热轧AZ31镁合金温变形中的微观组织演变

Microstructure Evolution in Warm Deformation of Hot-Rolled AZ31 Mg Alloy

在50～250℃的温度范围和1.4×10-3～1.4×10-1s-1的应变速率范围内通过单向拉伸试验检验了热轧AZ31镁合金的温变形性能。通过光学显微镜和透射电镜观察了温变形中的微观组织演变。结果表明:在温变形的初始阶段,孪生为主要的变形机理和硬化机制。由孪生变形积聚的畸变能和非基滑移的启动导致了动态再结晶的形核与长大。应变速率的提高对动态再结晶的抑制是造成AZ31镁合金温变形中应变速率敏感性的原因。

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.