Effect of repeated impacts on mechanical properties and fatigue fracture morphologies of 6061-T6 aluminum subject to laser peening

The effect of repeated impacts on mechanical properties and fatigue fracture morphologies of 6061-T6 aluminum subject to laser peening (LP) were investigated. Compared with the untreated samples, nano-hardness and fatigue lives of the samples subjected to 1-3 LP impacts increased by 18.1–59.1% and 7.3–99.4%, respectively. Residual stress presented compressive state on the superficial layer of the samples after LP, and the value increased with the increase of the impact number. LP caused the location of fatigue crack initiation (FCI) transferring from the top surface to sub-surface, and the distance from FCI to the top surface increased with the increase of the impact number. Meanwhile, the fatigue striation spacing (FSS) on the fatigue crack growth (FCG) area decreased with the increase of the impact number. In addition, the enhancement mechanism of LP on the resistance of FCI and FCG were discussed.