In materials science, the concept of the Cottrell atmosphere was introduced by A. H. Cottrell and B. A. Bilby in 1949[1] to explain how dislocations are pinned in some metals by boron, carbon, or nitrogen interstitials.
Cottrell atmospheres occur in body-centered cubic (BCC) and face-centered cubic (FCC) materials, such as iron or nickel, with small impurity atoms, such as boron,[2] carbon,[3] or nitrogen.[citation needed] As these interstitial atoms distort the lattice slightly, there will be an associated residual stress field surrounding the interstitial. This stress field can be relaxed by the interstitial atom diffusing towards a dislocation[citation needed], which contains a small gap at its core (as it is a more open structure), see Figure 1. Once the atom has diffused into the dislocation core the atom will stay. Typically only one interstitial atom is required per lattice plane of the dislocation.[citation needed] The collection of solute atoms around the dislocation core due to this process is the Cottrell atmosphere.
- ^ Cottrell, A. H.; Bilby, B. A. (1949), "Dislocation Theory of Yielding and Strain Ageing of Iron", Proceedings of the Physical Society, 62 (1): 49–62, Bibcode:1949PPSA...62...49C, doi:10.1088/0370-1298/62/1/308
- ^ Blavette, D.; Cadel, E.; Fraczkiewicz, A.; Menand, A. (1999). "Three-Dimensional Atomic-Scale Imaging of Impurity Segregation to Line Defects". Science. 286 (5448): 2317–2319. doi:10.1126/science.286.5448.2317. PMID 10600736.
- ^ Waseda, Osamu; Veiga, Roberto GA; Morthomas, Julien; Chantrenne, Patrice; Becquart, Charlotte S.; Ribeiro, Fabienne; Jelea, Andrei; Goldenstein, Helio; Perez, Michel (March 2017). "Formation of carbon Cottrell atmospheres and their effect on the stress field around an edge dislocation". Scripta Materialia. 129: 16–19. doi:10.1016/j.scriptamat.2016.09.032. ISSN 1359-6462.