On the Impurity Parameters for Impurities Detected in the Eutectics Co–C and Pt–C and Their Role in the Estimate of the Uncertainty in the Eutectic Temperatures

Abstract

In this paper, impurity parameters mi and ki have been calculated for a range of impurities I as detected in the eutectics Co–C and Pt–C, by means of the software package Thermo-Calc within the ternary phase spaces Co–C-I and Pt–C-I. The choice of the impurities is based upon a selection out of the results of impurity analyses performed for a representative set of samples for each of the eutectics in study. The analyses in question are glow discharge mass spectrometry (GDMS) or inductively coupled plasma mass spectrometry (ICP-mass). Tables and plots of the impurity parameters against the atomic number Zi of the impurities will be presented, as well as plots demonstrating the validity of van’t Hoff’s law, the cornerstone to this study, for both eutectics. For the eutectics in question, the uncertainty u(TE − Tliq ) in the correction TE − Tliq will be derived, where TE and Tliq refer to the transition temperature of the pure system and to the liquidus temperature in the limit of zero growth rate of the solid phase during solidification of the actual system, respectively. Uncertainty estimates based upon the current scheme SIE–OME, combining the sum of individual estimates (SIE) and the overall maximum estimate (OME) are compared with two alternative schemes proposed in this paper, designated as IE–IRE, combining individual estimates (IE) and individual random estimates (IRE), and the hybrid scheme SIE–IE–IRE, combining SIE, IE, and IRE.