A study on the effects of laser shock peening on the microstructure and substructure of Ti–6Al–4V manufactured by Selective Laser Melting

Ti‐6Al‐4V was fabricated by powder-bed fusion using different laser scanning strategies. The microstructure and deformation properties were investigated in the as-built condition, and also after the material had been subjected to a laser-shock-peening (LSP) treatment. The microstructure in each condition was surveyed using 3D optical microscopy, EBSD, and TEM. The post-manufacture residual stresses were determined. The results indicate a correlation between the residual stresses and the substructures observed in TEM: tensile residual stresses from the surface down to 1 mm depth were observed in the as-built material, corresponding to extensive deformation through twinning of the 101̅2 type and wavy slip structures; while after LSP the alloy showed a variety of dislocation arrangements, especially planar and in significantly higher density, along with 112̅2 twins and with the presence of compressive residual stresses. The findings indicate that the deformation capability is mechanistically aided by the peening process, which effectively promotes the replacement of tensile residual stresses by compressive ones, offering routes for potentially improving the mechanical properties of the additively manufactured Ti‐6Al‐4V, as well as its usability.