Investigating twin boundary-dislocation interactions in Mg-Y using quasi in-situ nanoindentation and electron channeling contrast imaging

Abstract

Defect–grain boundary interactions have been proven essential for the development of tailored microstructures for high-performance materials. We aim to unravel the mechanical response of grain boundaries by investigating dislocation activity in the vicinity of a tensile twin boundary (TB) in Mg-Y. A combined approach of quasi in-situ nanoindentation, electron channeling contrast imaging (ECCI), and high-resolution electron backscattered diffraction (HR-EBSD) was employed to induce localized deformation and analyze the resulting TB response. Nanoindentation in the parent grain near the TB produces distinct pop-ins, indicating deformation events close to the boundary. Observed slip includes pyramidal $〈c+a〉$ activity in the twin and prismatic slip in the parent grain. It is shown that dislocation pile-ups cause TB bulging rather than transmission, which is consistent with low slip transmission factors. However, limited slip transmission is observed. Peach–Koehler force calculations based on the Nye tensor and the elastic strain extracted from 2D HR-EBSD measurements confirm that TB motion may be induced by dislocation pile-ups.