Aging effects on cyclic deformation and fatigue of extruded Mg-Gd-Y-Zr alloy

The aging effects on the deformation and fatigue behavior of extruded Mg-8.0Gd-3.0Y-0.5Zr (GW83) magnesium (Mg) alloy were experimentally studied. The aging process significantly enhances the monotonic strengths under both tension and compression. The ductility under tension is unchanged but the elongation under compression is reduced due to the aging treatment. The cyclic stress-strain curve of the aged GW83 is much higher than that of the corresponding extruded state. The strain-life fatigue curve of the aged GW83 is similar to that of the extruded GW83, but the stress-life fatigue curve of the aged GW83 is much higher, indicating an improved fatigue strength due to the aging process. Similar to the other Mg alloys, a kink point in the strain-life fatigue curve was identified for the aged GW83 Mg alloy, and the kink point of a strain amplitude of 0.80% for the material demarcates the activation of bulk and persistent twinning/detwinning during cyclic deformation. The enhanced fatigue strength is discussed with respect to the observed fragmented persistent slip bands (PSBs) and the inhibition of microcracks by the precipitates in aged GW83.