Local Laser Annealing for Aluminium Alloy Parts
A method of local laser annealing for aluminium alloy parts was developed. In this study, the structural material 5251 H18 aluminium alloy was considered and the conditions for the removal of cold-hardening and formation of recrystallized structure were obtained. The method was implemented using a CO2 laser processing unit. In the laser optical transformation system, the focusing mirror was a diffractive optical element (DOE)–focusator of laser radiation. The power density was increased at the periphery of the rectangular-shaped heat source, which was moving at a constant speed. This resulted in uniform thermal conditions across the width of the heat affected zone (HAZ). The local laser annealing of plastic deformation areas provides an increase in the ultimate elongation, and a decrease in the minimum bend radius. Annealing by this method before cold stamping provides an opportunity to increase the strength of machine parts on account of using of cold-worked sheet and round billets.
Keywords: CO2 laser, 5251 H18 aluminium alloy, annealing, diffractive optical element (DOE), recrystallized metal structure, heat affected zone (HAZ)