Phase equilibria of the Al−Co−W system at 600 °C

Phase relationship in the ternary Al−Co−W system was established for the whole composition range at 600 °C by X-ray powder diffraction, scanning electron microscopy and energy dispersive spectroscopy. Isothermal section of this system comprises of 15 three-phase and 28 two-phase regions. Except the L1₂-γ′ phase, a new ternary phase T has been found. The average composition of the T phase is 22.6 at.% Al, 67.0 at.% Co and W in balance. The solubility of W in AlCo is 3.0 at%, the solubility of Al in Co₃W and Co₇W₆ is both 3.1 at%, and the solubility of Co in Al₄W reaches 3.6 at.%. Solubility of the third component in the other binary phases is limited. The present work is essential to develop a thermodynamic database for Co-related high-temperature alloy design. - Highlights: • The isothermal section at 600 °C of the Al−Co−W system was determined. • Except the L1₂-γ′ phase, a new ternary phase T were found at 600 °C. • Isothermal section of this system consists of 15 ternary phase regions and 28 binary phase regions.