Effect of cooling rate on deflection, microstructure, and mechanical response of butt-welded aluminium 6082-T6 joints

The correlation between weld-induced microstructural evolution and mechanical response is a key factor in joint performance. However, the combined influence of cooling rate on deflection and mechanical properties in aluminium welds has received limited attention. In this study, butt joints of 6082-T6 aluminium alloy were fabricated using gas metal arc welding under two distinct cooling conditions. Welding-induced deflection was predicted using a sequentially coupled finite element model and validated by experiments. The results showed that forced cooling increased peak deflection by approximately 24% compared with natural cooling, due to a more localized distribution of plastic strain. Between the two cooling conditions, the mechanical properties were broadly similar, although digital image correlation (DIC) indicated slightly higher ductility under forced cooling. Strain localization in the heat-affected zone (HAZ) was consistent with previously reported softening in precipitation-hardened aluminium alloys. Electron backscatter diffraction (EBSD) revealed that natural cooling produced finer grains, while forced cooling limited grain refinement, suggesting that faster cooling restricted recrystallization. Scanning electron microscopy (SEM) showed that both cooling strategies resulted in similar microstructural patterns.