Comparative Analysis of the Ternary Ti–REM–{Si, Ge, Sn, Ga} Phase Diagrams

 

I. M. Frantsevich Institute for Problems of Materials Science of the NAS of Ukraine, Omeliana Pritsaka str.,3, Kyiv, 03142, Ukraine
Powder Metallurgy - Kiev: Frantsevich Institute for Problems of Materials Science NASU, 2016, #03/04
http://www.materials.kiev.ua/article/2174

Abstract

The Ti–REM–p-element phase diagrams at up to 40 at.% p-element were analyzed. The features that distinguish the series systems is the presence of two-phase equilibria R5X3 + (Ti) and Ti5X3 + (R). According to these features, the systems are divided into three types. The system is attributed to a group by the relative thermodynamic stability of compounds R5X3 and Ti5X3. The factor δ = ΔfН [R5X3] / ΔfН [Ti5X3] is proposed to predict the nature of the phase diagrams of the unstudied systems Ti–R–{Si, Ge, Sn, Ga}. If δ < 1, the phase Ti5X3 defines the nature of the phase equilibria and the system belongs to type 1. The most characteristic topological feature of systems of this group is two–phase equilibrium Ti5X3 + (R). If δ > 1, the phase R5X3 defines the nature of the phase equilibria. The system belongs to type 2, its topological feature is two–phase equilibrium R5Х3 + (Ті). If δ ≈ 1, the phases Ti5X3 and R5Х3 equally define the nature of the phase equilibria, the system belongs to type 3, and its topological feature consists in no equilibria Ті5Х3 + (R) and R5X3 + (Ті) but in the presence of equilibria (Ті) + τ and (R) + τ.


FORMATION ENTHALPY, STATE DIAGRAM, THERMODYNAMICS