Substitution Behavior of Ni₃X-type Compounds with D0a Structure

Abstract

The site preference of ternary additions in GCP (geometrically close-packed) Ni 3 X-type compounds with D0a structure was determined from the direction of the single-phase region of the D0a phase in the reported ternary phase diagrams. The thermodynamic model based on the Bragg-Williams approximation, which is based on the change in heat of formation of the host compound by a small addition of ternary solute, was applied to predict the site preference of ternary additions. The heat of 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.

Alloying Behavior of Quaternary Elements in Ni<SUB>3</SUB>(Si,Ti)

“…2,3) The agreement for the substitution behavior of ternary elements between the prediction and the experimental results was found to be excellent. Later, the same treatment has been conducted on other GCP structures, that is, on Co 3 Ti with L1 2 structure, 4) Ni 3 Nb, Ni 3 Ta, and Ni 3 Mo with D0 a structure, Ni 3 V with D0 22 structure, and Ni 3 Ti with D0 24 structure by the present author's group [4][5][6][7][8] and was shown to be successful in predicting the substitution behavior of ternary elements. Regarding the solubility limits of ternary elements X in Ni 3 Al and Ni 3 Ga with L1 2 structure, a successful prediction was found by Ochiai et al, 1) based on the two-dimensional map, in which the difference in heats of formation between Ni 3 Al (or Ni 3 Ga) and Ni 3 X, and the changing rate of lattice parameter by alloying of Ni 3 Al (or Ni 3 Ga) were taken into calculation as two parameters.…”