Joint softening in heat affected zone during metal inert gas welding of Al–12·7Si–0·7Mg alloy

Al–12·7Si–0·7Mg alloy is a typical novel wrought Mg containing high Si aluminium alloy with good plasticity and high strength, which is manufactured at a low cost without the addition of a modifier during casting. After T6 treatment, the alloy exhibits much better mechanical properties. In this study, Al–12·7Si–0·7Mg alloy plates after T6 treatment were butt welded using the metal inert gas welding method using imported ER4047 welding wire. The microstructures and mechanical properties of welded joints were studied by a confocal laser scanning microscope, microhardness tests, tensile test methods and transmission electron microscopy. The results showed that the welded joints were seriously softened and the fracture position of the welded joints located in the heat affected zone (HAZ). The softening in the HAZ of the welded joints was mainly attributed to the aggregation and growth of precipitations under the influence of welding heat.