Alloying Behavior of Ni<SUB>3</SUB>Nb

Abstract

The site preference of ternary additions in Ni 3 Nb (D0 a ) was determined from the direction of solubility lobes of the GCP phases which were available from the reported ternary phase diagrams and constructed in the present work. It was shown that Cr, Co and Cu preferred the substitution for Ni-site, Ti, V, Hf, Ta and W the substitution for Nb-site, and Fe the substitution for both sites. The thermodynamic model, which was based on the change in total bonding energy of the host compound by a small addition of ternary solute, was applied to predict the site preference of ternary additions. The bond energy of each nearest neighbor pair used in the thermodynamic calculation was derived from the heat of compound formation by Miedema's formula. The agreement between the thermodynamic model and the experimental result was excellent. From both experimental and theoretical results, both the transition and B-subgroup elements have two possibilities, i.e., the case of substitution for Ni-site or the case of substitution for Nb-site, depending on the relative value of two interaction energies.

Substitution Behavior of Ni3X-type Compounds with D0a Structure

“…Therefore, the same thermodynamic treatment as that conducted for the L1 2 -type Ni 3 X compounds may be applicable to other Ni 3 X-type compounds. Actually, the alloying behavior of D0a-type Ni 3 Nb [15][16][17], D0 22 -type Ni 3 V [16,17] and D0 24 -type Ni 3 Ti [16,17] compounds has been investigated. Consequently, the agreement for preferable site occupation of the addition between the thermodynamic prediction and the experimental result was found to be excellent.…”

Alloying Behavior of Ni<SUB>3</SUB>M-Type Compounds with D0<SUB>a</SUB> Structure

“…Reported temperatures range between 1173 and 1473 K. The table shows the direction and the extent of solubility limit for each solute element. Fe 24) substitutes for both sites, Co 15,16,18,19) and Cu 23) mostly for Ni-site, and Hf, 15,16) Ta, 15,16) Ti, 15,16,25,26) V, 27) and W 28,29) mostly for Nbsite. The ternary systems with Al, 15,16) with Cr, [20][21][22] and with Si 15,16) did not provide a clear indications of substitution behavior in Ni 3 Nb because of very small solid solubility.…”

“…15) and Ti 15) at 1473 K are taken from literatures. The symbols ''Ni'', ''Ta'', and ''Ni/Ta'' in the column ''Substitution site'' mean that third element substitutes for Ni-site, Ta-site and both sites, respectively.…”

“…Therefore, the same thermodynamic treatment as that conducted on L1 2 -type Ni 3 M compound may be applicable to other Ni 3 M-type GCP compounds. Actually, the alloying behavior of D0 a -type Ni 3 Nb, 15,16) D0 22 -type Ni 3 V 16) and D0 24 -type Ni 3 Ti 16) compounds has been investigated and reviewed. Consequently, the agreement for preferable site occupation of the addition between the thermodynamic prediction and the experimental result was found to be excellent.…”

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.…”