Intermetallic Compounds and Mechanical Properties of Mg/Al Dissimilar Joints by Friction Stir Welding

The amount and shape of intermetallic compounds (IMCs) may influence the properties of the Al–Mg dissimilar welded joints. In this paper, friction stir welding with stir tool offset to the Al side was carried out to reduce IMC. The microstructure of joints was observed by OM and SEM. XRD and TEM were applied to do further study on the IMC phases. The result showed that the offset of the stirring tool affected the welding thermal cycle and element diffusion. Intermetallic compounds layer consisting of Al3Mg2 and Al12Mg17 formed in the Al/Mg interface and resulted in the fracture of the joint. Maximum hardness (102HV) appeared in the weld nugget area and the hardness value of the welded joints presented an uneven distribution.