Effect of age-hardening conditions on high-cycle fatigue performance of mechanically surface treated Al 2024

The present work was aimed at evaluating the effects of shot peening on the fatigue performance of the well known age-hardening aircraft aluminium alloy Al 2024. Shot peening to full coverage was performed using spherically shot (SCCW14) with an average shot size of 0.36 mm and an Almen intensity of 0.20 mmA. After applying the various mechanical surface treatments, the changes in the surface and near-surface layer properties such as surface topography, micro-hardness and residual stress-depth profiles were determined. In addition to the mechanically surface treated specimens, electrolytically polished conditions were used to serve as reference. The fatigue results will be interpreted in terms of the process-induced changes in the resistances to crack nucleation and micro-crack growth.