Interfacial microstructure characterization of aluminum/aluminum-lithium joints fabricated by magnetic pulse welding

Abstract Magnetic pulse welding (MPW) is a cost-effective solid-state welding technology, which is mainly used in the lap joining of similar and dissimilar materials. It has broad application prospects in aerospace, automotive and appliance industries. In this paper, the corrosion-resistant 5052 aluminum alloy (Al) and the high-strength 2A66 aluminum-lithium alloy (Al Li) were joined by MPW. The interface microstructure of Al/Al-Li welded joints was characterized and analyzed by scanning electron microscope (SEM) and transmission electron microscope (TEM). The results showed that the welding interface was composed of four zones: the molten zone with porous structure, the shear molten zone, the sine wave interface zone and the flat interface zone. It can be seen that the shear molten zone consisted of ultra-fine equiaxed grains, which were formed by the rapid melting and solidification of Al alloy at the interface. A fine grain layer was observed at the sine wave interface, and some precipitated phases disappeared inside the fine grains. These were caused by dynamic recrystallization and a certain temperature rise at the interface. The precipitated phases near the fine grain layer only deformed to a certain extent and did not dissolve. This showed that the grains outside the fine grain layer were only subjected to a certain impact without severe deformation and temperature rise, reflecting that the heat-affected zone (HAZ) of MPW was very narrow.