Abstract: In this study,a resistance spot welding process was employed to join 3mm thick cast aluminium and 2 mm thick 5-series extruded aluminium alloy.Shear-tensile tests were conducted on the welded joints,and their macroscopic morphology and microscopic structure were analyzed using metallographic microscopy.The fracture surfaces were examined using scanning electron microscopy.The results indicated that the joints were primarily composed of four typical regions:base metal,heat-affected zone,columnar grain zone,and equiaxed grain zone.The weld nugget is predominantly offset towards the cast aluminium side,and an optimal welding current could diminish the effects,thereby enhancing joint performance.Under an electrode force of 6kN and a welding current of 40kA,the average failure load of the joints reached a maximum of(7.09±0.33)kN.The fracture behaviour of the joint could be classified into two modes:fracture at the weld point and fracture at the cast aluminium,with the latter exhibiting higher performance and characterized as a ductile fracture.