Characterization of Deformation Mechanisms in Mg-1Y Alloy Utilizing In Situ Tensile Testing in SEM and High-Resolution Electron Backscattered Diffraction

Magnesium (Mg) alloys are viable candidates for lightweight structural materials application in aerospace, automotive, and defense industries. However, their widespread application is limited by low ductility due to the dominance of basal slip. Mg-Y alloys have been actively studied because of their enhanced ductility and non-basal slip. Nonetheless, the mechanisms underlying mechanical behavior remain unresolved due to complex interactions among grains and grain boundaries in polycrystalline Mg alloys. In this study, an in situ tensile test was performed on a polycrystalline Mg-1 wt.%Y alloy in a scanning electron microscope (SEM) in conjunction with high-resolution electron backscatter diffraction (HR-EBSD). A total of 93 grains were systematically investigated through pre-analysis of Schmid factor, in situ analysis of geometrically necessary dislocations (GNDs), and post-deformation analysis of slip traces. The results show that slip is activated both within grain interiors and near grain boundaries. The non-basal slip near grain boundaries was predominantly observed in grains with a low Schmid factor for pyramidal slip and exhibiting characteristic GND density evolution with increasing strain. These findings suggest that the enhanced ductility of Mg-Y alloys can be attributed to active slip independent of crystal orientation, which is promoted by grain boundaries.