回填搅拌摩擦点焊和传统搅拌摩擦点焊AA6061-T6接头的微观结构和力学性能的比较

在搅拌摩擦点焊过程中，通过添加填充板来改善摩擦成形过程，这种新工艺被称为回填搅拌摩擦点焊。分别采用回填搅拌摩擦点焊和传统的搅拌摩擦点焊工艺焊接AA6061-T6搭接焊样品，研究搅拌头的旋转速度对接头的力学性能和金相组织的影响。在不同的旋转速度下，回填搅拌摩擦点焊接头的静态剪切强度都比传统搅拌摩擦点焊接头的好。这归因于在回填搅拌摩擦点焊时，添加了填充板从而有更多的材料来填充孔洞，消除了形成的孔洞缺陷，从而使点焊焊核区的有效截面积增加。借助扫描电镜观察讨论了材料的失效机制，分析了断裂表面形貌。2种焊接接头的硬度曲线都呈W形，最小的硬度出现在热影响区。

Comparison of microstructure and mechanical properties of conventional and refilled friction stir spot welds in AA 6061-T6 using filler plate

Friction stir spot welding with refilling by friction forming process （FSSW-FFP） was successfully modified using filler plate. Both of this new refilling technique and conventional friction stir spot welding （FSSW） process were used to weld A1 6061-T6 lap shear specimens and the results were compared. Effects of tool rotational speeds on mechanical and metallurgical properties in both the cases were studied. Static shear strength of refilled weld samples was found to be better than those welded by conventional FSSW process at all tool rotational speeds. This is explained in terms of effective increase in cross-sectional area of weld nugget due to addition of more material from filler plate, thereby eliminating the probe hole. Failure mechanisms were discussed and fracture surfaces were analyzed through scanning electron microscopy （SEM）. The hardness profile of the welds exhibited a W-shaped appearance in both the processes and the minimum hardness was measured in the HAZ.