We used refill friction stir spot welding (RFSSW) to join 2-mm-thick AZ91D-H24 magnesium alloy sheets, and we investigated in detail the effect of tool plunge depth on the microstructure and fracture behavior of the joints. A sound joint surface can be obtained using plunge depths of 2.0 and 2.5 mm. Plunge depth was found to significantly affect the height of the hook, with greater plunge depths corresponding to more severe upward bending of the hook, which compromised the tensile-shear properties of the joints. The hardness reached a minimum at the thermo-mechanically affected zone due to the precipitation phases of this zone as it dissolved into the α-matrix during the welding process. The fracture modes of RFSSW joints can be divided into three types: shear fracture, plug fracture, and shear—plug fracture. Of these, the joint with a shear—plug fracture exhibited the best tensile-shear load of 6400 N.

我们使用填充摩擦搅拌点焊（RFSSW）将2毫米厚的AZ91D-H24镁合金薄板连接起来，并详细研究了刀具切入深度对接头的显微组织和断裂行为的影响。使用2.0和2.5毫米的切入深度可以获得良好的接合面。发现插入深度显着影响钩的高度，较大的插入深度对应于钩的更严重的向上弯曲，这损害了接头的拉伸剪切性能。由于在焊接过程中该区域溶解在α-基体中，因此该区域的沉淀相使硬度在热机械影响区域达到最低。RFSSW接头的断裂方式可分为三种：剪切断裂，塞子断裂和剪切—塞子断裂。这些，