Phase equilibria in scandium-silicon system

Differential thermal, X-ray phase and metallographic analyses are used to study structure of alloys and to plot the constitution diagram of the scandium-silicon system for the first time. Scandium is varified to produce three compounds with silicon. The Sc5Si3 silicide is melted congruously at 2060 deg C. ScSi and ScSi1.50 silicides are formed by peritectic reactions at 1785 and 1260 deg C, respectively. ScSi1.50 undergoes polymorphous transformation at 1070 deg C and decays at 925 deg C following the ScSi1.50→ScSi+ reaction. All silicides are phases of constant composition, i.e. no marked spheres of their homogeneity are found. Mutual solubility of the components in the solid state is not high (less than 1% at.). There are two eutectic equilibria: L0.77↔+β-ScSi1.50 (1155 deg C) and L0.12↔<α-Sc>+Sc5Si3 (1275 deg C) in the Sc-Si system