Melting Point of Pure Cr and Phase Equilibria in the Cr-Si Binary System

The melting point of pure Cr and phase equilibria in the Cr-Si binary system were determined by thermal analysis using a differential scanning calorimeter (DSC) and differential thermal analyzer (DTA). In addition, the composition of two-phase alloys was analyzed using an electron probe microanalyzer (EPMA). Heat treatment above 1500 °C was conducted in a high-frequency induction heating furnace, where the temperature was estimated by a two-color pyrometer with an accuracy of ± 20 °C. The melting point of pure Cr was determined to be 1861 ± 3 °C, considering the O and N impurities. The phase diagram of the Cr-Si system was determined in the whole composition range. The invariant reaction related to the formation of Cr 3 Si and Cr 5 Si 3 phases was confirmed as the eutectic reaction of liquid ↔ Cr 3 Si + Cr 5 Si 3 . The solubility range of Cr 3 Si phase is on the Cr-rich side from the stoichiometric composition, whereas the solubility range of Cr 5 Si 3 phase extends toward the Si-rich side. We found using the x-ray diffraction that the α-Cr 5 Si 3 /β-Cr 5 Si 3 transformation does not exist.