Hot compression deformation behavior of Mg-5Zn-3.5Sn-1Mn-0.5Ca-0.5Cu alloy

Abstract

The hot deformation behavior of Mg-5Zn-3.5Sn-1Mn-0.5Ca-0.5Cu alloy containing coarse second phase particles is studied. The flow stress increases with decreasing temperature and increasing strain rate. The stress-strain result is fitted to the hyperbolic sine equation to obtain the constitutive equation of the alloy. The processing map is constructed and it shows that low temperature and high strain rate lead to both low efficiency of power dissipation and instability and two domains with high efficiency of power dissipation out of the instability area is suitable for hot processing of the alloy: 580 K–670 K, 0.001 s−1–0.01 s−1 and 630 K–670 K, 0.01 s−1–1 s−1, the latter one is recommended for hot deformation for the higher strain rate. It was revealed that the effect of coarse particles on the restoration mechanism is dependent on the deformation condition. Under low Zener-Hollomon value, particles hinder discontinuous dynamic recrystallization through grain boundary pinning making dynamic recovery and continuous dynamic recrystallization the main restoration mechanism. Under high Zener-Hollomon value, the misorientation gradient near particles increases and the efficiency of particle stimulated nucleation increases. The enhanced particle stimulated nucleation accompanied by more active twinning and twin related recrystallization make the fraction of dynamic recrystallized grain to be higher under high Zener-Hollomon value.