Inductive measurement of thermophysical properties of electromagnetically levitated metallic melts

Abstract

For the containerless processing of high temperature metallic melts the electromagnetic levitation technique, which utilizes high frequency alternating magnetic fields for the contactless, inductive positioning and heating of electrically conducting samples, is well established. For the contactless measurement of surface tension and viscosity of levitated samples via the oscillating drop method optical methods are generally used. But the existence of alternating magnetic fields in electromagnetic levitation facilities suggests to use also inductive methods for non-contact measurements of liquid metal properties. Within a joint ESA project of DLR and TU Graz a measurement device was designed and constructed by DLR, which utilizes the high frequency magnetic fields of microgravity electromagnetic levitation facilities imultaneously also for an inductive determination of thermophysical properties of levitated metallic melts. Although originally planned for electrical resistivity measurements only, the device allows also the detection of surface oscillations, which can be used for a determination of surface tension and viscosity of the levitated droplets. The present paper compares the optical with the inductive measurement technique.