Mg-Al-Zn合金搅拌摩擦焊接头在同轴压缩过程中的组织演变规律

Microstructure Evolution of Mg-Al-Zn Alloy Friction Stir Welding Joint during Coaxial Compression Deformation

为了探究Mg-Al-Zn合金搅拌摩擦焊接头在变形过程中的失效规律,利用万能试验机系统研究了接头在同轴压缩过程中的应力-应变行为及微观组织演变规律。结果表明,Mg-Al-Zn合金接头不同区域在变形过程中会出现不均匀的凹凸现象,这主要由于在搅拌摩擦焊周期性的搅拌作用下接头形成不同的微区织构,从而造成接头中心和边部表现出不同的塑性变形能力。压缩过程中主要的塑性变形量发生在焊核区,并伴随大量孪晶的出现,随着变形量从3%增加到9%,孪生现象先增强后减缓,孪生的区域也不断变大。EBSD结果分析表明Mg-Al-Zn合金搅拌摩擦焊接头在压缩过程中产生的孪晶类型包括{1012}拉伸孪晶(86°)和{1011}压缩孪晶(56°),拉伸孪晶在协调接头塑性变形起主导作用。

In order to study the failure law of Mg-Al-Zn alloy friction stir welding joint during deformation, the stress-strain behavior and microstructure evolution law of the joint during coaxial compression were studied by using the universal testing machine system. The results show that uneven concave-convex phenomenon is observed in different areas of the Mg-Al-Zn alloy joint during the deformation process. Under the periodic stirring action of the friction stir welding tool,different micro-texture in the joint is formed, which results in different deformation capacity of the center and edge of the joint.During the compression process, the main deformation occurs in the weld nugget zone, accompanied by the emergence of a large number of twins. With the increase of the deformation amount from 3% to 9%, the twinning phenomenon enhances first then slows down, and the twinning area also becomes larger. The EBSD results show that the types of twins produced during the compression process of Mg-Al-Zn alloy friction stir welded joint include {1012} tensile twins(86°) and {1011}compression twins(56°), and the tensile twins play a leading role in the deformation process of the joint.