Sensitivity Analysis for Stress, Heat-Treating, and Rare- Earth Elements on Fatigue Lifetime of AZ91 Magnesium Alloy

In this article, the changes in High-Cycle Fatigue (HCF) lifetimes of the AZ91 magnesium alloy are investigated under the influences of the different heat treatments and also the Rare-Earth (RE) element addition. For this purpose, some different heat treatments, including a common solution treatment, with different ageing treatments and RE elements were performed. Then, the sensitivity analysis was done using the regression analysis by the DESIGN EXPERT software on the experimental data. At a similar fatigue lifetime, the RE element increased the strength or the stress level by at least 30%, and also, the RE element with heat-treating enhanced the material strength by at least 50%. The results of sensitivity analysis on the experimental data illustrated that the stress level, the heat treatment, and the RE element (RE) were the most effective parameters on the fatigue lifetime, respectively. Besides, the fatigue lifetime was sensitive to the interaction of the heat treatment and the RE element. In addition, the fracture surface analysis demonstrated that all samples had three different zones for the crack initiation, the crack growth, and the sudden final fracture.