Abstract: The warm deformation properties of hot-rolled AZ31 Mg alloy are examined by uniaxial tensile test at a temperature range of 50~250℃ and a strain rate range of 1.4×10^-3~1.4×10^-1s^-1. The microstructure evolution during the warm deformation is observed by optical microscopy (OM) and transmission electronic microscopy (TEM). It is demonstrated that twinning is the primary deformation mechanism and hardening mechanism at the initial stage of warm deformation. The distortion energy stored by twinning and the activation of non-basal slip are responsible for the nucleation and growth of dynamic recrystallization (DRX). The appreciable suppression of DRX due to the increase of strain rate is found to be the reason for the strain rate sensitivity in warm deformation of hot-rolled AZ31 Mg alloy.

Key words: AZ31 Mg alloy, warm deformation, microstructure evolution, twinning, dynamic recrystallization