Impact toughness and microstructural response of Ti-17 titanium alloy subjected to laser shock peening

Laser shock peening is an innovative surface treatment, which has been shown to greatly improve the fatigue performance of Ti-17 alloy. This work investigates the impact toughness of Ti-17 treated by LSP with different laser energies. The results show that impact toughness increases by 2.1%, 11.7%, 64.1%, and 53.5% compared with a non-peened surface as the laser energy changes to 1, 3, 5, and 7 J, respectively. Ti-17 exhibits a hardened layer after peening. A residual compressive stress of 382 MPa is induced after four impacts with a laser of energy 5 J. Fracture surface analysis and transmission electron micrographs are used to observe the microstructural changes. The micrographs establish a cleavage mechanism combined with the formation of a few dimples. The proliferation and tangling of dislocations in Ti-17 occurs and the dislocation density increases after LSP treatment. In addition, deformation twins are found after LSP treatment, which are helpful in improving the plasticity of the titanium alloy. (C) 2017 Published by Elsevier B.V.