Effect of Double Shot Peening on Room-Temperature Notched Fatigue Property of TC4 Titanium Alloy

Single shot peening (SSP) with cast-iron shot and double shot peening (DSP) with cast-iron shot and ceramic shot were applied to investigate the relationship between surface integrity status and the fatigue property of titanium alloy TC4 on the notched specimens (stress concentration coefficient Kt=1.7). Surface roughness, residual stress profile and fatigue curve of the notched specimens were tested using scanning profilometer, XRD residual stress tester and rotating-bending fatigue testing machine, respectively. The results showed that surface roughness decreased 18.3% from Ra 1.09 μm post SSP to Ra 0.89 μm after DSP. Moreover, the position of the maximum value of residual stress migrated out close to the surface and the value of surface residual stress raised 12.6% to-800MPa from SSP. Additionally, the fatigue limit of the notched specimens pose SSP increased 64.7% to 467MPa from 283 MPa of AM, furthermore, edged up by 8% from 432MPa on unpeened smooth samples. It may be concluded that the double shot peening on titanium alloy has, therefore, eliminated the weakness of fatigue property caused by stress concentration.