Enhanced extra-long life fatigue resistance of a bimodal titanium alloy by laser shock peening

• Published in: International journal of fatigue 2020-12, Vol.141, p.105868, Article 105868
• Main Authors: Yang, Kun, Huang, Qi, Zhong, Bin, Wang, Qingyuan, Chen, Qiang, Chen, Yao, Su, Ning, Liu, Hanqing
• Format: Article
• Language: English
• Subjects: Compressive properties; Compressor blades; Deformation twin; Dislocation density; Fatigue strength; Fatigue tests; Grain boundaries; High cycle fatigue; Laser shock peening (LSP); Laser shock processing; Lasers; Materials fatigue; Peening; Plastic deformation; Residual stress; Titanium alloys; Titanium base alloys; Very high cycle fatigue (VHCF)
• ISSN: 0142-1123; 1879-3452
• DOI: 10.1016/j.ijfatigue.2020.105868

•Microstructural evolution along the depth direction presents a gradient feature.•Four types of deformation twins are introduced into primary α phases.•High-angle grain boundaries are increased by deformation twins (~13%).•Strengthening mechanisms of extra-long life fatigue resistance are revealed. Ultrasonic fatigue tests were performed on notched specimens to investigate high and very high cycle fatigue behaviors in the laser shock peened region of a compressor blade titanium alloy (Ti–8Al–1Mo–1V). The plastic deformation and compressive residual stress, induced by the laser shock peening (LSP), present gradient distributions along the depth direction. High-angle grain boundaries (HAGB, >15°) are increased by deformation twins, which are introduced into primary α phases during the plastic deformation. The enhancement in fatigue resistance is ascribed to the comprehensive retardation effects of the compressive residual stress, high-density dislocations, and HAGBs.