Estimation of critical data and phase diagrams of pure molten metals
Wolffram Schröer and Gernot Pottlacher
Measurements of thermophysical properties of liquid metals are demanding and thus rare. A recently published collection provides high temperature data for a set of 22 metals. Although the measurements concern data in the range up to 5000 K, the critical region however, is mostly far beyond the region accessible experimentally at present, with the exception of alkali metals. Knowledge of the phase diagrams and of the critical data are of fundamental interest and important for high-temperature technologies. Thus an attempt is made to extrapolate the available data into the critical region. A novel approach for extrapolating the density data is applied taking into account recent theoretical developments in the field of critical phenomena, which are the crossover from the universal criticality of the 3d-Ising model towards mean-field behaviour, and the theory of complete scaling that describes the nonlinearity of the diameter of the phase diagrams. The method is tested on phase diagrams of cesium, for which accurate phase diagrams up to the critical region are available. Comparison is made with measurements of the critical temperature by the ‘exploding wire technique’ of gold, lead and zinc. Corresponding state behaviour of the metals is discussed.
Keywords: Critical point data, modelling, Au, Pb, Zn