The magnetic origin of anomalous high-temperature stability of dislocation loops in iron and iron-based alloys

The dominant occurrence of the b=a(001) prismatic edge dislocation loops in iron and iron-based alloys irradiated at temperatures approaching 500 °C is a striking anomaly distinguishing iron and its alloys from other bcc metals. It is surprising that the a(001) dislocation loops form at all, since there is an alternative b=a/2(111) dislocation loop configuration that, according to the conventional isotropic treatment of elasticity, has a lower self-energy. In this paper we highlight the magnetic aspect of the problem and note the fundamental link between the α–γα–γ phase transition, the elastic anisotropy of iron, which is particularly significant at elevated temperatures, and thermal magnetic fluctuations.