The kinetics of surface and grain boundary segregation in binary and ternary systems

Abstract

A theory for the kinetics of surface segregation is proposed that takes specific account of the driving force for segregation, the different surface binding energy at the surface, and also includes the effect of saturation in the surface layer. A general solution is found and applied to the experimental results of Sn segregation in Fe obtained by Lea and Seah (1977). The theory provides a good fit to these data in contrast to the earlier equations proposed by McLean (1957). The theory is then developed for more complex situations including the segregation of two species to a grain boundary when the heat of segregation of each species is related to the surface concentration of the other. Calculations basod on the results are Bhown to display the main features of the temperature-time dependence of temper brittleness in the system Fe–Ni–P.