Determination of thermodynamic properties of liquid ThMo, UMo, ThTa, UTa, ThW and UW alloys from their phase diagrams

Abstract

The liquidus data for Th-Mo, U-Mo, Th-Ta, U-Ta, Th-W and U-W systems have been measured previously using high purity materials and a newly developed and more precise method of determination of the liquidus. In the present investigation, thermodynamic properties of liquid binary alloys of these six systems have been derived as a function of temperature and composition from their liquidus data employing regular and subregular solution approximations. All these systems exhibit positive deviation from the Raoult law except U-Mo which exhibits regions of both positive and negative deviations. The calculated relative partial molar entropies of the solute (molybdenum, tantalum and tungsten) in the solution indicate considerable ordering in the Th-Mo and U-Mo liquid alloys. The other four systems approach more closely regular solution behaviour. The present thermodynamic data suggest the absence of an intermetallic compound ThTa 2 in the Th-Ta system which was reported previously.