Effects Of Laser Peening With Different Laser Power Densities On The Mechanical Properties Of Hydrogenated Tc4 Titanium Alloy

The mechanical properties of laser peening (LP) treated TC4 titanium alloy before and after hydrogen charging were compared by means of slow-rate tensile tests. Fracture morphologies of the specimens were observed by SEM to identify the fracture mechanism under the interaction of LP-induced compressive residual stress, refined microstructures and hydrogen permeation. Cross-sectional TEM observation was also conducted to investigate the effects of LP and hydrogen charging on the microstructural evolution of the alloy. Under hydrogenated and unhydrogenated conditions, the LPed specimen presented better UTS results. Furthermore, increasing laser power density decreases the rate of hydrogen induced elongation loss, as well as reducing the hydrogen-induced plasticity loss. LP induced microstructures, like high tangled dislocations, mechanical twins, and multi-directional slip bands are believed to be the potential factors of trapping hydrogen atoms movement, which ultimately reduced the hydrogen embrittlement (HE) of the alloy. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.