Improving heat-affected zone softening of aluminum alloys by in-situ cooling and post-weld rolling

Abstract

The welding of aluminum alloys (Al-alloys) is of great practical relevance in several industries, but the process can be problematic due to the prevalence of a well-known softening phenomenon in the fusion zone (FZ) and heat-affected zone (HAZ) surrounding the weld. This phenomenon has a unique gradient-like characteristic such that the HAZ near the FZ softens the most and the softening degree decreases as the distance from the FZ increases. To minimize the adverse effect of joint softening, this study proposes the use of a novel hybrid manufacturing process for joining AA5083-O and AA6061-T6 dissimilar Al-alloys, using tungsten inert gas (TIG) welding with filler wire under in-situ cooling conditions using specialized welding fixtures followed by the subsequent rolling of the weld reinforcement. The results show that welding under in-situ cooling conditions can improve the joint softening gradient, and the rolling of the weld reinforcement can introduce a strain hardening gradient, that greatly improves the integrity of the joint. By employing the proposed method, the fracture is successfully transferred from the HAZ of the AA6061-T6 side, where it normally occurs, to the base metal (BM) of the AA5083-O side. The proposed process has an extremely high impact potential as it can greatly increase the adoption of Al-alloys in the manufacturing of lighter automotive vehicles which will improve their efficiency and performance.