Effect of laser shock peening on the mechanical properties of a near-α titanium alloy

Laser shock peening (LSP) or laser shock processing is a novel surface treatment technique for strengthening metal materials. In this work, several investigations were performed to evaluate the effect of LSP on some mechanical properties of a near-alpha titanium alloy Ti834. Micro-hardness measurements of the untreated and LSP treated specimens were carried out by using a Vickers indenter. The depth profiles of subsurface micro-hardness of the shocked region were determined through the electro-polishing material removal in steps of 0.1 mm. It is observed that the micro-hardness of Ti834 alloy can be improved by LSP, and repeated shocks have a very beneficial effect on surface hardening. Residual stress distribution as a function of depth was determined by X-ray diffraction (XRD) with the sin(2)psi method. The high-cycle fatigue performance of the alloy was investigated and the fractographs of fatigue specimens were observed by SEM. Results reveal that the high-cycle fatigue life of Ti834 alloy increases after laser shock peening due to the introduction of compressive stress which can delay the initiation and growth of the fatigue crack. (C) 2014 Elsevier B.V. All rights reserved.