预压缩对挤压态镁合金屈服行为的影响

利用WDW3100电子万能试验机沿挤压态AZ31镁合金试样的挤压方向进行预压缩,研究了在不同施载模式下试样的屈服行为.结果表明:一方面,沿挤压方向的预压缩显著地降低了其拉伸屈服强度,使得其拉伸屈服强度与无预应变的压缩屈服强度几乎相等.造成这一现象的原因是经预压缩后的试样再拉伸时发生了退孪生.另一方面,沿挤压方向的预压缩显著地提高了垂直于挤压方向的压缩屈服强度.在不同施载模式下,分析{10-12}孪生施密特因子表明,孪生体系的最大施密特因子的大小对镁合金屈服强度有重要影响.对于{10-12}孪生主导的塑性变形,如果存在大量相同最大施密特因子的晶粒,则其具有相等的屈服强度,反之则不同.

On Effects of Prior Compression on Yielding Behavior in an Extruded Magnesium Alloy

In this study ,the prior compression along the extrusion direction in an extruded AZ 31 magnesi-um alloy has been carried out on the electronic universal testing machine CM T 5105 ,the yielding behavior of samples under different loading modes have been investigated .T he results show that ,on the one hand , the prior compression along extrusion direction markedly decreased their tensile yield stresses ,leading to that nearly equaled to their compression yield stresses without prior strain on the extruded magnesium al-loy AZ31 .The reason for this phenomenon is the occurrence of detwinning during tension after pre-com-pression in the sample .On the other hand ,the prior compression along extrusion direction could increase the compression yield stresses when compression perpendicular to extrusion direction .Schmid factors for the{10-12} twin variants under different loading modes have been analyzed .It shows that the values of the highest Schmid factor for{10-12}twinning had great effect on the yield stresses .For{10-12} twin-ning-dominated deformation ,if there are some grains with equivalent highest Schmid factor ,their yielding stresses seem to be equal .Otherwise ,their yield stresses would be different .