The microstructure and flow stress of the Mg-12Gd-3Y-0.5Zr magnesium alloy was investigated by compression test at temperatures ranging from 350 to 500 ~C and the strain rates ranging from 0.01 to 20 s-1. The flow stress of the magnesium alloy increased with strain rate and decreased with deformation temperature. Flow stress can be expressed in terms of the Zener-Hollomon parameter Z, which describes the combined influence of the strain rate and temperature using an Arrhenius function.The values of the deformation activation energy were estimated to be 245.9 and 171.5 kJ/mol at deformation temperatures below 400 ℃ and above 400 ℃, respectively. Two constitutive equations were developed to quantify the effect of the deformation conditions on the flow stress of the magnesium alloy. The effects of deformation temperature and strain rate on the microstriucture of the magnesium alloy were also examined and quantified by measuring the volume fraction of dYnahaically recrystallized grain Xd. Xd increased with increasing of deformation temperature. When the deformation temperature was below 475 ℃, X4 decreased with strain rate until it reached 0.15 s-1, then it increased again. When the deformation temperature was above 475 ℃, X4 increased with strain rate.
