Non-uniform interfacial impurity segregation

The mechanism of formation of a non-uniform distribution of segregating atoms along a segregation plane is described as a result of attractive impurity–impurity interactions followed by a two-dimensional spinodal-type decomposition at a given interface. The kinetics of decomposition, which is controlled by the uphill diffusion mechanism, is analysed theoretically. The characteristic size, density and coverage of impurity-rich pre-precipitates are non-monotonic functions of time, even under isothermal conditions. The formulae obtained are applied to the description of possible intergranular decomposition in a Cu–Bi system.