Fatigue Performance Improvement of Titanium Alloy with Microstructure Gradient and Residual Stress Gradient Produced by Laser Shock Peening

In the present paper, the fatigue performance of a TC6 titanium alloy with a microstructure gradient and residual stress gradient produced by laser shock peening (LSP) is investigated. After LSP, a 1 mm thickness gradient compressive residual stress layer with a maximum surface compressive residual stress of −708 MPa is introduced into the materials. Electron back-scattering diffraction (EBSD) and transmission electron microscopy (TEM) techniques are used to characterize the microstructural evolution of the TC6 titanium alloy subjected to LSP. The results show that a nanostructured layer forms on the surface of the TC6 titanium alloy. At a depth of 20 μm, high dense dislocation and nanocrystalline are observed on the top surface. Based on the results of the microstructural characterization, it is found that dislocation movement is the main reason for the formation of nanocrystalline on the top surface. A high-cycle fatigue test showed that the fatigue limit of the TC6 titanium alloy treated by LSP improves from 431 ± 10 MPa to 486 ± 14 MPa, increasing by 12.8%.