Fatigue Properties of Aluminum Alloy Sheet Treated with Shot-Peen Forming in Salt-Spray Environment

The effects of shot-peen forming on the fatigue properties of aluminum alloy samples were measured with a mechanical testing & simulation (MTS) tester in atmospheric and salt-spray environments. After shot-peen forming, the fatigue performance of the aluminum alloy sheet was significantly improved in both the atmospheric and the salt spray environment. Compared with the detail fatigue rating (DFR) value in the atmospheric environment, in the salt-spray environment, the DFR value of the original samples decreased to 110.82 MPa, decreasing by 4.47%. The DFR value of the shot-peen-forming samples decreased to 151.03 MPa, decreasing by 11.40%. Fatigue fracture characteristics demonstrate that the number of crack sources decreased after shot peening. However, the corrosion rate test in a neutral saline environment showed that the corrosion resistance of the aluminum alloy sheet decreased after shot peening. In the salt-spray environment, surface residual-stress analysis showed that there was about 30 MPa tensile stress on the original sample, and 100 MPa compressive stress on the shot-peened sample. Therefore, the improvement in the fatigue resistance of the aluminum alloy sheet after shot peening was largely due to the residual compressive stress introduced on the surface of the aluminum alloy.