Gradient microstructure and vibration fatigue properties of 2024-T351 aluminium alloy treated by laser shock peening

• Published in: Surface & coatings technology 2020-06, Vol.391, p.125698, Article 125698
• Main Authors: Meng, Xian-kai, Wang, Hui, Tan, Wen-sheng, Cai, Jie, Zhou, Jian-zhong, Liu, Lin
• Format: Article
• Language: English
• Subjects: 2024-T351 aluminium; Aluminum base alloys; Compressive properties; Compressive residual stress; Crack initiation; Crack propagation; Fatigue failure; Fatigue life; Grain boundaries; Laser shock peening; Laser shock processing; Lasers; Microstructure; Morphology; Nanohardness; Peening; Residual stress; Surface roughness; Vibration fatigue; Vibration measurement
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2020.125698

To investigate the improvement in vibration fatigue and the strengthening mechanism of laser shock peening, a nanosecond laser was used to strengthen the 2024-T351 aluminium alloy. Accordingly, the microstructure, residual stress, nanohardness and surface roughness of the treated alloy were measured. Subsequently, the vibration fatigue damage and fatigue life were evaluated, and the vibration fracture morphology was observed. The results showed that the grains in the peened surface were refined. A residual stress of −141 MPa and a nanohardness of 3.1 GPa were obtained by laser shock peening. Based on the relationship between the peened microstructure and fracture morphology, it was deduced that an increase in the grain boundaries led to a lower crack initiation rate and a higher crack initiation life. The compressive residual stress decreased the crack growth rate and increased the crack growth life. Therefore, laser shock peening increases the total vibration fatigue life by about 63.5%. •The distribution of microstructure had important effects on fatigue fracture process.•The mechanism of vibration fatigue life extension induced by LSP was studied.•Vibration fatigue damage was decreased and fatigue life was increased by LSP.