Measurements of thermophysical properties of liquid metals by noncontact techniques

Abstract

With the advent of containerless processing techniques such as electromagnetic levitation, it is now possible to study the properties of high-temperature liquid metalsin situ by applying sophisticated noncontact diagnostics, such as pyrometry and high-speed videography. Thermophysical properties of interest are, e.g., specific heat, thermal conductivity, and viscosity. Applying containerless processing, it is also possible to undercool the melt because of the lack of container-induced nucleation sites. This gives access to a metastable region of the phase diagram. The knowledge of thermophysical data in this region is very important, because undercooling plays a major role in any solidification process. The degree of undercooling not only determines the growth velocity, but also is crucial in selecting the eventually obtained metastable solid phase. In this paper, some recent developments are surveyed relating to the noncontact measurements of emissivity, specific heat, electrical conductivity, density, surface tension, and viscosity, as well as a discussion of possible experiments in microgravity.