Damage and fracture behaviours of 5A06 aluminium alloy welded joint under thermal cycling condition

The 5A06 aluminium alloy is widely used in the aerospace industry, owing to its good corrosion resistance and excellent weldability. The tensile strength of this material welded joint can reach 90% of that of the base alloy. However, when used in aerospace applications, thermal cycling conditions can affect the mechanical performance of the alloy. In this paper, the deterioration of mechanical properties and damage mechanism of 5A06 aluminium alloy welded joint under thermal cycling conditions were investigated. The tensile performance was examined after the thermal cycling test. The microstructural changes and fracture mechanism were analysed. Results show that the thermal cycling can induce more severe damage in the welded joint than in the base 5A06 aluminium alloy. The particles formed in the weld heat affected zone are the source of local damage during thermal cycling. The thermal mismatch stress plus the external stress can cause debonding between the particles and the base alloy. Microvoid nucleation and evolution around the particles cause the mechanical properties deterioration of the welded joint during thermal cycling.