Effect of Residual Stress on S–N Curves and Fracture Morphology of Ti6Al4V Titanium Alloy after Laser Shock Peening without Protective Coating

Materials

Liucheng Zhou¹  Weifeng He¹  Xinlei Pan¹  Xiaotai Feng¹  Sihai Luo¹  Xiang Li² 

[1] Science and Technology on Plasma Dynamics Laboratory, Air Force Engineering University, Xi’an 710038, China;The First Training Brigade of Shi Jiazhuang Flying College of PLA Airforce, Shijiazhuang 050000, China;

关键词: crack initiation;    mean stress;    fatigue performance;    laser shock peening;    ti6al4v titanium alloy;   

DOI  :  10.3390/ma12223799

来源: DOAJ

【 摘 要 】

In this paper, the effect of residual stress on the stress−life (S−N) curve and fracture morphology characteristics of Ti6Al4V titanium alloy after laser shock peening (LSP) without protective coating was experimentally investigated. The fatigue test and residual stress measurement were conducted on specimens before and after the LSP process. It was shown that LSP produced a high-amplitude compressive residual stress field on the surface of the specimen. After the LSP process, the fatigue life limit was increased by 16%, and the S−N curve shifted upward. Then, based on the theory of mean stress, the mechanism whereby the compressive residual stress improves the fatigue life of Ti6Al4V titanium alloy was analyzed. It indicated the improvement in fatigue life was because of the high-amplitude compressive residual stress on the surface and in depth induced by LSP to reduce the tensile stress produced by external loading. In addition, the scanning electron microscope (SEM) pattern of fatigue fracture demonstrated distinct differences in the fracture morphology before and after LSP. After LSP, the crack initiation sites of the samples moved to the subsurface where it was difficult for fatigue cracks initiating here. Moreover, after the LSP process, there were high density of fatigue striations and many secondary cracks on the fracture of the treated specimen.

【 授权许可】

Unknown