Effect of surface Nanostructuring on LCF behavior of aluminum alloy 2014

Effect of ultrasonic shot peening (USSP) on microstructure and low cycle fatigue behavior of the aluminium alloy 2014 and in general in age hardened condition was studied at room temperature. No phase change was observed due to USSP. The grains of the ultrasonic shot peened (USSPed) region were refined to nanosize (~30 nm). Microhardness of the USSPed surface was increased by 45% from shot peening for 15 min. Compressive residual stress of 550 MPa was maximum at the surface of the USSPed specimens. Ultrasonic shot peening was found to enhance the low cycle fatigue as well as high cycle fatigue life. LCF life of the USSPed specimens was further increased by the subsequent stress relieving treatment at 150 °C for 2 h, in particular at low strain amplitudes. The results are discussed in terms of increased resistance against fatigue crack initiation.