Three-dimensional atomic-scale mapping of a cottrell atmosphere around a dislocation in iron

Dislocation morphologies in field ion microscopic (FIM) tips of quenched and room-temperature aged Fe-C alloys are similar to those in thin foils, and the pinned dislocations are barely affected by FIM imaging conditions. Extensive segregation during quenching and aging produces a marked depletion in the C content of the martensite matrix. 3D Reconstruction of interstitial C Cottrell atmospheres around dislocations in iron is achieved for the first time. Atmospheres appear dispersed, with an asymmetric distribution and extend outwards from the dislocation core to a distance of ≈7±1 nm. The maximum C concentration within atmospheres is ≈8±2 at%C.