Multiaxial fatigue of extruded ZK60 magnesium alloy

Multiaxial monotonic and cyclic behaviors of ZK60-T5 magnesium extrusion are investigated. Strain-controlled tests were performed at standard laboratory condition with fully reversed straining. Twinning-detwinning deformation plays an important role in the cyclic axial behavior for tests that were performed under strain amplitudes higher than 0.4%. However, the hysteresis loop for the 0.4% was found symmetric and no sign of twinning-detwinning deformation was observed. On the contrary, the cyclic shear behavior was found to be similar to conventional alloys and no significant asymmetric or twinning-detwinning deformations were observed. The multiaxial fatigue tests suggest that multiaxiality and nonproportionality are not detrimental to fatigue life. Three multiaxial fatigue damage models were used: Smith-Watson-Topper, Fatemi-Socie, and Jahed-Varvani. While Fatemi-Socie and Jahed-Varvani models show comparable estimation, Smith-Watson-Topper overestimates shear and nonproportional lives.