Effect of laser shock peening on laser-repaired TC4

For the process of TC4 alloy in laser additive manufacturing, the laser shock peening was employed to modify the surface of the laser-repaired specimens. A relationship model between macroscopic experiments and microscopic molecular simulation was established to study the atomic internal structure and dislocation evolution laws. The shock response accompanied the generation of dislocations to achieve the plastic deformation strengthening of the material. LSP markedly refined the grains and promoted more random crystallographic orientations. Quantitatively, reduced the α-phase aspect ratio by approximately 60%, and decreased the α-Ti texture intensity by 39.98%, respectively, confirming that LSP improved microstructural uniformity. The combined molecular simulation, EBSD, and TEM results indicate that LSP-induced strengthening is mainly associated with grain rotation, dislocation tangles, low-angle grain boundaries, and compressive twins{11-22} <11-23>. LSP generated the compressive residual stress of the surface from 39.82 MPa to −234.33 MPa. LSP increased the tensile strength and yield strength of the repaired specimens by 11.8% and 6.5%. It also improved the corrosion resistance of the repaired TC4 alloy specimens. These findings demonstrate that the macro–micro correlation model, combined with mechanical property and electrochemical validation, provides a mechanistic basis for optimizing LSP post-treatment of laser-repaired titanium alloy components.