LAUSR

Abstract Phase equilibria at 1300 °C in the Ti–Ga–Sn system in the concentration interval 50–100 at.% Ti were studied by the methods of X–ray diffraction (XRD), scanning electron microscopy (SEM) and electron microprobe analysis. The partial isothermal section at 1300 °C was constructed. A ternary compound Ti 5 GaSn 2 (τ), found by us previously, was confirmed in this section (1300 °C). The phase locates along the isoconcentrate 62.5 at.% Ti and extends from 4.5 till 28 at.% Ga. The lattice parameters of the phase were calculated in a tetragonal Nb 5 SiSn 2 –type structure with the values: a  =  10.579(3)–10.307(1), c  =  5.310(2)–5.106(1) A . The binary based phase Ti 5 Ga 3 also locates along the isoconcentrate 62.5 at.% Ti due to mutual substitution of the Sn and Ga atoms. D8 8 –type compounds Ti 5 Sn 3 and Ti 5 Ga 4 form a continuous solid solution, denoted Ti 5 (Sn,Ga) 3-4 . Ga-poor part of it (below ∼12.5 at.% Ga) forms by an interstitial mechanism, while in the interval above ∼12.5 at.% Ga it is a substitution phase. The Sn and Ga atoms substitute each other. Isostructural Ti 2 Sn and Ti 2 Ga at 1300°С do not form a continuous solid solution, in contrast to the solidus projection. Solubility of Ga in Ti 3 Sn and Ti 2 Sn is 13.5 and 2 at.%, respectively. Solubility of Sn in Ti 2 Ga and Ti 5 Ga 3 is 14 and 6 at.%, respectively. At 1300 °C ternary compound τ coexists with all the phases based on binary compounds of the border systems (Ti 3 Sn, Ti 2 Sn, Ti 2 Ga, Ti 5 Ga 3 , Ti 5 (Sn,Ga) 3-4 ). The isothermal section at 1300°C in the concentration interval studied is characterized by six three-phase fields: (βTi) + (Ti 3 Sn) + (Ti 2 Ga), τ + (Ti 3 Sn) + (Ti 2 Sn), τ + (Ti 2 Sn) + Ti 5 (Sn,Ga) 3-4 , τ + (Ti 3 Sn) + (Ti 2 Ga), τ + (Ti 2 Ga) + (Ti 5 Ga 3 ) and τ + (Ti 5 Ga 3 ) + Ti 5 (Sn,Ga) 3-4 .