Melting Kinetics of Faceted and Non-Faceted Crystals

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Melting is among the most common physical phenomena known to mankind, yet it has been the most difficult to understand. This grant is aimed at a greater understanding of melting behavior of metals and alloys. The research will provide accurate data on the solid-liquid interface kinetics as a function of the interface superheating, melting rate, and composition. The interface superheating will be measured directly from the Seebeck potential difference generated across two solid-liquid interfaces; one stationary and the other melting at a given velocity. An important feature of the measurement technique is that it allows for a precise, non-intrusive and continuous monitoring of the interface temperature. The materials selected for the study will consist of single crystals of pure Sn (a non-facet forming metal) and Bi (a facet former), and Sn-Bi single crystals containing up to 4 at % Bi. The primary objective of the research is to obtain quantitative information on the interfacial kinetics as a function of melting velocity for single crystals, and on the solute redistribution during melting.The scientific significance of the investigation stems from the fact that melting kinetics provide information on the nature of the interface as it responds to deviations from local equilibrium. Such information will delineate whether the melting interface is diffuse, or whether it behaves similar to that during solidification. In addition to its theoretical significance, the melting kinetics laws are of interest for a series of technical problems such as in the formation of equiaxed structures in castings. Formation of such structures strongly depends on the melting and dissolution kinetics of inoculants, intrinsic solid particles, as well as on the local solidification conditions. The project will expose graduate students to fundamental research and measurement techniques in materials science and engineering.