Bonding mechanism and fracture behavior of inertia friction welded joint of 2219 aluminum alloy to 304 stainless steel

The 2219 aluminum (Al) alloy bars were welded to 304 stainless steel bars by inertia friction welding. The intermetallic compounds (IMCs) at the friction interface were characterized and analyzed and the bonding mechanism of the welded joint was studied in detail. Characterization of the microstructure at the friction interface revealed that there were two types of IMCs layers, the nanoscale Fe4Al13 layer and the microscale Cu-rich layer. In particular, the Cu-rich layer is bonded to the base material by Al2Cu and two Fe-Al-Cu ternary IMCs. Meanwhile, it was verified both theoretically and experimentally that the Fe4Al13 layer had less misfit with the base material with higher bonding strength at the interface. The formation of the Cu-rich layer increases the lattice mismatch, particularly at the interface of the ternary IMCs layer which becomes a weak area where the crack initiates and propagates easily.