Atomistic and continuum study of interactions between super-screw dislocations and coherent twin boundaries in L 12 -structured Ni 3 Al

Informed by previous experimental observations, this study employed a combination of molecular dynamics simulations and dislocation continuum theory to investigate the interplay of super-screw dislocations and coherent twin boundary (CTB) in Ni 3 Al . The results reveal multiple interaction mechanisms depending on both the applied stress and the pathway for dislocation gliding. A continuum model framework has been developed to quantitatively evaluate the critical shear stress necessary for the CTB to accommodate dislocations along different pathway with the effects of anti-phase boundary (APB) and Complex Stacking fault (CSF) considered. The critical shear stress exhibits a significant inverse dependence on the quantity of dislocations, rendering it unsuitable as a measure of twin boundary strength. Instead, the resistant force of the CTB against all gliding dislocations is suggested as a more appropriate metric for quantifying its strength. This enables a direct comparison of the twin boundary strength between Ni and Ni 3 Al containing different amounts of Shockley dislocations, thereby extending its applicability to a wider range of materials. Our work offers new mechanistic insights critical for understanding and quantitative analysis of the interplay of super-dislocations and micro twining in nickel-based superalloys.