Alloying Behavior of Ni₃M-Type Compounds with D0_a Structure

抄録

The atom substitution preference of ternary additions in Ni₃M-type GCP (geometrically close-packed) compounds with D0_a structure was determined from the direction of single-phase region of the GCP phase on the reported ternary phase diagrams. In Ni₃Nb, Co and Cu preferred the substitution for Ni-site, Hf, Ta, Ti, V and W the substitution for Nb-site, and Fe the substitution for both sites. In Ni₃Ta, Co, Cu, Fe, Ir, Mn and Re preferred the substitution for Ni-site, Mo and Nb the substitution for Ta-site, and Al and Cr the substitution for both sites. In Ni₃Mo, Pd and W preferred the substitution for Ni-site, and Al, Nb, Ta, Ti and Zr the substitution for Mo-site. The thermodynamic model, which was based on the change in heat of formation of the host compound by a small addition of ternary solute, was applied to predict the atom substitution preference of ternary additions. The heat of compound formation used in the thermodynamic calculation was derived from Miedema’s formula. Good agreement was obtained between the thermodynamic model and the result of the literature search. For Ni₃Mo, with a small negative heat of formation, a weak binding force between the constituent elements is often enhanced by the addition of the ternary elements that substitute for Mo-site.