Interfacial microstructure and mechanical properties of AZ31B/AA7075 joints using non-equilibrium thermal compensation resistance welding

In this study, a novel non-equilibrium thermal compensation resistance welding method was proposed for the welding of Al–Mg dissimilar metal overlap joints. The aim was to control the heat distribution of Al–Mg joints by applying the difference of Joule heat generated by different specifications of graphite electrodes on both sides of joints. The interface structure and joining mechanism of the joint were analyzed by adding zinc interlayer. The results show that the tensile strength of Al–Mg direct welded joint is as high as 99 MPa under this process, while the strength of Al–Mg joint with zinc interlayer is only 12 MPa. The reason for the above results is that the interface of Al–Mg direct welded joint is mainly composed of Al–Mg diffusion layer and a small amount of compounds, while a large number of brittle hardening compounds are formed at the interface of Al/Zn/Mg joint. This study provides a new idea and method for the design and manufacture of aluminum-magnesium high quality welded joint.