(1. 重庆交通大学交通土建工程材料国家地方联合工程实验室,重庆 400074;
2. 重庆大学材料科学与工程学院,重庆 400044)
摘 要: 沿热轧退火态AZ31镁合金轧制方向进行室温动态塑性变形,采用场发射扫描电子显微镜研究 孪生的变体类型及结构特征。结果表明:在 孪生机制主导塑性变形的初级阶段(ε<8%),AZ31镁合金中大部分晶粒内部仅产生一种 孪生变体或变体对,所以孪晶结构呈彼此平行状,将晶粒分割成片层组织;这种片层组织的厚度随着应变量的增加而减小,从5.55μm减小到2.49μm;少数晶粒形核产生不同的 孪生变体,且这种晶粒的数量随着塑性变形量的增大而增加;当ε>8%,孪生体积分数接近饱和,位错滑移成为镁合金主要的变形机制。
关键字: 镁合金;动态塑性变形;孪生变体;变形机制
(1. National and Local Joint Engineering Laboratory of Traffic Civil Engineering Materials,
Chongqing Jiaotong University, Chongqing 400074, China;
2. School of Materials Science and Engineering, Chongqing University, Chongqing 400044, China)
Abstract:Both variant type and structure characteristic of twinning in the as-rolled AZ31 magnesium alloy subjected to dynamic plastic deformation at room temperature along the rolling direction were investigated. The results show that at the stage of twinning-dominated deformation (ε<8%), mostly a twin variant or a twin variant pair is activated in the grain of AZ31 magnesium alloy, leading to a paralleltwin lamellar structure. The lamellar thickness decreases significantly from 5.55μm to 2.49μm with increasing the strain. Meanwhile, different variant pairs also generate in some grains, and the number of these grains increases with increasing the plastic strain. When the plastic strain is greater than 8%, the volume fraction of twins almost saturates and dislocation slips dominate the later deformation.
Key words: magnesium alloy; dynamic plastic deformation; twinning variant; deformation mechanism