Phase equilibria in the Ti-rich corner of the Ti-Si-Ga system

Phase relations in the ternary Ti-Si-Ga system have been established experimentally by means of a study of alloy samples in the as-cast condition and annealed at 1350 °C. The alloys were prepared by arc melting. The investigation was carried out using physico chemical methods of analyses (metallography, X-ray powder diffraction, differential thermal analysis, and electron probe microanalysis over a limited composition range with samples containing less than 38 at.% Ga and more than 62 at.% Ti. Liquidus and solidus surface projections, the isothermal section at 1350 °C, and the isopleth at 68 at.% Ti are presented. Three surfaces of primary crystallization of phases have been established: extended ones for Ti5(Si,Ga)3 and β (Ti-base solid solution) and a narrow one of Ti2Ga. The monovariant curves separating these are due to the eutectic reactions L↔β+Ti5(Si,Ga)3 and L↔β+Ti2Ga and to the L+Ti5(Si,Ga)3↔Ti2Ga peritectic reaction. The three-phase region (β+Ti5(Si,Ga)3+Ti2Ga) results from the four-phase eutectic reaction L↔β+Ti5(Si,Ga)3+Ti2Ga. The composition of the ternary eutectic point E and the compositions of the coexisting solid phases have been determined. The solubilities of Si in the gallides, and of Ga in Ti5Si3 and of both the elements in Ti are given.