Thermodynamic modeling of the Co–Ni–Y system

The thermodynamic properties of the Co–Ni–Y system have been analyzed by means of the CALPHAD technique. The solution phases (liquid, body-centered cubic, face-centered cubic and hexagonal close-packed) were modeled with the Redlich–Kister equation. The line intermetallic compounds (Co,Ni)17Y2 and (Co,Ni)5Y were treated as one phase with the formula (Co2,Ni2,Y)(Co2,Y)2(Co,Ni)15, based on their crystal structures, by a three-sublattice model with Co2, Ni2, and Y on the first sublattice, Co2 and Y, and Co and Ni on the second and third one, respectively. The other intermetallic compounds were treated as the line compounds (Co,Ni)mYn by a two-sublattice model with Co and Ni on the first sublattice, Y on the second one, respectively. A self-consistent thermodynamic description of the Co–Ni–Y system was obtained.