AZ31镁合金室温大塑性等静压复合挤压过程中压缩孪生行为的相关基础研究

Magnesium alloys show poor ductility at ambient. The major reason is the appearance of compression twinning. This project proposal is aimed at the behavior of compression twinning in plastic deformation of magnesium at room temperature. A Quasi-isostatic sheath extrusion method would be employed to impart ambient strain to an AZ31 magnesium alloy. By inhibiting the formation and propagation of micro-crack, a high strain would be obtained, which might also introduce high density of compression twinning. The evolution of twinning dominated texture and stress flow would be measured. The plastic mico-mechanism for localized shearing within twinned region could be revealed by micro-texture measurement combined with in-situ contrast analyses for dislocation types. In order to interpret the effect of morphology and texture change introduced by compression twinning, investigate their influence on Bauschinger effect and mechanical behavior under different stress condition. Explore the deformation mechanism of magnesium alloys at room temperature in order to provide reasonable rationale for improving the ambient formability of magnesium alloys.

镁合金室温塑性较差，其主要原因在于压缩孪晶的形成，本项目围绕镁合金室温变形过程中的压缩孪生行为展开研究。项目采用等静压复合挤压方式对AZ31镁合金进行室温变形，通过抑制裂纹形成与扩展获得大塑性应变量，促使高密度孪晶形成；研究高塑性应变阶段孪晶主导的宏观织构演变及流变行为规律；利用透射电镜测量孪晶区域微观织构取向，并原位分析位错滑移类型，揭示孪晶区域局部塑性变形微观机制；探索压缩孪晶在不同应力条件下对力学性能的影响以及在包辛格效应中所起的作用，阐明孪晶引起的形貌与织构软化效应作用机制，为深刻理解镁合金室温塑性变形机制，提高塑性成形性能提供理论依据。

镁合金室温塑性较差，其主要原因在于压缩孪晶的形成，本项目围绕镁合金室温变形过程中的压缩孪生行为展开研究。项目采用等静压复合挤压方式对AZ31镁合金进行室温变形，通过抑制裂纹形成与扩展获得大塑性应变量，促使高密度孪晶形成，成功制备了高应变阶段不同应变量的室温挤压棒材，基本揭示了镁合金常温大塑性应变阶段主导的宏观应力、微观组织、多晶择优取向演变规律，获得了镁合金中极端条件下压缩孪晶对性能影响规律的关键数据，对于镁合金中利用孪晶增强增韧的可行性进行了探索，对于开发新型高效率、低成本的镁合金塑性加工技术具有重要的理论指导意义。