Microstructure and mechanical properties of a welded joint obtained by friction stir welding of thin copper and aluminum plates

Abstract

Friction stir welding was used to produce a welded joint of 1 mm thick plates of copper M1 and aluminum alloy AMg2M. The microstructure of the shoulder-side of the joint had areas of mixing of aluminum and copper. In the area of aluminum, copper inclusions were observed, and in the area of copper, aluminum inclusions were observed in the form of particles and thin lamellas. The bottom side of the joint consists mainly of copper. X-ray diffraction showed the presence of intermetallic phases Al2Cu, Al4Cu9 from the side of the shoulder. The formation of intermetallic phases occurred in the solid-state, without melting the initial materials. The presence of copper particles in the region of aluminum and aluminum particles and lamellas of various lengths in the regions of copper, intermetallic phases led to the formation of a composite-like structure. The formation of a composite-like structure during friction stir welding of copper and aluminum plates affects the mechanical properties of the joint. Thus, the microhardness of the joint increased in comparison with the microhardness of the initial plates. The distribution of microhardness over the thickness of the joint is almost uniform. The formation of composite-like structure using friction stir welding are discussed.