Improvement in fatigue life of Al 7475-T7351 alloy specimens by applying ultrasonic and microshot peening

• The paper focus is the analyse of the possible benefits of shot peening and ultrasonic peening on the improvement of the fatigue life of AA7475-T7351 components in mind possible aerospace applications.
• A systematic study was carried out on the roughness, surface hardening, residual stress profiles and fatigue life.
• All of the surface treatments enhanced the specimens fatigue lives, despite having created different superficial conditions.

Shot peening and ultrasonic peening are widely used mechanical surface treatment in the automotive and aerospace industries to improve the fatigue life of metallic components. This work aims to further improve the mechanical properties of the AA7475-T7351 alloy by applying three different peening processes: Ultrasonic Peening (USP) and Microshot Peening with two different beads size (MSP).A systematic study was carried out on the roughness, surface hardening, residual stress profiles and fatigue life. Uniaxial fatigue tests were conducted. Residual stresses were evaluated by X-ray diffraction, and the fracture surface was observed and analysed with a Scanning Electron Microscope. The microstructures of the specimens were observed by optic microscope. Microhardness and roughness were also measured.All of the surface treatments enhanced the specimens fatigue lives, despite having created different superficial conditions. In addition, the experimental results and analytic predictions based on the Molski-Glinka approach were compared, and in general, agree well.