The composite process of fusion ifll-ing + friction stir repaired welding has been successfully used to repair the keyhole defect, and the microstructure and mechanical properties of the repaired joint have been analyzed. The microstructure of the TMAZ coarsens and grows up with the boundary morphology of the original parent metal gradually disappearing, and even there is part of columnar or dendrite crystals from the fusion filling process existing in the TMAZ. SEM observation shows that the precipitated phase in the TMAZ also coarsens and grows up with the network structure distributed. The re-sults of microhardness and tensile test present the inhomo-geneous mechanical behavior of the repaired joint. TMAZ is the weak link of the repaired joint, and the tensile speci-men also fractures in this zone. The fracture morphology shows the ductile fracture in the nugget zone and brittle fracture in the TMAZ.%采用熔焊填充+搅拌摩擦补焊复合工艺成功进行了搅拌摩擦焊缝匙孔型缺陷的修补，焊后对补焊接头的微观组织和力学性能进行了分析。结果表明，焊核区呈细小的再结晶等轴晶粒，热机影响区发生粗化长大，逐渐丧失了原始母材轧制晶粒边界形貌，并残留熔焊柱状晶或树枝状晶粒。第二相析出物粗化长大，呈网状结构分布于热机影响区域。热影响区/热机影响区是整个补焊接头的薄弱环节，拉伸试样亦断裂在该区域。补焊接头断口呈现出韧性断裂与铸态组织脆性断裂的混合断口形貌。
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