Effect of laser shock peening on mechanical and microstructural aspects of 6061-T6 aluminum alloy

Laser shock peening (LSP) of 6061-T6 aluminum alloy was performed and parametric effects post LSP on mechanical aspects and microstructural evolution are meticulously studied using various means of characterization techniques such as residual stress analysis, surface roughness, Vickers microhardness, tensile testing, X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM) and electron back scattered diffraction (EBSD). Work hardened layer of similar to 1500 mu m depth is obtained with significant improvement in cross-sectional microhardness up to 33.04 %. Beneficial compressive residual stress of maximum magnitude up to -273 MPa was induced in laser peened specimens concentrating its overall effect around the depth of 100 mu m along the effective depth region. Second phase Mg5Si6 (beta '') precipitates were observed post LSP while analyzing XRD profiles along with the peak broadening and peak shifting towards higher 2 theta angle justifying the results obtained in residual stress profile. Mg5Si6 (beta '') precipitates are attributed as contributing precipitates in improving the mechanical properties of LSPed specimens along with the dense dislocation density caused by severe plastic deformation during LSP. High angle grain boundaries (HAGBs) fraction was increased in LSPed specimens and its effect is noticed in microhardness profile. The collective contribution of strain hardening, second phase precipitates, peak broadening, dislocation density and increased fraction of HAGBs is observed in mechanical and microstructural aspects of LSPed specimens. The results are discussed in detailed and are strongly correlated with each other.