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Isothermal cross-section of the phase diagram of the HfNbGe system at 1170 K
Journal of the Less-Common
Metals,
135 (1987)
127 - 135
ISOTHERMAL CROSS-SECTION OF THE PHASE Hf-Nb-Ge SYSTEM AT 1170 K YU. D. SEROPEGIN
127
DIAGRAM
and M. V. RUDOMETKINA
Chemical Department, M. V. Lomonosov 119899 r%ll, B-234 (U.S.S.R.)
Moscow
State
University,
(Received
form February
17, 1987)
November
OF THE
20, 1986;in
revised
Moscow
Summary A variety of physicochemical analysis techniques (microstructure, X-ray phase and electron probe X-ray analysis; hardness and microhardness measurements) were employed in constructing the isothermal cross-section of the phase diagram of the Hf-Nb-Ge system at 1170 K. The formation of nine binary intermetallic compounds was confirmed. A new ternary compound, Hf2NbsGe,, was detected. The mechanical properties of a number of alloys of the system were studied.
1. Introduction Studies of diagrams showing the variation with phase and composition of the properties of multicomponent metal systems, open up new pathways to goal-oriented research into materials with specified properties. Alloys based on niobium and hafnium are characterized by high values of heat resistance, hardness and corrosion resistance. Research on the effect of alloying of niobium and hafnium germanides with transition metals on the properties of these compounds is of particular interest. This paper reports our studies of the phase diagram of the Hf-Nb-Ge system. Binary systems bounding the ternary system under discussion have been described in detail in the literature. Niobium and hafnium, as neighbouring are completely soluble in one elements in Mendeleev’s periodic system, another at temperatures above the polymorphic transformation temperature of hafnium [ 1 - 31. The interaction of the transition metals (hafnium and niobium) with germanium is of a more intricate character: a large number of intermetallic compounds with various crystal lattices are formed. Thus in the Hf-Ge system, as shown by earlier studies [4 - 61, six compounds are present: Hf,Ge (Ti,P-type structure), HfzGe (CuA12-type), Hf,Ge, (Mn,Si3type), Hf,Ge2 (U&-type), HfGe (FeB-type) and HfGe2 (ZrS&-type). Three compounds are formed in the Nb-Ge system: NbsGe (Cr,Si-type structure), Nb,Ge, (W&,-type) and NbGez (CrSi,-type) [ 7 - 91. The homogeneity 0022-5088/87/%3.50
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128
regions of most of the germanides in the Hf-Ge and Nb-Ge systems do not exceed 1 - 2 at.%. The homogeneity regions of the NbsGes and NbGez compounds are 3 and 4 at.% germanium respectively [lo].
2. Experimental
details
The present study was carried out on about 100 alloys. These were made in an electric arc furnace under an argon atmosphere using a nonconsumable tungsten electrode and a water-cooled copper tray. Hafnium obtained by thermal decomposition of Hf14 (purity, 99.9%), vacuum-melted niobium (purity, 99.96%) and semiconductor germanium (purity, 99.99%) were used as starting components. Titanium was used as a getter in melting. The alloys were remelted three times in order to achieve complete fusion and homogeneous composition. Alloys with losses after melting not exceeding 1 wt.% were chosen for the experiments. The composition of each alloy was selected using the results of an analysis of the binary phase diagrams. All melted alloys were subjected to homogenizing annealing in evacuated double quartz ampoules containing titanium chips as getter; the ampoules were placed in resistance furnaces. The alloys containing more than 60 at.% germanium were annealed at 1170 K for 700 h. The alloys with less than 60 at.% germanium underwent preliminary annealing at 1420 K for 750 h. All samples were quenched from 1170 K in ice-cold water. A variety of physicochemical analysis techniques were used in the present study : microstructure, X-ray phase and electron probe X-ray analysis; hardness and microhardness measurements. In the microstructure studies, the samples were sanded successively on rough and fine emery paper and then polished on felt with an aqueous suspension of chromium oxide. The structure was revealed by etching the surface of the section with a mixture of concentrated HNOs and HF with HzO, (1:3:1). The microstructure was examined and photographed under a “Neophot 2” microscope with a magnification of 400X. X-ray phase analysis was performed on a URS-60 unit (Cr Ko radiation). RKD-57 cameras with asymmetric film loading were used in X-ray studies. The crystal lattice parameters of a number of alloys were determined precisely with the help of an FR-552 focusing monochromator camera (Cu KCY,radiation). Germanium was taken as a standard. The X-ray patterns were identified by comparing the data obtained with the information contained in the ASTM card index. The results were processed on a D3-28 computer. Electron probe X-ray analysis was carried out using a “Camerca” analyser. The Vickers hardness of the alloys was measured on homogenized samples; the load was 74 N. Microhardness was measured by indenting a diamond pyramid with an apex angle of 136” 20’; the load was 0.98 N.
129
3. Results and discussion The results obtained were used in the construction of the isothermal cross-section of the Hf-Nb-Ge phase diagram at 1170 K presented in Fig. 1. The following intermetallic compounds were found in the binary systems bounding the ternary system: Nb,Ge, Nb,Ge,, NbGe,,, Hf,Ge, Hf,Ge, Hf,Ge3, HfJGez, HfGe and HfGe*. It was found that the system contains an extended region of a ternary solid solution based on /S-Nb and also a vast two-phase region of (P-Nb + cu-Hf). The interaction of the starting components with the ten intermetallic compounds gives rise to a large number of two- and three-phase regions. The differences in the lattices of compounds having identical stoichiometric compositions (Hf,Ge and Nb,Ge, Hf,Ge, and Nb,Ge,, HfGez and NbGe,) determine the absence of a continuous series of solid solutions between them. The homogeneity regions of most of the binary intermetallic compounds in the ternary system are insignificant. Thus hafnium solubility in Nb,Ge, Nb5Ge3 and NbGe, is 5, 8 and 11 - 12 at.% respectively. The solubility of niobium in Hf,Ge and Hf,Ge amounts to 3 - 4 and 1 - 2 at.% respectively. The largest extent of the homogeneity region is peculiar to the solid solution based on Hf,Ge, (42 at.% niobium). The extent of the regions of ternary solid solutions based on the HfGe and HfGe, compounds is about 8 and 2 - 3 at.% niobium respectively, and that of Hf,Ge, is 1 - 2 at.% niobium. The X-ray pattern of the alloy having the composition 25a.t.%Hf25at.%Nb-50at.%Ge showed a new system of reflections which was not identical to any of the binary compounds of the Hf-Nb-Ge system. Electron probe X-ray analysis determined this alloy as a single phase and it has a composition of 22.2at.%Hf-33.3at.%Nb-44_5at.%Ge. Comparison of the Xray patterns of this alloy with the ternary compound Zr,NbRGe, studied Hf
Ge, ot.% Fig. 1. Isothermal
cross-section
of the phase diagram
of the Hf-Nb-Ge
system
at 1170 K.
130
earlier [ 111 revealed that the compounds are isostructural. The compound Hf2Nb3Ge4 crystallized with a rhombic crystal structure with the lattice parameters a = 6.863 + 0,004 8, b = 13.361 2 0.005 a and c = 7,006 + 0.004 A. By a series of physicochemical analysis methods the region of homogeneity of Hf,NbsGe, (44 - 46 at.% germanium, 22 - 33 at.% hafnium) was determined. The lattice parameters for the binary intermetalhc compounds were measured precisely and on their basis the parameters for the alloys from the regions of ternary solid solutions were determined. The results of calculations for the alloys of the Hf,Ges-Nb,Ge, cross-section are hsted in Table 1 and Fig, 2, The alloys in the cross-section with a hafnium concentration up to 8 at.% gave (on X-ray patterns) the only set of reflections corresponding to the tetragonal lattice of the W5Si3-type structure. The X-ray patterns of alloys with hafnium concentrations ranging between 20 and 62.5 at.% show the presence of a set of reflections peculiar to Hf5Ge, (the hexagonal lattice of the Mn,Si,-type structure). In the two-phase region, the X-ray patterns have two sets of reflections, belonging to the Hf5Ge3 and Nb5Ge3 compounds. The dependence of the parameters and volumes of the crystal lattice on composition for the alloys of the HfGe,-NbGe, cross-section are presented in Fig. 3 (see Table 2).
TABLE1 Lattice parameters and volumesand hardness and microhardness valuesforafloysofthe HfsGerNbsGes(37.5 at.%germanium)cross-section ComposiParameter tion (at.%,) (A) Hf
Nb
a
62.5 60 55 50 45 40 37.5 35 30
-
Volume
(A31
Hardness (N mmm2)
c
25 20 15
32.5 37.5 42.5 47.5
10
52.5
10.219+ 0.004 5.167f 0.003 541.4 k 0.7
8800
5
57.5 62.5
IO.187k 0.005 5.152* 0.002 540.1k 0.5 10.163+ 0.001 5.140f 0.001 530.9+ 0.2
9400 + 100 9500 +_100
-
+ f * f f f + f 4 f f
303.1r 0.3 301.9+ 0.2 298.8* 0.2 296.5+ 0.3 293.8f0.6 290.6+ 0.4 0.001 289.6+ 0.4 0.004 287.8+ 0.4 0.002 285.75 0.2 0.003 282.2+ 0.4 0.003 280.2+0.2 -
7.941 * 0,001 5.542 7.936 + 0.001 5.534 7.919f 0.001 5.502 7.905 * 0.002 5.480 7.876 + 0.004 5.445 7.869 + 0.006 5.428 7.847 f 0.002 5.411 7.742 4 0.002 5.404 7.825 * 0.002 5.391 7.802 * 0,002 5,378 7.777 + 0.002 5.348 -
2.5 7.5 12.5 17.5 22.5 25.0 27.5
0.002 0.002 0.002 0.004 0.004 0.001
5400 + 200 6100 f 100 6700 * 100
Microhardness (N mm-l)
7700 7800 7900 7200+100 8600 9400 7500+100 9700 7900~100 8200+100 9800 8600+ 100 9900 8800flOO 10000
8700+100 8500~100 8600+100 * 100
k + + * k + + 4 *
200 200 300 200 200 300 200 200
100 9300+100 7300 4 100 r0000+100 7100~100 9800*100 7300~100 11000+ 200 10400+200
131
5
5 30
60
5 20 5 10
Fig. 2. Variation cross-section.
Fig. 3. Variation section.
in lattice
in lattice
parameters
parameters
and
volumes
and volumes
for
alloys
for alloys
of the
Hf5Ge3-NbsGe3
of the HfGez-NbGe2
cross-
10.0 8.4 3.4
23.4 25.0 30.0 33.4
* 0.001
f: 0.001 f: 0.002 + 0.003 + 0.003 * 0.002 ?J0.003 t 0.003 -f 0.002 + 0.002
3.792 3.793 3.792 3.791 5.010 5.012 5.004 4.979 4.977
5.0 10.0 15.0 20.0
33.4 28.4 23.4 18.4 13.4
3.751 3.758 3.759 3.759 3.758 6.874 6.877 6,819 6.811 6.809
14.882 14.871 14.872 14.871 14.873
+ 0.002 * 0.002 k 0.003 * 0.004 t 0.003 + 0.004 +- 0,006 + 0.006 t 0.005 + 0.003
values for alloys
C
f 0.005 * 0.005 * 0.005 +_0.007 + 0.008
and microhardness
b
and hardness
3.793
a
Nb
Hf
and volumes
Parameter (A)
parameters
Composition (at.%)
Lattice section
TABLE 2
211.8 211.8 211.8 211.8 211.8 149.4 149.7 146.7 146.3 146.1
* + + + f + * + + +
Volume (A?
0.2 0.3 0.3 0.4 0.4 0.9 0.3 0.3 0.2 0.2
of the HfGez-NbGes
6400 6700 7300 7800
4900 5400 5700 6100 6300 i: h * i:
100 100 100 100
+ 100 t 100 f; 100 + 100 +I 100
cross
7500 7800 8300 8400
5800 7150 7200 7200 7500 -
i + + *
+ f + 2 +
100 100 100 100
100 200 200 100 100
Microhardness (N mm-*)
at.% germanium)
Hardness (N mm12)
(66.6
2: N
133
Various alloys were investigated by electron probe X-ray analysis. With the help of the data obtained, the compositions of the ternary compounds and the boundaries of the ternary phase regions were determined. The results of this analysis for some alloys are given in Table 3. The mechanical properties (hardness and microhardness) of a number of alloys of the system were studied. The results of the studies demonstrated that the alloys of the Hf-Nb binary system possess the lowest hardness (1000 = 4000 N mmm2). This confirmed the presence of the phase constituents, P-NB and cr-Hf, in the two- and three-phase regions of the ternary system. The largest values of hardness characterize the alloys based on the Nb,Ge, compound and also those belonging to the (Hf,Ge3 + Nb,Ge,) two-phase region (Table 1). The hardness and microhardness values for the binary compounds of the system are listed in Table 4. The dependences of microTABLE
3
The results of electron Composition
probe
(at.%)
X-ray analysis Number phases
Hf
Nb
Ge
30
40
30
3a
20
30
50
3=
30
20
50
3
10
10
80
3
25
25
50
1
of some
of
alloys
of the Hf
Composition
Nb-Ge
of phase Nb
Ge
35.392 14.129 22.335 13.698 32.764 28.583 42.881 0.677 30.27 1 10.244 22.233
27.040 85.408 31.707 20.732 21.159 4.899 8.185 1.028 1.417 22.874 33.297
37.568 0.463 45.958 65.570 46.076 66.518 48.934 98.295 68.312 67.882 44.470
4
Microhardness
data for binary
compounds
of the Hf--Nb-Ge
system
Compound
Microhardness (N mm -2)
Hardness (N mmm2)
Hf,Ge Hf2Ge HfsGes Hf sGes HfGe HfGe2 NbsGe NbsGes NbGe2
9100 9000 7700 6000 5900 5800 9100 10400 8400
8000 8800 5400 5700 5700 4900 8500 8300 7800
+ f + + * + + + *
100 100 200 100 100 100 100 200 100
(at.%)
Hf
Yl’he third phase was small grained. TABLE
system
* 100 + 100 + 200 + 100 +_ 100 ? 100 + 100 2 100 2 100
134 H.
N/e,&
11000
10000
9000
woo zoo0 NB&
ia)
(b)
Fig. 4. Composition dependence of microhardness and hardness for alloys of the HfsGes-NbsGes cross-section
(a)
(b)
Fig. 5. Composition dependence of microhardness and hardness for alloys of the HfGezNbGez cross-section.
hardness and hardness on composition for the alloys of the Hf,Ge,-NbSGe3 and HfGe,-NbGe, cross-sections are given in Tables 1 and 2 and Figs. 4 and 5. A monotonous variation in these properties is observed in the solid solution regions of Hf,Ge,, NbsGe3, HfGez and NbGez. The data obtained by this method are in good agreement with the results of X-ray phase, electron probe X-ray and microstructure analyses.
References 1 A. Taylor and N. Doyle, J. Less-Common Met., 7 (1964) 37. 2 R. E. Siements, H. R. Babitzke and H. Kato, Rep. Invest. Bur. Mines U.S. Dept. Interior, 6492 (1964) 11. 3 P. K. Alekseenko and L. N. Alekandrova, Izv. ,Akad. Nouk SSSR, Met., 3 (1968) 170. 4 E. Parthe, Acta Crystallogr., 12 (1959) 559. 5 H. Nowotny, Radex Rundsch., 6 (1960) 367. 6 M. A. Marko and Yu. B. Kuz’ma, Zh. Neorg. Mater., 13 (1977) 926.
135 E. A. Shishkin, in Metallovedenie, fiziko-khimiya i sverkhprovodnikov. Trudy II i III soveshaniy po metallovedeniyu, i metallofizike sverkhprovodnikov, Nauka, Moscow, 1967, p. 157. 8 A. Miiller, Z. Naturforsch., 25 (1970) 1659. 9 J. L. Jorda, R. Fliikinger and A. Miller, J. Less-Common Met., 62 (1978) 25. 10 Yu. D. Seropegin, 0. 1. Bodak, I. A. Guseva and L. A. Pantelejmonov, Vestn. Mosk. Univ. Khim.. 21 (1980) 186. 11 Yu. D. Seropegin, V. V. Tabachenko and M. G. Myskiv, Kristallogr., 29 (1984) 161. 7 V. M. Pan, metallofitika fiziko-khimii
V. I. Latysheva,
Metals,
135 (1987)
127 - 135
ISOTHERMAL CROSS-SECTION OF THE PHASE Hf-Nb-Ge SYSTEM AT 1170 K YU. D. SEROPEGIN
127
DIAGRAM
and M. V. RUDOMETKINA
Chemical Department, M. V. Lomonosov 119899 r%ll, B-234 (U.S.S.R.)
Moscow
State
University,
(Received
form February
17, 1987)
November
OF THE
20, 1986;in
revised
Moscow
Summary A variety of physicochemical analysis techniques (microstructure, X-ray phase and electron probe X-ray analysis; hardness and microhardness measurements) were employed in constructing the isothermal cross-section of the phase diagram of the Hf-Nb-Ge system at 1170 K. The formation of nine binary intermetallic compounds was confirmed. A new ternary compound, Hf2NbsGe,, was detected. The mechanical properties of a number of alloys of the system were studied.
1. Introduction Studies of diagrams showing the variation with phase and composition of the properties of multicomponent metal systems, open up new pathways to goal-oriented research into materials with specified properties. Alloys based on niobium and hafnium are characterized by high values of heat resistance, hardness and corrosion resistance. Research on the effect of alloying of niobium and hafnium germanides with transition metals on the properties of these compounds is of particular interest. This paper reports our studies of the phase diagram of the Hf-Nb-Ge system. Binary systems bounding the ternary system under discussion have been described in detail in the literature. Niobium and hafnium, as neighbouring are completely soluble in one elements in Mendeleev’s periodic system, another at temperatures above the polymorphic transformation temperature of hafnium [ 1 - 31. The interaction of the transition metals (hafnium and niobium) with germanium is of a more intricate character: a large number of intermetallic compounds with various crystal lattices are formed. Thus in the Hf-Ge system, as shown by earlier studies [4 - 61, six compounds are present: Hf,Ge (Ti,P-type structure), HfzGe (CuA12-type), Hf,Ge, (Mn,Si3type), Hf,Ge2 (U&-type), HfGe (FeB-type) and HfGe2 (ZrS&-type). Three compounds are formed in the Nb-Ge system: NbsGe (Cr,Si-type structure), Nb,Ge, (W&,-type) and NbGez (CrSi,-type) [ 7 - 91. The homogeneity 0022-5088/87/%3.50
@ Elsevier
Sequoia/Printed
in The Netherlands
128
regions of most of the germanides in the Hf-Ge and Nb-Ge systems do not exceed 1 - 2 at.%. The homogeneity regions of the NbsGes and NbGez compounds are 3 and 4 at.% germanium respectively [lo].
2. Experimental
details
The present study was carried out on about 100 alloys. These were made in an electric arc furnace under an argon atmosphere using a nonconsumable tungsten electrode and a water-cooled copper tray. Hafnium obtained by thermal decomposition of Hf14 (purity, 99.9%), vacuum-melted niobium (purity, 99.96%) and semiconductor germanium (purity, 99.99%) were used as starting components. Titanium was used as a getter in melting. The alloys were remelted three times in order to achieve complete fusion and homogeneous composition. Alloys with losses after melting not exceeding 1 wt.% were chosen for the experiments. The composition of each alloy was selected using the results of an analysis of the binary phase diagrams. All melted alloys were subjected to homogenizing annealing in evacuated double quartz ampoules containing titanium chips as getter; the ampoules were placed in resistance furnaces. The alloys containing more than 60 at.% germanium were annealed at 1170 K for 700 h. The alloys with less than 60 at.% germanium underwent preliminary annealing at 1420 K for 750 h. All samples were quenched from 1170 K in ice-cold water. A variety of physicochemical analysis techniques were used in the present study : microstructure, X-ray phase and electron probe X-ray analysis; hardness and microhardness measurements. In the microstructure studies, the samples were sanded successively on rough and fine emery paper and then polished on felt with an aqueous suspension of chromium oxide. The structure was revealed by etching the surface of the section with a mixture of concentrated HNOs and HF with HzO, (1:3:1). The microstructure was examined and photographed under a “Neophot 2” microscope with a magnification of 400X. X-ray phase analysis was performed on a URS-60 unit (Cr Ko radiation). RKD-57 cameras with asymmetric film loading were used in X-ray studies. The crystal lattice parameters of a number of alloys were determined precisely with the help of an FR-552 focusing monochromator camera (Cu KCY,radiation). Germanium was taken as a standard. The X-ray patterns were identified by comparing the data obtained with the information contained in the ASTM card index. The results were processed on a D3-28 computer. Electron probe X-ray analysis was carried out using a “Camerca” analyser. The Vickers hardness of the alloys was measured on homogenized samples; the load was 74 N. Microhardness was measured by indenting a diamond pyramid with an apex angle of 136” 20’; the load was 0.98 N.
129
3. Results and discussion The results obtained were used in the construction of the isothermal cross-section of the Hf-Nb-Ge phase diagram at 1170 K presented in Fig. 1. The following intermetallic compounds were found in the binary systems bounding the ternary system: Nb,Ge, Nb,Ge,, NbGe,,, Hf,Ge, Hf,Ge, Hf,Ge3, HfJGez, HfGe and HfGe*. It was found that the system contains an extended region of a ternary solid solution based on /S-Nb and also a vast two-phase region of (P-Nb + cu-Hf). The interaction of the starting components with the ten intermetallic compounds gives rise to a large number of two- and three-phase regions. The differences in the lattices of compounds having identical stoichiometric compositions (Hf,Ge and Nb,Ge, Hf,Ge, and Nb,Ge,, HfGez and NbGe,) determine the absence of a continuous series of solid solutions between them. The homogeneity regions of most of the binary intermetallic compounds in the ternary system are insignificant. Thus hafnium solubility in Nb,Ge, Nb5Ge3 and NbGe, is 5, 8 and 11 - 12 at.% respectively. The solubility of niobium in Hf,Ge and Hf,Ge amounts to 3 - 4 and 1 - 2 at.% respectively. The largest extent of the homogeneity region is peculiar to the solid solution based on Hf,Ge, (42 at.% niobium). The extent of the regions of ternary solid solutions based on the HfGe and HfGe, compounds is about 8 and 2 - 3 at.% niobium respectively, and that of Hf,Ge, is 1 - 2 at.% niobium. The X-ray pattern of the alloy having the composition 25a.t.%Hf25at.%Nb-50at.%Ge showed a new system of reflections which was not identical to any of the binary compounds of the Hf-Nb-Ge system. Electron probe X-ray analysis determined this alloy as a single phase and it has a composition of 22.2at.%Hf-33.3at.%Nb-44_5at.%Ge. Comparison of the Xray patterns of this alloy with the ternary compound Zr,NbRGe, studied Hf
Ge, ot.% Fig. 1. Isothermal
cross-section
of the phase diagram
of the Hf-Nb-Ge
system
at 1170 K.
130
earlier [ 111 revealed that the compounds are isostructural. The compound Hf2Nb3Ge4 crystallized with a rhombic crystal structure with the lattice parameters a = 6.863 + 0,004 8, b = 13.361 2 0.005 a and c = 7,006 + 0.004 A. By a series of physicochemical analysis methods the region of homogeneity of Hf,NbsGe, (44 - 46 at.% germanium, 22 - 33 at.% hafnium) was determined. The lattice parameters for the binary intermetalhc compounds were measured precisely and on their basis the parameters for the alloys from the regions of ternary solid solutions were determined. The results of calculations for the alloys of the Hf,Ges-Nb,Ge, cross-section are hsted in Table 1 and Fig, 2, The alloys in the cross-section with a hafnium concentration up to 8 at.% gave (on X-ray patterns) the only set of reflections corresponding to the tetragonal lattice of the W5Si3-type structure. The X-ray patterns of alloys with hafnium concentrations ranging between 20 and 62.5 at.% show the presence of a set of reflections peculiar to Hf5Ge, (the hexagonal lattice of the Mn,Si,-type structure). In the two-phase region, the X-ray patterns have two sets of reflections, belonging to the Hf5Ge3 and Nb5Ge3 compounds. The dependence of the parameters and volumes of the crystal lattice on composition for the alloys of the HfGe,-NbGe, cross-section are presented in Fig. 3 (see Table 2).
TABLE1 Lattice parameters and volumesand hardness and microhardness valuesforafloysofthe HfsGerNbsGes(37.5 at.%germanium)cross-section ComposiParameter tion (at.%,) (A) Hf
Nb
a
62.5 60 55 50 45 40 37.5 35 30
-
Volume
(A31
Hardness (N mmm2)
c
25 20 15
32.5 37.5 42.5 47.5
10
52.5
10.219+ 0.004 5.167f 0.003 541.4 k 0.7
8800
5
57.5 62.5
IO.187k 0.005 5.152* 0.002 540.1k 0.5 10.163+ 0.001 5.140f 0.001 530.9+ 0.2
9400 + 100 9500 +_100
-
+ f * f f f + f 4 f f
303.1r 0.3 301.9+ 0.2 298.8* 0.2 296.5+ 0.3 293.8f0.6 290.6+ 0.4 0.001 289.6+ 0.4 0.004 287.8+ 0.4 0.002 285.75 0.2 0.003 282.2+ 0.4 0.003 280.2+0.2 -
7.941 * 0,001 5.542 7.936 + 0.001 5.534 7.919f 0.001 5.502 7.905 * 0.002 5.480 7.876 + 0.004 5.445 7.869 + 0.006 5.428 7.847 f 0.002 5.411 7.742 4 0.002 5.404 7.825 * 0.002 5.391 7.802 * 0,002 5,378 7.777 + 0.002 5.348 -
2.5 7.5 12.5 17.5 22.5 25.0 27.5
0.002 0.002 0.002 0.004 0.004 0.001
5400 + 200 6100 f 100 6700 * 100
Microhardness (N mm-l)
7700 7800 7900 7200+100 8600 9400 7500+100 9700 7900~100 8200+100 9800 8600+ 100 9900 8800flOO 10000
8700+100 8500~100 8600+100 * 100
k + + * k + + 4 *
200 200 300 200 200 300 200 200
100 9300+100 7300 4 100 r0000+100 7100~100 9800*100 7300~100 11000+ 200 10400+200
131
5
5 30
60
5 20 5 10
Fig. 2. Variation cross-section.
Fig. 3. Variation section.
in lattice
in lattice
parameters
parameters
and
volumes
and volumes
for
alloys
for alloys
of the
Hf5Ge3-NbsGe3
of the HfGez-NbGe2
cross-
10.0 8.4 3.4
23.4 25.0 30.0 33.4
* 0.001
f: 0.001 f: 0.002 + 0.003 + 0.003 * 0.002 ?J0.003 t 0.003 -f 0.002 + 0.002
3.792 3.793 3.792 3.791 5.010 5.012 5.004 4.979 4.977
5.0 10.0 15.0 20.0
33.4 28.4 23.4 18.4 13.4
3.751 3.758 3.759 3.759 3.758 6.874 6.877 6,819 6.811 6.809
14.882 14.871 14.872 14.871 14.873
+ 0.002 * 0.002 k 0.003 * 0.004 t 0.003 + 0.004 +- 0,006 + 0.006 t 0.005 + 0.003
values for alloys
C
f 0.005 * 0.005 * 0.005 +_0.007 + 0.008
and microhardness
b
and hardness
3.793
a
Nb
Hf
and volumes
Parameter (A)
parameters
Composition (at.%)
Lattice section
TABLE 2
211.8 211.8 211.8 211.8 211.8 149.4 149.7 146.7 146.3 146.1
* + + + f + * + + +
Volume (A?
0.2 0.3 0.3 0.4 0.4 0.9 0.3 0.3 0.2 0.2
of the HfGez-NbGes
6400 6700 7300 7800
4900 5400 5700 6100 6300 i: h * i:
100 100 100 100
+ 100 t 100 f; 100 + 100 +I 100
cross
7500 7800 8300 8400
5800 7150 7200 7200 7500 -
i + + *
+ f + 2 +
100 100 100 100
100 200 200 100 100
Microhardness (N mm-*)
at.% germanium)
Hardness (N mm12)
(66.6
2: N
133
Various alloys were investigated by electron probe X-ray analysis. With the help of the data obtained, the compositions of the ternary compounds and the boundaries of the ternary phase regions were determined. The results of this analysis for some alloys are given in Table 3. The mechanical properties (hardness and microhardness) of a number of alloys of the system were studied. The results of the studies demonstrated that the alloys of the Hf-Nb binary system possess the lowest hardness (1000 = 4000 N mmm2). This confirmed the presence of the phase constituents, P-NB and cr-Hf, in the two- and three-phase regions of the ternary system. The largest values of hardness characterize the alloys based on the Nb,Ge, compound and also those belonging to the (Hf,Ge3 + Nb,Ge,) two-phase region (Table 1). The hardness and microhardness values for the binary compounds of the system are listed in Table 4. The dependences of microTABLE
3
The results of electron Composition
probe
(at.%)
X-ray analysis Number phases
Hf
Nb
Ge
30
40
30
3a
20
30
50
3=
30
20
50
3
10
10
80
3
25
25
50
1
of some
of
alloys
of the Hf
Composition
Nb-Ge
of phase Nb
Ge
35.392 14.129 22.335 13.698 32.764 28.583 42.881 0.677 30.27 1 10.244 22.233
27.040 85.408 31.707 20.732 21.159 4.899 8.185 1.028 1.417 22.874 33.297
37.568 0.463 45.958 65.570 46.076 66.518 48.934 98.295 68.312 67.882 44.470
4
Microhardness
data for binary
compounds
of the Hf--Nb-Ge
system
Compound
Microhardness (N mm -2)
Hardness (N mmm2)
Hf,Ge Hf2Ge HfsGes Hf sGes HfGe HfGe2 NbsGe NbsGes NbGe2
9100 9000 7700 6000 5900 5800 9100 10400 8400
8000 8800 5400 5700 5700 4900 8500 8300 7800
+ f + + * + + + *
100 100 200 100 100 100 100 200 100
(at.%)
Hf
Yl’he third phase was small grained. TABLE
system
* 100 + 100 + 200 + 100 +_ 100 ? 100 + 100 2 100 2 100
134 H.
N/e,&
11000
10000
9000
woo zoo0 NB&
ia)
(b)
Fig. 4. Composition dependence of microhardness and hardness for alloys of the HfsGes-NbsGes cross-section
(a)
(b)
Fig. 5. Composition dependence of microhardness and hardness for alloys of the HfGezNbGez cross-section.
hardness and hardness on composition for the alloys of the Hf,Ge,-NbSGe3 and HfGe,-NbGe, cross-sections are given in Tables 1 and 2 and Figs. 4 and 5. A monotonous variation in these properties is observed in the solid solution regions of Hf,Ge,, NbsGe3, HfGez and NbGez. The data obtained by this method are in good agreement with the results of X-ray phase, electron probe X-ray and microstructure analyses.
References 1 A. Taylor and N. Doyle, J. Less-Common Met., 7 (1964) 37. 2 R. E. Siements, H. R. Babitzke and H. Kato, Rep. Invest. Bur. Mines U.S. Dept. Interior, 6492 (1964) 11. 3 P. K. Alekseenko and L. N. Alekandrova, Izv. ,Akad. Nouk SSSR, Met., 3 (1968) 170. 4 E. Parthe, Acta Crystallogr., 12 (1959) 559. 5 H. Nowotny, Radex Rundsch., 6 (1960) 367. 6 M. A. Marko and Yu. B. Kuz’ma, Zh. Neorg. Mater., 13 (1977) 926.
135 E. A. Shishkin, in Metallovedenie, fiziko-khimiya i sverkhprovodnikov. Trudy II i III soveshaniy po metallovedeniyu, i metallofizike sverkhprovodnikov, Nauka, Moscow, 1967, p. 157. 8 A. Miiller, Z. Naturforsch., 25 (1970) 1659. 9 J. L. Jorda, R. Fliikinger and A. Miller, J. Less-Common Met., 62 (1978) 25. 10 Yu. D. Seropegin, 0. 1. Bodak, I. A. Guseva and L. A. Pantelejmonov, Vestn. Mosk. Univ. Khim.. 21 (1980) 186. 11 Yu. D. Seropegin, V. V. Tabachenko and M. G. Myskiv, Kristallogr., 29 (1984) 161. 7 V. M. Pan, metallofitika fiziko-khimii
V. I. Latysheva,