受力方式和变形速度对AZ31挤压板材平面应变过程中孪生的影响

采用X射线衍射、断口扫描、金相观察、应力-应变曲线等分析手段,通过对AZ31镁合金挤压板材在室温下的平面应变试验,研究了不同受力方式和不同变形速度对孪生产生的影响。结果表明,N向拉伸变形以{1012}孪生为主;N向压缩变形仅在变形末期在少量具有有利取向的晶粒内发生孪生;N向限制变形中,变形初期发生{1012}孪生变形,随着变形程度的增加,孪生停止。变形速度影响孪晶的形核和长大。当主要变形机制为孪生时,变形速度越慢,越有利于孪晶的形核与长大,提高材料的强度和塑性。

Influence of loading direction and strain rate on twinning of AZ31 magnesium alloy in plane-strain compression

In this paper,we discuss the influence of loading direction and strain rate on the twinning of AZ31 magnesium alloy in plane-strain compression in room temperature through X-ray diffraction, fracture scan, observation with optician microscope and stress-strain curve. The results show that the dominant deformation mechanism in N-extension is twinning on { 1012 } plane. In N-compression, twinning is initiated only in few crystals which have highest orientation factor in the latter deformation. And in N-constraint, twinning is activated in the beginning of the deformation, and ended with the increase of the deformation. The strain rate can influence the nucleation and growth of twin. High strain rate can enhance the nucleation and growth of twin, and result in the increase of peak intensity and plastic property.