Influence of heat treatment on the microstructures and mechanical properties of sand-cast Mg-4Y-2Nd-1Gd-0.4Zr magnesium alloy was investigated,and the tensile fracture mechanisms of the studied alloys under different ...Influence of heat treatment on the microstructures and mechanical properties of sand-cast Mg-4Y-2Nd-1Gd-0.4Zr magnesium alloy was investigated,and the tensile fracture mechanisms of the studied alloys under different conditions were also discussed.The results show that the optimum T4 and T6 heat treatment conditions for the as-cast Mg-4Y-2Nd-1Gd-0.4Zr alloy are 525°C,8 h and（525°C,8 h）＋（225°C,16 h）,respectively,with regard to the microstructure observation,DSC heating curve and mechanical properties.The hardness,yield strength,ultimate tensile strength and elongation of the Mg-4Y-2Nd-1Gd-0.4Zr alloy treated by optimum T6 heat treatment are HV91,180 MPa,297 MPa and 7.4%,respectively.Moreover,the Mg-4Y-2Nd-1Gd-0.4Zr alloys under different heat treatment conditions exhibit different tensile fracture modes.展开更多
Hot compression tests of Mg–11 Gd–4 Y–2 Zn–0.4 Zr alloy(GWZK114)were conducted at a deformation temperature range of 300–500°C and a strain rate range of 0.01–10.0 s-1.Based on systematic microstructure obs...Hot compression tests of Mg–11 Gd–4 Y–2 Zn–0.4 Zr alloy(GWZK114)were conducted at a deformation temperature range of 300–500°C and a strain rate range of 0.01–10.0 s-1.Based on systematic microstructure observation,it is confirmed that long period stacking ordered(LPSO)phase displays essential and evolving roles on the dynamic recrystallization(DRX)behavior.The results indicate that the plastic deformation is mainly coordinated by simultaneous exist of LPSO kinking of lamella 14 H-LPSO phase and DRX at 350–450℃,and DRX at 500℃.Further,it is found that the LPSO kinking induced during 350–450℃can delay the DRX.A phenomenological DRX model of GWZK114 alloy is established to be XDRX=1.exp[-0.5((ε-εc)/ε^*)0.91].Non-uniform distribution of plastic strain during compression was considered via finite element method and it ensures a good prediction of DRX fraction under a large plastic strain.Meanwhile,an enhanced DRX model,taking its formulation as XDRX={1.exp[-0.5((ε-εc)/ε*)0.91]}(T/(226.8)-1)n,n=3.82ε0.083,is proposed for the first time to capture the hindering effect of 14 H-LPSO kinking on DRX behavior.The predicted results of this enhanced DRX model agree well with the experimental cases,where 14 H-LPSO kinking is dominated or partially involved(300–450℃).Besides,a size model of DRX grains is also established and can depict the evolution of DRX grain size for all the investigated compression conditions with accounting for temperature rising at high strain rates(5 s^-1 and 10 s^-1).展开更多
基金Project(0502)supported by the Aerospace Science and Technology Innovation Fund of China Aerospace Science and Technology CorporationProject(2007CB613701)supported by the National Basic Research Program of ChinaProject(2009AA033501)supported by the National High-tech Research and Development Program of China
文摘Influence of heat treatment on the microstructures and mechanical properties of sand-cast Mg-4Y-2Nd-1Gd-0.4Zr magnesium alloy was investigated,and the tensile fracture mechanisms of the studied alloys under different conditions were also discussed.The results show that the optimum T4 and T6 heat treatment conditions for the as-cast Mg-4Y-2Nd-1Gd-0.4Zr alloy are 525°C,8 h and（525°C,8 h）＋（225°C,16 h）,respectively,with regard to the microstructure observation,DSC heating curve and mechanical properties.The hardness,yield strength,ultimate tensile strength and elongation of the Mg-4Y-2Nd-1Gd-0.4Zr alloy treated by optimum T6 heat treatment are HV91,180 MPa,297 MPa and 7.4%,respectively.Moreover,the Mg-4Y-2Nd-1Gd-0.4Zr alloys under different heat treatment conditions exhibit different tensile fracture modes.
文摘Hot compression tests of Mg–11 Gd–4 Y–2 Zn–0.4 Zr alloy(GWZK114)were conducted at a deformation temperature range of 300–500°C and a strain rate range of 0.01–10.0 s-1.Based on systematic microstructure observation,it is confirmed that long period stacking ordered(LPSO)phase displays essential and evolving roles on the dynamic recrystallization(DRX)behavior.The results indicate that the plastic deformation is mainly coordinated by simultaneous exist of LPSO kinking of lamella 14 H-LPSO phase and DRX at 350–450℃,and DRX at 500℃.Further,it is found that the LPSO kinking induced during 350–450℃can delay the DRX.A phenomenological DRX model of GWZK114 alloy is established to be XDRX=1.exp[-0.5((ε-εc)/ε^*)0.91].Non-uniform distribution of plastic strain during compression was considered via finite element method and it ensures a good prediction of DRX fraction under a large plastic strain.Meanwhile,an enhanced DRX model,taking its formulation as XDRX={1.exp[-0.5((ε-εc)/ε*)0.91]}(T/(226.8)-1)n,n=3.82ε0.083,is proposed for the first time to capture the hindering effect of 14 H-LPSO kinking on DRX behavior.The predicted results of this enhanced DRX model agree well with the experimental cases,where 14 H-LPSO kinking is dominated or partially involved(300–450℃).Besides,a size model of DRX grains is also established and can depict the evolution of DRX grain size for all the investigated compression conditions with accounting for temperature rising at high strain rates(5 s^-1 and 10 s^-1).
