Prior heat treatment effects on microstructure and corrosion of arc-welded Al–Zn–Mg alloys

The impact of prior heat treatment on the welding performance and corrosion resistance of sand-cast Al-Zn-Mg alloys was investigated by treating samples before the welding process. The study utilized a 3 × 2 experimental designs consisting of six groups: three prior heat treatment states (as-cast, normalized, and quenched) and two welding conditions (welded and unwelded). All these samples were subjected to tensile and hardness tests as well as corrosion resistance assessments. Ultimate tensile strength (UTS) ranged from a minimum of 220 MPa for the as-cast welded samples to a maximum of 350 MPa for the quenched unwelded samples. A significant reduction in hardness was observed in the as-cast welded fusion zone (56.1 Hv) compared to the quenched unwelded condition, which maintained a maximum value of 92.8 Hv. The heat-treated Al-Zn-Mg alloy demonstrated superior corrosion resistance in near-neutral media but suffered a significant decline in stability when exposed to acidic environments. The research validates that the properties of sand-cast Al-Zn-Mg alloys can be successfully tailored and improved through targeted prior heat treatment processes.