THE MICROSCOPIC THEORY OF HOMOGENEOUS NUCLEATION IN ALLOYS - II - CALCULATIONS OF NUCLEATION PARAMETERS FOR VARIOUS ALLOY MODELS

The earlier-described microscopical theory of homogeneous nucleation i n alloys is used to calculate the nucleation rate and the critical emb ryo parameters for several alloy models. The results of the calculatio ns provide both qualitative and quantitative information about the cha racteristics of nucleation in alloys and their variations with the sup ersaturation s, the temperature T, and the inter-atomic interaction ra nge r(int). Several approximations of various levels of sophistication are used to treat the composition fluctuation effects which are shown to be usually important for the thermodynamics of nucleation. With in creasing supersaturation or temperature the nucleation barrier lowers and the embryo interface with the exterior phase gets more diffuse, in agreement with the results of previous treatments, but making allowan ce for the fluctuative effects provides significant quantitative refin ements for the results. The limitations of the conventional theories o f nucleation due to neglecting the interaction of different embryos ar e discussed, and their region of validity, depending on the parameters s, T, and r(int), is estimated.