699.017.3.24'295'793'The Ti-Ni-Sc diagram has been examined for nickel contents of 50-100 at. %. The alloys were prepared by arc melting and were examined by metallography, differential thermal analysis, and microprobe analysis. There are four nonvariant equilibria: two incongruent ones and two congruent ones. The minimum melting point of 980°C occurs in alloys with the base composition (TiNi3) + (ScNi2) + (TiNi), which form a eutectic.Nothing has been published on component interaction in the ternary Ti-Ni-Sc system. For that reason, and also because of interest in scandium as a metal that simultaneously shows the properties of the d-transition and rare-earth metals, we examined the structure and properties of alloys in the Ti-Ni-Sc system to derive the phase diagram, as those properties undoubtedly have effects on the interaction with other metals.It has been shown [1] that the section between the equiatomic 6 phases based on compounds TiNi and ScNi (leaving aside deviations from 1:1 stoichiometry in the sense of a higher scandium content at Scl.13Ni) is quasibinary, which allows one to treat the Ti-Ni-Sc ternary system as conminting two independent subsystems TiNi-Ni-ScNi and Ti-TiNi-ScNi-Sc, with the phase equilibria between them considered simultaneously.Here we present data on the equilibria at the solidus surface and the reactions in the crystallization in the partial TiNi-Ni-ScNi system, for which one of the intermediate states is the above section. The compounds TiNi and ScNi form a continuous series of 6-solid solutions having crystal structures of CsC1 type at subsolidus temperatures. In the separate regions of the subordinate Ti-Ni and Sc-Ni systems, the phase diagrams are partly unknown [2], apart from the presence of equiatomic 6 phases and a phase based on TiNi 3 (e, principal structure type), Laves phase ScNi 2 (h 2, MgCu 2 type), and two phases derived from Laves phases: Sc2Ni 7 0', Ce2Ni7 type) and ScNi 5 (~, CaCu 5 type). The 6 phases (TiNi and ScNi) and the e, ~2, and u phases crystallize from the liquid at temperatures of 1310, 1270, 1380, 1310, and 1290°C respectively. The ~ phase is formed by L + u ~ /~ peritectic reaction at 1170°C.The e phase in the Ti-Ni system does not have an extensive homogeneity region and forms eutectics with the 3' solid solution based on nickel at 1304°C and 85 at.% Ni and the 6 phase at 1118°C and 61.5 at.% Ni. The solubility of titanium in nickel is 12 at. %, while that of nickel in the 6 phase is 6 at. % at the temperatures of the corresponding eutectics [2]. The Sc-Ni system shows eutectic crystallization between the 3' and ~ phases, the ~, and ~'2 ones, and the X 2 and 6 ones: L ~ 3" + ~j (1140°C, 88 at.% Ni); L ~ ~, + )~2 ( 1260°C, 75 at.% Ni) and L ~ X 2 + 6 (IlI0°C, 60 at.% Ni).To derive the phase diagram for the TiNi-Ni-ScNi system, we used studies on the phase equilibria of the alloys in the subsolidus temperature range in this composition region and results obtained on examining the behavior of the cast alloys.The alloys were melted in an arc furaace ha...
