Effect of crystallographic texture on the kinetics of hot deformation of rolled Mg–3Al–1Zn alloy plate

Abstract

The hot deformation behavior of a rolled plate of Mg–3Al–1Zn (AZ31) alloy has been studied on cylindrical specimens with their compression axis parallel to the rolling direction (RD), the transverse direction (TD) or the normal to the rolling plane (ND) with a view to evaluate the effect of crystallographic texture. Constant true strain rate isothermal hot compression tests were conducted in the temperature range 300-550°C and strain rate range 0.0003–10 s⁻¹. The temperature and strain rate dependence of steady-state flow stress follows the standard kinetic rate equation. The apparent activation energy is estimated to be 143, 180 and 168 kJ/mole for RD, TD and ND specimens, respectively, the value for RD specimens being close to that for self-diffusion in magnesium. The texture existing in the starting rolled plate ({0002}{101̅0}) favors the activation of both first- and second-order pyramidal slip systems during the hot deformation of RD specimens. On the other hand, deformation of TD specimens involves first-order pyramidal slip while in ND specimens the second-order pyramidal slip dominates. The results on RD specimens suggest that the occurrence of extensive slip on both the first- and second-order pyramidal systems along with simultaneous dynamic recovery by cross-slip give rise to a higher rate of nucleation for dynamic recrystallization in comparison with that in ND and TD specimens.