NUCLEATION AND PHASE SELECTION IN UNDERCOOLED FE-CR-NI MELTS .1. THEORETICAL-ANALYSIS OF NUCLEATION BEHAVIOR

The selection of the primary solidifying phase in undercooled stainles s steel melts is theoretically analyzed in terms of nucleation theory. Nucleation phenomena are considered using different models for the so lid-liquid interface energy. The classical nucleation theory for sharp interfaces and an improved modification, the diffuse interface theory , are applied.:The influence of deviations of the nucleus composition from the overall: alloy composition is also revealed. A preferred nucl eation of the metastable bcc phase in fee equilibrium solidification-t ype alloys is predicted. The critical undercooling of metastable cryst allization as a function of alloy composition is calculated for an iso plethal section at 69 at. pct Fe of Fe69Cr31-xNix alloys. The results are summarized in a phase selection diagram predicting the primary sol idification mode as a function of undercooling and melt composition.