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The HfNi and ZrNi systems in the region 65 – 80 at.% Ni
Journal
of the Less-Common
@ Elsevier
Sequoia
Metals,
S.A., Lausanne
63 (1979) 171 179 - Printed in the Netherlands
THE Hf-Ni AND Zr-Ni SYSTEMS IN THE REGION
171
65 - 80 AT.% Ni
LARS BSENKO Institute
of Chemistry,
(Received
University
of Uppsala,
Box
531,
S-751
21 Uppsala
(Sweden)
May 26, 1978)
Summary
The Hf-Ni and Zr-Ni systems have been examined in the region 65 - 80 at.% Ni by microscope and X-ray analyses. In the Hf-Ni system the following intermediate phases were observed: HfsNi,, Hfs Nizl, HfNia (h. t.), HfNia (1. t.) and Hf,NiT . HfaNi,, which is formed peritectically at 1250 + 20 “C!,decomposes eutectoidally at 1016 * 3 “C into Hf,Nira and HfNi, (1. t.). HfsNizr is stable from 1300 f 20 “C, where it forms peritectically, to 1175 f 10 “C where it decomposes eutectoidally into HfsNi, and HfNis (1. t.). HfNi, (h. t.) is a high temperature phase, forming peritectically at 1350 f 20 “C and transforming into HfNia(1. t.) below 1200 + 10 “C. HfzNi, melts congruently. A eutectic between Hf,NiiO and HfaNi, occurs at 1190 ? 10 “C. In the Zr-Ni system only one phase forming peritectically exists; this which is stable at least down to 800 “C. ZrNi, is formed in a reacis Zrs Ni,, , tion between ZrsNizi and ZrzNi, at 920 + 10 “C. Crystallographic data for the intermediate phases in the Hf-Ni and Zr-Ni systems in the region 65 - 75 at.% Ni are presented.
1. Introduction
The Ni-rich part of the Zr-Ni system was determined by Smith and Guard [ 11, who found two intermediate phases in the region 65 - 80 at.% Ni. ZrzNi, was found to melt congruently at 1450 “C and ZraNis to form peritectically at 1180 + 10 “C. The structure types of the two phases were not determined. Kramer [2] confirmed the phase ZrzNi, and indicated a homogeneity range of 1.5 at.% Ni. In an investigation of the entire Zr-Ni system by Kirkpatrick and Larsen [ 31, the existence of the phases ZrzNi, and Zr,N&, was confirmed. They were able to obtain single crystals of these compounds, but the indexing of the powder patterns was not successful. The crystal structure of ZrzNi, was solved by Eshelman and Smith [4], and the compound was found to crystallize with monoclinic symmetry.
172
According to Petkov et al. [ 51 three intermediate phases occur in the region 65 - 75 at.% Ni, namely ZrNiz with the MgCuz-type structure, ZrzN&, and ZrNis. Van Vucht [ 61 tried unsuccessfully to obtain ZrNia by replacement of Ti by Zr in TiNis. By heat treatment of an alloy of composition ZrNi, at 900 “C!for 3 d, the existence of ZrNis with the NisSn-type structure was established by Becle et al. [ 71. Kirkpatrick and Larsen [ 31 stated that the Hf-Ni system was similar to the Zr-Ni system [3], but no quantitative data regarding the phases HfsNi, and HfsNis were given. Dattagupta and Schubert [ 81 showed that Hf,Ni, and ZrzNi7 are isostructural. In an investigation of the entire Hf-Ni system by Svechnikov et al. [9], three phases were said to exist between 65 and 80 at.% Ni, namely Hf,Ni,, HfNi, and HfzNi,. HfNis was reported to possess the TiNis-type structure, but no cell parameters were given. Petkov et al. [ 51 found a phase with the composition HfNis, which they stated crystallized with the MgCuz-type structure. In view of the discrepancies between the results of various investigations of the Hf-Ni and Zr-Ni systems, especially in the composition range 65 - 80 at.% Ni, a re-investigation of these systems seemed desirable.
2. Experimental The zirconium and hafnium used in this investigation (of stated purity 99.9%) were from Koch-Light, Colnbrook, England. The hafnium contained 3% zirconium. The nickel (Specpure) was from Johnson Matthey & Co. Ltd., London. A series of alloys ranging from 64 to 78 at.% Ni in steps of 1 at.% were prepared by arc melting turnings of metals on a watercooled copper hearth under a purified argon atmosphere. Homogeneity was ensured by turning the alloy buttons upside down and remelting. The compositions of the alloys reported here are the nominal ones, since the weight losses were found to be very small (less than 0.5%). For heat treatments at temperatures below 1200 “C, the alloys were placed in ZrO, crucibles inside silica tubes. The tubes were evacuated and sealed off and heated in a resistance furnace. The temperature measurements were made using a Pt/Pt-10% Rh thermocouple. The accuracy was estimated to be + 1 “C!. After the thermal treatments, the alloys were quenched in water. For heat treatments at temperatures above 1200 “C a tantalum resistance furnace (Hereaus) with a very pure argon atmosphere was used. The temperature was recorded with an optical pyrometer. Both the heat-treated and the arc-melted alloys were subjected to metallographic examination. The alloys were cut into two pieces using a diamond saw. The surfaces of the specimens were polished with alumina powder and etching was performed using a solution of 1 part 40% HF, 2 parts concentrated HNO, and 7 parts HsO. X-ray powder photographs were recorded using a Guinier-HIgg-type focusing camera (Philips XDC 700) with Cu K,i radiation (h = 1.54059 a).
173
Zone-refined silicon (a = 5.43088 A) was used as an internal calibration standard. Most alloys were ductile, so the samples had to be filed to a fine powder and re-annealed at the previous temperature in order to obtain sharp diffraction patterns. Single crystals of the various phases were examined in a Weissenberg camera and indexing of the powder patterns was accomplished starting from the approximate cell dimensions obtained from the Weissenberg photographs. The cell dimensions were refined using the least-squares program CELNE
[lOI * 3. Results 3.1. The Hf-Ni system in the region 65 - 80 at.% Ni Figure 1 shows the phase diagram of the Hf-Ni system in the composition region 64 - 80 at.% Ni. Table 1 gives the structural data for the intermediate phases in the region 65 - 75 at.% Ni. The following observations are noteworthy.
64
66
66
ATOMIC
Fig. 1. The Hf-Ni
70
72
74
76
76
00
PER CENT NICKEL
phase diagram
in the region 64 - 80 at.% Ni.
3.1.1. The eutectic reaction The eutectic composition of 65 at.% Ni was established from the as-cast alloys. Hfo.s,Nio_6s shows a pure eutectic structure, consisting of Hf,Nilo and HfsNi,, while Hf0.34Ni0.66 consists of a eutectic and a minor amount of primary nucleated HfaNi, (Figs. 2 and 3, respectively). The eutectic temperature at 1190 f 10 “C could be established by comparing the microstructure of two alloys. In the case of Hfo.,,Ni0,6s heat treated for 24 h at 1200 “C,
New New HfBNi,
BaPb3
r-Ta(Pd, Rh), Ni$n
Hf,Ni, HfaNiv
HfNi, fh. t*)
HfNi3 (1, t.)
P6almmc
P6, immc
PT Pf R3m
Pi
Space group
5.3125(5)
5.2787(l) 5.2822(Z)
6.4721/13)
6.5138(11) 6.4275( 12)
a (a)
5.3125(5)
5.2787(l) 5.2822(2)
8.0645/15)
6.5890( 11) 8.OOO7( 15)
b (2%)
Lattice parameters
7.6271(10)
4.3029(5)
19.2324(10) 21.39X(18)
8.5540(16) 8.5878( 14)
Standard deviations as given in parentheses refer to the least significant decimal places.
ZrNi,
Zr,Nia
Structure type
Ideal cumposition
90.0
90.0 90.0
104.87( 1) 75.18( 1) 75.1911)
Structural data for intermediate phases in the HE-Ni and Zr-Ni systems in the regian 65 - 75 at.% Ni
TABLE 1
90.0
68.04(l) 90.0 90.0
68.14( 2)
104.60(3)
120.0
75.26(l) ?.20.0 120.0
112.71(l) 75.61(2)
CL 4 rp
Fig. 2. Hfo.3sNio.c,, as-cast. Pure eutectic Fig. 3. Hfo,MNio.a,
as-cast.
Fig. 4. Hfo,~Nio.~, annealed Hf,Ni,o HfsNiT eutectic.
Primary
hetween
nucleated
Hf,Ni,n
HfsNi,
and HfsNi7.
and Hf,Nilo
for 24 h at 1200 ‘C. Large crystals
Fig. 5. Hf0.33Ni0,6,, as-cast. Primary nucieated Hf,Ni,, formed HfsNi, in a matrix of Hf,Ni,o- HfzNiy eutectic.
surrounded
Hf,Ni,
eutectic.
of HfsNiT and an hy prritecticaliy
the sample partly melted and large crystals of Hf,Ni7 were produced (Fig. 4). The alloy Hfo.31 Nio.ss heat treated for 24 h at 1180 “C showed no sign of melting, indicating that the eutectic isotherm lies between 1180 “C and 1200 “C. Kirkpatrick and Larsen [ 31 estimated the eutectic composition to be at 64 at.% Ni, while Svechnikov et al. [9] give a eutectic temperature of 1200 “C.
176
3.1.2.
The HfzNi7 phase
The alloy Hfo.soNio.,,, heat treated for 100 h at 1100 “C proved to be single phase. A single-crystal structure determination confirmed the composition HfsNi, [ 111 . Hf,Ni, is formed peritectically from the melt and HfsNi,, . The peritectic point, situated between 66 and 67 at.% Ni, could be established by comparing the as-cast alloys Hfo.34Nio.6s and Hfo,33Nio,6, (Figs. 3 and 5). Hfo.34Nio.66 shows primary nucleation of Hf,Ni,, while Hfo,aaNio,s7 shows primary nucleation of HfsN& and peritectic formation of Hf3Ni7. The peritectic temperature 1250 f 20 “C was determined by the same method as the eutectic temperature. Svechnikov et al. [9] give a peritectic temperature of 1250 “C. Hf,Ni, decomposes eutectoidally at 1016 ? 3 “C. The decomposition of the alloy Hfo.3, Nio.6a heat treated for 24 h at 1200 “C and annealed for 119 h at 1005 “C!is shown in Fig. 6. X-ray powder photographs of this alloy show that the decomposition products are Hf,Ni,o and HfNi3 (1. t.).
, Fig. 6. Hf0.31Ni~~,~, annealed for 24 h at 1200 “C and re-annealed for Eutectoidal decomposition of Hf,Ni, into Hf,Ni,o and HfNi3 (1. t.).
119 h at 1005
Fig. 7. Hfo,~Ni0.72, annealed for 24 h at 1270 “C and re-annealed for 26 h at 1150 Eutectoidal decomposition of HfeNi,, into Hf,Ni, and HfNi3 (I. t.).
75pm
“C.
“C.
3.1.3. The Hf8NizI phase The occurrence of an intermediate phase of composition Hf,Nis has been proposed in earlier investigations [ 3, 91. Single crystals of a phase with the approximate composition Hf,Ni,, could be isolated from an alloy heat treated for 24 h at 1270 “C. The structure determination Hfo.,sNio.,2 showed that the true composition is HfsNizl [ 121. This phase is formed peritectically from the melt and HfNi, (h. t.). The peritectic point near 70 at.% Ni and the peritectic temperature were determined in the same way as for Hf,Ni,. HfsNi,, decomposes eutectoidally at 1175 + 10 “C into Hf,NiT and HfNi, (1. t.). Figure 7 shows this decomposition.
,
3.1.4. The HfNi, phases Two phases of composition HfNis were found to exist, one high temperature form stable above 1200 “C and one low temperature form stable below 1200 “C. HfNis (h. t.) is a nine-layered type of structure [ 131, forming peritectically from the melt and Hf,Ni? at 1350 + 20 “C. The alloy Hf0,26Ni0,7d, heat treated at 1320 “C for 24 h, shows large crystals of HfNis (h. t.) surrounded by a eutectic (Fig. 8). The peritectic point and the peritectic temperature were established in the same way as for HfsNi,. HfNi, (1. t.) is a ten-layered type of structure stable down to at least 800 “C.
Fig. 8. Hfo,ENi0.$4, annealed HfTNilo HfaNiy eutcctic.
24 h at 1320
C. Large crystals
of HfNis (h. t.) and an
3.1.5. The Hf2Nii phase The existence of this phase was confirmed, but no measurement of its melting point was made. Svechnikov et al. [9] give a melting point of 1480 “c. 3.1.6. The HfNi, phase According to Petkov et al. [ 51, an HfNia phase with the MgCua type of structure exists. They heat treated an alloy cont~ning 66.7 at.% Ni for 500 h at 900 “C and in their X-ray powder patterns they found evidence for the existence of a cubic HfNia phase. An alloy Hf,.saNi0.s7 was heat treated in a silica tube as above and the X-ray powder pattern, taken from material from the bulk of the alloy button, showed only lines belonging to the Hf7Ni10 and the HfNi, (1. t.) phases. If, however, material from the surface of the alloy button was used, lines belonging to a cubic phase appeared in the X-ray powder pattern. The intensities of these lines correspond to an MgCu, type of structure. This phase is probably a ternary phase containing silicon, originating from the silica tube. The metallographic examination also supports this conclusion, since the heat-treated alloy showed only the decomposition of the Hf,Niar phase and an unaffected eutectic.
178
3.2. The Zr-Ni system in the region 63 - 80 at.% Ni A phase diagram for the Zr-Ni system in the region 63 - 80 at.% Ni is given in Fig. 9. The cell dimensions for the intermediate phases are given in Table 1.
64
66
68
ATOMIC
Fig. 9. The Zr-Ni
70
72
74
76
78
80
PER CENT NICKEL
phase diagram
in the region 63 _ 80 at.% Ni.
3.2.1. The eu tectic reaction The eutectic temperature was established as 1075 rt 10 “C and the eutectic composition as 64 at.% Ni. Kirkpatrick and Larsen [3] give 1060 “C and 64 at.% Ni, while Smith and Guard [ 1] give 1070 i 10 “C and 63 at.% Ni for the eutectic temperature and the eutectic composition, respectively. 3.2.2. The ZrblNiZl phase The phase denoted ZraNis in earlier investigations could be indexed using the cell parameters obtained for HfsNiai. ZrsNiai is formed peritectitally from Zr,Ni, and the melt. The peritectic point was found to be between 68 and 69 at.% Ni. The peritectic temperature was not detrained but Kirkpatrick and Larsen [3] give a value of 1180 “C. In contrast to HfsN&, which decomposes eutectoidally, no decomposition of ZrsNiar could be detected and the phase is stable down to at least 800 “C (Fig. 10). 3.2.3. The ZrNi3 phase The phase ZrNia was obtained by heat treatment of an alloy of eompoa. Won Zro_wNio,,5 at 900 “C for 500 h. The X-ray powder pattern for this sampfe could be indexed using a hexagonal unit cell. According to Becfe et al. [7] the phase is isostructural with NisSn. The ZrNi, phase is formed from ZrsNi,i and ZrsNi, at 920 + 10 “C.
179
Fig. 10. Zrn.aNio.72, annealed for 24 h at 1085 ‘C and Large crystals of ZraNizt in a Zr7Nilc ZraNi, eutectic.
re-annealed
for
144 h at 800
C.
3.2.4. The Zr,Ni7 and ZrNi? phases The occurrence of the phase Zr,Ni, was confirmed. The ZrNi, phase as reported by Petkov et al. [5] is probably a ternary phase containing silicon in analogy to the HfNi, phase. No lines in the X-ray powder pattern belonging to a ZrNi, phase could be observed, if the material used was taken r from the bulk of the alloy Lr,).ss Ni es7 heat treated for 500 h at 900 “C!. If material taken from the surface of the alloy was used, lines belonging to a cubic phase appeared.
References
6 7 8 9 10 11 12 13
E. Smith and R. W. Guard, Trans. Metall. Sot. AIME, 209 (1957) 1189. D. Kramer, Trans. Metall. Sot. AIME, 215 (1959) 256. M. E. Kirkpatrick and W. L. Larsen, Trans. Am. Sot. Met., 54 (1961) 580. F. R. Eshelman and J. F. Smith, Acta Crystallogr., Sect. B, 28 (1972) 1594. V. V. Petkov, V. Ya. Markiv and V. V. Gorskiy, Izv. Akad. Nauk SSSR, Met., 2 (1972) 188. J. H. N. Van Vucht, J. Less-Common Met., 11 (1966) 308. C. Bkcle, G. Develey, J.-L. Glimois and M. Saillard, C. R. Acad. Sci., Ser. B, 280 (1975) 43. J. K. Dattagupta and K. Schubert, Z. Metallkd., 64 (1973) 789. V. N. Svechnikov, A. K. Shurin and G. P. Dmitriyeva, Russ. Metall. Fuels, 6 (1967) 95. J.-L. Lundgren, Crystallographic Computer Programs, UUIC-B13-4-03, Univ. of Uppsala, Sweden, 1976. L. Bsenko, Acta Crystallogr., Sect. B, 34 (1978) 3207. L. Bsenko, Acta Crystsllogr., Sect. B, 34 (1978) 3204. L. Bsenko, Acta Crystallogr., Sect. B, 34 (1978) 3201.
of the Less-Common
@ Elsevier
Sequoia
Metals,
S.A., Lausanne
63 (1979) 171 179 - Printed in the Netherlands
THE Hf-Ni AND Zr-Ni SYSTEMS IN THE REGION
171
65 - 80 AT.% Ni
LARS BSENKO Institute
of Chemistry,
(Received
University
of Uppsala,
Box
531,
S-751
21 Uppsala
(Sweden)
May 26, 1978)
Summary
The Hf-Ni and Zr-Ni systems have been examined in the region 65 - 80 at.% Ni by microscope and X-ray analyses. In the Hf-Ni system the following intermediate phases were observed: HfsNi,, Hfs Nizl, HfNia (h. t.), HfNia (1. t.) and Hf,NiT . HfaNi,, which is formed peritectically at 1250 + 20 “C!,decomposes eutectoidally at 1016 * 3 “C into Hf,Nira and HfNi, (1. t.). HfsNizr is stable from 1300 f 20 “C, where it forms peritectically, to 1175 f 10 “C where it decomposes eutectoidally into HfsNi, and HfNis (1. t.). HfNi, (h. t.) is a high temperature phase, forming peritectically at 1350 f 20 “C and transforming into HfNia(1. t.) below 1200 + 10 “C. HfzNi, melts congruently. A eutectic between Hf,NiiO and HfaNi, occurs at 1190 ? 10 “C. In the Zr-Ni system only one phase forming peritectically exists; this which is stable at least down to 800 “C. ZrNi, is formed in a reacis Zrs Ni,, , tion between ZrsNizi and ZrzNi, at 920 + 10 “C. Crystallographic data for the intermediate phases in the Hf-Ni and Zr-Ni systems in the region 65 - 75 at.% Ni are presented.
1. Introduction
The Ni-rich part of the Zr-Ni system was determined by Smith and Guard [ 11, who found two intermediate phases in the region 65 - 80 at.% Ni. ZrzNi, was found to melt congruently at 1450 “C and ZraNis to form peritectically at 1180 + 10 “C. The structure types of the two phases were not determined. Kramer [2] confirmed the phase ZrzNi, and indicated a homogeneity range of 1.5 at.% Ni. In an investigation of the entire Zr-Ni system by Kirkpatrick and Larsen [ 31, the existence of the phases ZrzNi, and Zr,N&, was confirmed. They were able to obtain single crystals of these compounds, but the indexing of the powder patterns was not successful. The crystal structure of ZrzNi, was solved by Eshelman and Smith [4], and the compound was found to crystallize with monoclinic symmetry.
172
According to Petkov et al. [ 51 three intermediate phases occur in the region 65 - 75 at.% Ni, namely ZrNiz with the MgCuz-type structure, ZrzN&, and ZrNis. Van Vucht [ 61 tried unsuccessfully to obtain ZrNia by replacement of Ti by Zr in TiNis. By heat treatment of an alloy of composition ZrNi, at 900 “C!for 3 d, the existence of ZrNis with the NisSn-type structure was established by Becle et al. [ 71. Kirkpatrick and Larsen [ 31 stated that the Hf-Ni system was similar to the Zr-Ni system [3], but no quantitative data regarding the phases HfsNi, and HfsNis were given. Dattagupta and Schubert [ 81 showed that Hf,Ni, and ZrzNi7 are isostructural. In an investigation of the entire Hf-Ni system by Svechnikov et al. [9], three phases were said to exist between 65 and 80 at.% Ni, namely Hf,Ni,, HfNi, and HfzNi,. HfNis was reported to possess the TiNis-type structure, but no cell parameters were given. Petkov et al. [ 51 found a phase with the composition HfNis, which they stated crystallized with the MgCuz-type structure. In view of the discrepancies between the results of various investigations of the Hf-Ni and Zr-Ni systems, especially in the composition range 65 - 80 at.% Ni, a re-investigation of these systems seemed desirable.
2. Experimental The zirconium and hafnium used in this investigation (of stated purity 99.9%) were from Koch-Light, Colnbrook, England. The hafnium contained 3% zirconium. The nickel (Specpure) was from Johnson Matthey & Co. Ltd., London. A series of alloys ranging from 64 to 78 at.% Ni in steps of 1 at.% were prepared by arc melting turnings of metals on a watercooled copper hearth under a purified argon atmosphere. Homogeneity was ensured by turning the alloy buttons upside down and remelting. The compositions of the alloys reported here are the nominal ones, since the weight losses were found to be very small (less than 0.5%). For heat treatments at temperatures below 1200 “C, the alloys were placed in ZrO, crucibles inside silica tubes. The tubes were evacuated and sealed off and heated in a resistance furnace. The temperature measurements were made using a Pt/Pt-10% Rh thermocouple. The accuracy was estimated to be + 1 “C!. After the thermal treatments, the alloys were quenched in water. For heat treatments at temperatures above 1200 “C a tantalum resistance furnace (Hereaus) with a very pure argon atmosphere was used. The temperature was recorded with an optical pyrometer. Both the heat-treated and the arc-melted alloys were subjected to metallographic examination. The alloys were cut into two pieces using a diamond saw. The surfaces of the specimens were polished with alumina powder and etching was performed using a solution of 1 part 40% HF, 2 parts concentrated HNO, and 7 parts HsO. X-ray powder photographs were recorded using a Guinier-HIgg-type focusing camera (Philips XDC 700) with Cu K,i radiation (h = 1.54059 a).
173
Zone-refined silicon (a = 5.43088 A) was used as an internal calibration standard. Most alloys were ductile, so the samples had to be filed to a fine powder and re-annealed at the previous temperature in order to obtain sharp diffraction patterns. Single crystals of the various phases were examined in a Weissenberg camera and indexing of the powder patterns was accomplished starting from the approximate cell dimensions obtained from the Weissenberg photographs. The cell dimensions were refined using the least-squares program CELNE
[lOI * 3. Results 3.1. The Hf-Ni system in the region 65 - 80 at.% Ni Figure 1 shows the phase diagram of the Hf-Ni system in the composition region 64 - 80 at.% Ni. Table 1 gives the structural data for the intermediate phases in the region 65 - 75 at.% Ni. The following observations are noteworthy.
64
66
66
ATOMIC
Fig. 1. The Hf-Ni
70
72
74
76
76
00
PER CENT NICKEL
phase diagram
in the region 64 - 80 at.% Ni.
3.1.1. The eutectic reaction The eutectic composition of 65 at.% Ni was established from the as-cast alloys. Hfo.s,Nio_6s shows a pure eutectic structure, consisting of Hf,Nilo and HfsNi,, while Hf0.34Ni0.66 consists of a eutectic and a minor amount of primary nucleated HfaNi, (Figs. 2 and 3, respectively). The eutectic temperature at 1190 f 10 “C could be established by comparing the microstructure of two alloys. In the case of Hfo.,,Ni0,6s heat treated for 24 h at 1200 “C,
New New HfBNi,
BaPb3
r-Ta(Pd, Rh), Ni$n
Hf,Ni, HfaNiv
HfNi, fh. t*)
HfNi3 (1, t.)
P6almmc
P6, immc
PT Pf R3m
Pi
Space group
5.3125(5)
5.2787(l) 5.2822(Z)
6.4721/13)
6.5138(11) 6.4275( 12)
a (a)
5.3125(5)
5.2787(l) 5.2822(2)
8.0645/15)
6.5890( 11) 8.OOO7( 15)
b (2%)
Lattice parameters
7.6271(10)
4.3029(5)
19.2324(10) 21.39X(18)
8.5540(16) 8.5878( 14)
Standard deviations as given in parentheses refer to the least significant decimal places.
ZrNi,
Zr,Nia
Structure type
Ideal cumposition
90.0
90.0 90.0
104.87( 1) 75.18( 1) 75.1911)
Structural data for intermediate phases in the HE-Ni and Zr-Ni systems in the regian 65 - 75 at.% Ni
TABLE 1
90.0
68.04(l) 90.0 90.0
68.14( 2)
104.60(3)
120.0
75.26(l) ?.20.0 120.0
112.71(l) 75.61(2)
CL 4 rp
Fig. 2. Hfo.3sNio.c,, as-cast. Pure eutectic Fig. 3. Hfo,MNio.a,
as-cast.
Fig. 4. Hfo,~Nio.~, annealed Hf,Ni,o HfsNiT eutectic.
Primary
hetween
nucleated
Hf,Ni,n
HfsNi,
and HfsNi7.
and Hf,Nilo
for 24 h at 1200 ‘C. Large crystals
Fig. 5. Hf0.33Ni0,6,, as-cast. Primary nucieated Hf,Ni,, formed HfsNi, in a matrix of Hf,Ni,o- HfzNiy eutectic.
surrounded
Hf,Ni,
eutectic.
of HfsNiT and an hy prritecticaliy
the sample partly melted and large crystals of Hf,Ni7 were produced (Fig. 4). The alloy Hfo.31 Nio.ss heat treated for 24 h at 1180 “C showed no sign of melting, indicating that the eutectic isotherm lies between 1180 “C and 1200 “C. Kirkpatrick and Larsen [ 31 estimated the eutectic composition to be at 64 at.% Ni, while Svechnikov et al. [9] give a eutectic temperature of 1200 “C.
176
3.1.2.
The HfzNi7 phase
The alloy Hfo.soNio.,,, heat treated for 100 h at 1100 “C proved to be single phase. A single-crystal structure determination confirmed the composition HfsNi, [ 111 . Hf,Ni, is formed peritectically from the melt and HfsNi,, . The peritectic point, situated between 66 and 67 at.% Ni, could be established by comparing the as-cast alloys Hfo.34Nio.6s and Hfo,33Nio,6, (Figs. 3 and 5). Hfo.34Nio.66 shows primary nucleation of Hf,Ni,, while Hfo,aaNio,s7 shows primary nucleation of HfsN& and peritectic formation of Hf3Ni7. The peritectic temperature 1250 f 20 “C was determined by the same method as the eutectic temperature. Svechnikov et al. [9] give a peritectic temperature of 1250 “C. Hf,Ni, decomposes eutectoidally at 1016 ? 3 “C. The decomposition of the alloy Hfo.3, Nio.6a heat treated for 24 h at 1200 “C and annealed for 119 h at 1005 “C!is shown in Fig. 6. X-ray powder photographs of this alloy show that the decomposition products are Hf,Ni,o and HfNi3 (1. t.).
, Fig. 6. Hf0.31Ni~~,~, annealed for 24 h at 1200 “C and re-annealed for Eutectoidal decomposition of Hf,Ni, into Hf,Ni,o and HfNi3 (1. t.).
119 h at 1005
Fig. 7. Hfo,~Ni0.72, annealed for 24 h at 1270 “C and re-annealed for 26 h at 1150 Eutectoidal decomposition of HfeNi,, into Hf,Ni, and HfNi3 (I. t.).
75pm
“C.
“C.
3.1.3. The Hf8NizI phase The occurrence of an intermediate phase of composition Hf,Nis has been proposed in earlier investigations [ 3, 91. Single crystals of a phase with the approximate composition Hf,Ni,, could be isolated from an alloy heat treated for 24 h at 1270 “C. The structure determination Hfo.,sNio.,2 showed that the true composition is HfsNizl [ 121. This phase is formed peritectically from the melt and HfNi, (h. t.). The peritectic point near 70 at.% Ni and the peritectic temperature were determined in the same way as for Hf,Ni,. HfsNi,, decomposes eutectoidally at 1175 + 10 “C into Hf,NiT and HfNi, (1. t.). Figure 7 shows this decomposition.
,
3.1.4. The HfNi, phases Two phases of composition HfNis were found to exist, one high temperature form stable above 1200 “C and one low temperature form stable below 1200 “C. HfNis (h. t.) is a nine-layered type of structure [ 131, forming peritectically from the melt and Hf,Ni? at 1350 + 20 “C. The alloy Hf0,26Ni0,7d, heat treated at 1320 “C for 24 h, shows large crystals of HfNis (h. t.) surrounded by a eutectic (Fig. 8). The peritectic point and the peritectic temperature were established in the same way as for HfsNi,. HfNi, (1. t.) is a ten-layered type of structure stable down to at least 800 “C.
Fig. 8. Hfo,ENi0.$4, annealed HfTNilo HfaNiy eutcctic.
24 h at 1320
C. Large crystals
of HfNis (h. t.) and an
3.1.5. The Hf2Nii phase The existence of this phase was confirmed, but no measurement of its melting point was made. Svechnikov et al. [9] give a melting point of 1480 “c. 3.1.6. The HfNi, phase According to Petkov et al. [ 51, an HfNia phase with the MgCua type of structure exists. They heat treated an alloy cont~ning 66.7 at.% Ni for 500 h at 900 “C and in their X-ray powder patterns they found evidence for the existence of a cubic HfNia phase. An alloy Hf,.saNi0.s7 was heat treated in a silica tube as above and the X-ray powder pattern, taken from material from the bulk of the alloy button, showed only lines belonging to the Hf7Ni10 and the HfNi, (1. t.) phases. If, however, material from the surface of the alloy button was used, lines belonging to a cubic phase appeared in the X-ray powder pattern. The intensities of these lines correspond to an MgCu, type of structure. This phase is probably a ternary phase containing silicon, originating from the silica tube. The metallographic examination also supports this conclusion, since the heat-treated alloy showed only the decomposition of the Hf,Niar phase and an unaffected eutectic.
178
3.2. The Zr-Ni system in the region 63 - 80 at.% Ni A phase diagram for the Zr-Ni system in the region 63 - 80 at.% Ni is given in Fig. 9. The cell dimensions for the intermediate phases are given in Table 1.
64
66
68
ATOMIC
Fig. 9. The Zr-Ni
70
72
74
76
78
80
PER CENT NICKEL
phase diagram
in the region 63 _ 80 at.% Ni.
3.2.1. The eu tectic reaction The eutectic temperature was established as 1075 rt 10 “C and the eutectic composition as 64 at.% Ni. Kirkpatrick and Larsen [3] give 1060 “C and 64 at.% Ni, while Smith and Guard [ 1] give 1070 i 10 “C and 63 at.% Ni for the eutectic temperature and the eutectic composition, respectively. 3.2.2. The ZrblNiZl phase The phase denoted ZraNis in earlier investigations could be indexed using the cell parameters obtained for HfsNiai. ZrsNiai is formed peritectitally from Zr,Ni, and the melt. The peritectic point was found to be between 68 and 69 at.% Ni. The peritectic temperature was not detrained but Kirkpatrick and Larsen [3] give a value of 1180 “C. In contrast to HfsN&, which decomposes eutectoidally, no decomposition of ZrsNiar could be detected and the phase is stable down to at least 800 “C (Fig. 10). 3.2.3. The ZrNi3 phase The phase ZrNia was obtained by heat treatment of an alloy of eompoa. Won Zro_wNio,,5 at 900 “C for 500 h. The X-ray powder pattern for this sampfe could be indexed using a hexagonal unit cell. According to Becfe et al. [7] the phase is isostructural with NisSn. The ZrNi, phase is formed from ZrsNi,i and ZrsNi, at 920 + 10 “C.
179
Fig. 10. Zrn.aNio.72, annealed for 24 h at 1085 ‘C and Large crystals of ZraNizt in a Zr7Nilc ZraNi, eutectic.
re-annealed
for
144 h at 800
C.
3.2.4. The Zr,Ni7 and ZrNi? phases The occurrence of the phase Zr,Ni, was confirmed. The ZrNi, phase as reported by Petkov et al. [5] is probably a ternary phase containing silicon in analogy to the HfNi, phase. No lines in the X-ray powder pattern belonging to a ZrNi, phase could be observed, if the material used was taken r from the bulk of the alloy Lr,).ss Ni es7 heat treated for 500 h at 900 “C!. If material taken from the surface of the alloy was used, lines belonging to a cubic phase appeared.
References
6 7 8 9 10 11 12 13
E. Smith and R. W. Guard, Trans. Metall. Sot. AIME, 209 (1957) 1189. D. Kramer, Trans. Metall. Sot. AIME, 215 (1959) 256. M. E. Kirkpatrick and W. L. Larsen, Trans. Am. Sot. Met., 54 (1961) 580. F. R. Eshelman and J. F. Smith, Acta Crystallogr., Sect. B, 28 (1972) 1594. V. V. Petkov, V. Ya. Markiv and V. V. Gorskiy, Izv. Akad. Nauk SSSR, Met., 2 (1972) 188. J. H. N. Van Vucht, J. Less-Common Met., 11 (1966) 308. C. Bkcle, G. Develey, J.-L. Glimois and M. Saillard, C. R. Acad. Sci., Ser. B, 280 (1975) 43. J. K. Dattagupta and K. Schubert, Z. Metallkd., 64 (1973) 789. V. N. Svechnikov, A. K. Shurin and G. P. Dmitriyeva, Russ. Metall. Fuels, 6 (1967) 95. J.-L. Lundgren, Crystallographic Computer Programs, UUIC-B13-4-03, Univ. of Uppsala, Sweden, 1976. L. Bsenko, Acta Crystallogr., Sect. B, 34 (1978) 3207. L. Bsenko, Acta Crystsllogr., Sect. B, 34 (1978) 3204. L. Bsenko, Acta Crystallogr., Sect. B, 34 (1978) 3201.