Inhomogeneous microstructure and mechanical properties of rotary friction welded joints between 5052 aluminum alloy and 304 stainless steel

The reaction layer of rotary friction welded 5052 aluminum alloy/304 stainless steel dissimilar joints consisted of Fe2Al5 and Fe4Al13 phases, and the distribution of intermetallic compounds (IMCs) and mechanical properties were inhomogeneous due to the inhomogeneity of heat generation along the radius direction. Almost no brittle IMCs formed in center part, while continuous and thicker IMCs formed in R/4, R/2, 3R/4 and edge locations, and the thickness of IMCs reached the maximum value in 3R/4 rather than in edge location. The joint efficiency was 99.51% in center location, higher than that in R/4, R/2, 3R/4 and edge locations. Meanwhile, the width of heat-affected zone on 304 stainless steel side decreased, but that of softened zone on 5052 aluminum alloy side increased from center to edge location. The entire joint fractured through the interface and predominantly presented brittle fracture feature. Cracks mainly propagated along the IMCs/AA5052 substrate interface for samples from center and R/4 locations, between the IMCs and the IMCs/AA5052 substrate interface alternately from R/2 and partial 3R/4 locations, and along the IMCs/304SS substrate interface from partial 3R/4 and edge locations.