预置拉伸孪晶诱发动态再结晶的镁合金晶粒细化机制

This project regards the rolled AZ31 magnesium alloy sheet with basal texture as the research object, and {10-12}<10-11> tensile twins introduced by pre-deformation are used to accelerate the dynamic recrystallization process during subsequent warm compression deformation to achieve grain refinement, thus proposing a method for preparing fine-grained magnesium alloy by dynamic recrystallization induced by pre-introducing tensile twins. The project will study effects of pre-introducing tensile twins on deformation twinning, dislocation movement, substructure changes and deformation texture transformation during warm compression deformation to obtain the evolution law of microstructure. The microstructure characteristics in grain nucleation region such as grain boundaries, sub-boundaries, twin boundaries etc. will be examined, and then the crystallography behaviors and nucleation mechanisms of dynamic recrystallization induced by pre-introducing tensile twins will be studied to reveal the grain refinement mechanisms. The present work will also quantitatively study effects of pre-introducing tensile twins on grain refinement by dynamic recrystallization, and combine the warm compression process parameters in order to obtain the optimal grain refinement effect induced by pre-introducing tensile twins. The research results have important theoretical value and practical application significance to preparing of fine-grained magnesium alloy. It will show a new way for improving properties of magnesium alloy and expanding its application.

本项目以具有基面织构的AZ31镁合金轧制板材为研究对象，通过预变形预置{10-12}<10-11>拉伸孪晶，在随后热压缩变形过程中利用预置拉伸孪晶加速动态再结晶进程以实现晶粒细化，提出了预置拉伸孪晶诱发动态再结晶制备细晶镁合金材料的新方法。项目将研究热压缩变形过程中预置拉伸孪晶对变形孪生、位错运动、亚结构变化以及变形织构转变等的影响，获得组织演变规律；考察晶界、亚晶界及孪晶界等晶粒形核区域的组织特征，研究预置拉伸孪晶诱发的动态再结晶晶体学行为、动态再结晶形核机制，揭示预置拉伸孪晶诱发的晶粒细化机制；定量研究预置拉伸孪晶对动态再结晶晶粒细化效果的影响，并结合热压缩工艺参数，获得最优化预置拉伸孪晶诱发的晶粒细化效应。项目研究成果对细晶镁合金材料的制备具有重要的理论价值与实际应用意义，将为提升镁合金性能，扩展镁合金应用展示一条新途径。

本项目以具有基面织构的AZ31镁合金轧制板材为研究对象，在室温条件下垂直于晶粒 c 轴方向预变形，在镁合金中预置大量｛10-12｝拉伸孪晶，随后退火（低于523K）以消除位错影响，在随后热压缩变形过程中利用预置拉伸孪晶加速动态再结晶进程以实现晶粒细化，提出了预置拉伸孪晶诱发动态再结晶制备细晶镁合金材料的新方法。项目研究了预置孪晶 AZ31 镁合金在不同温度下的力学性能与组织演变；对比研究了初始镁合金板与预置孪晶镁合金板在不同变形阶段的显微组织特征；研究了镁合金晶粒形核区域（包括晶界、亚晶界、孪晶界等）的组织特征，揭示了预置孪晶诱发的动态再结晶晶体学行为、再结晶形核机制等晶粒细化机制；研究了预置拉伸孪晶结合热压缩变形制备的细晶镁合金的力学性能，研究了预置拉伸孪晶结合轧制变形制备的细晶镁合金的力学性能，并结合细晶显微组织进行了分析。研究成果可为通过预置拉伸孪晶诱发动态再结晶制备细晶镁合金材料提供理论依据，对细晶镁合金材料的制备具有重要的理论价值与实际应用意义，为提升镁合金性能，扩展镁合金应用展示了一条新途径。