Effect of laser peening with different power densities on vibration fatigue resistance of hydrogenated TC4 titanium alloy. (February 2020)

• Record Type: Journal Article
• Authors: Huang, Shu; Zhao, Jiaxi; Sheng, Jie; Meng, Xiankai; Agyenim-Boateng, Emmanuel; Ma, Donghui; Li, Jing; Zhou, Jianzhong
• Is Part Of: International journal of fatigue. Volume 131(2020)
• Publication Date: 2020-02
• Subjects: Laser peening -- Vibration fatigue resistance -- Hydrogen embrittlement -- Fracture morphology -- TC4 titanium alloy; Materials -- Fatigue -- Periodicals; Materials -- Fatigue; Periodicals; 620.1122
• DOI: 10.1016/j.ijfatigue.2019.105335
• Languages: English
• ISSNs: 0142-1123

Abstract

Graphical abstract: Laser peening process introduces high level of compressive residual stress and beneficial microstructures (dislocations, dislocation cells, dislocation walls, dislocation entanglements) in the superficial layer of treated TC4 alloy, and effectively inhibiting the initiation and propagation of hydrogen-induced cracks. Highlights: Effect of LP-induced CRS on fatigue crack initiation and propagation was investigated. Micro-structure evolution of hydrogenated non-LPed and LPed specimens were determined. Vibration fatigue fracture morphologies of hydrogenated LPed specimens were studied. Proposed a strengthening mechanism of LP on vibration fatigue resistance of samples. Abstract: Laser peening (LP) treatment with different power densities was used to improve the vibration fatigue resistance of hydrogenated TC4 titanium alloy. Compressive residual stress (CRS), micro-hardness and micro-structure of hydrogenated LPed specimens were firstly measured. Vibration fatigue test was then carried out to compare the fatigue life and fractures of LPed and non-LPed hydrogenated specimens. It was found that LP-induced high level CRS suppressed the permeation of hydrogen atoms through material surface, which may reduce the hydrogen embrittlement sensitivity. The CRS also prohibited the fatigue crack initiation and propagation by increasing the fatigue limit and crack propagation threshold of hydrogenated specimen. Grain morphologies of α phase and β phase were refined after LP. Beneficial crystal defects inside the α phase and β phase tangled more free hydrogen atoms, which was believed to be crucial factors to inhibit the generation of initial hydrogen-induced crack. Fracture morphologies further confirmed that LP changed the location of fatigue crack initiation (FCI) and slowed down the fatigue crack growth (FCG) rate of hydrogenated specimens. Finally, a strengthening mechanism of LP on the vibration fatigue resistance of hydrogenated specimen was proposed.