Defect-controlled twin activation in crystallographically equivalent magnesium micropillars
Abstract
Tensile twinning plays a central role in accommodating -axis plasticity in Mg. In bulk Mg, it typically shows a relatively deterministic response with a low critical stress, whereas in confined volumes it exhibits broad yield-stress distributions that complicate the prediction of small-scale mechanical behavior. Here, site-specific compression tests are performed on 4 μm-diameter pillars fabricated in a parent Mg crystal and an adjacent {10-12} twin. The two regions share the same [11-20] compression axis but experienced different prior deformation histories, allowing the influence of the residual microstructural state to be examined at fixed crystallographic orientation. Among 27 pillars, most parent-region pillars yield near 300 MPa, whereas pillars from the twin region span approximately 30 to 300 MPa. Interrupted tests combined with cross-sectional EBSD link individual load drops to discrete twin formation and further show that a pillar containing a pre-existing twin yields at approximately 80 MPa through the migration of the existing twin boundary. Molecular dynamics simulations of 30 nm-diameter pillars resolve possible atomistic pathways at the nanoscale. The simulations illustrate how contact geometry and pre-existing twin embryos alter event selection, and how an activated twin advances rapidly, while coherent twin boundary migration proceeds through disconnection motion accompanied by crystallographically required atomic shuffles. The results attribute the experimental scatter to the local availability of embryos and mobile interfaces, such that the first plastic event is governed by the twinning pathway accessible from the local microstructural state rather than by a single characteristic critical stress. Deformation history can therefore strongly modify the distribution of first plastic events even when the loading orientation is fixed.
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BibTeX
@misc{wang2026defectcontrolled,
title = {{Defect-controlled twin activation in crystallographically equivalent magnesium micropillars}},
author = {Hexin Wang and Fatim Zahra Mouhib and Chunhua Tian and Sang-Hyeok Lee and Henry Ovri and Julien Guénolé and Sandra Korte-Kerzel and Talal Al-Samman and Zhuocheng Xie},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2608.13703},
eprint = {2608.13703},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.13703},
}
RIS
TY - UNPB
TI - Defect-controlled twin activation in crystallographically equivalent magnesium micropillars
AU - Hexin Wang
AU - Fatim Zahra Mouhib
AU - Chunhua Tian
AU - Sang-Hyeok Lee
AU - Henry Ovri
AU - Julien Guénolé
AU - Sandra Korte-Kerzel
AU - Talal Al-Samman
AU - Zhuocheng Xie
PY - 2026
DA - 2026/09/28
PB - arXiv
DO - 10.48550/arxiv.2608.13703
UR - https://arxiv.org/abs/2608.13703
AB - Tensile twinning plays a central role in accommodating -axis plasticity in Mg. In bulk Mg, it typically shows a relatively deterministic response with a low critical stress, whereas in confined volumes it exhibits broad yield-stress distributions that complicate the prediction of small-scale mechanical behavior. Here, site-specific compression tests are performed on 4 μm-diameter pillars fabricated in a parent Mg crystal and an adjacent {10-12} twin. The two regions share the same [11-20] compression axis but experienced different prior deformation histories, allowing the influence of the residual microstructural state to be examined at fixed crystallographic orientation. Among 27 pillars, most parent-region pillars yield near 300 MPa, whereas pillars from the twin region span approximately 30 to 300 MPa. Interrupted tests combined with cross-sectional EBSD link individual load drops to discrete twin formation and further show that a pillar containing a pre-existing twin yields at approximately 80 MPa through the migration of the existing twin boundary. Molecular dynamics simulations of 30 nm-diameter pillars resolve possible atomistic pathways at the nanoscale. The simulations illustrate how contact geometry and pre-existing twin embryos alter event selection, and how an activated twin advances rapidly, while coherent twin boundary migration proceeds through disconnection motion accompanied by crystallographically required atomic shuffles. The results attribute the experimental scatter to the local availability of embryos and mobile interfaces, such that the first plastic event is governed by the twinning pathway accessible from the local microstructural state rather than by a single characteristic critical stress. Deformation history can therefore strongly modify the distribution of first plastic events even when the loading orientation is fixed.
ER -