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其余的工艺参数保持不变的条件下研究了9种不同形状搅拌头对异质搅拌摩擦焊铜铝接头性能的影响。采用宏观组织、显微组织、拉伸试验、硬度、扫描电子显微镜和电子X射线光谱仪等力学和冶金方法评估异质接头的性能。结果表明，采用直径为8 mm的圆柱形搅拌头得到的接头强度最大。此外，当多边形搅拌头的边数减少时，碎屑缺陷增加，因此，多边形接头不适合异质搅拌摩擦焊对接接头。而且，当多边形搅拌接头边数增加时，抗拉强度也随之增大。对同一焊肩表面，相对于圆柱形的搅拌头，多边形搅拌头的搅拌区较硬脆。采用多边形搅拌头得到的焊缝的最大硬度为 HV 283。在搅拌区明显存在硬脆金属间化合物。在异质铜铝接头搅拌区存在金属间化合物，如CuAl、CuAl2、Cu3Al 和Cu9Al4。

Dissimilar friction stir welding (FSW) of copper and aluminum was investigated by nine different tool designs, while the rest of the process parameters were kept constant. Mechanical and metallurgical testssuch as macrostructure, microstructure, tensile test, hardness, scanning electron microscope and electronX-ray spectrographs were performed to assess the properties of dissimilar joints. The results exhibited that, the maximum joint strength was achieved by the tool of cylindrical pin profile having 8 mm pin diameter. Besides, thefragmental defectsincreasedas the number of polygonal edges decreased, hence the polygonal pin profiles were unsuitable for dissimilar FSW butt joints. Furthermore, the tensile strengthincreasedas the number of polygonal edges increased. Stir zone ofpolygonal pin profiles was hard and brittle relative to cylindrical tool pin profiles for same shoulder surface. Maximum hardness ofHV283wasobtainedat weld made by the polygonal square pin profile. The hard and brittleintermetallic compounds (IMCs)were prominently presented in the stir zone. Phases of IMCs such as CuAl, CuAl2, Cu3Al and Cu9Al4were presented in the stir zone of dissimilar Cu?Al joints.