IMPURITY SEGREGATION IN AN FE-3.5 AT PERCENT-SI BICRYSTAL

In polycrystalline materials, the segregation kinetics is determined by complex transport phenomena like grain boundary diffusion, volume diffusion and surface diffusion. A fundamental investigation of these phenomena was performed, studying the simplest model system, which provides two grains and a well defined grain boundary. In the temperature range between 600 and 750-degrees-C the segregation of Si, P and S in an Fe-3.5 at.%Si bicrystal was investigated by means of AES. In early segregation runs, diffusion of P and S out of the grain boundary accompanied the segregation via bulk diffusion, while in later runs a combined bulk and surface diffusion was found. Model calculations were performed to analyse the segregation kinetics of subsequent segregation runs.