Microstructure evolution during magnetic pulse welding of dissimilar aluminium and magnesium alloys

Microstructure evolution has been investigated for magnetic pulse welding of dissimilar aluminium and magnesium alloys using optical microscopy, laser confocal microscopy and electron backscatter diffraction. The welded joints were made with discharge voltages of 4 kV, 4.5 kV and 5 kV and they are characterised by the aluminium region, the weld interface and the magnesium region. The interfacial waves become more regular and much smoother with increasing discharge voltage from 4 kV to 5 kV. The grains were extremely refined and the grain size became larger with increasing distance to the weld interface at a discharge voltage of 5 kV. The gradual grain refinement closer to the weld interface can be attributed to dynamic recrystallization. Different recrystallization behaviour was observed for the aluminium region and the magnesium region near the weld interface. The occurrence of the extension twinning {1 0 1¯ 2} in the dynamic recrystallized grains indicating twin related dynamic recrystallization behaviour in the magnesium region near the weld interface.