Influence of multiple laser shock peening treatments on the microstructure and mechanical properties of Ti–6Al–4V alloy fabricated by electron beam melting

Laser shock peening (LSP) is an attractive post-processing method to tailor surface microstructure and enhance mechanical performances of additive manufactured (AM) components. The effects of multiple LSP treatments on the microstructure and mechanical properties of Ti–6Al–4V part produced by electron beam melting (EBM), as a mature AM process, were studied in this work. Microstructure, surface topography, residual stress, and tensile performance of EBM-manufactured Ti–6Al–4V specimens were systematically analyzed subjected to different LSP treatments. The distribution of porosities in EBM sample was assessed via X-ray computed tomography. The results showed that EBM samples with two LSP treatments possessed a lower porosity value of 0.05% compared to the value of 0.08% for the untreated samples. The strength of EBM samples with two LSP treatments was remarkably raised by 12% as compared with the as-built samples. The grains of α phase were refined in near-surface layer, and a dramatic increase in the depth and magnitude of compressive residual stress (CRS) was achieved in EBM sample with multiple LSP treatments. The grain refinement of α phase and CRS with larger depth were responsible for the strength enhancement of EBM samples with two LSP treatments.