Research on microstructure and mechanical properties of RSW joints of 7075T-6 alloy containing Sc

Nowadays, Resistance spot welding is a common welding method used in automobiles and other industries, and 7000 series Al alloy has become a very common industrial material because of its high strength and easy machinability. Scandium (Sc) is often used for alloy strengthening, however, there are few studies on resistance spot welding joint of Al alloy containing Sc. Here, 7075-T6 alloys containinga small amount of Sc were obtained to investigate the joint of resistance spot weldability. The simulation shows that the effective contact area between the Al sheet surface is about 19.5%, which is an important factor in nucleation. It has been found that the average grain size of the nugget decreased from 51.51 ± 5.74 μm to 8.15 ± 1.09 μm when Sc was added from 0 to 0.4 wt%, which is mainly due to the Al3Sc particles acting as the heterogeneous nucleus in the melt. The test results show that the tensile shear strength of welded joints with 0.4 wt% Sc addition is 29.2% higher than that of the joints without Sc because of grain refine strengthening.