show that the porosity of samples is in range of 31%~46%, while the volume fraction of space holder between 20 vol.% and 40 vol.%. While compacting pressure in the range of 200~400 MPa, the porosity, cell size and permeability of samples decrease with compacting pressure increasing; while sintering temperature in the range of 850~1000 ℃, the cell size and permeability increase first, then slowly decrease with the sintering temperature increasing, the peak value at 950 ℃.While the volume fraction of space holder is 30%, compacting pressure 200 MPa, sintering temperature 950 ℃, the porosity, maximum cell size and permeability of the porous Monel sample are 37%, 21.5μm, 76.77 m3/(h?kPa?m2), respectively.
In order to prepare Monel alloy porous filtration material, Monel powder was used as raw material and K2CO3 as a space holder, the porous Monel samples with different porosity were fabricated by a sintering-dissolution process. The influence of space holder, compacting pressure and sintering temperature on the porosity, cell size and permeability of samples were investigated and discussed. The experimental results show that the porosity of samples is in range of 31%~46%, while the volume fraction of space holder between 20 vol.% and 40 vol.%. While compacting pressure in the range of 200~400 MPa, the porosity, cell size and permeability of samples decrease with compacting pressure increasing; while sintering temperature in the range of 850~1000 ℃, the cell size and permeability increase first, then slowly decrease with the sintering temperature increasing, the peak value at 950 ℃.While the volume fraction of space holder is 30%, compacting pressure 200 MPa, sintering temperature 950 ℃, the porosity, maximum cell size and permeability of the porous Monel sample are 37%, 21.5μm, 76.77 m3/(h?kPa?m2), respectively.
2020, 49(8):2636-2643.
DOI: 10.12442/j.issn.1002-185X.20190440
Abstract:
Dissolution between Zinc, Aluminum and Zn-Al alloys are common in soldering, hot-dipping and coating, for example, when preparing galvalumed steel and Galfan-coated steel products. For manufacturers, they need to ensure that Zn wet Al well in order to endow the prepainted material with excellent corrosion resistance. This work aims at finding some key factors whichSdetermineSthe degree of dissolution in different Zn/Al binary systems. The consideration of investigating kinetic factors in dissolutive wetting process is brought into molecular dynamic (MD) simulation. Different atomic scale wetting process are performed with LAMMPS, simulation performances include Zn-5 wt.% Al, Zn-6.8 wt.% Al liquid models spreading on Al(100), Al(110), Al(111) solid substrates. By changing the temperature, elevating the percentage ratio of Zn, Al, it is found that Zn-Al binary dissolution can be pushed ahead by elevating temperature, or raising Al concentration in the liquid phase. Effects of temperature and atom percentages on dissolved volume and diffusion coefficient are also demonstrated by analyzing dissolutive parameters.
Dissolution between Zinc, Aluminum and Zn-Al alloys are common in soldering, hot-dipping and coating, for example, when preparing galvalumed steel and Galfan-coated steel products. For manufacturers, they need to ensure that Zn wet Al well in order to endow the prepainted material with excellent corrosion resistance. This work aims at finding some key factors whichSdetermineSthe degree of dissolution in different Zn/Al binary systems. The consideration of investigating kinetic factors in dissolutive wetting process is brought into molecular dynamic (MD) simulation. Different atomic scale wetting process are performed with LAMMPS, simulation performances include Zn-5 wt.% Al, Zn-6.8 wt.% Al liquid models spreading on Al(100), Al(110), Al(111) solid substrates. By changing the temperature, elevating the percentage ratio of Zn, Al, it is found that Zn-Al binary dissolution can be pushed ahead by elevating temperature, or raising Al concentration in the liquid phase. Effects of temperature and atom percentages on dissolved volume and diffusion coefficient are also demonstrated by analyzing dissolutive parameters.
2020, 49(8):2644-2648.
DOI: 10.12442/j.issn.1002-185X.20190452
Abstract:
The microstructures and mechanical properties of Mg-4.5Gd-2.6Nd-0.5Zn-0.5Zr new casting magnesium alloy were researched.It is found that the microstructure of the as-cast experimental alloy is composed of near equiaxed α-Mg, Mg12(Nd,Gd) and Mg3Gd phases. After optimizing the heat treatment parameters, the value of YS , UTS and A reach 205MP, 320MP and 4.0% at room temperature 145MPa,245MPa and 18.5% at 250℃.The strengthening principle of the alloy is studied in this paper. The fracture surfaces of Mg-4.5Gd-2.6Nd-0.5Zn-0.5Zr alloy was brittle fracture at room temperature tensile with and ductile fracture at 250℃ tensile with lots of dimples and tear ridges.
The microstructures and mechanical properties of Mg-4.5Gd-2.6Nd-0.5Zn-0.5Zr new casting magnesium alloy were researched.It is found that the microstructure of the as-cast experimental alloy is composed of near equiaxed α-Mg, Mg12(Nd,Gd) and Mg3Gd phases. After optimizing the heat treatment parameters, the value of YS , UTS and A reach 205MP, 320MP and 4.0% at room temperature 145MPa,245MPa and 18.5% at 250℃.The strengthening principle of the alloy is studied in this paper. The fracture surfaces of Mg-4.5Gd-2.6Nd-0.5Zn-0.5Zr alloy was brittle fracture at room temperature tensile with and ductile fracture at 250℃ tensile with lots of dimples and tear ridges.
2020, 49(8):2649-2657.
DOI: 10.12442/j.issn.1002-185X.20190462
Abstract:
In this work, multilayered niobium/zirconium (Nb/Zr) composites with different initial Zr thicknesses were processed by accumulative roll bonding (ARB). Microstructure, texture and mechanical property of the composites at different ARB cycles were systematically investigated. The results showed that the heterophase interfaces were well bonded and no intermetallic compounds formed. With increasing ARB cycles, shear bands formed cutting through the multiple metal layers. Necking and fracture of the Zr layers occurred preferentially in the composites with an initial Zr thickness of 1 mm. Dislocation cell structures were predominated in Nb layers, while a mixture consisting of grains with dense dislocations and dynamically recovered grains with a low dislocation density were predominant in Zr layers. In addition, texture evolution in Nb layers changed with varied initial thickness of Zr. When the initial Zr thickness was 1 mm, strong Cube orientation appeared in Nb layers. However, when the initial Zr thickness was 2 mm, rotated-Cube was the dominant texture in Nb layers with increasing ARB cycles. The textures in Zr layers were similar in the composites with different initial Zr thicknesses. After the first ARB cycle, the {10-13}<3032> orientation was the dominant texture. With increasing ARB cycles, this orientation was slightly weakened and minor {11-20} fiber texture developed. With the increase of the ARB cycles both yield strength and ultimate tensile strength increased monotonically for the composites with different initial Zr thicknesses. However, the maximum elongation firstly decreased and then increased with increasing ARB cycles. After the third ARB cycle, the maximum elongation reached 14.2% and 16.5% for the composites with the initial Zr thicknesses of 1 and 2 mm, respectively. The high strength and good plasticity of the composites originated from the significant grain refinement in the individual metals and the recovered Zr grains during ARB, together with the featured texture evolution in the Zr layers.
In this work, multilayered niobium/zirconium (Nb/Zr) composites with different initial Zr thicknesses were processed by accumulative roll bonding (ARB). Microstructure, texture and mechanical property of the composites at different ARB cycles were systematically investigated. The results showed that the heterophase interfaces were well bonded and no intermetallic compounds formed. With increasing ARB cycles, shear bands formed cutting through the multiple metal layers. Necking and fracture of the Zr layers occurred preferentially in the composites with an initial Zr thickness of 1 mm. Dislocation cell structures were predominated in Nb layers, while a mixture consisting of grains with dense dislocations and dynamically recovered grains with a low dislocation density were predominant in Zr layers. In addition, texture evolution in Nb layers changed with varied initial thickness of Zr. When the initial Zr thickness was 1 mm, strong Cube orientation appeared in Nb layers. However, when the initial Zr thickness was 2 mm, rotated-Cube was the dominant texture in Nb layers with increasing ARB cycles. The textures in Zr layers were similar in the composites with different initial Zr thicknesses. After the first ARB cycle, the {10-13}<3032> orientation was the dominant texture. With increasing ARB cycles, this orientation was slightly weakened and minor {11-20} fiber texture developed. With the increase of the ARB cycles both yield strength and ultimate tensile strength increased monotonically for the composites with different initial Zr thicknesses. However, the maximum elongation firstly decreased and then increased with increasing ARB cycles. After the third ARB cycle, the maximum elongation reached 14.2% and 16.5% for the composites with the initial Zr thicknesses of 1 and 2 mm, respectively. The high strength and good plasticity of the composites originated from the significant grain refinement in the individual metals and the recovered Zr grains during ARB, together with the featured texture evolution in the Zr layers.
2020, 49(8):2658-2664.
DOI: 10.12442/j.issn.1002-185X.20190484
Abstract:
ZrCo0.8M0.2 (M = Co, Cu, Cr, Mn, and Al) alloys were prepared via the arc melting method in an argon atmosphere. The major phase of the alloys arranges itself in a ZrCo structure. The partial addition of Cr, Mn, and Al leads to the formation of a secondary phase. The Zr2Co and ZrCr2 phases, the Zr2Co and ZrMn2 phases, and the Zr3Co and Zr6CoAl2 phases are formed upon Cr, Mn, and Al substitution, respectively. The cell volume of the alloys decreases upon Cr and Mn substitution, and increases upon Cu and Al replacement. Moreover, the hydrogen storage capacity of the alloys decreases when Cu, Cr, Mn, or Al are present in the alloy. However, the plateau of the desorption pressure remains nearly unchanged for all the alloys. The ZrCo alloy activation performance drastically improves upon Cr and Mn addition at room temperature, while the disproportionation reaction rate decreases, due to the decrease in its driving force. A modification of the 8f2 and 8e sites results in a change in the disproportionation driving force in all the investigated alloys.
ZrCo0.8M0.2 (M = Co, Cu, Cr, Mn, and Al) alloys were prepared via the arc melting method in an argon atmosphere. The major phase of the alloys arranges itself in a ZrCo structure. The partial addition of Cr, Mn, and Al leads to the formation of a secondary phase. The Zr2Co and ZrCr2 phases, the Zr2Co and ZrMn2 phases, and the Zr3Co and Zr6CoAl2 phases are formed upon Cr, Mn, and Al substitution, respectively. The cell volume of the alloys decreases upon Cr and Mn substitution, and increases upon Cu and Al replacement. Moreover, the hydrogen storage capacity of the alloys decreases when Cu, Cr, Mn, or Al are present in the alloy. However, the plateau of the desorption pressure remains nearly unchanged for all the alloys. The ZrCo alloy activation performance drastically improves upon Cr and Mn addition at room temperature, while the disproportionation reaction rate decreases, due to the decrease in its driving force. A modification of the 8f2 and 8e sites results in a change in the disproportionation driving force in all the investigated alloys.
2020, 49(8):2665-2673.
DOI: 10.12442/j.issn.1002-185X.20190506
Abstract:
The microstructures, mechanical properties and eutectic silicon growth mechanism of A356 aluminum alloy treated by novel Al-5Ti-1B-1RE and Al-10Sr master alloy with individual or composite refinement and modification were studied. The results showed that under individual addition condition, the Al-5Ti-1B-1RE master alloy had a significant refinement effect on α-Al phase in A356 aluminum alloy and the tensile strength σb, yield strength σs and Vickers hardness of the alloy were significantly improved. Al-10Sr master alloy had a strong modification effect on eutectic silicon, and the elongation δ of the alloy was obviously improved. Under composite addition condition, the shape and size of α-Al phase in A356 aluminum alloy became more uniform and finer, and the grain boundaries were clearer. The eutectic silicon phases were almost converted into dispersed, fine fibrous shape, and the lamellar eutectic silicon almost completely disappeared. The length of the eutectic silicon was reduced from the as-cast state of 40-60 μm to 1-2 μm, achieving a complete modification effect. Its mechanical properties were much higher than those of the as-cast, any single refiner and modifier treated A356 aluminum alloy. The growth mode of eutectic Si in the unrefined and unmodified A356 aluminum alloy was typical small-plane step growth. The eutectic silicon with composite refinement and modification was mainly grown by the twin plane re-entrant edge mechanism, and the growth characteristics of the facet were gradually weakened until disappeared.
The microstructures, mechanical properties and eutectic silicon growth mechanism of A356 aluminum alloy treated by novel Al-5Ti-1B-1RE and Al-10Sr master alloy with individual or composite refinement and modification were studied. The results showed that under individual addition condition, the Al-5Ti-1B-1RE master alloy had a significant refinement effect on α-Al phase in A356 aluminum alloy and the tensile strength σb, yield strength σs and Vickers hardness of the alloy were significantly improved. Al-10Sr master alloy had a strong modification effect on eutectic silicon, and the elongation δ of the alloy was obviously improved. Under composite addition condition, the shape and size of α-Al phase in A356 aluminum alloy became more uniform and finer, and the grain boundaries were clearer. The eutectic silicon phases were almost converted into dispersed, fine fibrous shape, and the lamellar eutectic silicon almost completely disappeared. The length of the eutectic silicon was reduced from the as-cast state of 40-60 μm to 1-2 μm, achieving a complete modification effect. Its mechanical properties were much higher than those of the as-cast, any single refiner and modifier treated A356 aluminum alloy. The growth mode of eutectic Si in the unrefined and unmodified A356 aluminum alloy was typical small-plane step growth. The eutectic silicon with composite refinement and modification was mainly grown by the twin plane re-entrant edge mechanism, and the growth characteristics of the facet were gradually weakened until disappeared.
2020, 49(8):2674-2682.
DOI: 10.12442/j.issn.1002-185X.E20190096
Abstract:
To further improve the numerical calculation of variable-polarity plasma arc (VPPA)–metal inert gas (MIG) welding, the heating behavior of VPPA-MIG welding was analyzed using a high-speed camera. A variable-polarity finite element model was developed and optimized for the numerical analysis of the thermal process in VPPA–MIG welding. This model incorporated the heating mode of the VPPA with its periodic variations. Moreover, in order to more accurately express the hybrid welding conditions, the coupling interaction between the two heat sources in the electrode-negative and electrode-positive phases was taken into account. Experiments were conducted to obtain weld dimensions to verify the predicted results. This simulation results showed that the fusion width of the VPPA–MIG welded joint was smaller than that of the MIG welded joint, and the penetration ability of hybrid welding was also stronger. There was a conspicuous difference in the form of heat input and thermal process between VPPA-MIG and MIG welding, which directly affected the microstructure and mechanical properties of the welds. Comparing the microstructures of the VPPA-MIG and the traditional MIG welds, it was found that the swing of the hybrid arc in VPPA-MIG welding can facilitate the production of fine aluminum grains in thick aluminum alloy plates. Consequently, the hardness and tensile properties of the hybrid welded joints were significantly higher than those produced under MIG traditional welding.
To further improve the numerical calculation of variable-polarity plasma arc (VPPA)–metal inert gas (MIG) welding, the heating behavior of VPPA-MIG welding was analyzed using a high-speed camera. A variable-polarity finite element model was developed and optimized for the numerical analysis of the thermal process in VPPA–MIG welding. This model incorporated the heating mode of the VPPA with its periodic variations. Moreover, in order to more accurately express the hybrid welding conditions, the coupling interaction between the two heat sources in the electrode-negative and electrode-positive phases was taken into account. Experiments were conducted to obtain weld dimensions to verify the predicted results. This simulation results showed that the fusion width of the VPPA–MIG welded joint was smaller than that of the MIG welded joint, and the penetration ability of hybrid welding was also stronger. There was a conspicuous difference in the form of heat input and thermal process between VPPA-MIG and MIG welding, which directly affected the microstructure and mechanical properties of the welds. Comparing the microstructures of the VPPA-MIG and the traditional MIG welds, it was found that the swing of the hybrid arc in VPPA-MIG welding can facilitate the production of fine aluminum grains in thick aluminum alloy plates. Consequently, the hardness and tensile properties of the hybrid welded joints were significantly higher than those produced under MIG traditional welding.
2020, 49(8):2683-2690.
DOI: 10.12442/j.issn.1002-185X.20190495
Abstract:
Since the individual use of C/C composite is limited, the joining with other materials becomes a key technology in its application. Brazing is one kind of joining method that has been studied most, maturest and most widely used for C/C composite in recent decades. Nonetheless, there are still many deficiencies in the brazing of C/C composites because of the characteristic of the composite itself, which cannot meet the needs of specific conditions. The current brazing situation of C/C composite is reviewed in this paper. The difficulties of joining C/C composites and metals, the bonding systems that had been studied, and the joining mechanisms are included. The brazing methods and basic joining mechanisms of C/C composite are summarized emphatically, mainly including: direct brazing with active filler materials, using micro-nano particles reinforced or stress buffer layer added composite filler materials, surface modifying of C/C composite, and changing the interface structure, and so on. The current research breakthroughs and remaining problems are analyzed. The feasibility measures of brazing C/C composite are analyzed and summarized to provide basic reference for subsequent research on the brazing of C/C composites and the improvement of joint performance.
Since the individual use of C/C composite is limited, the joining with other materials becomes a key technology in its application. Brazing is one kind of joining method that has been studied most, maturest and most widely used for C/C composite in recent decades. Nonetheless, there are still many deficiencies in the brazing of C/C composites because of the characteristic of the composite itself, which cannot meet the needs of specific conditions. The current brazing situation of C/C composite is reviewed in this paper. The difficulties of joining C/C composites and metals, the bonding systems that had been studied, and the joining mechanisms are included. The brazing methods and basic joining mechanisms of C/C composite are summarized emphatically, mainly including: direct brazing with active filler materials, using micro-nano particles reinforced or stress buffer layer added composite filler materials, surface modifying of C/C composite, and changing the interface structure, and so on. The current research breakthroughs and remaining problems are analyzed. The feasibility measures of brazing C/C composite are analyzed and summarized to provide basic reference for subsequent research on the brazing of C/C composites and the improvement of joint performance.
2020, 49(8):2691-2696.
DOI: 10.12442/j.issn.1002-185X.20190625
Abstract:
Tungsten-chromium alloy (W-Cr alloy) is a primary candidate for plasma-facing materials (PFM) in future fusion devices because of its excellent properties. The knowledge of the interaction between solute Cr atoms and vacancy in W-Cr alloys is the key to understand the mechanism of the evolution of radiation damage. In this work the occupation of solute Cr atoms, the interaction between solute Cr atoms and vacancy, and the effect of the solute Cr concentration were studied by first-principles calculation. We found that the solute Cr atoms prefers to occupy the substitutional position with formation energy of ~0.3eV. The point defects induced by radiation will facilitate the segregation of the solute Cr atoms. The formation energy of solute Cr increases linearly with increasing of the concentration of solute Cr, indicating a strong segregation. It was also found that there exists a very weak attractive interaction between the solute Cr atoms and vacancy, and the interaction tends to be stronger when the concentration of the solute Cr increases. These results are important for understanding the long-term micro-structural evolution of materials under irradiation.
Tungsten-chromium alloy (W-Cr alloy) is a primary candidate for plasma-facing materials (PFM) in future fusion devices because of its excellent properties. The knowledge of the interaction between solute Cr atoms and vacancy in W-Cr alloys is the key to understand the mechanism of the evolution of radiation damage. In this work the occupation of solute Cr atoms, the interaction between solute Cr atoms and vacancy, and the effect of the solute Cr concentration were studied by first-principles calculation. We found that the solute Cr atoms prefers to occupy the substitutional position with formation energy of ~0.3eV. The point defects induced by radiation will facilitate the segregation of the solute Cr atoms. The formation energy of solute Cr increases linearly with increasing of the concentration of solute Cr, indicating a strong segregation. It was also found that there exists a very weak attractive interaction between the solute Cr atoms and vacancy, and the interaction tends to be stronger when the concentration of the solute Cr increases. These results are important for understanding the long-term micro-structural evolution of materials under irradiation.
2020, 49(8):2697-2705.
DOI: 10.12442/j.issn.1002-185X.20200202
Abstract:
Firstly, the fatigue life prediction model of shot-peened 25CrMo axle steel was established by using BP neural network. Then, genetic algorithm (GA) was used to optimize the prediction accuracy of BP neural network. In addition, radial basis function neural network (RBF) was used for modeling and analysis, and compared with the prediction results of the above two models. The results showed that GA-BP had higher prediction accuracy than BP and RBF neural network, and the average prediction accuracy of training set and test set were 91.5% and 85.4% respectively. Then, sensitivity analysis was carried out based on the connection weight matrix of GA-BP neural network model and Garson equation, so as to further quantify the relative influence proportion of the input influencing factors on the fatigue life of shot-peened 25CrMo axle steel. Finally, GA-BP neural network was used to predict the relaxation behavior of compressive residual stress on the surface of shot-peened 25CrMo axle steel. The results showed that the average prediction error of the test set was only 3.4%, indicating that the network prediction performance was good. In conclusion, this paper used neural network modeling to analyze the fatigue performance and compressive residual stress relaxation behavior of shot-peened 25CrMo axle steel, which significantly reduced the cost of traditional fatigue test and ensured high accuracy.
Firstly, the fatigue life prediction model of shot-peened 25CrMo axle steel was established by using BP neural network. Then, genetic algorithm (GA) was used to optimize the prediction accuracy of BP neural network. In addition, radial basis function neural network (RBF) was used for modeling and analysis, and compared with the prediction results of the above two models. The results showed that GA-BP had higher prediction accuracy than BP and RBF neural network, and the average prediction accuracy of training set and test set were 91.5% and 85.4% respectively. Then, sensitivity analysis was carried out based on the connection weight matrix of GA-BP neural network model and Garson equation, so as to further quantify the relative influence proportion of the input influencing factors on the fatigue life of shot-peened 25CrMo axle steel. Finally, GA-BP neural network was used to predict the relaxation behavior of compressive residual stress on the surface of shot-peened 25CrMo axle steel. The results showed that the average prediction error of the test set was only 3.4%, indicating that the network prediction performance was good. In conclusion, this paper used neural network modeling to analyze the fatigue performance and compressive residual stress relaxation behavior of shot-peened 25CrMo axle steel, which significantly reduced the cost of traditional fatigue test and ensured high accuracy.
2020, 49(8):2706-2711.
DOI: 10.12442/j.issn.1002-185X.20190566
Abstract:
The fatigue properties and fracture mechanism of TC21 titanium alloy notched specimens in two kinds of corrosive environments (tank water, 3.5% NaCl aqueous solution) and room temperature air environment were studied. The fatigue properties of the smooth samples were compared in a room temperature air environment. The results show that when the fatigue life of both samples reaches 5×105 cycles, the cyclic stress value of the notched sample is 52.7% lower than that of the smooth sample; As the stress decreases in the same environment, the fatigue life of the alloy increases; Under the same stress conditions, the alloy has the lowest fatigue life under salt water environment, and the tank water storage environment is next. The fatigue life of TC21 alloy is the highest under room temperature air; When the stress is low, the difference is more significant. In the corrosive environment, the ions in the solution react with the metal atoms electrochemically, which accelerates the initiation and expansion of the crack. The concentration of ions in the 3.5% NaCl aqueous solution is larger and the electrochemical reaction is more intense.
The fatigue properties and fracture mechanism of TC21 titanium alloy notched specimens in two kinds of corrosive environments (tank water, 3.5% NaCl aqueous solution) and room temperature air environment were studied. The fatigue properties of the smooth samples were compared in a room temperature air environment. The results show that when the fatigue life of both samples reaches 5×105 cycles, the cyclic stress value of the notched sample is 52.7% lower than that of the smooth sample; As the stress decreases in the same environment, the fatigue life of the alloy increases; Under the same stress conditions, the alloy has the lowest fatigue life under salt water environment, and the tank water storage environment is next. The fatigue life of TC21 alloy is the highest under room temperature air; When the stress is low, the difference is more significant. In the corrosive environment, the ions in the solution react with the metal atoms electrochemically, which accelerates the initiation and expansion of the crack. The concentration of ions in the 3.5% NaCl aqueous solution is larger and the electrochemical reaction is more intense.
2020, 49(8):2712-2717.
DOI: 10.12442/j.issn.1002-185X.20190581
Abstract:
In order to optimize the subsequent rolling process, the Gleeble-3800 thermal simulator was used to test the isothermal constant strain rate compression of the as-rolled 254SMo super austenitic stainless steel. The thermal deformation behavior and microstructure evolution of 254SMo in the temperature range of 900-1100℃ under the strain rates of 0.005-5 s-1 was studied. The results show that the peak stress reduces with the deformation temperature increasing and the strain rate decreasing, the single peak characteristic of flow curves become obvious, which indicates that 254SMo is prone to dynamic recrystallization under high temperature and low strain rate;three forms of Arrhenius The prediction accuracy comparison of the three forms of Arrhenius constitutive equations shows that the exponential form has the highest accuracy, the correlation coefficient is 97.496%, and the deformation activation energy is 546 kJ/mol.
In order to optimize the subsequent rolling process, the Gleeble-3800 thermal simulator was used to test the isothermal constant strain rate compression of the as-rolled 254SMo super austenitic stainless steel. The thermal deformation behavior and microstructure evolution of 254SMo in the temperature range of 900-1100℃ under the strain rates of 0.005-5 s-1 was studied. The results show that the peak stress reduces with the deformation temperature increasing and the strain rate decreasing, the single peak characteristic of flow curves become obvious, which indicates that 254SMo is prone to dynamic recrystallization under high temperature and low strain rate;three forms of Arrhenius The prediction accuracy comparison of the three forms of Arrhenius constitutive equations shows that the exponential form has the highest accuracy, the correlation coefficient is 97.496%, and the deformation activation energy is 546 kJ/mol.
2020, 49(8):2718-2723.
DOI: 10.12442/j.issn.1002-185X.20190582
Abstract:
Hastelloy is widely used in the aerospace industry for its excellent performance. Hastelloy X surface is modified by high-current pulsed electron beam (HCPEB) bombardment and its microstructure is analyzed and discussed. The sample after corrosion was observed by a scanning electron microscope (SEM), and the unetched sample was observed by electron backscattered diffraction (EBSD). The results show: The grain boundary of the untreated sample was corroded from the SEM micro-morphology. After the bombardment, there was a remelted layer of about 2μm on the surface of the sample. The sample possessed good corrosion resistance and granular carbides appeared at the grain boundary; It can be seen that the grain size of the sample was the smallest in 5 times of bombardment, and the grain orientation of the sample is better in 5 and 10 times of bombardment, mostly [101] and [110]. Experiments show that high-current pulsed electron beam bombardment can cause the remelted layer on the surface of Hastelloy X and change its grain size and crystal orientation.
Hastelloy is widely used in the aerospace industry for its excellent performance. Hastelloy X surface is modified by high-current pulsed electron beam (HCPEB) bombardment and its microstructure is analyzed and discussed. The sample after corrosion was observed by a scanning electron microscope (SEM), and the unetched sample was observed by electron backscattered diffraction (EBSD). The results show: The grain boundary of the untreated sample was corroded from the SEM micro-morphology. After the bombardment, there was a remelted layer of about 2μm on the surface of the sample. The sample possessed good corrosion resistance and granular carbides appeared at the grain boundary; It can be seen that the grain size of the sample was the smallest in 5 times of bombardment, and the grain orientation of the sample is better in 5 and 10 times of bombardment, mostly [101] and [110]. Experiments show that high-current pulsed electron beam bombardment can cause the remelted layer on the surface of Hastelloy X and change its grain size and crystal orientation.
2020, 49(8):2724-2729.
DOI: 10.12442/j.issn.1002-185X.20190590
Abstract:
In this paper, the immersion method was used to study the dissolution behavior of Cu/Sn system with or without ultrasound at 523K, 553K and 573K.SIt is found that the dissolution rate of Cu wire in molten Sn under ultrasonic action is 6.79~24.106 times without ultrasonic effect.SCombined with the method of finite element simulation, this phenomenon is explained from the perspectives of ultrasonic cavitation effect, micro jet effect and acoustic streaming.SThe results show that the cavitation bubble collapse will produce a high temperature of about 1500K at the Cu/Sn interface, which not only increases the solid solubility limit of Cu in the Sn liquid, but also melts the Cu in the "micro-point" region; The micro jet effect can reduce the thickness of the intermetallic compound (IMC) layer and change its morphology, and increase the channel of atomic diffusion; the acoustic streaming will produce a stirring effect, and the solute Cu atom at the front of the Cu/Sn solid-liquid interface is continuously pushed to the Sn liquid.SInternally, the solute atom solubility is always lower than the saturated solubility.SCombining the above factors, the dissolved amount and dissolution rate of solid Cu in the Sn solution are significantly increased under the action of ultrasonic waves.
In this paper, the immersion method was used to study the dissolution behavior of Cu/Sn system with or without ultrasound at 523K, 553K and 573K.SIt is found that the dissolution rate of Cu wire in molten Sn under ultrasonic action is 6.79~24.106 times without ultrasonic effect.SCombined with the method of finite element simulation, this phenomenon is explained from the perspectives of ultrasonic cavitation effect, micro jet effect and acoustic streaming.SThe results show that the cavitation bubble collapse will produce a high temperature of about 1500K at the Cu/Sn interface, which not only increases the solid solubility limit of Cu in the Sn liquid, but also melts the Cu in the "micro-point" region; The micro jet effect can reduce the thickness of the intermetallic compound (IMC) layer and change its morphology, and increase the channel of atomic diffusion; the acoustic streaming will produce a stirring effect, and the solute Cu atom at the front of the Cu/Sn solid-liquid interface is continuously pushed to the Sn liquid.SInternally, the solute atom solubility is always lower than the saturated solubility.SCombining the above factors, the dissolved amount and dissolution rate of solid Cu in the Sn solution are significantly increased under the action of ultrasonic waves.
2020, 49(8):2730-2737.
DOI: 10.12442/j.issn.1002-185X.20190607
Abstract:
In order to evaluate the damage of microstructure and the deterioration of mechanical properties after long-term service of single crystal turbine blades. This paper selects the high pressure turbine blades of gas turbines that have served 25000h and 50000h respectively. The material in the middle of the blade body was selected for metallographic structure quantitative analysis and microhardness test. The γ" phase size, γ" phase volume fraction, secondary γ" phase size, γ matrix channel width with different service time and at different positions were measured. And the Vickers hardness were tested. The results show that the γ" phase size of different positions in the same leaf is different; The γ" phase size at the leading edge and the trailing edge which working at high temperature is larger than Pressure side and Suction side;however, the γ" phase volume fraction is slightly smaller than the other two; the γ" phase size of serviced 50,000h blade is greater than the serviced 25000h γ" phase size at the same position; the volume fraction is in the opposite order; secondary γ" phase appears in some positions, the width of the base channel is significantly increase at the secondary γ" phase precipitation position; it is verified by 1100 °C/2h-air+cooling/furnace cooling experiment that the secondary γ" phase precipitation is related to the working high temperature and cooling way; the TCP phase which contains many W, Re elements appears in the abnormally high temperature region of the trailing edge, and the phase is identified as the μ phase; the microhardness of the leading edge and trailing edge position of different service time decrease significantly, and the decrease of microhardness is positively correlated with the increase of γ" phase size and decline of volume fraction.; therefore, the γ" phase size and volume fraction can be used as the evaluation parameters of the tissue damage of the material.
In order to evaluate the damage of microstructure and the deterioration of mechanical properties after long-term service of single crystal turbine blades. This paper selects the high pressure turbine blades of gas turbines that have served 25000h and 50000h respectively. The material in the middle of the blade body was selected for metallographic structure quantitative analysis and microhardness test. The γ" phase size, γ" phase volume fraction, secondary γ" phase size, γ matrix channel width with different service time and at different positions were measured. And the Vickers hardness were tested. The results show that the γ" phase size of different positions in the same leaf is different; The γ" phase size at the leading edge and the trailing edge which working at high temperature is larger than Pressure side and Suction side;however, the γ" phase volume fraction is slightly smaller than the other two; the γ" phase size of serviced 50,000h blade is greater than the serviced 25000h γ" phase size at the same position; the volume fraction is in the opposite order; secondary γ" phase appears in some positions, the width of the base channel is significantly increase at the secondary γ" phase precipitation position; it is verified by 1100 °C/2h-air+cooling/furnace cooling experiment that the secondary γ" phase precipitation is related to the working high temperature and cooling way; the TCP phase which contains many W, Re elements appears in the abnormally high temperature region of the trailing edge, and the phase is identified as the μ phase; the microhardness of the leading edge and trailing edge position of different service time decrease significantly, and the decrease of microhardness is positively correlated with the increase of γ" phase size and decline of volume fraction.; therefore, the γ" phase size and volume fraction can be used as the evaluation parameters of the tissue damage of the material.
2020, 49(8):2738-2745.
DOI: 10.12442/j.issn.1002-185X.20190623
Abstract:
The solubility curves of Er in Al-Er alloys were investigated by means of first principles calculations based on the density functional theory. The solution energies of Er atoms in these Al-Er alloys were calculated by using the “Frozen core” approximation and “Standard potential” approximation for the 4f electrons, respectively. The calculated results showed that the solution energies of hR20, cP4 and hP8-Al3Er were -1.003 and -0.767 eV/Er atom, -0.989 and -0.787 eV/Er atom, -0.967 and -0.713 eV/Er atom, respectively, obtained from the two approximations. The lattice dynamics calculation showed that the excess enthalpies of hR20, cP4 and hP8-Al3Er were 3.301, 3.226 and 3.309 kB/Er atom. The simulated solubility curves were obtained by combining the lattice dynamics values and the weighted average of the solution energy values. The calculated solubility curves of cP4-Al3Er were consistent with the experimental values, which indicates that the 4f electrons play a very important role. In addition, the solubility curve of cP4-Al3Er was very close to that of the hR20-Al3Er, but lower than that of hP8-Al3Er at the same temperature. The chemical driving forces corresponding to the solubility curves of hR20 and cP4-Al3Er were also close to each other, but larger than that of the hP8-Al3Er. Due to the smaller interfacial energy in Al matrix of cP4-Al3Er than that of hR20-Al3Er, it could be deduced that the cP4-Al3Er precipitation was the first in priority order, which was consistent with the experimental observations.
The solubility curves of Er in Al-Er alloys were investigated by means of first principles calculations based on the density functional theory. The solution energies of Er atoms in these Al-Er alloys were calculated by using the “Frozen core” approximation and “Standard potential” approximation for the 4f electrons, respectively. The calculated results showed that the solution energies of hR20, cP4 and hP8-Al3Er were -1.003 and -0.767 eV/Er atom, -0.989 and -0.787 eV/Er atom, -0.967 and -0.713 eV/Er atom, respectively, obtained from the two approximations. The lattice dynamics calculation showed that the excess enthalpies of hR20, cP4 and hP8-Al3Er were 3.301, 3.226 and 3.309 kB/Er atom. The simulated solubility curves were obtained by combining the lattice dynamics values and the weighted average of the solution energy values. The calculated solubility curves of cP4-Al3Er were consistent with the experimental values, which indicates that the 4f electrons play a very important role. In addition, the solubility curve of cP4-Al3Er was very close to that of the hR20-Al3Er, but lower than that of hP8-Al3Er at the same temperature. The chemical driving forces corresponding to the solubility curves of hR20 and cP4-Al3Er were also close to each other, but larger than that of the hP8-Al3Er. Due to the smaller interfacial energy in Al matrix of cP4-Al3Er than that of hR20-Al3Er, it could be deduced that the cP4-Al3Er precipitation was the first in priority order, which was consistent with the experimental observations.
2020, 49(8):2746-2753.
DOI: 10.12442/j.issn.1002-185X.20190630
Abstract:
In this work, first-principles density functional theory was applied to investigate the effect of Co-doping on the stability of γ′ -Ni3Al. The optimal parameters were determined by comparing the simulations and experimental results. Based on the plane wave pseudopotential method, the crystal structure, total energy, formation enthalpy, cohesive energy, electronic density of states and electron density difference of γ′-Ni3Al phases were calculated, which was used to analyze the stability and bonding characteristics of the crystal structure. The calculation results indicate that the structure of unit cell is more stable after the Al atom is replaced by Co atom. In the range from -10 eV to Fermi energy, the orbital hybridization among Co (Ni) 3d electrons and Al s, p electrons occurs, and the charge transfer among atoms increases obviously, which enhances the covalent bonding in doped γ′ phases. When the Co atom replaces the Al atom instead of the Ni atom, the number of bonding electrons increases at low Fermi energy, and surrounding valence electron interactions are enhanced, so the stability γ′ -Ni3Al phase will be improved. Finally, the simulation results were confirmed by long time aging heat treatment experiments of Inconel 718 alloy.
In this work, first-principles density functional theory was applied to investigate the effect of Co-doping on the stability of γ′ -Ni3Al. The optimal parameters were determined by comparing the simulations and experimental results. Based on the plane wave pseudopotential method, the crystal structure, total energy, formation enthalpy, cohesive energy, electronic density of states and electron density difference of γ′-Ni3Al phases were calculated, which was used to analyze the stability and bonding characteristics of the crystal structure. The calculation results indicate that the structure of unit cell is more stable after the Al atom is replaced by Co atom. In the range from -10 eV to Fermi energy, the orbital hybridization among Co (Ni) 3d electrons and Al s, p electrons occurs, and the charge transfer among atoms increases obviously, which enhances the covalent bonding in doped γ′ phases. When the Co atom replaces the Al atom instead of the Ni atom, the number of bonding electrons increases at low Fermi energy, and surrounding valence electron interactions are enhanced, so the stability γ′ -Ni3Al phase will be improved. Finally, the simulation results were confirmed by long time aging heat treatment experiments of Inconel 718 alloy.
2020, 49(8):2754-2759.
DOI: 10.12442/j.issn.1002-185X.20190633
Abstract:
Nd-Fe-based rare earth transition compounds are composed of many different types, and most of the structures of the compounds can be converted into each other under certain conditions. The transition between the phases existing in the preparation of the rare earth permanent magnet material has a great influence on the magnetic properties of the permanent magnet material. However, the previous studies have less analysis of the phase transition process in Nd-Fe compounds. In this paper, NdFe12 ingots were prepared and EDS spectra were used to analyze the phase transformation process in the ingot during cooling, and the melt quenching method was used. The NdFe12 ribbon was prepared and the composition of the phase in the ribbon was analyzed by X-ray diffraction. It has been found that the phase composition in the ingot and the ribbon is affected by the cooling rate. Controlling the phase composition and phase transformation process of NdFe12 compounds is of great significance for the preparation of NdFe12Nx low rare earth new generation permanent magnet materials.
Nd-Fe-based rare earth transition compounds are composed of many different types, and most of the structures of the compounds can be converted into each other under certain conditions. The transition between the phases existing in the preparation of the rare earth permanent magnet material has a great influence on the magnetic properties of the permanent magnet material. However, the previous studies have less analysis of the phase transition process in Nd-Fe compounds. In this paper, NdFe12 ingots were prepared and EDS spectra were used to analyze the phase transformation process in the ingot during cooling, and the melt quenching method was used. The NdFe12 ribbon was prepared and the composition of the phase in the ribbon was analyzed by X-ray diffraction. It has been found that the phase composition in the ingot and the ribbon is affected by the cooling rate. Controlling the phase composition and phase transformation process of NdFe12 compounds is of great significance for the preparation of NdFe12Nx low rare earth new generation permanent magnet materials.
Yuhua Hou
,
Xiaotong Yan
,
Cheng Chen
,
Xiaokun Fu
,
Xianjin Ge
,
Wei Li
,
Youlin Huang
,
Junming Luo
,
Pang Zaisheng
,
Zhong Zhenchen
2020, 49(8):2760-2764.
DOI: 10.12442/j.issn.1002-185X.20190639
Abstract:
Using Al powder as diffused source, the influence of grain boundary diffused processes on the microstructure and magnetic properties were investigated. It is found that the optimum magnetic properties including the coercivity of 1131 kA/m and the maximum energy product of 252 kJ/m3 can be achieved, increasing by 16% and 9.6%, respectively, meanwhile, the temperature stability is also improved. Microstructural investigation reveals that Al is mainly distributed in the intergranular RE-rich phase, and the morphology of RE-rich phase changes from large block to thin layer. Smoother and more straight interface can be obtained, which can restrain the nucleation of anti-magnetization domain, reducing the demagnetization field. In addition, the Al in the intergranular phase is beneficial in elevating the corrosion potential, and the decreased corrosion current density should be attributed to the changes of RE-rich phase distribution.
Using Al powder as diffused source, the influence of grain boundary diffused processes on the microstructure and magnetic properties were investigated. It is found that the optimum magnetic properties including the coercivity of 1131 kA/m and the maximum energy product of 252 kJ/m3 can be achieved, increasing by 16% and 9.6%, respectively, meanwhile, the temperature stability is also improved. Microstructural investigation reveals that Al is mainly distributed in the intergranular RE-rich phase, and the morphology of RE-rich phase changes from large block to thin layer. Smoother and more straight interface can be obtained, which can restrain the nucleation of anti-magnetization domain, reducing the demagnetization field. In addition, the Al in the intergranular phase is beneficial in elevating the corrosion potential, and the decreased corrosion current density should be attributed to the changes of RE-rich phase distribution.
2020, 49(8):2765-2772.
DOI: 10.12442/j.issn.1002-185X.20190662
Abstract:
Electrochemical test methods such as cathodic scanning voltammetry and chronoamperometry were used in the acidic system to study the influence mechanism of sodium dodecyl sulfate (SDS) on the electrodeposition process of copper. The results show that the addition of SDS causes the deposition potential to shift positively and reduces the cathodic polarization. When the SDS concentration is lower than the critical micelle concentration of 1g/L, the nucleation relaxation time of copper is prolonged and the nucleation rate is decreased. When the concentration of SDS is higher than the critical micelle concentration, SDS spherical micelles are formed, and the nucleation relaxation time of copper is reduced and the nucleation rate is accelerated. The copper nucleation process conforms to the three-dimensional nucleation/growth mechanism of Scharitker?Hill. When the SDS is 1g/L, in the low overpotential zone of -0.2V, the copper crystals proceed in a progressive nucleation mode at -0.23-0.28V. In the high overpotential zone, the copper crystals proceed in a progressive nucleation mode. When the SDS is 0.5 g/L, copper conforms to the progressive nucleation in the potential region of -0.2V to -0.28V.
Electrochemical test methods such as cathodic scanning voltammetry and chronoamperometry were used in the acidic system to study the influence mechanism of sodium dodecyl sulfate (SDS) on the electrodeposition process of copper. The results show that the addition of SDS causes the deposition potential to shift positively and reduces the cathodic polarization. When the SDS concentration is lower than the critical micelle concentration of 1g/L, the nucleation relaxation time of copper is prolonged and the nucleation rate is decreased. When the concentration of SDS is higher than the critical micelle concentration, SDS spherical micelles are formed, and the nucleation relaxation time of copper is reduced and the nucleation rate is accelerated. The copper nucleation process conforms to the three-dimensional nucleation/growth mechanism of Scharitker?Hill. When the SDS is 1g/L, in the low overpotential zone of -0.2V, the copper crystals proceed in a progressive nucleation mode at -0.23-0.28V. In the high overpotential zone, the copper crystals proceed in a progressive nucleation mode. When the SDS is 0.5 g/L, copper conforms to the progressive nucleation in the potential region of -0.2V to -0.28V.
2020, 49(8):2773-2778.
DOI: 10.12442/j.issn.1002-185X.20190586
Abstract:
The FFC process is an important method to replace the traditional titanium preparation methods that high pollution and high energy consumption. However, low efficiency and long electrolysis time hinder the development of the FFC process. Therefore, in order to improve the deoxidation rate, the effect of cathode thickness on the deoxidation rate was studies. Meanwhile, the quantum mechanics method was used to study the conduction mechanism of TiO2. Based on the experimental and calculated results, a multi-layer cathode was proposed to improve the deoxidation rate. The titanium sponge with 3 500-4 000 ppm oxygen content was obtained after 6 h electrolysis. The electrolysis speed is effectively improved when compared to the tradional cathode. Another benefit of multi-layer cathode is to slove the problem of contradiction between deoxidation rate and production of FFC process.
The FFC process is an important method to replace the traditional titanium preparation methods that high pollution and high energy consumption. However, low efficiency and long electrolysis time hinder the development of the FFC process. Therefore, in order to improve the deoxidation rate, the effect of cathode thickness on the deoxidation rate was studies. Meanwhile, the quantum mechanics method was used to study the conduction mechanism of TiO2. Based on the experimental and calculated results, a multi-layer cathode was proposed to improve the deoxidation rate. The titanium sponge with 3 500-4 000 ppm oxygen content was obtained after 6 h electrolysis. The electrolysis speed is effectively improved when compared to the tradional cathode. Another benefit of multi-layer cathode is to slove the problem of contradiction between deoxidation rate and production of FFC process.
2020, 49(8):2779-2785.
DOI: 10.12442/j.issn.1002-185X.20191096
Abstract:
Single-phase Mg2Si1-xSnx crystal was successfully directionally solidified from the melt. Thermoelectric properties were tested for 1.5at%Bi-doped crystals with different Sn contents, and electronic transport properties were predicted by the first-principle calculation. At x=0.625, tested Seebeck coefficient and power factor is -247μVK-1 and 5.7mWm-1K-2, respectively, because the band structure of Mg2Si0.375Sn0.625 is converged. This result is consistent with the calculated values, and the power factor enhanced 25%. The predicted and tested results of ZT maximum are 1.3 and 1.16 at T=700K, respectively. In the medium temperature range of 550K-800K, the predicted and tested ZT values can keep above 0.9. Power factor optimization is an effective way to improve the thermoelectric properties of Mg2Si1-xSnx crystal. In addition, the performance deterioration of thermoelectric devices induced by nano-sized grain growth at high service temperature can be avoided.
Single-phase Mg2Si1-xSnx crystal was successfully directionally solidified from the melt. Thermoelectric properties were tested for 1.5at%Bi-doped crystals with different Sn contents, and electronic transport properties were predicted by the first-principle calculation. At x=0.625, tested Seebeck coefficient and power factor is -247μVK-1 and 5.7mWm-1K-2, respectively, because the band structure of Mg2Si0.375Sn0.625 is converged. This result is consistent with the calculated values, and the power factor enhanced 25%. The predicted and tested results of ZT maximum are 1.3 and 1.16 at T=700K, respectively. In the medium temperature range of 550K-800K, the predicted and tested ZT values can keep above 0.9. Power factor optimization is an effective way to improve the thermoelectric properties of Mg2Si1-xSnx crystal. In addition, the performance deterioration of thermoelectric devices induced by nano-sized grain growth at high service temperature can be avoided.
33 Modeling, simulation and experimental study of porous bone scaffold by using Selective laser melting
2020, 49(8):2786-2790.
DOI: 10.12442/j.issn.1002-185X.20190575
Abstract:
Metal 3D printing technology has become one of the most potential and promising industrial manufacturing technologies. Through laser selective sintering (SLS) technology, reasonable sintering parameters are selected to sinter metal powder. Complex three-dimensional models of porous scaffolds with different pore sizes were established, and porous scaffold stress and strain distribution were simulated by using finite element analysis. The optimized three-dimensional model of porous scaffolds was obtained. The theoretical basis for subsequent experimental analysis was established. Then 316L stainless steel porous scaffolds were prepared by SLS technology. The porous scaffolds were tested by post-heat treatment, compression and metallographic experiments. The mechanical properties, hardness tests and surface microstructures of the specimens were analyzed. Through the simulation analysis, the optimized pore size of the porous scaffold was obtained, and a porous scaffold which is more suitable for the weight bearing of the human bone defect site was obtained, which can guide the subsequent research. It was found that the strength and modulus of elasticity of 300μm porous scaffolds were higher than those of natural bone. Metal parts with porous structure ensured the biomechanical properties of bone prostheses and had good mechanical properties.
Metal 3D printing technology has become one of the most potential and promising industrial manufacturing technologies. Through laser selective sintering (SLS) technology, reasonable sintering parameters are selected to sinter metal powder. Complex three-dimensional models of porous scaffolds with different pore sizes were established, and porous scaffold stress and strain distribution were simulated by using finite element analysis. The optimized three-dimensional model of porous scaffolds was obtained. The theoretical basis for subsequent experimental analysis was established. Then 316L stainless steel porous scaffolds were prepared by SLS technology. The porous scaffolds were tested by post-heat treatment, compression and metallographic experiments. The mechanical properties, hardness tests and surface microstructures of the specimens were analyzed. Through the simulation analysis, the optimized pore size of the porous scaffold was obtained, and a porous scaffold which is more suitable for the weight bearing of the human bone defect site was obtained, which can guide the subsequent research. It was found that the strength and modulus of elasticity of 300μm porous scaffolds were higher than those of natural bone. Metal parts with porous structure ensured the biomechanical properties of bone prostheses and had good mechanical properties.
2020, 49(8):2791-2799.
DOI: 10.12442/j.issn.1002-185X.20190584
Abstract:
Inconel 738 alloy is a precipitation strengthened nickel-base superalloy mainly used in today’s heavy-duty gas turbines for hot gas path components such as blades, vanes and heat shields due to its possesses an exceptional combination of high-temperature strength and oxidation resistance. However, the high Al and Ti contents are highly hot cracking susceptibility during selective laser melting (SLM) forming, easily formed the microcracks, leading to the result in premature failure of the alloy during service, causing major accidents. In this work, the crack formation mechanism, microstructure anisotropy and their effect on mechanical property by SLM forming was investigated by means of SEM, EBSD, DSC, XRD and Universal Tensile Testing Machine. The results show that austenite in Inconel 738 alloy mainly precipitates phase and MC carbide during SLM forming, where the solidification process is L→ → +MC→ + +MC. The low melting point eutectic structure liquefies due to reheat to form crack source, and microcracks are formed under residual tensile stress. Meanwhile, the residual stress around the microcrack distributes uniformly, and the grain misorientation near the initiation of microcrack is higher than that without microcrack zone. In addition, the direction of microcrack on XY plane is perpendicular to the direction of laser scanning, and the direction of microcrack on XZ plane is parallel to Z axis. The preferred orientation of Inconel 738 alloy formed by SLM is related to the maximum temperature gradient. The mechanical properties of SLM formed specimens along XY and XZ directions are higher than those of precision casting specimens, and the strength in XZ direction is higher than that in XY direction, while the elongation in XZ direction is lower than that in XY direction.
Inconel 738 alloy is a precipitation strengthened nickel-base superalloy mainly used in today’s heavy-duty gas turbines for hot gas path components such as blades, vanes and heat shields due to its possesses an exceptional combination of high-temperature strength and oxidation resistance. However, the high Al and Ti contents are highly hot cracking susceptibility during selective laser melting (SLM) forming, easily formed the microcracks, leading to the result in premature failure of the alloy during service, causing major accidents. In this work, the crack formation mechanism, microstructure anisotropy and their effect on mechanical property by SLM forming was investigated by means of SEM, EBSD, DSC, XRD and Universal Tensile Testing Machine. The results show that austenite in Inconel 738 alloy mainly precipitates phase and MC carbide during SLM forming, where the solidification process is L→ → +MC→ + +MC. The low melting point eutectic structure liquefies due to reheat to form crack source, and microcracks are formed under residual tensile stress. Meanwhile, the residual stress around the microcrack distributes uniformly, and the grain misorientation near the initiation of microcrack is higher than that without microcrack zone. In addition, the direction of microcrack on XY plane is perpendicular to the direction of laser scanning, and the direction of microcrack on XZ plane is parallel to Z axis. The preferred orientation of Inconel 738 alloy formed by SLM is related to the maximum temperature gradient. The mechanical properties of SLM formed specimens along XY and XZ directions are higher than those of precision casting specimens, and the strength in XZ direction is higher than that in XY direction, while the elongation in XZ direction is lower than that in XY direction.
2020, 49(8):2800-2806.
DOI: 10.12442/j.issn.1002-185X.20190592
Abstract:
In order to explore the effect of rare earth (RE) element on the strength and toughness of steel, mixed La+Ce elements have been incorporated into Nb-alloyed steel at the content of La+Ce: 36ppm, La+Ce: 44ppm, La+Ce: 51ppm and reference sample (no RE). The mechical properties and microstructure of the materials were analyzed by using tensile test, low temperature impact test and SEM observation coupled with EDS. The results indicated that the reduction of Nb and the increase of the La+Ce influenced the mechanical performance of Fe-0.07%C-0.025%Nb-x%(La+Ce) component system, with the?increase of RE, dimples were enlarged and deepened, and the yield strength and tensile strength of Nb-alloyed structural steels tended to increase. meanwhile the elongation did not show a significant reduction with the increase of RE content. These results demonstrates that the mixed La+Ce rare earth compound is promising to replace the Nb element to improve the mechanical performance of the product. The comparison of fracture morphology and absorbed impact energy of different kinds of hot rolled steel belt show that the low-temperature impact toughness maximized at -40℃ and -60℃ when the content of La+Ce rare earth compounds was 36ppm, due to the fact that inclusions were modified to form precipitated LaCeO2S particles which delayed the crack growth.
In order to explore the effect of rare earth (RE) element on the strength and toughness of steel, mixed La+Ce elements have been incorporated into Nb-alloyed steel at the content of La+Ce: 36ppm, La+Ce: 44ppm, La+Ce: 51ppm and reference sample (no RE). The mechical properties and microstructure of the materials were analyzed by using tensile test, low temperature impact test and SEM observation coupled with EDS. The results indicated that the reduction of Nb and the increase of the La+Ce influenced the mechanical performance of Fe-0.07%C-0.025%Nb-x%(La+Ce) component system, with the?increase of RE, dimples were enlarged and deepened, and the yield strength and tensile strength of Nb-alloyed structural steels tended to increase. meanwhile the elongation did not show a significant reduction with the increase of RE content. These results demonstrates that the mixed La+Ce rare earth compound is promising to replace the Nb element to improve the mechanical performance of the product. The comparison of fracture morphology and absorbed impact energy of different kinds of hot rolled steel belt show that the low-temperature impact toughness maximized at -40℃ and -60℃ when the content of La+Ce rare earth compounds was 36ppm, due to the fact that inclusions were modified to form precipitated LaCeO2S particles which delayed the crack growth.
TANG Jinliang
,
YAN Xiaofeng
,
WANG Zhongmin
,
WANG Feng
,
YAO Qingrong
,
DENG Jianqiu
,
ZHOU Huaiying
2020, 49(8):2807-2812.
DOI: 10.12442/j.issn.1002-185X.20190602
Abstract:
Doping is an effective way to eliminate the problem of hydrogen brittleness of Nb metal. Phase structure, hydride formation enthalpy, hydrogen diffusion coefficient (DH) and mechanical properties of W-doped Nb100-xWx (x=2,5,8,10,16) alloys have been investigated by XRD, SEM, PCT analysis, electrochemical method and three-point bending test respectively. The results indicated that melting-prepared Nb100-xWx samples are Nb-based solid solutions with bcc structure. W-doping will induce the lattice distortion and shrink, the distortion behavior is more obvious with the increase of W-doping content. Non-equilibrium transformation microstructure is observed in these Nb100-xWx samples, which presents dendritic morphology with W-poor region dispersed in W-rich matrix. Dense and refined dendritic morphology is observed obviously in Nb100-xWx (x=10, 16) samples. W-doping results in the increase of the value of hydride-formation enthalpy, and benefits H-release of corresponding hydride. Higher H-diffusion coefficient (DH=1.66×10-9 cm2·s-1) is obtained in Nb84W16 sample, which is about 1.8 times that of Nb98W2 sample. W-doping also improve the anti-hydrogen embrittlement capacity, Nb84W16 sample has the largest maximum load (78.4N) and maximum displacement (0.83mm), which is about 1.9 and 1.8 times that of Nb98W2 sample respectively, indicating that the improvement of mechanical properties is related to its microstructure.
Doping is an effective way to eliminate the problem of hydrogen brittleness of Nb metal. Phase structure, hydride formation enthalpy, hydrogen diffusion coefficient (DH) and mechanical properties of W-doped Nb100-xWx (x=2,5,8,10,16) alloys have been investigated by XRD, SEM, PCT analysis, electrochemical method and three-point bending test respectively. The results indicated that melting-prepared Nb100-xWx samples are Nb-based solid solutions with bcc structure. W-doping will induce the lattice distortion and shrink, the distortion behavior is more obvious with the increase of W-doping content. Non-equilibrium transformation microstructure is observed in these Nb100-xWx samples, which presents dendritic morphology with W-poor region dispersed in W-rich matrix. Dense and refined dendritic morphology is observed obviously in Nb100-xWx (x=10, 16) samples. W-doping results in the increase of the value of hydride-formation enthalpy, and benefits H-release of corresponding hydride. Higher H-diffusion coefficient (DH=1.66×10-9 cm2·s-1) is obtained in Nb84W16 sample, which is about 1.8 times that of Nb98W2 sample. W-doping also improve the anti-hydrogen embrittlement capacity, Nb84W16 sample has the largest maximum load (78.4N) and maximum displacement (0.83mm), which is about 1.9 and 1.8 times that of Nb98W2 sample respectively, indicating that the improvement of mechanical properties is related to its microstructure.
2020, 49(8):2813-2819.
DOI: 10.12442/j.issn.1002-185X.20190610
Abstract:
Ti6Al4V/Inconel718 functionally graded materials were prepared by laser additive manufacturing technology. The composition, phase composition, microstructure and microhardness of the gradient materials were studied. The research shows that a series of phase transitions occur along the composition gradient direction: α+β→α+β+Ti2Ni→β+TiNi→γ, and the transition layer is mainly composed of TiNi and Ti2Ni and binary phases such as Ti-Cr and Ti-Fe. The composition of the mixture; the microstructure from the bottom to the top of the material has undergone a transformation from Widmanst?tten α-laths to fine dendritic structure; the microhardness test of the deposited structure shows that the transition layer with the higher Ti2Ni phase area fraction is the hardest. This study found a maximum of 823 HV.
Ti6Al4V/Inconel718 functionally graded materials were prepared by laser additive manufacturing technology. The composition, phase composition, microstructure and microhardness of the gradient materials were studied. The research shows that a series of phase transitions occur along the composition gradient direction: α+β→α+β+Ti2Ni→β+TiNi→γ, and the transition layer is mainly composed of TiNi and Ti2Ni and binary phases such as Ti-Cr and Ti-Fe. The composition of the mixture; the microstructure from the bottom to the top of the material has undergone a transformation from Widmanst?tten α-laths to fine dendritic structure; the microhardness test of the deposited structure shows that the transition layer with the higher Ti2Ni phase area fraction is the hardest. This study found a maximum of 823 HV.
2020, 49(8):2820-2824.
DOI: 10.12442/j.issn.1002-185X.20190617
Abstract:
The new TiZrHfNbSc refractory high-entropy alloy was prepared by vacuum arc melting with argon shield. The microstructure were studied by XRD, SEM and DSC, the hardness and mechanical properties were measured by vickers microhardness tester and micro-control electronic universal testing machine. The results showed that the TiZrHfNbSc refractory high-entropy alloy had a single disordered BCC solid solution structure with the lattice parameter a=3.443? .The alloy density was 7.16 g/cm3 and the Vickers microhardness was 380. The alloy had high compression yield strength(σ0. 2=650MPa) and the compression deformation rate is more than 60%.The strengthening mechanism of the alloy is solid solution strengthening.
The new TiZrHfNbSc refractory high-entropy alloy was prepared by vacuum arc melting with argon shield. The microstructure were studied by XRD, SEM and DSC, the hardness and mechanical properties were measured by vickers microhardness tester and micro-control electronic universal testing machine. The results showed that the TiZrHfNbSc refractory high-entropy alloy had a single disordered BCC solid solution structure with the lattice parameter a=3.443? .The alloy density was 7.16 g/cm3 and the Vickers microhardness was 380. The alloy had high compression yield strength(σ0. 2=650MPa) and the compression deformation rate is more than 60%.The strengthening mechanism of the alloy is solid solution strengthening.
WANG Qingyang
,
ZHANG Kerong
,
XIONG Xiaomei
,
YANG Fang
,
XI Dan
,
WANG Dayou
,
LI Chengshan
,
YAN Guo
,
FENG Yong
,
ZHANG Pingxiang
2020, 49(8):2825-2829.
DOI: 10.12442/j.issn.1002-185X.20190619
Abstract:
The filament fractures or wire breaks in multi core MgB2 wire was appeared frequent while using the traditional in-situ powder in tube (PIT) method with Cu as the sheath material. For this problem, the 37 filament MgB2 long wires with the diameter of 1 mm, sheathed with higher strength Monel alloys (Monel 400) is fabricated with compound fabrication process including rotary swage, drawing, rolling and middle annealing heat treatment。Microstracture showed that the sub component including MgB2 filament and NbCu replacement is uniformly distributed and the Nb diffusion barrier is no breaking points. The mean diameter in MgB2 filament is only 80 μm in final wires. The yield strength is around 759 MPa. for the as-drawn wire and 248 MPa for the sintered wire. The critical current density (Jc) and engineering current density (Je) are arrived 2.31×105 A.cm-2 and 3.16×104A.cm-2 at 4.2 K、4 T respectively.
The filament fractures or wire breaks in multi core MgB2 wire was appeared frequent while using the traditional in-situ powder in tube (PIT) method with Cu as the sheath material. For this problem, the 37 filament MgB2 long wires with the diameter of 1 mm, sheathed with higher strength Monel alloys (Monel 400) is fabricated with compound fabrication process including rotary swage, drawing, rolling and middle annealing heat treatment。Microstracture showed that the sub component including MgB2 filament and NbCu replacement is uniformly distributed and the Nb diffusion barrier is no breaking points. The mean diameter in MgB2 filament is only 80 μm in final wires. The yield strength is around 759 MPa. for the as-drawn wire and 248 MPa for the sintered wire. The critical current density (Jc) and engineering current density (Je) are arrived 2.31×105 A.cm-2 and 3.16×104A.cm-2 at 4.2 K、4 T respectively.
2020, 49(8):2830-2838.
DOI: 10.12442/j.issn.1002-185X.20190621
Abstract:
A high corrosion resistant and active protection composite coating designed combining Layered Double Hydroxides (LDH) layer and Micro-arc Oxidation (MAO) to further improve the anti-corrosion of Mg alloy. In this paper, MgCr-LDHs/MAO composite coating prepared through in-situ growing LDH layer including NO3- on the surface of MAO coating. The morphology、composition and microstructure of MgCr-LDHs/MAO composite coating were characterized by XRD, XPS, FT-IR, SEM, besides the interaction of LDH and original MAO coating was investigated. The corrosion properties of MgCr-LDHs/MAO coating was tested through immersion in 3.5wt%NaCl solution and electrochemical experiments. The results show that: (1) the LDHs forms a dense sheet like layer on the original MAO coating surface, which can effectively cover the inherent defects of MAO coating, and LDH layer is preferentially formed in the pores of original MAO coating. (2) LDHs don"t damage the original MAO coating during the growth process, besides the adhesion of LDH layer and MAO layer are strong and stable. (3) The composite coating showed the most superior corrosion protection, since MgCr-LDH layer growing on the original MAO coating can hinder the penetration of chloride ions and effectively adsorb a large number of NO3? to exchange Cl- in corrosion solution.
A high corrosion resistant and active protection composite coating designed combining Layered Double Hydroxides (LDH) layer and Micro-arc Oxidation (MAO) to further improve the anti-corrosion of Mg alloy. In this paper, MgCr-LDHs/MAO composite coating prepared through in-situ growing LDH layer including NO3- on the surface of MAO coating. The morphology、composition and microstructure of MgCr-LDHs/MAO composite coating were characterized by XRD, XPS, FT-IR, SEM, besides the interaction of LDH and original MAO coating was investigated. The corrosion properties of MgCr-LDHs/MAO coating was tested through immersion in 3.5wt%NaCl solution and electrochemical experiments. The results show that: (1) the LDHs forms a dense sheet like layer on the original MAO coating surface, which can effectively cover the inherent defects of MAO coating, and LDH layer is preferentially formed in the pores of original MAO coating. (2) LDHs don"t damage the original MAO coating during the growth process, besides the adhesion of LDH layer and MAO layer are strong and stable. (3) The composite coating showed the most superior corrosion protection, since MgCr-LDH layer growing on the original MAO coating can hinder the penetration of chloride ions and effectively adsorb a large number of NO3? to exchange Cl- in corrosion solution.
2020, 49(8):2839-2844.
DOI: 10.12442/j.issn.1002-185X.20190643
Abstract:
The effects of different heat treatment regimes on the microstructure, hardness and friction and wear properties of laser deposited DZ125 superalloys were investigated. The results show that the dendritic morphology of the depositional area is columnar dendrite growing on the outer edge, and the average primary dendrite spacing is about 7.8μm. After single-stage aging (870 °C/20h, AC) and two-stage aging (1100 °C/4h, AC to 870 °C/20h, AC), the dendritic morphology and sedimentary state of the sample are not much different, γ" The coarsening phenomenon occurs in each phase, and the γ" phase coarsening degree and the size distribution are more uniform after the two-stage aging heat treatment; Under the two-stage aging heat treatment system, the average size and content of different aging temperature γ" phases are different, including 1100 °C/4h, AC to 870 °C/20h, and the average size and content of γ" phase are the largest under AC system; After single-stage aging and two-stage aging heat treatment, the content of Ti in the carbides showed a downward trend; After two-stage aging heat treatment, two kinds of irregularly shaped MC carbides are precipitated, which are M23C6 type carbides rich in Cr and Co elements and M6C type carbides rich in W and Mo elements; The wear mechanism of the unipolar aging and the two-stage aging heat treatment specimens is abrasive wear. The microhardness and wear resistance of the two-stage aging heat treatment samples are better than the single-stage aging.
The effects of different heat treatment regimes on the microstructure, hardness and friction and wear properties of laser deposited DZ125 superalloys were investigated. The results show that the dendritic morphology of the depositional area is columnar dendrite growing on the outer edge, and the average primary dendrite spacing is about 7.8μm. After single-stage aging (870 °C/20h, AC) and two-stage aging (1100 °C/4h, AC to 870 °C/20h, AC), the dendritic morphology and sedimentary state of the sample are not much different, γ" The coarsening phenomenon occurs in each phase, and the γ" phase coarsening degree and the size distribution are more uniform after the two-stage aging heat treatment; Under the two-stage aging heat treatment system, the average size and content of different aging temperature γ" phases are different, including 1100 °C/4h, AC to 870 °C/20h, and the average size and content of γ" phase are the largest under AC system; After single-stage aging and two-stage aging heat treatment, the content of Ti in the carbides showed a downward trend; After two-stage aging heat treatment, two kinds of irregularly shaped MC carbides are precipitated, which are M23C6 type carbides rich in Cr and Co elements and M6C type carbides rich in W and Mo elements; The wear mechanism of the unipolar aging and the two-stage aging heat treatment specimens is abrasive wear. The microhardness and wear resistance of the two-stage aging heat treatment samples are better than the single-stage aging.
2020, 49(8):2845-2854.
DOI: 10.12442/j.issn.1002-185X.20190664
Abstract:
Closed-cell Al composite foam with high specific strength and high specific stiffness is a typical lightweight material, which has broad application prospectsSin the fields of automobile and aerospaceSapplication. However, the pore structure of aluminum foams prepared by traditional methods is difficult to control, which seriously hinders the production. In this paper, a new preparation process for closed-cell CNTs/Al composite foam based on friction stir welding was proposed. The microstructure and elemental composition of the CNTs/Al composite foams with different rotationSspeeds (1000-1300rpm) were analyzed by scanning electron microscopy and energy dispersive analysis (SEM/EDS). The temperature distribution of the CNTs/Al precursor foam was studied by infrared thermometer and numerical simulation. The mechanical properties of pure Al foam and the CNTs/Al composite foam with different porosity were compared and analyzed by the quasi-static compression test. The results show that when the rotary speed of the stirring is 1000rpm, the surface of the CNTs/Al precursor foam is smooth and dense. Simultaneously, a blowing agent TiH2, a stabilization agent Al2O3 and reinforcedSphase CNTs are uniformly distributed on the cross section of the composite foam. The comparison between the foaming temperature of 680℃ and 700℃ shows that when the foaming temperature is 680℃ for 15min, the pore structure is uniform and mainly consists of circular pores. TheSmaximum pore diameterSisS0.48mm. Infrared thermometer and numerical simulation temperature field show that the temperature gradually decreases with the increase of the distance to the center of the stirring head, and the peak welding temperature is located in the stirring head which exhibits aSbowl-shaped distribution. The stress-strain curves of the CNTs/Al composite foam show the deformation characteristics combining brittleness and ductility at room temperature. When the porosity is 30.5%, the yield stress and platform stress values of the CNTs/Al composite foam are the largest. Compared with the pure Al foam, the yield stress of the CNTs/Al composite foam is increased by about 2-2.8 times, and the platform stress is increased by about 1.4-2.9 times.
Closed-cell Al composite foam with high specific strength and high specific stiffness is a typical lightweight material, which has broad application prospectsSin the fields of automobile and aerospaceSapplication. However, the pore structure of aluminum foams prepared by traditional methods is difficult to control, which seriously hinders the production. In this paper, a new preparation process for closed-cell CNTs/Al composite foam based on friction stir welding was proposed. The microstructure and elemental composition of the CNTs/Al composite foams with different rotationSspeeds (1000-1300rpm) were analyzed by scanning electron microscopy and energy dispersive analysis (SEM/EDS). The temperature distribution of the CNTs/Al precursor foam was studied by infrared thermometer and numerical simulation. The mechanical properties of pure Al foam and the CNTs/Al composite foam with different porosity were compared and analyzed by the quasi-static compression test. The results show that when the rotary speed of the stirring is 1000rpm, the surface of the CNTs/Al precursor foam is smooth and dense. Simultaneously, a blowing agent TiH2, a stabilization agent Al2O3 and reinforcedSphase CNTs are uniformly distributed on the cross section of the composite foam. The comparison between the foaming temperature of 680℃ and 700℃ shows that when the foaming temperature is 680℃ for 15min, the pore structure is uniform and mainly consists of circular pores. TheSmaximum pore diameterSisS0.48mm. Infrared thermometer and numerical simulation temperature field show that the temperature gradually decreases with the increase of the distance to the center of the stirring head, and the peak welding temperature is located in the stirring head which exhibits aSbowl-shaped distribution. The stress-strain curves of the CNTs/Al composite foam show the deformation characteristics combining brittleness and ductility at room temperature. When the porosity is 30.5%, the yield stress and platform stress values of the CNTs/Al composite foam are the largest. Compared with the pure Al foam, the yield stress of the CNTs/Al composite foam is increased by about 2-2.8 times, and the platform stress is increased by about 1.4-2.9 times.
Wang Haiying
,
Yang Fang
,
Guo Zhimeng
,
Feng Zhaohong
,
Zhang Ce
,
Wang Shuying
,
Lan Bo
,
Lu Boxin
2020, 49(8):2855-2860.
DOI: 10.12442/j.issn.1002-185X.20190934
Abstract:
Abstract: In this study, powder metallurgy (PM) Ti6Al4V alloy was forged in different ways. The properties and microstructure of the alloy before and after forging were also analyzed. The results showed that forging was an effective way to improve the density and mechanical properties of PM titanium alloys. Firstly, the PM Ti6Al4V alloy was performed a once forging deformation at different temperatures. The alloy forged at 960℃ had better ductility with an elongation of 15.44%. With the increasing of forging temperature, the equiaxial α phases decreased, and gradually changed to the basket weave structure, resulting in the plasticity decreasing. However, due to the inhibition of the original powder particle boundary on grain growth, there was no obvious grain growth in the alloy forged at 1150℃. The grain smaller than 20??m accounted for about 71%. As fine grain size was beneficial to the plasticity, the elongation still reached to 14.3%. Therefore, the PM Ti6Al4V alloy had a wider forging temperature window compared to the traditional cast titanium alloy. Besides, the PM Ti6Al4V alloy was performed a twice forging deformation at different temperature. In such case, the alloy was firstly forged at high temperature to improve the density with small deformation, and then was forged at lower temperature to obtain the required microstructure. The Ti6Al4V alloy with twice forging deformation had an elongation of higher than 17%, tensile strength of higher than 990MPa, and yield strength of higher than 960MPa.
Abstract: In this study, powder metallurgy (PM) Ti6Al4V alloy was forged in different ways. The properties and microstructure of the alloy before and after forging were also analyzed. The results showed that forging was an effective way to improve the density and mechanical properties of PM titanium alloys. Firstly, the PM Ti6Al4V alloy was performed a once forging deformation at different temperatures. The alloy forged at 960℃ had better ductility with an elongation of 15.44%. With the increasing of forging temperature, the equiaxial α phases decreased, and gradually changed to the basket weave structure, resulting in the plasticity decreasing. However, due to the inhibition of the original powder particle boundary on grain growth, there was no obvious grain growth in the alloy forged at 1150℃. The grain smaller than 20??m accounted for about 71%. As fine grain size was beneficial to the plasticity, the elongation still reached to 14.3%. Therefore, the PM Ti6Al4V alloy had a wider forging temperature window compared to the traditional cast titanium alloy. Besides, the PM Ti6Al4V alloy was performed a twice forging deformation at different temperature. In such case, the alloy was firstly forged at high temperature to improve the density with small deformation, and then was forged at lower temperature to obtain the required microstructure. The Ti6Al4V alloy with twice forging deformation had an elongation of higher than 17%, tensile strength of higher than 990MPa, and yield strength of higher than 960MPa.
2020, 49(8):2861-2868.
DOI: 10.12442/j.issn.1002-185X.20191070
Abstract:
Cu/graphite composite coating was prepared on TC4 alloy by cyanide free electroplating. The wear behavior and wear mechanisms of the coating were investigated. The results show that Cu/graphite composite coatings with compact structure and relatively strong coating/substrate combination can be obtained by cyanide free electroplating on TC4 alloy. However, increasing the graphite content in the coating would reduce the bonding strength between the coating and the substrate, and lead to a small decrease in coating hardness.The wear tests show that Cu/graphite composite coating can protect the TC4 substrate from wear effectively, demonstrated by its much lower friction coefficients and wear rates than both TC4 substrate and the pure copper coating. Based on a comprehensive analysis of the wear morphologies, wear products and friction coefficients of the coatings, the main wear mechanisms of the pure copper coating can be deduced as ploughing wear, adhesion wear and peeling wear, while those of the Cu/graphite composite coating are concluded as slight layer cutting wear and fatigue wear.
Cu/graphite composite coating was prepared on TC4 alloy by cyanide free electroplating. The wear behavior and wear mechanisms of the coating were investigated. The results show that Cu/graphite composite coatings with compact structure and relatively strong coating/substrate combination can be obtained by cyanide free electroplating on TC4 alloy. However, increasing the graphite content in the coating would reduce the bonding strength between the coating and the substrate, and lead to a small decrease in coating hardness.The wear tests show that Cu/graphite composite coating can protect the TC4 substrate from wear effectively, demonstrated by its much lower friction coefficients and wear rates than both TC4 substrate and the pure copper coating. Based on a comprehensive analysis of the wear morphologies, wear products and friction coefficients of the coatings, the main wear mechanisms of the pure copper coating can be deduced as ploughing wear, adhesion wear and peeling wear, while those of the Cu/graphite composite coating are concluded as slight layer cutting wear and fatigue wear.
2020, 49(8):2869-2874.
DOI: 10.12442/j.issn.1002-185X.20191107
Abstract:
In this work, a novel method for stripping Erbium from the pre-loaded P507-kerosene organic solution by a Y-type microchannel reactor was investigated. The effects from the microchannel size (length and diameter), the concentration of HCI, the flow rate and the concentration of loaded Erbium in organic phase on the Erbium stripping performance were focused on. The results showed that when the diameter of the microchannel and its length were 0.6 mm and 200 cm respectively, and the residence time of the organic phase in the microchannel reactor was 33.91s, and the concentration of HCI was 6 mol/L, the percent stripping of Erbium from the pre-loaded organic phase could reach 88.41%. Compared to the traditional mixer-settler extractor, the microchannel reactor exhibits a higher striping percentage under the same conditions, and the total mass transfer coefficient is 2 to 3 times than that of the traditional extraction methods.
In this work, a novel method for stripping Erbium from the pre-loaded P507-kerosene organic solution by a Y-type microchannel reactor was investigated. The effects from the microchannel size (length and diameter), the concentration of HCI, the flow rate and the concentration of loaded Erbium in organic phase on the Erbium stripping performance were focused on. The results showed that when the diameter of the microchannel and its length were 0.6 mm and 200 cm respectively, and the residence time of the organic phase in the microchannel reactor was 33.91s, and the concentration of HCI was 6 mol/L, the percent stripping of Erbium from the pre-loaded organic phase could reach 88.41%. Compared to the traditional mixer-settler extractor, the microchannel reactor exhibits a higher striping percentage under the same conditions, and the total mass transfer coefficient is 2 to 3 times than that of the traditional extraction methods.
2020, 49(8):2875-2879.
DOI: 10.12442/j.issn.1002-185X.20200017
Abstract:
To further increase the binding force between titanium substrate and carbon film and enhance the protective properties of the coatings, a titanium oxide coating structure with metallurgical bonding for the substrate has been prepared using a ion beam deposition technique micro-arc oxidation (MAO) technique, and then a carbon film was deposited using ion beam deposition combined magnetron sputtering technique on this titanium oxide coating to obtain the duplex coating. Microstructure and properties of the coatings were comparatively studied by SEM+EDS, AFM, wear test and electrochemical experiment. Results showed that the surface carbon film could not completely cover the micropores of the MAO coating, and the MAO titanium oxide coating on Ti substrate had porous features, which effectively increased the binding force between the top carbon film and the Ti substrate. The Ti substrate/MAO coating/carbon film system had the lowest friction coefficient, smallest fluctuation and width of wear scar in the process of friction, showing the most excellent tribological performance. However, the corrosion resistance of the new design composite coating was worse than the Ti substrate/Ti interlayer/carbon film. This was related to a thin carbon film and porous characteristics of MAO coating of the composite coating, resulting in the corrosion medium easily into the interface between the carbon film and MAO coating through the micropores and reducing the resistance corrosion.
To further increase the binding force between titanium substrate and carbon film and enhance the protective properties of the coatings, a titanium oxide coating structure with metallurgical bonding for the substrate has been prepared using a ion beam deposition technique micro-arc oxidation (MAO) technique, and then a carbon film was deposited using ion beam deposition combined magnetron sputtering technique on this titanium oxide coating to obtain the duplex coating. Microstructure and properties of the coatings were comparatively studied by SEM+EDS, AFM, wear test and electrochemical experiment. Results showed that the surface carbon film could not completely cover the micropores of the MAO coating, and the MAO titanium oxide coating on Ti substrate had porous features, which effectively increased the binding force between the top carbon film and the Ti substrate. The Ti substrate/MAO coating/carbon film system had the lowest friction coefficient, smallest fluctuation and width of wear scar in the process of friction, showing the most excellent tribological performance. However, the corrosion resistance of the new design composite coating was worse than the Ti substrate/Ti interlayer/carbon film. This was related to a thin carbon film and porous characteristics of MAO coating of the composite coating, resulting in the corrosion medium easily into the interface between the carbon film and MAO coating through the micropores and reducing the resistance corrosion.
2020, 49(8):2880-2887.
DOI: 10.12442/j.issn.1002-185X.20200120
Abstract:
Investigate the microstructure, texture and high-temperature endurance properties of TC4 titanium alloys under different molds. the optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron back scattering diffraction (EBSD) were used to observe and analyze the microstructure and persistent fracture behavior of TC4 titanium alloy.The results show that the phases of TC4 titanium alloy by different molds are all composed of α phase, β phase and ω phase, and the main phase is α phase (about 90%). Compared with the graphite type, the ceramic type is favorable for the β→α phase transition, the α phase is 5.3% higher, the average grain size is large (dmean = 37.021μm), the grain boundaries are less, and the grains are relatively uniform and relatively stable. When it is large, the material strength decreases and the plasticity increases. Simultaneously, the ceramic-type texture has high strength and obvious orientation. The texture type is {11-20} <1-100>, and the angle with the Y direction is about 45°, it further verified that the samples are in (101), (002),(101) .The reason for the increase in peak intensity is related to the formation of texture，The high temperature durability of ceramic samples is better than that of graphite. At the temperature (400℃，430℃，460℃), the persistent stress fracture life has increased by 1.174%, 15.401, 6.998%, all of which are ductile fracture. Appearance is a dimple pattern. In addition, temperature directly affects the long-term life of TC4 titanium alloy. as the temperature increases, the stress fracture life of TC4 titanium alloy gradually decreases.
Investigate the microstructure, texture and high-temperature endurance properties of TC4 titanium alloys under different molds. the optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron back scattering diffraction (EBSD) were used to observe and analyze the microstructure and persistent fracture behavior of TC4 titanium alloy.The results show that the phases of TC4 titanium alloy by different molds are all composed of α phase, β phase and ω phase, and the main phase is α phase (about 90%). Compared with the graphite type, the ceramic type is favorable for the β→α phase transition, the α phase is 5.3% higher, the average grain size is large (dmean = 37.021μm), the grain boundaries are less, and the grains are relatively uniform and relatively stable. When it is large, the material strength decreases and the plasticity increases. Simultaneously, the ceramic-type texture has high strength and obvious orientation. The texture type is {11-20} <1-100>, and the angle with the Y direction is about 45°, it further verified that the samples are in (101), (002),(101) .The reason for the increase in peak intensity is related to the formation of texture，The high temperature durability of ceramic samples is better than that of graphite. At the temperature (400℃，430℃，460℃), the persistent stress fracture life has increased by 1.174%, 15.401, 6.998%, all of which are ductile fracture. Appearance is a dimple pattern. In addition, temperature directly affects the long-term life of TC4 titanium alloy. as the temperature increases, the stress fracture life of TC4 titanium alloy gradually decreases.
2020, 49(8):2888-2894.
DOI: 10.12442/j.issn.1002-185X.20190688
Abstract:
In this paper, pulsed laser deposition (PLD) is attempted to be an alternative synthesis method for Cu-Ga-In (CIGS) thin films and the application of PLD on CIGS thin film solar cell materials was studied. Cu-In-Ga prefabricated metal films were grown on the quartz substrates by PLD method. Then the CIGS films with different Se content were synthesized by the post-selenization-annealing process. The structure, element component proportion and optical properties of the CIGS films with different deposition orders and thicknesses of the CuGa/In prefabricated metal layers were investigated. The experimental results indicate that, (1) The CIGS solar cell absorption layer with properties such as pure phase and high crystallinity can be obtained by PLD technique and Se-annealing processes. (2) The deposition order and thickness of prefabricated CuGa/In metal layers, as well as the Se-annealing temperature, have great influences on the crystallization, grain sizes and component proportion of the CIGS thin films. Compared to the CIGS film with In/CuGa double-prefabricated layers, the CIGS film with CuGa/In/CuGa trinal-prefabricated layers possesses better crystallization. (3) The prepared CIGS films all present low transmittance and high absorption coefficient in visible light region. Moreover, the largest value of Eg up to 1.21 eV was obtain in the CIGS films, which is higher than that in CuInSe ternary materials, and is benefit for the absorption of the high-energy photons in visible light. This work provided a novel technological method for obtaining the absorption layer of CIGS thin film solar cell with excellent performance.
In this paper, pulsed laser deposition (PLD) is attempted to be an alternative synthesis method for Cu-Ga-In (CIGS) thin films and the application of PLD on CIGS thin film solar cell materials was studied. Cu-In-Ga prefabricated metal films were grown on the quartz substrates by PLD method. Then the CIGS films with different Se content were synthesized by the post-selenization-annealing process. The structure, element component proportion and optical properties of the CIGS films with different deposition orders and thicknesses of the CuGa/In prefabricated metal layers were investigated. The experimental results indicate that, (1) The CIGS solar cell absorption layer with properties such as pure phase and high crystallinity can be obtained by PLD technique and Se-annealing processes. (2) The deposition order and thickness of prefabricated CuGa/In metal layers, as well as the Se-annealing temperature, have great influences on the crystallization, grain sizes and component proportion of the CIGS thin films. Compared to the CIGS film with In/CuGa double-prefabricated layers, the CIGS film with CuGa/In/CuGa trinal-prefabricated layers possesses better crystallization. (3) The prepared CIGS films all present low transmittance and high absorption coefficient in visible light region. Moreover, the largest value of Eg up to 1.21 eV was obtain in the CIGS films, which is higher than that in CuInSe ternary materials, and is benefit for the absorption of the high-energy photons in visible light. This work provided a novel technological method for obtaining the absorption layer of CIGS thin film solar cell with excellent performance.
Zhang Qinglei
,
Hao Zhenhua
,
Li Jing
,
Song Jianxun
,
Che Yusi
,
Zhu Jinpeng
,
Shu Yongchun
,
He Jinlin
2020, 49(8):2895-2903.
DOI: 10.12442/j.issn.1002-185X.20190516
Abstract:
The quality of raw powder materials have become key factors that restrict the development of metal 3D printing. The metal powders prepared by induction plasma spheroidization have many advantages, such as high spheroidization ratio、high sphericity、low impurity content and controllable particle size, which makes induction plasma spheroidization the most promising technology for large-scale industrial production of high properties spherical metal powders for 3D printing. In this paper, the development history, working principle and technical characteristics of plasma spheroidization were described. The research status of fabrication of spherical tungsten、molybdenum and titanium powders by this technology was emphatically introduced. The difficult problems to be solved and the development trend of induction plasma spheroidization were discussed as well.
The quality of raw powder materials have become key factors that restrict the development of metal 3D printing. The metal powders prepared by induction plasma spheroidization have many advantages, such as high spheroidization ratio、high sphericity、low impurity content and controllable particle size, which makes induction plasma spheroidization the most promising technology for large-scale industrial production of high properties spherical metal powders for 3D printing. In this paper, the development history, working principle and technical characteristics of plasma spheroidization were described. The research status of fabrication of spherical tungsten、molybdenum and titanium powders by this technology was emphatically introduced. The difficult problems to be solved and the development trend of induction plasma spheroidization were discussed as well.
2020, 49(8):2904-2912.
DOI: 10.12442/j.issn.1002-185X.20200216
Abstract:
Due to the unique amorphous/nanocrystal dual-phase structure, Fe-based nanocrystaliine alloys have excellent soft magnetic properties, which are profound progress in the development of soft magnetic materials. In this paper, the development and research history of the Fe-based nanocrystalline soft magnetic alloys are reviewed. The development and properties of the typical Fe-based nanocrystallne alloys are introduced，and the nanocrystallization mechanism, the soft magnetic mechanism and the corrosion resistant properties of Fe-based nanocrystalline alloys are depicted. At the end, the application and prospect of the Fe-based nanocrystalline alloys in the power and electronic information are proposed. The major objective of this paper is to provide some helps for the material researchers in designing and developing of new Fe-based nanocrystalline alloy and other advanced functional materials.
Due to the unique amorphous/nanocrystal dual-phase structure, Fe-based nanocrystaliine alloys have excellent soft magnetic properties, which are profound progress in the development of soft magnetic materials. In this paper, the development and research history of the Fe-based nanocrystalline soft magnetic alloys are reviewed. The development and properties of the typical Fe-based nanocrystallne alloys are introduced，and the nanocrystallization mechanism, the soft magnetic mechanism and the corrosion resistant properties of Fe-based nanocrystalline alloys are depicted. At the end, the application and prospect of the Fe-based nanocrystalline alloys in the power and electronic information are proposed. The major objective of this paper is to provide some helps for the material researchers in designing and developing of new Fe-based nanocrystalline alloy and other advanced functional materials.
