A Study On Interactions Of Ratcheting, Low Cycle Fatigue And Corrosion Of AZ31B Mg Alloy

Wrought magnesium alloys are very attractive for lightweight design and biological materials justified by their low density, high strength-to-weight ratio, high specific stiffness, good machinability and recyclability. It have great significance to evaluate the low cycle fatigue(LCF) properties of magnesium alloys, and give an insight into the studies on the corrosion fatigue properties of magnesium alloys.A miniaturized corrosion fatigue testing system for round bar specimens was developed. Through performing cyclic fatigue tests under the environment with and without corrosive medium, the ratcheting and low cycle fatigue properties of an as-extruded AZ31 B alloy were investigated. In the three stages of ratcheting strain evolution, the ratcheting strain rate of specimen testing in air and corrosion environment was similar at the transient and steady stages. Corrosion rate and ratcheting strain increased with the stress amplitude and mean stress. The occurrence of twining and de-twining further increased the sensitivity to the corrosion environment. The fatigue life of the alloy in PBS solution was significantly shorter than that in air and its reduction ratio of fatigue life to that in air could vary from 50% to 90%. To reflect the effects of mean stress, corrosion and maximum compressive stress to the fatigue behavior, FP parameter fatigue life model and Ellyin's energy model were employed and modified for predicting the fatigue life under complicated loading conditions. Based on the modified Ellyin's energy model, the predicted results can be well fitted with the experimental results...