Temperature dependence of the phosphorus segregation at the twin boundary in an Fe–4 at.% Si alloy

AES of in situ fractured bicrystals of an Fe–4 at.% Si alloy containing traces of phosphorus was used to study the temperature dependence of the segregation at the symmetrical {112} (coherent twin) grain boundary between 773 and 1173 K. The observed enrichment of P decreases with temperature, whereas that of Si increases slightly. This behaviour is described by a mutual repulsive interaction coefficient α′ = 92 kJ mol −1 of P and Si and the corre‐sponding pure binary segregation enthalpies Δ H 0 P = −7.9 kJ mol −1 and Δ H 0 Si = −3.0 kJ mol −1 , the absolute values of which are considerably lower than those reported for polycrystalline samples of FeP and FeSi. The differences are explained on the basis of orientation, concentration and interaction effects.