(上海交通大学 轻合金精密成型国家工程研究中心，上海200030)
摘 要: 研究挤压态和等通道角挤压(ECAE)态AZ31镁合金的变形行为与微观组织的相关性。结果表明，ECAE态AZ31镁合金的室温拉伸屈服强度与晶粒尺寸之间表现出反Hall-Petch关系，且拉压不对称性明显减弱；在室温压缩时表现出应变速率敏感性，并随变形温度升高，应变速率敏感性因子变大。挤压态合金的晶粒度为20 mm，具有典型的挤压丝织构，主要变形方式为基面位错滑移和孪生，导致了合金中明显的拉压不对称性。ECAE态合金平均晶粒尺寸约为2 mm，织构相对随机化，导致合金压缩时孪生比率明显下降，其他变形模式比率增加，提高了变形抗力，降低了拉压不对称性。ECAE态AZ31镁合金压缩的激活能接近其晶界扩散激活能，晶界滑移在一定程度上导致了合金的反Hall-Petch关系的出现以及应变速率敏感性的增强。
关键字: AZ31镁合金；等通道角挤压；变形行为；拉压不对称性；应变速率敏感性
equal channel angular extrusion
（National Engineering Research Center of Light Alloy Net Forming, Shanghai Jiao Tong University,
Shanghai 200030, China）
Abstract: The correlation between the microstructure and the deformation behavior of AZ31 alloys processed by as-extrusion and equal channel angular extrusion (ECAE) was investigated. The results show that there is a reverse Hall-Petch relationship between the yield stress and the grain size of ECAE AZ31 Mg alloy, and the tension-compression asymmetry is weakened; ECAE alloy also exhibits a strain rate sensitivity, and the strain rate sensitivity factor will be increased with increasing the process temperature. The average grain size is 20 μm for the as-extruded alloy with a typical ring basal texture, and the main deformation models at room temperature are basal slip and twinning, which result in the strong tension-compression asymmetry. The average grain size is about 2 μm for ECAE Mg alloy with a texture randomized relatively, which results in remarkably a decrease of twin volume fraction under compression loading, and then the tension-compression asymmetry in ECAE AZ31 alloy is weakened. The calculated apparent activation energy in the ECAE Mg AZ31 is approached to the activation energy of grain boundary diffusion Mg alloy, which provides an evidence to support that the deformation on grain boundaries plays an important role on the deformation behavior, and the possible grain boundary sliding (GBS) has contribution to the reverse Hall-Petch relationship and strain rate sensitivity in ECAE Mg alloy.
Key words: AZ31 Mg alloy; equal channel angular extrusion (ECAE); deformation behavior; tension-compression asymmetry; strain rate sensitivity
