Hot Deformation Behaviour and Constitutive Equation of Mg-9Gd-4Y-2Zn-0.5Zr Alloy

The thermal deformation behaviour of Mg-9Gd-4Y-2Zn-0.5Zr alloy at temperatures of 360-480 degrees C, strain rates of 0.001-1 s(-1) and a maximum deformation degree of 60% was investigated in uniaxial hot compression experiments on a Gleeble 3800 thermomechanical simulator. A constitutive equation suitable for plastic deformation was constructed from the Arrhenius equation. The experimental results indicate that due to work hardening, the flow stress of the alloy rapidly reached peak stress with increased strain in the initial deformation stage and then began to decrease and stabilize, indicating that the deformation behaviour of the alloy conformed to steady-state rheological characteristics. The average deformation activation energy of this alloy was Q = 223.334 kJ center dot mol(-1). Moreover, a processing map based on material dynamic modelling was established, and the law describing the influence of the machining parameters on deformation was obtained. The experimental results indicate that the effects of deformation temperature, strain rate and strain magnitude on the peak dissipation efficiency factor and instability range were highly significant. With the increase in the strain variable, the flow instability range increased gradually, but the coefficient of the peak power dissipation rate decreased gradually. The optimum deformation temperature and strain rate of this alloy during hot working were 400-480 degrees C and 0.001-0.01 s(-1), respectively.

Automated summary

The thermal deformation behavior of Mg-9Gd-4Y-2Zn-0.5Zr alloy was investigated in this study. The alloy exhibited steady-state rheological characteristics and a constitutive equation and deformation activation energy were obtained. The effects of deformation temperature, strain rate, and strain magnitude on peak dissipation efficiency factor and instability range were found to be significant. The optimum deformation temperature and strain rate for this alloy were determined to be 400-480 degrees C and 0.001-0.01 s(-1), respectively.