Quantitative investigation on the deformation modes and cracking behavior during cyclic torsional loading of extruded pure Mg and Mg-3Y alloy

This study explores the effect of adding 3 wt.% Y to pure magnesium (Mg) on its mechanical behavior under cyclic torsional loadings at room temperature. The research examines deformation and cracking modes in both pure Mg and Mg-3Y samples. Deformation modes are monitored using quasi-in-situ EBSD observations coupled with slip trace analysis. The findings reveal that basal slip dominates the cyclic deformation throughout the fatigue life of the pure Mg sample, while both basal and pyramidal slip dominate the cyclic deformation in the Mg-3Y sample. Intergranular cracking is the primary cracking mode for both samples under cyclic torsional loadings. Basal and pyramidal slip persistent slip band (PSB) cracking serves as a primary transgranular cracking mode in the pure Mg and Mg-3Y samples, respectively. The study also investigates the underlying mechanism governing the activity of various deformation modes, cracking modes, and mechanical behavior. Under cyclic torsional loadings, the Mg-3Y sample exhibited enhanced activity of nonbasal slip. Intergranular cracking was a dominant cracking mode for the pure Mg and Mg-3Y samples under cyclic torsional loadings. Basal slip and pyramidal slip PSB cracking was a primary transgranular cracking mode in the pure Mg sample and Mg-3Y sample, respectively. The increased activity of nonbasal slip in the Mg-3Y sample is possibly responsible for its longer fatigue life.