Selective laser melting(SLM)is an emerging layer-wise additive manufacturing technique that can generate complex components with high performance.Particulate-reinforced aluminum matrix composites(PAMCs)are important m...Selective laser melting(SLM)is an emerging layer-wise additive manufacturing technique that can generate complex components with high performance.Particulate-reinforced aluminum matrix composites(PAMCs)are important materials for various applications due to the combined properties of Al matrix and reinforcements.Considering the advantages of SLM technology and PAMCs,the novel SLM PAMCs have been developed and researched in recent years.Therefore,the current research progress about the SLM PAMCs is reviewed.Firstly,special attention is paid to the solidification behavior of SLM PAMCs.Secondly,the important issues about the design and fabrication of high-performance SLM PAMCs,including the selection of reinforcement,the influence of parameters on the processing and microstructure,the defect evolution and phase control,are highlighted and discussed comprehensively.Thirdly,the performance and strengthening mechanism of SLM PAMCs are systematically figured out.Finally,future directions are pointed out on the advancement of high-performance SLM PAMCs.展开更多
One important problem in casting wrought aluminum alloys is the high tendency to the formation of hot tears in the solidification process.By using semi-solid metal(SSM) processing,the hot tearing tendency of alloys ca...One important problem in casting wrought aluminum alloys is the high tendency to the formation of hot tears in the solidification process.By using semi-solid metal(SSM) processing,the hot tearing tendency of alloys can be minimized during casting.In the present research,the semi-solid slurry of wrought aluminum alloy 2024 was firstly prepared with a novel self-inoculation method(SIM),and then the microstructure characteristics of the semi-solid slurry and the rheo-diecastings cast with the semi-solid slurry were investigated.The results indicate that finer and more uniform globular primary α-Al particles can be obtained when the semi-solid slurry are isothermally held for a short period within the semi-solid temperature range,and the primary α-Al particles without entrapped liquid are uniformly fine,globular grains in the rheo-diecastings.The holding temperature and time affect the solid fraction,particle size,and shape factor.After the semi-solid slurry is held at 625 ℃ for 3 min and 5 min,the optimal values for the average equivalent diameter are 70.80 μm and 74.15 μm,and for the shape factor are 1.32 and 1.42,respectively.The solidification process of the rheo-diecastings is composed of the following two distinct stages:primary solidification process and secondary solidification process.The secondary solidification process consists further of the following three stages:(1) direct growth of secondary primary(α 2) phase from the surface of the primary α-Al phase particles without re-nucleation,(2) independent nucleation and growth of α 3 phase from the residual liquid,and(3) eutectic reaction at the end.展开更多
To understand the solidification behavior of austenitic stainless steel in pulsed magnetic field, the solidification process is investigated by means of the self-made high voltage pulse power source and the solidifica...To understand the solidification behavior of austenitic stainless steel in pulsed magnetic field, the solidification process is investigated by means of the self-made high voltage pulse power source and the solidification tester. The results show that the solidification structure of austenitic stainless steel can be remarkably refined in pulsed magnetic field, yet the grains become coarse again when the magnetic intensity is exceedingly large, indicating that an optimal intensity range existed for structure refinement. The solidification temperature can be enhanced with an increase in the magnetic intensity. The solidification time is shortened obviously, but the shortening degree is reduced with the increase of the magnetic intensity.展开更多
Magnesium alloys containing rare earth elements (RE) have received considerable attention in recent years due to their high mechanical strength and good heat-resisting performance. Among them, Mg–5%Y–4%RE (WE54) mag...Magnesium alloys containing rare earth elements (RE) have received considerable attention in recent years due to their high mechanical strength and good heat-resisting performance. Among them, Mg–5%Y–4%RE (WE54) magnesium alloy is a high strength sand casting magnesium alloy for use at temperatures up to 300 ℃, which is of great interest to engineers in the aerospace industry. In the present work, the solidification behavior of Zr-containing WE54 alloy and Zr-free alloy was investigated by computer-aided cooling curve analysis (CA-CCA) technique. And the solidification microstructure and mechanical properties of them were also investigated comparatively. It is found from the cooling curves and as-cast microstructure of WE54 alloy that the nucleation temperature of α-Mg in WE54 alloy increases after Zr addition, and the as-cast microstructure of the alloy is significantly refined by Zr. While the phase constitution of WE54 alloy is not changed after Zr addition. These phenomena indicate that Zr acts as heterogeneous nuclei during the solidification of WE54 alloy. Due to refined microstructure, the mechanical properties of Zr-containing WE54 alloy is much higher than Zr-free WE54 alloy.展开更多
High entropy alloy(HEA)-based alloy design is experiencing a conceptual broadening from equiatomic alloys to non-equiatomic alloys.To provide experimental basis for designing Cu-rich non-equiatomic HEAs,in the current...High entropy alloy(HEA)-based alloy design is experiencing a conceptual broadening from equiatomic alloys to non-equiatomic alloys.To provide experimental basis for designing Cu-rich non-equiatomic HEAs,in the current study,a dual phase(Cu-rich and CoCrFeNi-rich phases) face-centered cubic CoCrFeNiCu_(4) alloy was systematically investigated.We provided initial and experiment-based understanding of the behavioral change of the alloy during a variety of thermal cycles and thermomechanical processing.The current results indicate that,during heating,preferred precipitation of Cu-rich particles occurs,leading to more pronounced compositional differences between the two constituent FCC phases and increased relative volume fraction of the Cu-rich phase.The Alloy exhibits a continuous melting and discontinuous solidification of the Cu-rich and CoCrFeNi-rich phases.After being cold-rolled to ~90 % thickness reduction,the alloy exhibits a recrystallization temperature higher than 800℃.Annealing at 300 and 500℃ led to strength reduction and/or ductility decrease;further increasing annealing temperature monotonically caused softening and ductilization due to decreased density of pre-existing dislocations.The yield-drop phenomena observed for the 900℃-and 1000℃-annealed specimens are associated with the locking of pre-existing dislocations by some "atmosphere",the nature of which warrants further elucidation.展开更多
The immiscible Cu-Fe alloy was characterized by a metastable miscibility gap.With the addition element Zr,the miscibility gap can be extended into the Cu-Fe-Zr ternary system.The effect of the atomic ratio of Cu to Fe...The immiscible Cu-Fe alloy was characterized by a metastable miscibility gap.With the addition element Zr,the miscibility gap can be extended into the Cu-Fe-Zr ternary system.The effect of the atomic ratio of Cu to Fe and Zr content on the behavior of liquid-liquid phase separation was studied.The results show that liquid-liquid phase separation into Cu-rich and Fe-rich liquids took place in the as-quenched Cu-Fe-Zr alloy.A glassy structure with nanoscale phase separation was obtained in the as-quenched(Cu0.5Fe0.5)40Zr60 alloy sample,exhibiting a homogeneous distribution of glassy Cu-rich nanoparticles in glassy Fe-rich matrix.The microstructural evolution and the competitive mechanism of phase formation in the rapidly solidified Cu-Fe-Zr system were discussed in detail.Moreover,the electrical property of the as-quenched Cu-Fe-Zr alloy samples was examined.It displays an abnormal change of electrical resistivity upon temperature in the nanoscale-phase-separation metallic glass.The crystallization behavior of such metallic glass has been discussed.展开更多
The semisolid slurry of the 6061 wrought aluminum alloy was prepared by the self-inoculation method（SIM）. The effects of the isothermal holding parameters on microstructures of rheo-diecastings were investigated, an...The semisolid slurry of the 6061 wrought aluminum alloy was prepared by the self-inoculation method（SIM）. The effects of the isothermal holding parameters on microstructures of rheo-diecastings were investigated, and the solidification behavior of 6061 wrought aluminum alloy during the rheo-diecasting process was analyzed using OM, SEM, EDS and EBSD. The results indicate that the isothermal holding process during slurry preparation has great effect on primary α（Al） particles（α1）, but has little effect on the microstructure of secondary solidification in the process of thin-walled rheo-diecasting. Nucleation is expected to take place in the entire remaining liquid when the remaining liquid fills the die cavity, and the secondary solidification particles（α2） are formed after the process of stable growth, unstable growth and merging. The solute concentration of remaining liquid is higher than that of the original alloy due to the existence of α1 particles, hence the contents of Mg and Si in α2 particles are higher than those in α1 particles.展开更多
基金Project(GJHZ20190822095418365)supported by Shenzhen International Cooperation Research,ChinaProject(2019011)supported by NTUT-SZU Joint Research Program,China+2 种基金Project(2019040)supported by Natural Science Foundation of Shenzhen University,ChinaProject(JCYJ20190808144009478)supported by Shenzhen Fundamental Research Fund,ChinaProject(ZDYBH201900000008)supported by Shenzhen Bureau of Industry and Information Technology,China。
文摘Selective laser melting(SLM)is an emerging layer-wise additive manufacturing technique that can generate complex components with high performance.Particulate-reinforced aluminum matrix composites(PAMCs)are important materials for various applications due to the combined properties of Al matrix and reinforcements.Considering the advantages of SLM technology and PAMCs,the novel SLM PAMCs have been developed and researched in recent years.Therefore,the current research progress about the SLM PAMCs is reviewed.Firstly,special attention is paid to the solidification behavior of SLM PAMCs.Secondly,the important issues about the design and fabrication of high-performance SLM PAMCs,including the selection of reinforcement,the influence of parameters on the processing and microstructure,the defect evolution and phase control,are highlighted and discussed comprehensively.Thirdly,the performance and strengthening mechanism of SLM PAMCs are systematically figured out.Finally,future directions are pointed out on the advancement of high-performance SLM PAMCs.
基金financially supported by the National Natural Science Foundation of China(No.50964010)the Basic Scientific Research Fund for the Universities in Gansu Province(No.1201ZTC056)
文摘One important problem in casting wrought aluminum alloys is the high tendency to the formation of hot tears in the solidification process.By using semi-solid metal(SSM) processing,the hot tearing tendency of alloys can be minimized during casting.In the present research,the semi-solid slurry of wrought aluminum alloy 2024 was firstly prepared with a novel self-inoculation method(SIM),and then the microstructure characteristics of the semi-solid slurry and the rheo-diecastings cast with the semi-solid slurry were investigated.The results indicate that finer and more uniform globular primary α-Al particles can be obtained when the semi-solid slurry are isothermally held for a short period within the semi-solid temperature range,and the primary α-Al particles without entrapped liquid are uniformly fine,globular grains in the rheo-diecastings.The holding temperature and time affect the solid fraction,particle size,and shape factor.After the semi-solid slurry is held at 625 ℃ for 3 min and 5 min,the optimal values for the average equivalent diameter are 70.80 μm and 74.15 μm,and for the shape factor are 1.32 and 1.42,respectively.The solidification process of the rheo-diecastings is composed of the following two distinct stages:primary solidification process and secondary solidification process.The secondary solidification process consists further of the following three stages:(1) direct growth of secondary primary(α 2) phase from the surface of the primary α-Al phase particles without re-nucleation,(2) independent nucleation and growth of α 3 phase from the residual liquid,and(3) eutectic reaction at the end.
基金Item Sponsored by National Natural Science Foundation of China (50274050) and Shanghai Baoshan Iron and Steel Group
文摘To understand the solidification behavior of austenitic stainless steel in pulsed magnetic field, the solidification process is investigated by means of the self-made high voltage pulse power source and the solidification tester. The results show that the solidification structure of austenitic stainless steel can be remarkably refined in pulsed magnetic field, yet the grains become coarse again when the magnetic intensity is exceedingly large, indicating that an optimal intensity range existed for structure refinement. The solidification temperature can be enhanced with an increase in the magnetic intensity. The solidification time is shortened obviously, but the shortening degree is reduced with the increase of the magnetic intensity.
基金This work was funded by the National Basic Research Program of China(973 Program)through project No.2013CB632202.
文摘Magnesium alloys containing rare earth elements (RE) have received considerable attention in recent years due to their high mechanical strength and good heat-resisting performance. Among them, Mg–5%Y–4%RE (WE54) magnesium alloy is a high strength sand casting magnesium alloy for use at temperatures up to 300 ℃, which is of great interest to engineers in the aerospace industry. In the present work, the solidification behavior of Zr-containing WE54 alloy and Zr-free alloy was investigated by computer-aided cooling curve analysis (CA-CCA) technique. And the solidification microstructure and mechanical properties of them were also investigated comparatively. It is found from the cooling curves and as-cast microstructure of WE54 alloy that the nucleation temperature of α-Mg in WE54 alloy increases after Zr addition, and the as-cast microstructure of the alloy is significantly refined by Zr. While the phase constitution of WE54 alloy is not changed after Zr addition. These phenomena indicate that Zr acts as heterogeneous nuclei during the solidification of WE54 alloy. Due to refined microstructure, the mechanical properties of Zr-containing WE54 alloy is much higher than Zr-free WE54 alloy.
基金supported financially by the National Natural Science Foundation of China(No.51901077)the Science and Technology Innovation Platform and Talent Plan of Hunan Province(No.2019RS1020)the open Foundation of State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body(No.71865003),Hunan University,Changsha,China。
文摘High entropy alloy(HEA)-based alloy design is experiencing a conceptual broadening from equiatomic alloys to non-equiatomic alloys.To provide experimental basis for designing Cu-rich non-equiatomic HEAs,in the current study,a dual phase(Cu-rich and CoCrFeNi-rich phases) face-centered cubic CoCrFeNiCu_(4) alloy was systematically investigated.We provided initial and experiment-based understanding of the behavioral change of the alloy during a variety of thermal cycles and thermomechanical processing.The current results indicate that,during heating,preferred precipitation of Cu-rich particles occurs,leading to more pronounced compositional differences between the two constituent FCC phases and increased relative volume fraction of the Cu-rich phase.The Alloy exhibits a continuous melting and discontinuous solidification of the Cu-rich and CoCrFeNi-rich phases.After being cold-rolled to ~90 % thickness reduction,the alloy exhibits a recrystallization temperature higher than 800℃.Annealing at 300 and 500℃ led to strength reduction and/or ductility decrease;further increasing annealing temperature monotonically caused softening and ductilization due to decreased density of pre-existing dislocations.The yield-drop phenomena observed for the 900℃-and 1000℃-annealed specimens are associated with the locking of pre-existing dislocations by some "atmosphere",the nature of which warrants further elucidation.
基金This work was supported by the National Natural Science Foundation of China(Nos.51774264,51574216,51974288 and 51374194)the Natural Science Foundation of Liaoning Province of China(No.2019-MS-332).
文摘The immiscible Cu-Fe alloy was characterized by a metastable miscibility gap.With the addition element Zr,the miscibility gap can be extended into the Cu-Fe-Zr ternary system.The effect of the atomic ratio of Cu to Fe and Zr content on the behavior of liquid-liquid phase separation was studied.The results show that liquid-liquid phase separation into Cu-rich and Fe-rich liquids took place in the as-quenched Cu-Fe-Zr alloy.A glassy structure with nanoscale phase separation was obtained in the as-quenched(Cu0.5Fe0.5)40Zr60 alloy sample,exhibiting a homogeneous distribution of glassy Cu-rich nanoparticles in glassy Fe-rich matrix.The microstructural evolution and the competitive mechanism of phase formation in the rapidly solidified Cu-Fe-Zr system were discussed in detail.Moreover,the electrical property of the as-quenched Cu-Fe-Zr alloy samples was examined.It displays an abnormal change of electrical resistivity upon temperature in the nanoscale-phase-separation metallic glass.The crystallization behavior of such metallic glass has been discussed.
基金Project(51464031)supported by the National Natural Science Foundation of China
文摘The semisolid slurry of the 6061 wrought aluminum alloy was prepared by the self-inoculation method（SIM）. The effects of the isothermal holding parameters on microstructures of rheo-diecastings were investigated, and the solidification behavior of 6061 wrought aluminum alloy during the rheo-diecasting process was analyzed using OM, SEM, EDS and EBSD. The results indicate that the isothermal holding process during slurry preparation has great effect on primary α（Al） particles（α1）, but has little effect on the microstructure of secondary solidification in the process of thin-walled rheo-diecasting. Nucleation is expected to take place in the entire remaining liquid when the remaining liquid fills the die cavity, and the secondary solidification particles（α2） are formed after the process of stable growth, unstable growth and merging. The solute concentration of remaining liquid is higher than that of the original alloy due to the existence of α1 particles, hence the contents of Mg and Si in α2 particles are higher than those in α1 particles.
