Comparison of the effects of submerged laser peening, cavitation peening and shot peening on the improvement of the fatigue strength of magnesium alloy AZ31

To investigate the improvement in the fatigue strength of magnesium alloy by peening methods, magnesium alloy AZ31 was treated by submerged laser peening (SLP), cavitation peening (CP), and shot peening (SP), and the fatigue properties were evaluated by a plane bending fatigue test. In the case of SLP, both the impact induced by laser ablation (LA) and that caused by laser cavitation (LC), which developed after LA, were used. In the present study, the fatigue life at a constant bending stress was examined to determine the suitable coverage. It was found that the fatigue strengths at N = 107 for the SLP, CP, and SP specimens treated by each optimum condition were 56%, 18%, and 16% higher, respectively, than that of the non-peened (NP) specimen, which was 97 MPa. The key factors in the improvement of fatigue strength by peening methods were work hardening and the introduction of compressive residual stress.