Stability range of the ternary W-phase in the system Al-Co-Ni

The stability range of the ternary W-phase, an approximant to decagonal Al-Co-Ni, has been determined at 900 and 1000 °C. The phase equilibria in the system Al-Co-Ni have been revised in view of the existence of this ternary compound. Isothermal sections have been constructed at 800, 900, 1000 °C in the range from 0 to 11 at.% Ni and from 68 to 74 at.% Al. The W-phase is stable in the temperature range from 900 to 1070 °C. It undergoes a ternary eutectoid reaction W ⇔ X + D + (Co,Ni)2Al5 at the temperature slightly below 900 °C.