Activation of <c> dislocations in Mg with solute Y

Mg-Y cast alloy shows excellent ductility (elongation to failure > 15%) compared with pure Mg and commercial Mg cast alloys. By monitoring the microstructure evolution during an in situ tensile test of a Mg-2.5 wt%Y alloy, we identify the activation of prismatic <c> slip, which is rare in Mg. Synchrotron X-ray micro-beam Laue diffraction (μ-Laue) and transmission electron microscopy revealed the morphology of prismatic <c> slip bands and individual <c> dislocations. Density functional theory and molecular dynamics calculations indicate that solute Y can significantly reduce the stacking fault energy (SFE) along <c> direction on prismatic plane in Mg lattice and thus facilitate the nucleation of <c> dislocations during deformation. The presence of free <c> dislocations in the Mg lattice can also lead to nucleation of {10–12} twins even under unfavorable geometric conditions.