Low temperature study of phase equilibria in the Co–Ni–W ternary system: Evidence of a new intermetallic phase Co3W-D0a

Abstract Tungsten heavy alloys (Co–Ni–W) of different compositions were prepared by powder metallurgy (solid sintering), heat treated at 800 °C and 1000 °C and subsequently analyzed. The experimental phase identifications and composition measurements emphasized discrepancies compared to the isothermal ternary sections simulated with commercial thermodynamic databases. The isothermal sections at 800 °C and 1000 °C were found more complex than expected since a new intermetallic phase appeared to be stable (D0a structure - Cu3Ti prototype). Likewise, an interpretation of phase equilibria evolution with temperature was established to reach agreement with high temperature data. Formation enthalpies associated with the new phase were obtained through first-principles calculations and supported experimental results as they confirmed the stabilizing role of Ni addition for the D0a structure.