Influence of Repair Welding on Mechanical Property and Residual Stress of Laser-MIG Hybrid Welded 6082 Aluminum Alloy Butt Joint

Abstract

Aluminium welded plate structures are widely used in industry for the sake of the lightweight design. During welding of aluminium plates, unacceptable weld flaws may be found. A gouging and repair welding is usually an economical solution. However, mechanical property and residual stress changes due to repair welding are not well understood. In this study, the coupled thermo-mechanical welding and repair welding simulations were performed. The welding experiments and residual stress tests were also conducted. Samples were evaluated through metallography, tensile test and hardness. The results showed that, owing to the composite effect of the decreased hardness in heat affected zone and increased porosity of the weld, the tensile strength of the joint decreased as the times of repair welding increasing. Numerical and experimental residual stresses agree well with each other. It was showed that, in the original welded joint, the residual stress concentrates in the weld and surrounding of heat affected zone. In the repaired joint, the maximum longitudinal residual stress located in centre of the heat affected zone next to the weld. While the minimum and maximum transverse residual stress appeared on lower and upper surface of the butt joint, respectively. Both the maximum longitudinal and transverse residual stress increased with repair times.