Hf-Ni Provisional

The Hf-Ni (Hafnium-Nickel) System 178.49 58.69

By P. Nash and A. Nash Illinois Institute of Technology

Equilibrium Diagram General Features. The Ni-Hf equilibrium diagram, based mostly on the work of [79Bse] and [67Sve], is shown in Fig. 1. The system is quite complex due to the number of intermediate phases formed. The general features of the d iagram are the nine i n t e rmed ia t e phases (two of which--Ni7Hf2 and N i H f - - a r e congruent ly melt ing whereas the other seven are formed peritectically), the very limited terminal solid solutions, and the metatectic reaction involving the allotropic transformation in Hf. Be- cause no information is abailable regarding solubility in the intermediate phases, these have been taken to be line compounds. A recent review of this system by [81Nas] omits the metatectic reaction.

It should be noted that the Hf used in all of the experi- mental studies contained zirconium, in some instances as much as 3 wt.% Zr. Generally, authors have not worried about this because the Ni-Zr system is considered to be very similar to Ni-Hf; however, the addition of Zr to Hf lowers its melting point. This will probably have an effect on the Ni-Hf diagram, with the greatest effect being at the Hf-rich end. In addition, the possibilities of contamination due to oxygen have never been addressed.

Intermediate Phases. There has been some confusion over the number of intermediate phases, which is caused partly by alternative designations for the same phase and partly

by contradictory evidence concerning the existence of cer- tain phases. However, those shown in Fig. 1 and listed in Table 1 are fairly well established.

A very limited study of this system by [61Kir], using met- allographic and X-ray experiments, found the system to be analogous with Ni-Zr, with seven compounds desig- nated NiHf2, NiHf, NinHfg, NiloHfT, NisHf, NisHf2, and Ni7Hf2. Another limited study, by [60Dea], found five compounds--NiHf2, NiHf, Ni3Hf2, Ni2Hf, and Ni4Hf-- and a depression of the Hf transition temperature on addi- tion of Ni, with the transition occurring above the (Hf + NiHf2) eutectic giving a metatectic reaction. This work was not published other than as an internal report because the author had insufficient confidence in the results. An extensive study of the system by [67Sve], using thermal, microscopic, and X-ray techniques, revealed the existence of eight compounds designated NiHf2, NiHf, NiHHf,, Ni3Hf2, NisHf2, Ni3Hf, Ni7Hf2, and NisHf. In addition, they determined the solidus and liquidus and confirmed the presence of a metatectic reaction (flHf) -+ (aHf) + L. Thus, the existence of the phases NiHf2 and NiHf was established, having been found in three independent in- vestigations. The compound designated Ni3Hf2 by [67Sve] and [60Dea] is the same as the Ni~oHf7 phase found by [61Kir]. Further independent work confirmed the exis- tence of the phases NisHf[61Dwi], Ni7Hf2173Dat, 79Bse], and NiaHf[79Bse], which has two polymorphs.

Fig. 1 Ni-Hf Phase Diagram Weight Percent Hafnium

, 2o 30 40 50 ,.~ 7o 00 . . . . . . . , . . , ..,. . . . . I . , . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . t . . . . . . . . . . . . . . . . ~ . . . . . . . . . ~ . . . . . . . . . . . . '00

~00 L

~ 15~~

1100 " ( ~ .~1. i i1 , . . . . . . i~ =

. . . . . . . . . i . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . , . . . . . . . . . r . . . . . . . . . J . . . . . . . . i . . . . . . . . 0 10 20 30 4-0 50 60 70 80 90 100

00O

Ni

Kelvin -ZZ00

;000

1800

1800

1400

Atomic Percent Hafnium

1200

Hf

P. N a s h a n d A . N a s h , 1 9 8 3 .

250 Bulletin of Alloy Phase Diagrams Vol. 4 No. 3 1983

Provisional Hf-Ni

Table I Ni-Hf Crystal Structure Data Approximate Lattice parameters, n m

composition(a), Pearson Space a b c Phase at.% Hf symbol group Prototype a /3 ~, References

(Ni) . . . . . . . . . . . . . . . . . . 0 to 1 cF4 NisHf . . . . . . . . . . . . . . . . 16.7 cF24 Ni7Hf2 . . . . . . . . . . . . . . . 2 2 . 2 Monoclinic

aNizHf(b) . . . . . . . . . . . . 25.0

flNizHf(c) . . . . . . . . . . . . . 25.0

Ni2iHf8 . . . . . . . . . . . . . . . 27.6

NiTHf3 . . . . . . . . . . . . . . . 30.0 Triclinic

NiloHf7 . . . . . . . . . . . . . . . 41.2

NillHf9 . . . . . . . . . . . . . . . 45.0

NiHf . . . . . . . . . . . . . . . . . 50.0

Orthorhombic, base-centered Tetragonal,

body-centered oC8

NiHf2 . . . . . . . . . . . . . . . . 66.7 t/12 (flHf) . . . . . . . . . . . . . . . . . 98-100 c12 (aHf) . . . . . . . . . . . . . . . . . 99-100 hP2

Metastable phases

NiHfz . . . . . . . . . . . . . . . . 80(f) oC16 Amorphous NiHf. . . . . . 11 to 80 ...

(a) From the phase diagram. (b) Stable above 1200 ~ Hf. (f) Starting composition; see text.

Fm3m Cu 0.36147 . . . . . . . . . ' . ' AuBe5 0 .6683 . . . . . . [61Dwi] �9 " Ni7Zr2 1.2102 0.8191 0.4657 [73Dat]

95.5090 R3m BaPbz 0 . 5 2 7 8 7 0 .52787 1 . 9 2 3 2 4 [78Bsel]

90.00 90.00 120.00 P6Jmrnc 7 T a ( P d , 0 . 5 2 8 2 2 0 .52822 2 . 1 3 9 1 6 [78Bsel]

Rh)3 90.00 90.00 120.00 P1 ".. 0.64275 0 .80007 0 . 8 5 5 4 0 [78Bse2]

75.180 68.140 75.610 P1 ... 0.65138 0 .65890 0 . 7 6 2 7 1 [78Bse3]

104.870 104 .600 112.710 C2ca NiloZr7 1.2275 0.9078 0.9126 [61Kir, 62Kirl]

I4/m ... 0.979 "" 0.653 [61Kir]

Cmcm CrB 0.322 0.982 0.412 [61Kir, 62Kir2, 67Sve]

I4/mcm A1Cu2 0.6743 ... 0.558 [61Kir, 62Kir2] Im3m W -3.50 . . . . . . [Pearson](d)

P6Jmmc Mg 0.31946 ... 0.50511 [Pearson](e)

�9 .. BRe3 0.3235 1.089 0.8777 ---

(c) Stable below 1200 ~ (d) Pure/3Hf extrapolated to room temperature. (e) Pure

The existence of a Cu2Mg-type Laves phase has not been clearly established. [72Pet] and [73Koc] claimed the exis- tence of the phase Ni2Hf on the basis of X-ray, microprobe, and thermal arrest data. [54Ell], on the basis of X-ray diffraction data from an alloy of Ni-33 at.% Hf, concluded there was no obvious similarity to a Laves-type pattern. [79Bse] suggested that such a phase is stabilized by silicon contamination from the silica tubes in which the alloys are equilibrated. However, both [72Pet] and [73Koc] noted the presence of the NiHf2 phase in as-cast alloys prior to any heat treatments. Thus, the formation of Ni2Hf may be promoted by some other impurities, such as oxygen. Both the microprobe and thermal arrest data of [72Pet] and [73Koc] can be interpreted without involving a Ni2Hf phase, but using the Ni7Hf3 phase found by [79Bse]. The complexity of this region of the diagram means that it is not amenable to determination by use of dynamic methods such as thermal analysis.

Recently, the central portion of the diagram was studied by [79Bse] with the result that a phase, Ni7Hfz, was found to exist with a limited range of stability from 1250 • 20 to 1016 -+ 3 ~ at which temperature the phase decomposes into NiloHf7 and flNi3Hf. On the basis of crystal structure determination, [79Bse] designated the phase NisHf, found in previous work as Ni2~Hfs. The stability range is from 1300 • 20 ~ where Ni21Hfs forms peritectically from liq- uid and Ni3Hf, down to 1175 - 10 ~ where it decomposes eutectoidally into Ni7Hf3 and ~Ni3Hf. The Ni3Hf phase was found to form peritectically at 1350 • 20 ~ from liq- uid and NivHf2 and to undergo a polymorphic transition at 1200 - 10 ~

[67Sve] obtained thermal arrests in the solid state around the composition NiHf, which they attributed to a poly- morphic transition in that compound. They also deter-

mined the congruent melting temperatures of NiHf and Ni7Hf2 as 1530 and 1480 ~ respectively.

Liquidus and Solidus. The only data available on the liq- uidus are from [67Sve], determined by thermal-arrest measurements. [54Ell] reported the incipient melting tem- perature of an Ni2Hf alloy as 1790 ~ which cannot be reconciled with the liquidus data of [67Sve] because it is approximately 540 ~ higher. The incipient melting tem- perature was probably determined by observing the change in angularity of a specimen suspended in a vacuum furnace, as described by [52Han]. Because Hf is highly reactive, Ni-Hf alloys readily form a tenacious oxide layer, even in a vacuum, that is probably capable of maintaining the specimen geometry even when the alloy itself is mol- ten. The data for the liquidus, therefore, were taken only from [67Sve].

The peritectic reactions were determined by [67Svel and [79Bse], as already discussed, with confirmation of the reactions for NiloHfv, Ni21Hfs, and NisHf from [61Kir]. The L ~ (Ni) + NisHf eutectic composition was determined as 88 at.% Ni at 1190 ~ by [67Sve]. The L ~ Ni7Hfz + NiloHf7 eutectic was determined as 63 at.% Ni at 1200 ~ by [67Sve], as 65 at.% Ni at 1190 • 10 ~ by [79Bse], and around 64 at.% Ni by [61Kir]. The two other eutectics found by [67Sve] are supported by [61Kir], who found the composition of L --* (aHf) + NiHf2 to be around 75 at.% Ni and of the L ~ (Ni) + NisHfeutectic to be around 89 at.% Ni. [61Kir] suggested that the compound NiHf2 is congru- ently melting, analogous with its zirconium counterpart, and that there is an associated eutectic, L--* NiHf + NiHf2, around 25 at.% Ni. The more extensive work of [67Sve] has been preferred and the phase NiHf2 taken as forming peritectically from the melt and NiHf.

Bulletin of Alloy Phase Diagrams Vol. 4 No. 3 1983 251

Hf-Ni Provisional

Terminal Solid Solutions. Although few data are avail- able on the temperature variation of solid solubility of Hf in Ni and Ni in Hf, it is clear that they are very restricted. [60Rei] found a maximum solubility of 0.7 at.% Hf in Ni at approximately 1200 ~ whereas [67Sve] stated that the solubility of Hf in Ni is 1 at.% at 1050 ~ However, their data point appears at 1150 ~ on their phase diagram. [72Kau] found the solubility of Hf in Ni to be less than 0.2 at.% at room t e m p e r a t u r e on the basis of ion- implantation studies. In Fig. 1, the maximum solubility of Hf in Ni has been taken to be 1 at.% Hf at 1190 ~

Crystallography NI-Rich and Hf-Rich Terminal Solutions. There are no lattice parameter data available on the Ni-rich and Hf- rich terminal solutions. However, the solubility ranges are very restricted and, considering the atomic radii of Ni and Hf, one would exi~ect a slight increase in the Ni lattice parameter and a slight decrease in the Hf lattice parameter.

NisHf. This alloy has the structure type of AuBe5 (see Table 1).

NiTHf2. The crystal structure of NivHf2 was identified by [73Dat] and found to be isotypic to Ni7Zr2. This phase has monoclinic structure, with the lattice parameters shown in Table 1.

NisHf. This phase was first identified by [67Sve] as a Ni3Ti-type structure, but no unit cell parameters were de- termined. Later, [78Bsel] identified two forms of Ni3Hf with two distinct crystal structures and properties, aNi3Hf is a ductile high-temperature modification, stable above 1200 ~ The aNi3Hf has a triple primitive hexagonal unit cell. The structure is described as a stacking of nine trian- gularly ordered, close-packed, A B 3 layers. The flNi3Hf form is stable below 1200 ~ The structure type is TTa(Pd, Rh)z, with the stacking of ten A B s layers in the sequence A B C B C A C B C B .

Ni21Hfs. This phase was previously denoted as NisHf2 by [61Kir] and [67Sve]. Using single-crystal diffraction data, [78Bse2] determined that this phase crystallizes with a triclinic unit cell, and its true composition is Ni21Hfs. Bsenko determined the cell parameters given in Table 1. The coordination number for each Hf atom is 15 and for the 11 nonequivalent sets of Ni atoms it varies from 12 to 13 [78Bse2].

NiTHfs. The crystal structure of this phase was originally identified by [78Bse3]. This phase crystallizes in the tri- clinic system. The structure is considered to consist of a stacking of three slightly puckered layers parallel to the (011) plane. The lattice parameters shown in Table I were determined from single-crystal X-ray diffraction data.

NiloHfT. The crystal structure of this phase is base-centered orthorhombic [61Kir, 62Kir1]. The lattice dimensions (Table 1) were determined from single-crystal data.

NillHfo. This alloy was identified by [61Kir] as a body- centered tetragonal structure and determined the lattice parameters given in Table 1. The space group symmetry

was determined from crystals having the composition of the Hf-rich phase boundaries.

NiHf. The crystal structure of NiHf was determined by [61Kir] and [62Kir2] from crystals having the composition of the Hf-rich phase boundary. The structure of this phase is base-centered orthorhombic. The lattice dimensions de- termiried at room temperature are given in Table 1.

NiHt2. This phase has a body-centered tetragonal structure [61Kir,62Kir2]. The lattice dimensions were determined from crystals having the composition of the Hf-rich phase boundary (see Table 1).

Metastable Phases Buschow and Beekmans [79Bus] prepared Nil-xHfx amor- phous alloys by arc melting followed by melt spinning in an atmosphere of purified argon for the concentration range 0.11 - x -< 0.80. X-ray diffraction patterns of the as-melt-spun ribbon showed amorphous structures. The crystallization temperatures were determined by means of differential-scanning calorimetry. Their results were as follows:

�9 Ni2oHfso. Three transformations were found to occur at 465, 525, and 630 ~ A set of X-ray lines present in the first, second, and third transformations indicated the crystallization of (aHf). The second transformation prod- uct showed a second set of lines, which were indexed on the basis of the orthorhombic BRe3 structure type as NiHf3 and gave the lattice parameters shown in Table 1. The difference between the samples heated to 525 and 630 ~ was the relative amount of (aHf) and NiHf3. Al- though the main phase in the 525 ~ product was (aHf), NiHf3 (a metastable phase) formed the main phase in the 630 ~ product. From this observation, it was con- cluded that the crystallization of NiHf3 may take place by two different mechanisms, one slower than the other. Where (aHf) is the only crystalline phase (when heated to 465 ~ or the main crystalline phase (when heated to 525 ~ it would follow that either a Ni-enriched amor- phous matrix or a microcrystalline Ni-rich phase is also present that cannot give a crystalline pattern.

�9 Ni~Hfe2. This alloy showed a thermal effect at 535 ~ that is thought to be due to some atomic rearrangement in the amorphous phase, or partial microcrystallization that could not give a crystalline diffraction pattern. A second transformation occurred at 590 ~ with a similar thermal effect to that at 535 ~ Crystallization was evidenced only at temperatures above that of the second thermal effect. Some of the X-ray lines in the crystalline pattern were indexed on the basis ofa (NiTi2)-type struc- ture with a lattice parameter, a = 1.2001 nm [79Bus]. This cubic structure was thought to be the stable NiHf2 phase. However, the structure type and lattice parame- ter do not match those accepted for NiHf2 (see Table 1).

�9 Ni~Hf~. A single crystallization peak is reported to occur in the DSC trace of amorphous Ni84Hf38, but re- mains unidentified.

�9 N i ~ H f , . Two overlapping peaks are reported and not identified in the DSC trace of amorphous NissHf~l.

From this work it was concluded tha t the crystalli- zation temperatures, Tcr, increased with the 3d metal concentration over a fairly large concentration range, 0.2 -< x -< 0.8, and decreased again at fairly high 3d metal concentrations, about 0.89 [79Bus].

252 Bulletin of Alloy Phase Diagrams Vol. 4 No. 3 1983

Provisional Hf-Ni

Table 2 Estimated Free Energies of Formation of Some Ni-Hf Compounds [75Kau] at 300 K

Enthalpy of Entropy of Composition, formation (AHf), formation (ASf),

Compound at. fraction Ni J/mol J/mol . K

NiHf2 . . . . . . . . . . . . . . 0.333 -47 400 NiHf . . . . . . . . . . . . . . . 0.50 -64 960 NiloHf2 . . . . . . . . . . . . . 0.588 -62 530 NisHf2 . . . . . . . . . . . . . 0.714 -57 070 Ni7Hf2 . . . . . . . . . . . . . 0.778 -52 470 NisHf . . . . . . . . . . . . . . 0.833 -42 150

0.0 0.0 0.0 0.0 0.0 0.0

Thermodynamics No exper imenta l t he rmodynamic da ta a re ava i l ab le for the Ni -Hf system. K a u f m a n and Nesor [73Kau] modeled this system to produce a Ni -Hf d i ag ram tha t is a compro- mise between the da t a of [Elliott] and [67Sve]. The de- script ion used indica ted la rge negat ive free energies of formation for Ni -Hf compounds (Table 2).

Cited References 52Han: M. Hansen, H.D. Kessler, and D.J. McPherson, "The

Titanium-Silicon System", Trans. ASM, 44, 518-538 (1952). (Equi Diagram; Experimental)

54Elh R.P. Elliott, "A Study of a Family of Laves Type Inter- mediate Phases", Armour Research Foundation Technical Re- port No. 1, OSR-TN-54-247; AD-42, 490, 13 (Aug 1954). (Equi Diagram, Crys Structure; Experimental)

60Dea: D. K. Deardorf, referred to in The Metallurgy of Hafnium, D.E. Thomas and E.T. Hayes, Ed., 202 (1960). The author confirmed that the work was not published due to lack of confidence (private communication). (Equi Diagram; Experimental)

60Rei: R. Reinbach, "Hafnium as an Alloying Element in Copper, Iron and Nickel", Z. Metallkd., 51,292-294 (1960). (Equi Dia- gram; Experimental)

60Tho: D.E. Thomas and E.T. Hayes, The Metallurgy of Haf- nium, U.S. Atomic Energy Commission (1960). (Crys Structure, Equi Diagram; Review)

61Dwi: A.E. Dwight, "Factors Controlling the Occurrence of Laves Phases and AB5 Compounds Among Trans i t ion Elements", Trans. ASM, 53,479 (1961). (Equi Diagram, Crys Structure; Experimental)

*61Kir: M.E. K i rkpa t r i ck and W.L. Larsen, "Phase Re- lationships in the Nickel-Zirconium and Nickel-Hafnium Alloy Systems", Trans. ASM, 54, 580-590; Discussion, 851-853 (1961). (Equi Diagram, Crys Structure; Experimenal; #)

6 2 K i r l : M.E. Kirkpatr ick , J .E. Smith, and W.L. Larsen, "Structures of the Intermediate Phases NiloZrv and Ni~oHfT",

Acta Crystallogr., 15, 894-903 (1962). (Crys Structure; Experimental)

62Kit2: M.E. Kirkpatrick, D.M. Bailey, and J.F. Smith, ~Tne Structures of NiZr2, NiZr and Their Hafnium Analogs", Acta Crystallogr., 15, 252-255 (1962). (Crys Structure; Experimental)

66Gan: E. Ganglberger, H. Nowotny, and F. Benesovsky, "New G Phases", Monatsh. Chem., 97,829-832 (1966). (Crys Structure; Experimental)

66Kis: F. Kissell, T. Tsuchida, and W.E. Wallace, "Magnetic Characteristics of NisZr and NisHf and Some Lanthanide-N", J. Chem. Phys., 44, 4651-4652 (1966). (Thermo; Experimental)

*67Sve: V.N. Svechnikov, A.K. Shurin, and G.P. Dmitriyeva, "The Hafnium-Nickel Equil ibrium Diagram", Russ. Met. (Met.), 6, 95-96 (1967). (Equi Diagram; Experimental; #)

72Pet: V.V. Pet'kov, V.Ya. Markiv, and V.V. Gorskiy, "Com- pounds with a MgCu2-Type Structure in Nickel Alloys with Zirconium and Hafnium", Russ. Met. (Met.), 2,137-139 (1972). (Crys Structure; Experimental)

73Dat: J.K. Dattagupta and K. Schubert, "On the Isotypic Re- lation of Ni7Zr2 and NivHf2", Z. MetaUkd., 64(11), 789-792 (1973). (Crys Structure; Experimental)

73Kau: E.N. Kaufman, J.M. Poate, and W.M. Augustyniak, "Lattice-Location Study of Hf Implanted in Ni", Phys. Rev. B, 7(3), 951-955 (1973). (Crys Structure; Experimental)

73Koc: Yu. A. Kocherzhinskiy, V. Ya. Markiv, and V. V. Pet'kov, "The Laves Phases in Hafnium Alloyed with Group IV Transi- tion Metals", Russ, Met. (Met.), 1,134-140 (1973). (Equi Dia- gram, Crys Structure; Experimental; #)

75Kau: L. Kaufman and H. Nesor, "Calculation of the Ni-AI-W, Ni-A1-Hf and Ni-Cr-Hf Systems", Can. Metall. Quarterly, 14(3), 221-232 (1975). (Thermo; Theory)

78Bse l : L. Bsenko, "The Crystal Structures of Two Modifications of Ni3Hff, Acta CrystaUogr., B34, 3201-3204 (1978). (Crys Structure; Experimental)

78Bse2: L. Bsenko, "The Crystal Structure of Ni21Hfs", Acta Crystallogr., B34, 3204-3207 (1978). (Crys St ruc ture ; Experimental)

78Bse3: L. Bsenko, "The Crystal Structure of Ni7Hfs", Acta Crystallogr., B34, 3207-3210 (1978). (Crys St ruc ture ; Experimental)

*79Bse: L. Bsenko, "The Hf-Ni and Zr-Ni Systems in the Region 65-80 at.% Ni", J. Less-Common Met., 63,171-179 (1979). (Equi Diagram, Crys Structure; Experimental; #)

79Bus: K. H.J. Buschow and N.M. Beekmans, "Formation, De- composition and Electrical Transport Properties of Amorphous Hf-Ni and Hf-Co Alloys", A. Appl. Phys., 50(10), 6348-6351 (1979). (Thermo, Crys Structure; Experimental)

81Nas: P. G. Nash and D. R. F. West, "Phase Equilibria in Ni-Rich Region of Ni-A1-Hf System", Met. Sci., 15, 347-352 (1981). (Equi Diagram, Crys Structure; Review; #)

*Indicates key paper. #Indicates presence of a phase diagram.

Hf-Ni evaluation contributed by Philip Nash and Azra Nash, Illinois Institute of Technology, Metallurgical and Materials Engineering, 10 West 33rd Street, Chicago, IL 60616. This work was funded by NASA, Grant No. NAG 3-302, through American Society for Metals. Literature searched through 1981. Professor P. Nash is Category Editor for binary nickel alloys.

Bul le t in of Al loy Phase Diagrams Vol. 4 No. 3 1983 253