镁合金铸造缺陷塑性变形弥合与修复过程

通过电子显微镜、透射电镜并结合塑性变形数值模拟,观察镁合金铸造缺陷(晶间缩松和缩孔)在变形过程中的形貌变化及缺陷附近应力分布,讨论塑性变形消除铸造缺陷的力学行为,提出镁合金铸造缺陷塑性变形弥合过程为:缺陷体积压缩→界面闭合→界面两侧基体相切变→界面附近再结晶→缺陷部分弥合.结果表明:变形过程中缺陷附近应力集中明显,变形后应力集中大大降低,部分铸造缺陷得以弥合与修复.

Closing and repairing process of Mg alloy casting imperfections in plastic deformation

The effects of press deformation on the morphologies evolution of Mg alloy casting imperfections (shrinkage porosity and cavity) and the stress distribution around the casting imperfections were observed by electro microscopy, transmission electron microscopy (TEM) and numerical simulation. The mechanical behavior of casting imperfections closing in pressing was investigated. The closing mechanism of press deformation on Mg alloy casting imperfections was proposed, which was volume of casting imperfections shrinking→interfaces closing→shearing deformation of α-Mg matrix grains around interfaces→dynamic recrystallization around interfaces→casting imperfections closing partly. The results show that the stress concentration becomes more evident in pressing and reduces greatly after deformation. At the same time, the casting imperfections are closed and repaired partly.