Фазовая диаграмма системы Sc-Ti

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Sc-Ti (Scandium-Titanium) J.L. Murray The Ti-Sc phase diagram was studied by [62Bea] and [61Sav]. The present assessment is based on [62Bea], because the Sc used was of greater purity. The assessed diagram is the result of thermodynamic calculations, using Gibbs energies obtained by least-squares optimization with respect to the experimental data of [62Bea]. The monotectoid and eutectoid temperatures and (bTi,bSc)/(aSc) boundaries were determined by thermal analysis on heating and cooling. For the three-phase reactions, the average of heating and cooling arrests were taken, and the uncertainties indicate the difference between the arrests on heating and cooling. For the solid-state reactions, the arrest on heating is probably closer to the equilibrium reactions, giving 1060 and 883 C as possibly more accurate temperatures. The accuracy of the congruent melting point is about с5 to 10 C. The accuracy for alloys with a melting range is probably less. Based on the composition increments of the alloys examined, the accuracy of the solvus is about с1 at.%. The compositions of the phases in equilibrium at the monotectoid temperature are less well known (с2 to 3 at.%), because they are based on extrapolations to the monotectoid temperature of curves with low slopes. The solubility of Ti in (aSc) can be extended to 41 at.% by rapid solidification [76Wan]. The extended solubility arises from solute trapping during the L <259> b <259> a transformation; the b <259> a transformation is martensitic. 61Sav: E.M. Savitskii and G.S. Burkhanov, Zh. Neorg. Khim., 6(5), 1253-1255 ( 1961) in Russian; TR: Russ. J. Inorg. Chem., 6(5), 642-643 (1961). 62Bea: B.J. Beaudry and A.H. Daane, Trans. AIME, 224, 770-775 (1962). 76Wan: R. Wang, Mater. Sci. Eng., 23(2-3), 135-140 (1976). Published in Phase Diagrams of Binary Titanium Alloys, 1987. Complete evaluation contains 3 figures, 3 tables, and 4 references. Special Points of the Ti-Sc System