Development and Application of Methods for Predicting the Temperature-Composition Stability of Refractory Phases

摘要

Computer programs have been developed by generating ternary phase diagrams of frequency transition metals. Solutions for equilibria between liquid, bcc, hcp and fcc phases as well as miscibility gap formation in these phases are presented based upon the regular solution model. Interactions between these phases and Laves and AuCu3 type compounds are treated to compute the effect of compound intrusion on solution phase equilibria. This development can be applied to compute 286 ternary systems containing zirconium, hafnium, niobium, tantalum, molybdenum, tungsten, rhenium, ruthenium, osmium, rhodium, iridium, palladium and platinum. This development permits computation of the vapor pressure and vaporization rates of individual components and estimates of the heats of formation of ternary compound phases. Ternary sections in the Mo-W-Os, Zr-Ta-W, Re-W-Ta and Re-Hf-Mo systems at temperatures between 1800K and 3000K have been computed for comparison with the limited number of experimental ternary phase diagrams of refractory transition metals. (Author)