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

The dominant occurrence of the b = a ( 0 0 1 ) 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 ( 0 0 1 ) dislocation loops form at all, since there is an alternative b = a / 2 ( 1 1 1 ) 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 – γ phase transition, the elastic anisotropy of iron, which is particularly significant at elevated temperatures, and thermal magnetic fluctuations.