Effect of joining time on intermetallic compound thickness and mechanical properties of refill friction stir spot welded dissimilar Al/Mg alloys

Abstract Refill friction stir spot welding (RFSSW) was successfully used to join dissimilar Al/Mg in this work. The effect of joining time on the microstructure and mechanical properties of the welded joints was studied. The results showed Al/Mg alloys were joined through the liquid eutectic phase caused by the stirring of tool. An obvious intermetallic compounds (IMCs) layer formed in the joint center after welding. An IMC with a thickness of approximately 1100 μm formed at the pin affected zone and only a 10 μm diffusion layer formed at the sleeve affected zone. Little liquid eutectic phase formed at 1 s, resulting into a 10 μm IMC at the pin affected zone. Thicker IMC formed with increasing the welding time. Lap shear failure load of the joint first increased and then decreased with increasing the welding time. The maximum failure load of 3.6 kN was obtained at 2 s. Joint fractured through the IMC layer and presented brittle fracture mode.