Intermetallic compounds growth and morphology evolution of Al6061/SS304 electromagnetic pulse welding joint interface during post-weld heat treatment

The effects of heat treatment on the intermetallic compounds (IMCs) and morphology at the interface of stainless steel 304 bonded to aluminum 6061 by electromagnetic pulse welding (EMPW) were investigated in this study. A thin discontinuous non-uniform wavy transition layer with an average thickness of 1.144 μm was formed at the interface of the as-welded joint. After heat treatment, the average grain size of the Al/SS304 interface grew from 6.85 μm to 7.42 μm. The thickness of the transition layer increased significantly, reaching an average thickness of 4.109 μm after heating at 210 °C for 4 h. In addition, the wavy interface grew gradually and became smooth with increasing heating temperature, suggesting the growth rate of the IMCs at the trough was greater than that at the adjacent crest. Then the effect of heating time on the growth of IMCs was studied. According to the characteristics of the transition layer and the diffusion law, the IMCs grew faster at the trough than at the crest of the transition layer. Differences in element concentration, crystal deformation, grain boundaries, dislocation density, and energy storage were observed at the trough and crest of the interface as a result of the different growth rates of the IMCs.