Abstract
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.
Highlights
With advantages like high strength, excellent corrosion resistance, and good compatibility with composites, titanium alloys have wide application potentiality in the field of the aero-astronautical industry [1,2]
The results showed that the laser shock peening (LSP) process could be applied in a variety of metallic materials, and the specimens with LSP treatment always exhibited effectively improvement of material fatigue life [13,14,15,16,17,18]
Due to the existence of compressive residual stress induced by LSP, the tensile stress produced by external loading was decreased, and the real stress which the specimen suffered from during the fatigue test was lower than the tensile stress which external loading exerted
Summary
With advantages like high strength, excellent corrosion resistance, and good compatibility with composites, titanium alloys have wide application potentiality in the field of the aero-astronautical industry [1,2]. In order to promote the widespread application of the LSP process and give instructions around the technical optimization of LSP without a coating process, there is a need to investigate the CRS distribution induced by LSP without coating and its effects on stress–life (S–N) curves and the fracture morphology of Ti6Al4V titanium alloy. With this in mind, this study is to systematically investigate the residual stress distribution after. The fracture morphology was observed by a scanning electron microscope (SEM)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
