Hot Compressive Deformation Behavior Of ZK60 And ZK60-1.0Er Magnesium Alloy

Hot compressive deformation of ZK60 and ZK60-1.0Er magnesium alloys occurring homogenization have been studied by Gleeble-1500 D thermal simulator. Thermal compression parameters: deformation temperature T: 160℃, 260℃, 320℃and 420℃; strain rate ?: 0.0001 s-1, 0.001 s-1, 0.01 s-1 and 1.0 s-1. Constitutive equation of thermal compression of ZK60 and ZK60-1.0Er magnesium alloys was developed by the Zener-Hollomon parameter, the hyperbolic sine function and rheological stress-strain curve, the critical stress value of dynamic recrystallization happening was determined by the curve of strain hardening rate and stress, according to the material dynamic model, the processing map was obtained to determine the appropriate hot working range. The experiment results show that: in the process of hot compression deformation of ZK60 and ZK60-1.0Er magnesium alloys, with the increase of deformation temperature, the flow stress decreases; with the increase of strain rate, the flow stress increases, meanwhile, with the increase of deformation temperature, stress value of dynamical recrystallization critical decreases, and with the increase of strain rate, stress value of dynamical recrystallization critical increases; theoretical stress value which was calculated according to the constitutive equation is in accordance with the actual stress value, average deformation activation energy, respectively 183 KJ/mol and 153 KJ/mol; hot working safety range of ZK60 and ZK60-1.0Er magnesium alloys is high temperature and high strain rate, respectively T=235~420℃, ?=0.3~1.0 s-1 and T=270~420℃, ?=0.2~1.0 s-1. Combined with the microstructure observation analysis: within experimental parameters, the addition of rare earth 1.0 wt.% Er can increase the flow stress and stress sensitivity index n, but decreases average deformation activation energy. At 420℃/1.0 s-1, the addition of rare earth Er can decrease critical stress value of dynamic recrystallization grain nucleation, promote the recrystallization. Meanwhile, the addition of rare earth Er can narrow instability range of ZK60 magnesium alloy, change the trend of the power dissipation efficiency contour, increase power dissipation efficiency value at high temperature, at processing security region peak efficiency increases from ηmax= 35 % to ηmax= 45 %, promote the recrystallization grain nucleation, refine the grain size.