A new thermal vibration mechanical shot peening coupling strengthening method

Compressive residual stress (CRS) is induced to delay fatigue crack initiation and prolong fatigue life, in which CRS amplitude and influence depth play an important role, but the traditional mechanical shot peening (MSP) treatment can not further increase the strengthening effect. An innovative thermal vibration MSP (TVMSP) coupling method is proposed to improve the distribution of induced residual stress (RS). Firstly, four strengthening treatments are performed in TA19 titanium alloy by coupling different loads. Subsequently, the gradient RS along the depth, surface morphology and roughness and the microstructure along the depth section are measured and characterized. The experimental results show that the maximum CRS (MCRS) amplitude is increased by 25.43 % and its depth is significantly increased by 100 %. The surface roughness increases slightly due to thermal softening, while the residual iron oxides are shaken off by vibration. The electron back scatter diffraction (EBSD) results indicate that grains are refined, and higher kernel average misorientation (KAM) is aggregated near the surface and deeper positions. Finally, based on these results, the macroscopic mechanical mechanism and microstructure evolution mechanism of RS formation and the formation of surface impact dimple are revealed.