Melting Kinetics of Faceted and Non-Faceted Crystals

融化是人类已知的最常见的物理现象之一，但它是最难理解的。该基金旨在更好地理解金属和合金的熔化行为。该研究将提供准确的数据上的固-液界面动力学作为界面过热，熔化速率和组合物的函数。界面过热将直接从两个固液界面产生的塞贝克电势差测量;一个固定，另一个以给定的速度熔化。测量技术的一个重要特点是它允许对界面温度进行精确、非侵入性和连续的监测。选择用于研究的材料将由纯Sn（非刻面形成金属）和Bi（刻面形成剂）的单晶以及含有高达4at% Bi的Sn-Bi单晶组成。研究的主要目的是获得定量信息的界面动力学作为熔化速度的函数单晶，并在熔化过程中的溶质再分配，调查的科学意义源于这样一个事实，即熔化动力学提供的界面的性质，因为它响应偏离局部平衡的信息。这种信息将描述熔化界面是否是扩散的，或者它的行为是否类似于凝固期间的行为。熔化动力学规律除具有理论意义外，还对铸件等轴组织的形成等一系列技术问题具有重要意义。这种结构的形成强烈地依赖于孕育剂、固有固体颗粒的熔化和溶解动力学以及局部凝固条件。该项目将使研究生接触材料科学和工程领域的基础研究和测量技术。

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.