Magnetic pulse joining of aluminum alloy–carbon steel tubes

The magnetic pulse joining (MPJ) between 3A21 aluminum alloy and steel 20 tubes was experimentally investigated with a solenoid coil assisted by a field shaper. The mechanical properties and microstructure of MPJ joints were tested and observed. The results show that the metallurgical joints can be obtained at a voltage of 15 kV, a radial gap of 1.2–1.4 mm, and a slope angle of 3°–7° in the lapping area. The joint comprises a transition zone with different widths, two matrix metals and two interfaces between the zone and the two metals. The interface presents a typical wavy pattern and mutual diffusion of Fe and Al elements happens in the zone. The transition zone is composed of Fe–Al intermetallics, micro cracks and micro pores. The microhardness of the transition zone is much higher than that of the matrix metals.