Measuring the twinning stress at the micron scale: A comprehensive comparison of testing geometries

Three micro mechanical testing geometries including micro-pillars, micro-cantilevers and micro-shear specimen, were employed to measure the twinning stress of the Cantor high entropy alloy. This study presents a comparative analysis of the challenges in specimen preparation, effectiveness in activating deformation twinning and complexity of post mortem analyses associated with each geometry. Our findings demonstrate that micro-shear testing represents the optimal approach for twinning studies, offering direct activation of the twinning system with the superior reproducibility compared to other geometries. Micro-pillar compression is also suitable for twinning investigations, providing statistical analysis of mechanical data with relatively faster sample preparation. However, micro-cantilever testing presents challenges with a lower success rate in twinning activation and the stress gradients, which complicates quantitative interpretation, resulting in the least favorable geometry for twinning studies.