Improvement of fatigue properties by shot peening for Mg–10Gd–3Y alloys under different conditions

In the present study we investigated the influence of shot peening on the high cycle fatigue (HCF) performance of the Mg–10Gd–3Y magnesium alloys in four different conditions referred to as-cast, cast-T6, as-extruded and extruded-T5, respectively. The results show that shot peening can cause different degree of enhancement of fatigue performance for Mg–10Gd–3Y alloys depending on the Almen peening intensity applied; and that the Almen intensity could always be found that conferred the optimum improvement. The effect of shot peening was quantified, and for the as-extruded and extruded-T5 alloys it was found to be superior to that for the as-cast and cast-T6 alloys. The peened extruded-T5 Mg–10Gd–3Y alloy showed the highest fatigue strength at 107 cycles of 240 MPa. The results of the analyses established a connection between the grain size, ductility and precipitates within the studied alloys. Microstructure affected the magnitude of the surface roughness induced by shot peening and also the maximum compressive residual stress and its relaxation during fatigue, and then determine the beneficial effect of shot peening.

► Shot peening can improve the fatigue performance of Mg–10Gd–3Y alloy.
► The Mg–10Gd–3Y alloys in different conditions exhibit different peening strengthening effect.
► The peened Mg–10Gd–3Y alloys in different conditions exhibit different fatigue fracture mechanism.
► Grain size, ductility and precipitates are main effect factors on the shot peening strengthening.