Hot Deformation Behaviors And Processing Parameters Optimizing Of Mg-9.5Gd-3.8Y-0.6Zr Alloy

Abstract:The thermocompression test of Mg-9.5Gd-3.8Y-0.6Zr alloy were studied on Gleeble1500thermal-mechanical simulator. The deformation temperature is350℃,400℃,450℃,500℃, and the strain rate is0.001s-1,0.01s-1,0.1s-1,1s-1, respectively. The true stress-strain curves of Mg-9.5Gd-3.8Y-0.6Zr alloy were drawed by thermocompression results, With variations of the strain rate and the temperature, law of the curves were studied. The deformation activation energy Q and the corresponding stress index n were calculated at different deformation condition, and constitutive equation was established. The microstructures of the experimental alloy at different conditions was observed by optical microscopy(OM), and scanning electron microscopy(SEM). The change law of microstructures during the compression deformation was discussed. The processing map of the alloy was established, and it was discussed by combining with the microstructure. Eventually hot working technology of the alloy was optimized. The results reveal as follow:1. The true stress-strain curves of Mg-9.5Gd-3.8Y-0.6Zr alloy during the compression deformation was characteristic as dynamic recrystallization. Increasing of temperature and decreasing of strain rate were benefical to dynamic recrystallization, which makes peek stress ap, flow stress σ and peek strain sp reduce.2. With temperature increasing, the deformation activation energy Q of Mg-9.5Gd-3.8Y-0.6Zr alloy at different strain rate increased. The average deformation activation energy Q was225kJ·mol-1, and the corresponding stress index n was4.25. The constitutive equation of the alloy was:3. With the strain rate decreasing, the temperature and deformation degree increasing, dynamic recrystallization level increases, and the new grain grow up. The deformation is easy to happen twin dynamic recrystallization at lower temperature and higher strain rate. With increasing of temperature and decreasing of strain rate, the proportion of twin dynamic recrystallization in dynamic recrystallization reduced.4. The power dissipation diagrams of Mg-9.5Gd-3.8Y-0.6Zr alloy at different strains were almost same. With strain increase, unstable region extended. The safe area was450℃～500℃of temperature and0.001s-1～0.1s-1of strain rate.5. The optimum rolling processing of Mg-9.5Gd-3.8Y-0.6Zr alloy was475℃of temperature and10%of reduction per pass, corresponding to mechanical properties of plate as follows:σb=360MPa, σ0.2=280MPa and δ>8%.