Thermophysical properties of Ni-Nb and Ni-Nb-Sn bulk metallic glass-forming melts by containerless electrostatic levitation processing

The containerless high-temperature high vacuum electrostatic levitation (ESL) technique was used for the determination of thermo-physical properties of the binary eutectic alloy, Ni_59.5Nb_40.5, and the ternary alloy Ni₆₀Nb_34.8Sn_5.2. The thermo-physical properties measured were density, specific heat over hemispherical total emissivity, surface tension and viscosity. The density for both the melts was found to be higher than that predicted by the rule of mixtures. This was attributed to strong attractive interaction between the constituents. The temperature dependent specific heat capacity of the binary alloy was determined by fitting with TEMPUS results. The hemispherical total emissivity was estimated to be 0.27. Using the specific heat data and the hemispherical total emissivity, the enthalpy and entropy of fusion were calculated for the binary alloy. The viscosities for both the alloys were fit with the Vogel-Fulcher-Tammann equation to obtain the fragility parameter. The surface tension for the binary alloy showed an anomalous positive gradient while that of the ternary alloy showed a small negative gradient with temperature.