Formation and interaction mechanisms of dipolar dislocation loops in fcc metals

TL;DR

This study uses 3D dislocation dynamics simulations to explore how dipolar dislocation loops form, interact, and influence plastic deformation in fcc metals, revealing mechanisms behind their patterning and effects on material hardening.

Contribution

It identifies two main formation mechanisms of dipolar loops enabled by cross-slip and analyzes their interactions, providing new insights into their role in plastic deformation.

Findings

Dipolar loops form mainly via cross-slip mechanisms.

Interactions can produce immobile segments leading to hardening.

Dipolar loops cluster within slip band walls due to glide dislocation activity.

Abstract

Dipolar dislocation loops, prevalent in fcc metals, are widely recognized as controlling many physical aspects of plastic deformation. We present results of 3D dislocation dynamics simulations that shed light on the mechanisms of their formation, motion, interactions, and large-scale patterning. We identify two main formation mechanisms, enabled by cross-slip, and show that arrays of dipoles can be easily formed as a result of the interaction between glide screw dislocations. We present a systematic analysis of the spectrum of possible junctions that can form as a result of mutual interaction between dipoles, and between dipoles and glide dislocations. We show that fully immobile dislocation segments arise in particular cases of these interactions, leading to hardening and Frank-Read type sources. We reveal that the collective motion of dipolar loop arrays can be induced by glide dislocations in the channels of Persistent Slip Bands (PSB), and result in their clustering within PSB channel walls. An efficient tripolar drag mechanism is found to contribute to the clustering of dipolar loops near channel walls.