Prismatic dislocation loop and helical dislocation generation from ellipsoidal inclusion in inhomogeneous materials: A comprehensive discrete dislocation dynamics simulation

Abstract

Thermal mismatch in inhomogeneous materials can be alleviated by the formation of prismatic dislocation loops (PDLs). While previous studies focused on PDL generation from spherical inclusions, mechanisms for PDL generation from non-spherical inclusions remain unclear. To address this gap, this work employs discrete dislocation dynamics (DDD) simulations to systematically investigate PDL generation from ellipsoidal inclusions. Our results demonstrate PDL can be generated from the ellipsoidal inclusions with varying aspect ratios and orientations, even from non-rotationally symmetric regions. PDL generation from the fiber side and continuous generation from the fiber tip match experimental observations well. We have refined the mechanism of helical dislocation formation that larger inclusion size weakens the attraction between opposite screw dislocations, and higher misfit strain increases the difference in resolved Peach-Koehler force on relevant slip planes due to inclusion, both of which suppress pinch-off process. We identify the acceleration mechanism for atom transfer that when demands for atom transfer rise due to larger ideal PDL size or higher misfit strain, helical dislocations tend to form, accelerating atom transfer. These findings align well with experiments and simulations in the literature. This study advances the understanding of dislocation behavior and stress state near non-spherical inclusions, offering guidance for designing inhomogeneous materials with superior mechanical properties.