Microstructure homogeneity and its role in the mechanical properties of the magnetic pulse welded steel/Al tubular joint

The steel and aluminum alloy tubes were successfully joined by magnetic pulse welding (MPW). Part of the joints fractured at the interface, yet part of them fractured at the base metal (BM) of aluminum alloy. The tensile test results revealed a fluctuation of the mechanical properties of the steel/Al MPW joints, demonstrating the microstructure inhomogeneity of the MPW joints. The typical wavy interfacial morphology could be observed at the interface of the MPW joints. The element transition zone composed of elements Fe and Al were detected while no obvious intermetallic compound (IMC) layer could be traced. The good mechanical properties of steel/Al MPW joints could be attributed to the longer effective bonding length and larger element transition area. Besides, the grain refinement was observed at the interface of the MPW joint, which explained its microhardness increase.