The effect of temperature on microstructure and mechanical properties of Al/Mg lap joints manufactured by magnetic pulse welding

TLDR

The study examined Al/Mg lap joints after heat preservation at various temperatures using optical microscopy, scanning electron microscopy, energy‑dispersive spectrometry, and mechanical testing. Heat preservation below 150 °C leaves the joint morphology unchanged, while temperatures of 200–250 °C form brittle intermetallic layers (Al₁₂Mg₁₇ and Al₃Mg₂) that degrade strength, so the joint should not be used above 150 °C.

Abstract

The microstructure and mechanical properties of Al/Mg welded joints after heat preservation at different temperatures were examined by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and mechanical property test. The results showed that the treatment has no obvious effects on the morphology of the Al/Mg welding interface, but the morphology of the grain structure on the magnesium alloy side was improved. When the temperature was below 150 °C, there was no significant change in the microstructure and mechanical properties of Al/Mg welded joint. While, the intermetallic compound layer composed of Al12Mg17 was formed at the interface when the temperature was raised to 200 °C. The welding interface generated two intermetallic compound layers composed of Al12Mg17 and Al3Mg2 as the temperature reached to 250 °C. Intermetallic compounds severely affected the strength of the welded joint because of greater brittleness. In order to maintain reliable performance, the use temperature of the Al/Mg welded structural parts should not exceed 150 °C.