多向压缩中AZ31镁合金变形行为的EBSD跟踪研究

DEFORMATION BEHAVIOR OF AZ31 MAGNESIUM ALLOY DURING MULTIAXIAL COMPRESSION BY EBSD TRACKING

利用显微硬度点法结合电子背散射衍射(EBSD)技术,跟踪研究了多向压缩路径下AZ31镁合金的变形行为.采用先沿板材横向(TD)压缩然后沿板材法向(ND)进行压缩的应变路径.结果表明,绝大多数晶粒TD压缩变形中主要以{1012}拉伸孪生为主,ND压缩变形过程中主要以退孪生为主,少数晶粒变形行为不同的原因是由于其初始取向偏离基面织构太大.在ND压缩变形中发生退孪生行为的晶粒内,没有发现新的孪生变体出现,表明退孪生比激活一个新的孪生变体要容易.剩余孪晶面积分数减少到0时,ND压缩变形中的局部区域应变小于TD压缩变形.表明完全退孪生所需应变比孪生小.

Cross rolling and multidirectional forging deformation modes are effective methods to improve the plastic forming ability of magnesium alloy. In these plastic forming process, multi directional compression deformation is often involved. In this study, the deformation behavior during multi-directional compression of a AZ31 magnesium alloy was investigated using a micro-grid method in combination with electron backscatter diffraction （EBSD） tracking method. The sheets were com- pressed along transverse direction （TD） followed by compression along normal direction （ND）. The experimental results show that {1012}〈1011〉 tensile twinning dominates the deformation process during initial compression along TD, and that for most grains detwinning of these {10i2}〈1011〉 tensile twins dominates the deformation process during a following compression along ND. For some grains with a large deviation from the basal texture, a different deformation behavior is seen. No new twin variants are found in grains that underwent detwinning during compression along ND. This indicates that detwinning of {10i2}〈1011〉 tensile twins is favored over the activation of a different twin variants during deformation of the AZ31 magnesium alloy. The remaining twin area fraction can reduce to near-zero even when the local strain subjected during ND compression is less than thatsubjected during the initial TD compression, demonstrating that a smaller strain is required for de- twinning than for the initial twinning.