Cyclic deformation and fatigue of extruded Mg–Gd–Y magnesium alloy

Cyclic deformation and fatigue of extruded rare-earth Mg–8.0Gd–3.0Y–0.5%Zr (GW83) magnesium (Mg) alloy were experimentally investigated by carrying out fully reversed strain-controlled tension–compression experiments along the extrusion direction with the strain amplitudes varying from 0.275% to 5.0%. Monotonic tension and compression stress–strain curves display a smooth transition from elastic to elastic–plastic deformation and exhibit a fairly yielding symmetry. Different from conventional Mg alloys, the material shows near-symmetric stress–strain hysteresis loops and marginal cyclic hardening with almost zero mean stress in the fully reversed strain-controlled experiments conducted. With increasing number of loading cycles, a transition of stress–strain response from concave-down shape to sigmoidal shape occurs in both tension and compression reversals when the strain amplitudes are larger than 2.0%. The strain-life fatigue curve displays a similar feature to that of conventional Mg alloys: A detectable transition from low-cycle region to high-cycle region occurs at a kink point in the vicinity of a strain amplitude of 0.75%. The cyclic deformation and fatigue properties of GW83 Mg alloy and the associated cyclic deformation mechanism are discussed and compared with those of a typical conventional Mg alloy.