Effect of laser peen forming process parameters on bending and surface quality of Ti-6Al-4V sheets

Laser peen forming (LPF) is a metal forming process that utilizes laser-induced mechanical shock waves to form desired shapes or modify bent structures. The present work focuses on the applicability of LPF to Ti-6Al-4V sheets, to identify an optimal LPF process parameter window and achieve desired bending without compromising the surface quality within the peened region. The effect of LPF process parameters, i.e. laser power density, overlap, type of sacrificial overlay, and the number of peening sequences was investigated for specimens with different thicknesses. The laser power density and number of peening sequences were the most influential parameters that affect the bending of the specimens. Using sacrificial overlay has a significant effect on the bending and surface quality of the specimens. Surface quality after LPF was assessed by measuring the roughness in the peened region. In experiments without a sacrificial overlay, a black titanium oxide residue on the peened region was observed and additionally, small micro-cracks were found in the near surface region. Further characterization of the peened region revealed that the average crack length increased with increase in laser power density. Two possible LPF process parameter combinations were identified to obtain bending in the peened region, where LPF with sacrificial overlay resulted in no surface damage. Furthermore, residual stresses were determined at various LPF process parameters by incremental hole-drilling method in the peened region.