Segregation at selective grain boundaries and its role in temper embrittlement of low alloy steels

Abstract

The experiments have clearly shown that segregation of Sb and Ni occurs in large amounts to only certain grain boundaries in a low alloy steel embrittled at 480°C for 24 hrs. These observations are explained on the basis of Gibb's adsorption; segregation occurring to lower the energy of high-energy, high-angle boundaries. Phosphorous on the other hand, segregated more uniformly to all boundaries in the same steel. The results are used in explaining the segregation and embrittlement behaviour of low alloy steels in quenching and tempering operations. The inhomogenity of segregation observed in the present experiments can be used to advantage at least in some materials. By generating suitable textures so that the high energy boundaries are oriented in preferred directions, the embrittlement can be made anistropic. Such treatments, if plausible, could give rise to large improvement in properties in preferred directions.