Direct drive friction welding of a multi-phase Al₁₃Cr_23.5Fe₂₀Co₂₀Ni_23.5 high-entropy alloy

Al₁₃Cr_23.5Fe₂₀Co₂₀Ni_23.5 high-entropy alloy with three phases (face-centered cubic [FCC], A2 and B2) was joined successfully by direct drive friction welding. The microhardness of the welded samples gradually increases as approaching the weld interface, which was related to the microstructural evolution across the weld interface. The weld joint can be divided into four regions: dynamic recrystallisation zone, thermal-mechanically affected zone, heat affected zone and base metal. It is found that the volume fraction ratio of FCC to body-centered cubic (BCC) (A2+B2) phases slightly decreases as approaching the weld interface. The hardening of the joint is attributed to the refined structure, large deformation and the increased volume fraction of the hard BCC phases in the weld joint.