Effect of long period stacking ordered phase on the fatigue properties of extruded Mg-Y-Zn alloys

The fatigue properties of two Mg-Y-Zn alloys with different amount of long-period stacking order (LPSO) phase, Mg97Zn1Y2 and Mg89Zn4Y7, were investigated. Low-cycle fatigue experiments were conducted under strain-controlled conditions. Both the monotonic and cyclic yield strength increased with the LPSO volume fraction. Cleavage-like facets were found to be at the origin of crack initiation in both alloys. High-cycle fatigue experiments were conducted under microscopy monitoring. Increasing the LPSO-phase volume fraction decreased the fatigue life but improved the endurance limit. Cracks initiated from alpha-Mg grains in both materials. Crack growth rates were found to be relatively similar.