Texture-driven transition from isolated to collective twinning in magnesium alloy

This is the authors' abstract. We don't add key points for this paper.

This work uncovers a non-intuitive picture of twinning evolution in rolled AZ31 magnesium alloy by combining in-situ neutron diffraction with rotational sampling and EBSD. Contrary to expectations based on nearly uniform Schmid factor distributions for the same grain families around the rotation axis of the specimen, twinning activity exhibits a pronounced orientation selectivity: the strongest twinning-associated response is observed for grains with basal planes perpendicular to the sheet normal direction. Even more intriguingly, the twinning-associated depletion of the parent (0002) orientation population follows a robust power-law scaling with grain orientation density (MRD), with an exponent that remains nearly constant over most of the deformation and increases above approximately 6–7% true strain, indicating a change in how the twinning-associated response is distributed among orientation populations. Unlike commonly reported dynamic power laws associated with intermittent plasticity, this scaling describes a population-based relation and does not resolve individual twinning events. Local twin variant selection is asymmetric, while DIC, EBSD, and supplementary time-resolved observations are consistent with interaction-assisted, potentially autocatalytic twinning across neighboring grains. This behavior is accompanied by the formation of organized mesoscopic twin-rich deformation bands. Together, these findings show that the observed azimuthal twinning response is not described by Schmid factor considerations alone, but also reflects texture, grain interactions, and mesoscopic strain compatibility.