Laser Shock Processing of ENAW 6082 Aluminium Alloy Surface

The present paper treats results of laser shock processing applied to a precipitationhardened ENAW 6082-T651 aluminium alloy. Processing was performed with a Nd:YLF-yttrium lithium fluoride crystal laser with power densities of 2 and 4 GW/cm2, producing a pulse of 18 ns. Laser shock processing experiments were performed with the closed ablation method, the application of an ablative coating and a transparent tamping medium to obtain a higher shock-wave pressure. In the first phase, the surface study focused on the record of surface profile with a roughness gauge and on an evaluation of surface topography at a scanning electron microscope. In the second phase, residual stresses were measured using the relaxation hole-drilling method at a processed specimen surface. Then followed measurement of microhardness in the cross section. The hardening results obtained were evaluated on the basis of variations of residual stresses and of microhardness, and of macro and microstructural changes of the surface, i.e. the surface layer. The purpose of processing was to improve fatigue strenght and, consequently, extend the life of a machine component in operation.