Depletion effects in surface segregation of sulfur from polycrystalline high-purity α-iron

Abstract

Recently, scanning Auger microscopical investigations of repeated surface segregation of non-metallic impurities like sulfur, nitrogen and carbon from high-purity polycrystalline α-iron have revealed significant differences in the segregation kinetics of sulfur at the surfaces of the individual grains. This is a consequence of the different extent of the sulfur from grains which zone which extends to several 10 μm into the bulk. These differences diminish when surface diffusion of sulfur from grains which have nearly reached the equilibrium S coverage leads to an almost homogeneous equilibrium distribution of sulfur. A computer model is presented which combines the advantages of the layer-by-layer approach and the solutions of the continuous diffusion equations and allows the segregation kinetics to be calculated of highly dilute multi-component alloys. Model calculations performed to simulate the segregation kinetics of sulfur from iron are in good alphaeement with experimental results.