Interaction of glissile dislocations with perfect and truncated stacking-fault tetrahedra in irradiated metals

Mechanisms for the collapse and absorption of truncated stacking-fault tetrahedra (SFTs) by approaching dislocations are proposed. Both self-energy and elastic interaction energy in a straight dislocation-SFT system are calculated analytically. Although an isolated perfect or truncated SFT is in many cases more stable than a perfect dislocation loop or Frank sessile loop, it can become metastable under the influence of strain fields of surrounding dislocations. Interaction between incident dislocations and SFTs can cause instability of the perfect SFT relative to a truncated SFT, Frank sessile loop and perfect dislocation loop. In general, the interaction between a single SFT and a single dislocation is found to be not large enough for thermal activations to overcome the elastic barriers between a metastable truncated SFT and a stable unfaulted loop. Pinning through core reactions and dislocation pile-ups in certain glide systems approaching the SFT are shown to lower the activation barriers considerably. These collapse and absorption mechanisms can explain the production of defect-free channels in irradiated materials.