Vibration fatigue performance and strengthening mechanism of TC6 titanium alloy by laser shock peening

Laser shock peening (LSP) of TC6 titanium alloy was designed and the characteristics of the residual stress distribution with different power density were tested by XRD. The microstructure after LSP was observed by transmission electron microscope (TEM). And then, vibration fatigue test was carried out on TC6 samples with and without LSP. Results show that the optimal power density to process TC6 titanium alloy is 3 GW/cm². LSP could induce high residual compressive stress field in material, and the residual stress on surface could reach -660 MPa. The maximum residual stress is -690 MPa, locating at 0.1 mm below the surface. There is no new phase produced by LSP. The grain refinement and the permanent micro-deformation make the width of Bragg diffraction peak broad. High density dislocation and nanocrytallization are produced after LSP, and the nanocrystal sizes range from several nanometers to dozens of nanometers. LSP improves the endurance fatigue limit of TC6 sample from 438.6 MPa to 526.7 MPa, about 20.1% higher than the endurance limit before LSP. Typical fracture appearance indicates that residual stress and microstructure refinement by LSP together enhance the fatigue ability of TC6 titanium alloy.