Formation and interaction mechanisms of dipolar dislocation loops in fcc metals

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.