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An investigation of Fe3Zr phase
ScriptaMetallurgicaet Materialia,Vol. 32,
No. 8, pp, 1129- 1132.1995 Copyright 8 1995 Elsevier Science Ltd Printed in the USA. AII rights reserved 0956=116X/95 $9.50 + .OO
0956-716X(95)00113-1
AN INVESTIGATION OF Fe@ PHASE Yaping Liu, Samuel M. Allen and James D. Livingson Department of Materials Science and Engineering Massachusetts Institute of Technology Cambridge, MA 02139, USA (Received September 21,1994) (Revised November 1,1994) Introduction Fe-Zr alloys of low iron content have been studied extensively and the phases in these alloys have been identified successfully. However, previous results on the number, composition and structure of intermediate phases in low Zr content Fe-Zr alloys are still contradictory. The phase diagram given by [l] shows a Fe,Zr phase existing in a composition range of 22.5-25.0 at% Zr. But this phase doesn’t exist in the diagram given by [2]. Svechnikov et al. [3] are the first investigators to find the Fe,Zr compound formed after long annealing (56-100 hr) at 12.50-1450°C, of alloys of Fe-(20-45)wt% Zr by X-ray diffraction analysis. He suggested the name q for the Fe,Zr (structure of Ti,Ni, space group of 0; or Fdsm). Kripyakevich et al. [4] calculated the intensities of the lines of the Fe3Zr X-ray diagram for different variants of the structure and compared them to the results with the experimental values given in [3], finding that a much better agreement between the observed and calculated intensiries was obtained for the ThgMnz3-type structure than for the Ti,Ni structure. But many later investigators still doubt the existence of the phase of Fe3Zr. Aubertin et al. [5] could not find Fe3Zr in ltheir experiments, thinking that Fe,Zr might only be a high-temperature phase existing above 950°C or, more probably, was the result of contamination of the Fe-Zr alloy with crucible material (Al,O,) at high temperatures. Most recently, Alekseeva and Korotkova[6] suggested the newest phase diagram of Fe-Zr system, in which no Fe,Zr exists. They claimed that they failed to synthesize it using the preparation technology suggested in [3]. They did not agree that the phase with a cubic lattice and 1.1691 nm period was Fe16Zr6Si formed in heat treatment with quartz, as suggested by some other authors. Instead, they suggested the phase was the product of Fe reacting with MO (FejMogC) and W, used in the annealing furnace. The present paper concentrates on the phase identification and microstructure analysis in Fe-10 at% Zr alloys. Resolution of these questions will contribute to clarification of long-standing questions in the literature concerning the Fe-Zr phase diagram. Experimental The Fe-10 at% Zr alloy was prepared by arc melting. The annealing samples were encapsulated in a high vacuum of 10m4Pa to prevent oxidation, and were annealed at 700,900 and 1190 OC for 4,24 and 48 hours, at each temperature. To avoid the influence of the reaction of the material with furnace crucible and quartz, the samples used for the study were cut from the inner part of the annealed bulk alloy. To prepare TEM and STEM samples, sections approximately 0.4 mm thick were cut using a diamond saw, then ground to a thickness of about 0.1 mm and electropolished in a solution of 10 ~01% perchloric acid-90 ~01% methanol. The electron microscopy work was performed using JEOL 200 CX and EM-002B transmission electron microscopes operating at an accelerating voltage of 200kV. A Vg HB5 scanning transmission electron microscope with a minimum probe size of 0.5 nm was used in the composition micro-analysis. X-ray diffraction analysis on slice specimens were performed on an RU-300 diffractometer with Cu-Ka radiation and a rotating mode. The samples for metallographic examination were etched using a solution of 1 ~01% HF, 9 ~01% HNO, and 90 ~01% distilled H,O. Quantitative metallography was also carried out on an optical microscope. The volume fraction of a phasewas measured by point-counting method at a magnification of 1600 X using 600 grid points. The number of counting points assured that the 95 percent confidence limit was within 0.1 of the mean values for all the measured data.
1129
1130
Fe&r PHASE
Vol. 32. No. 8
Observations and Dicussion The phases observed in the Fe- 10 at% Zr alloy were a-Fe, Fe3Zr and the Laves phase Fe2Zr. The dominant structures in as-cast alloy are proeutectic Fe2Zr and eutectic cr-Fe and Fe2Zr. The eutectic structure has two forms: Cell lamellar and long linear lamellar structures. The former coarsens quickly and the latter is relatively stable during annealing. The microstructure and the transformation of the Laves phase Fe,Zr has been discussed in detail in another paper[7]. The results of TEM micrographs, electron diffraction, optical micrographs and STEM micro-analysis in the research provide sufficient evidence confirming the existence of a small volume fraction of Fe3Zr in the as-cast samples and the samples annealed at 700. 900 and 1190 OC. In the as-cast samples, Fe,Zr has a cubic shape size of 3-10 micrometers. The cross sections cut on the optical microscopy and TEM samples show some concentric squares and triangles, as shown in a TEM micrograph, Fig.1. During annealing, Fe3Zr cubes dissolved gradually. Some residual Fe,Zr cubes still remain in the 1190 OC, 4 hour annealed samples, but they completely disappear in the samples annealed for longer times. Meanwhile, new Fe3Zr particles of different shape began to nucleate and grow during the annealing. Their deeper-etched character and flower-like shape make them easy to recognize in the optical microscope. In TEM micrographs, Fe3Zr can also be distinguished easily from the Laves phase in cl-Fe matrix, as the latter contains dense faults. In these samples, some Fe3Zr regions have a very large size of about 20-30 microns and are polycrystalline. It is reasonable to think they are the product of the direct change and growth of the cubic Fe3Zr in as-cast samples. Others have smaller size of about 3-5 micrometers, consisting of only one or several grains. They are thought to be the products of the phase transformation: Fe,Zr + Fe = FegZr. Careful observation on the smaller size Fe,Zr revealed that they usually connected to Fe+ phase. This is shown in Fig.2. A preferred nucleation site for Fe3Zr seems to be the long lamellar structure. Many polycrystalline Fe3Zr particles grew from and interrupt the long lamellar phases, as shown in Fig.3. It is interesting that, in the center of the polycrystalline Fe3Zr, there usually is a small “island” remaining untransformed, which still has the same lamellar structure as the surrounding lamellae. This makes the Fe+ phase more “flower-like”. Multiple-point micro-analysis by STEM on both as-cast and annealed samples showed the composition of the Fe,Zr phase was in the range of 23-25 at% Zr (the error of the composition determination is less than la), which is the equilibrium composition with a-Fe. In the energy dispersive analysis in STEM, the crucible material and furnace winding elements, such as Si, MO, W, Al, C, 0, were not found in either the cubic shape or the flower-like phase, eliminating the possibility that the phases were produced in the reaction of Fe and Zr with crucible material in the annealing, as suggested by [3] and [5]. The selected-area diffraction patterns of some typical crystallographic planes are given in Fig.4, showing some characteristics of fee type structure. From these patterns, we may determine if the structure belongs to Ti,Ni type or ThgMn23 typ e easily. A distinctive difference between the general reflection conditions of Fd?m-0; (Ti,Ni type) and Fm?m-0: (TheMn23 typ e ) is that the former has a reflection condition of h = 4n in hO0, whereas the latter has a condition of h = 2n in hOO[8]. The orientations of the patterns in Fig.4 were chosen to be suitable to show the ho0 reflections. It should be noted from the index that the [ 200) reflections are present in both the patterns. When the sample is moved to a thin area, which is the case in figure (a), the relative intensity of (2001 reflections has no obvious change. This implies a low possibility of double diffraction, so the crystal structure of Fe+ is more likely to belong to Th,Mn,, type, as concluded by [4], rather than Ti,Ni structure[3]. The lattice parameter determined from the selected-area diffraction patterns is a, = 1.166 nm. The phase rule limits the number of equilibrium phases in a two-component system at constant temperature and pressure to two. Since the samples characterized in the study contain three phases, one of the high Zr phases must not be an equilibrium phase. The appearance of newly formed Fe,Zr particles and their growth in long time annealing indicate that the equilibrium phase is Fe3Zr rather than Fe,Zr. The presence of a large amount of Fe.+ in the alloy may result from either of the following causes: First, possibly the Fe3Zr peritectoid temperature is much lower than 1480 OC, so that the 10 at% alloy can enter this region before the peritectoid reaction Fe2Zr + Fe(a) = Fe+ occurs in the cooling. Secondly, and more likely, the formation of Fe,Zr is the result of non-equilibrium cooling. In this case, a possible free energy plot is shown in Fig.5 When the 10 at% alloy is cooled to a temperature below the liquidus line in a noneqilibrium condition, the driving force for the transformation to Fe,Zr (A,G*-~z~ is larger than that to Fe+ (AGl-&a’), even if the free energy of FegZr is lower than that of Fe,Zr. So Fe,Zr may come out first to form a me&stable proeutectic phase, and also reaches the eutectic point first in the cooling. These are illustrated clearly in the figure. Even though Fe3Zr is a stable phase in the temperature range, its precipitation is quite slow. Fig.6 gives the variation of measured volume fraction x of Fe,Zr with annealing time t at 1190 OC, which can be described in the equation x = kt”
Fe&r PHASE
Vol. 32. No. 8
1131
with m = 517. The very small exponent is consistent with the observed low growth rate of the phase. The reaction FezZr + a-Fe = Fe& in the long time annealing is very similar to a peritecroid reaction in this non-equilibrium sohdified alloy. Fe,Zr must nucieate on the surface of Fe,Zr particles. The growing Fe,Zr then gradually surrounds some parts of a Fe?Zr particle completely. Later transformation of the surrounded part of Fe,Zr relies on the slow diffusion of Fe atoms through the outer layer of Fe,Zr to the interface between Fe3Zr and Fe+. An incomplete transformation usually leaves an untransformed Fe2Zr core in the center of a Fe3Zr particle. This is what we have seen in Fig.3, a Fe2Zr “island” in the “flower-like” Fe-& particle. The slow diffusion rate of Fe atoms limits the rate of the transformation. It can be seen in Fig.6 that the volume fraction of Fe,Zr is still less than 4% after 48 hour annealing, making it very difficult to be detected by X-ray diffraction or Mossbauer measurement. This may explain why so many investigators failed to find the phase in their experiments. To reduce the diffusion distance, Fe,Zr particles prefer to form in the fine lamellar region, especially the long lamellar lines which have a low coarsening rate in the annealing, as shown in Fig.3.
The existence o’f the controversial Fe,Zr is confirmed in this study by optical and TEM imaging, electron diffraction and STEM composition analysis. Fe,Zr has a cubic morphology in the as-cast alloy and a polycrystalline morphology in the annealed alloy. Electron diffraction patterns indicate its crystal structure belongs to Th,Mn,, type rather than Ti,Ni type. Fe3Zr and a-.Fe should be equilibrium phases in the alloy in the temperatures. The presence of the metastable phase Fe,Zr may be the result of a larger driving force for its formation and the extremely slow growth rate of Fe,Zr. Fe3Zr particles are a product of a reaction similar to a peritectoid reaction: Fe,Zr + Fe(a) = Fe,Zr. Its growth rate in most cases depends on the diffusion of Fe atoms through the Fe,Zr outer layer to the Fe2Zr core. The volume fraction of FegZr is less than 4% after a 48 hour annealing at 119O’C. Acknowledgement Financial support from the Department of Energy, Division of Basic Energy Sciences, Grant No. DEFGO2-90ER45426, is greatly appreciated. We also acknowledge the helpful discussions with Professor John B. Vander Sande, Professor Bemhardt J. Wuensch and Kathy Chen. References [ 11. Q. Kubaschewski, Iron-Binary Phase Diagrams, 1982. [2]. W. G. Moffatt, The Handbook of Binary Phase Diagrams, 1984. [3]. V. N. Svechnikov, V. M. Pan and A. Ts. Spector, Russ. J. Inorg. Chem., Vol. IO, No. I, Sep. 1963, pp. 1106. [4]. P. I. Kripyakevich, V. S. Protasov and E. E. Cherkashin, Russ. J. Inorg. Chem., Vol. 10, No. 1, Jan 1965, nn. 151. [5]. F. Aubertin, IJ. Gonser, S. J. Campbell and H. Wagner, Z. Metallkunde, Vol. 76, 1985, pp.237. [6]. Z. M. Alekseeva and N. V. Korotkova, Russ. Met. R., No. 4, 1989, pp. 197. [7]. Yaping Liu, James D. Livingston, and Samuel M. Allen: Met. Trans. A, Dec. 1992, Vol. 23A, No 12, pp, 3303-3308. 181. T. Hahn, International Tables for Crystallography, Vol. A, Second, Revised Edition, D. Reidel Publishing Company, 1987.
Fig. 1. Concentric cubes of Fe+
in as-cast alloy.
Fig.2. Polycrystalline Fr,Zr connecting Fe2Zr in annealed samples (annealed at 1190OC for 48 hours).
1132
Fe& PHASE
Vol. 32. No. 8
(b) Fig.3. “Flower-like” Polycrystalline Fe,Zr grown from long straight Inmellar Fe,%
I
,
I
I
I
,
Fig.4. Electron diffraction patterns of Fe,Zr phase. (a) B=[OOll. (b)B=[Ol 11.' '
.^
Fig.5. Free energy curves of the phases in Fe- IO at% Zr alloy at cooling.
Fig.6. Change of volume fraction of Fe,Zr ph:isc vs. time in the annealing (I 190 T).
No. 8, pp, 1129- 1132.1995 Copyright 8 1995 Elsevier Science Ltd Printed in the USA. AII rights reserved 0956=116X/95 $9.50 + .OO
0956-716X(95)00113-1
AN INVESTIGATION OF Fe@ PHASE Yaping Liu, Samuel M. Allen and James D. Livingson Department of Materials Science and Engineering Massachusetts Institute of Technology Cambridge, MA 02139, USA (Received September 21,1994) (Revised November 1,1994) Introduction Fe-Zr alloys of low iron content have been studied extensively and the phases in these alloys have been identified successfully. However, previous results on the number, composition and structure of intermediate phases in low Zr content Fe-Zr alloys are still contradictory. The phase diagram given by [l] shows a Fe,Zr phase existing in a composition range of 22.5-25.0 at% Zr. But this phase doesn’t exist in the diagram given by [2]. Svechnikov et al. [3] are the first investigators to find the Fe,Zr compound formed after long annealing (56-100 hr) at 12.50-1450°C, of alloys of Fe-(20-45)wt% Zr by X-ray diffraction analysis. He suggested the name q for the Fe,Zr (structure of Ti,Ni, space group of 0; or Fdsm). Kripyakevich et al. [4] calculated the intensities of the lines of the Fe3Zr X-ray diagram for different variants of the structure and compared them to the results with the experimental values given in [3], finding that a much better agreement between the observed and calculated intensiries was obtained for the ThgMnz3-type structure than for the Ti,Ni structure. But many later investigators still doubt the existence of the phase of Fe3Zr. Aubertin et al. [5] could not find Fe3Zr in ltheir experiments, thinking that Fe,Zr might only be a high-temperature phase existing above 950°C or, more probably, was the result of contamination of the Fe-Zr alloy with crucible material (Al,O,) at high temperatures. Most recently, Alekseeva and Korotkova[6] suggested the newest phase diagram of Fe-Zr system, in which no Fe,Zr exists. They claimed that they failed to synthesize it using the preparation technology suggested in [3]. They did not agree that the phase with a cubic lattice and 1.1691 nm period was Fe16Zr6Si formed in heat treatment with quartz, as suggested by some other authors. Instead, they suggested the phase was the product of Fe reacting with MO (FejMogC) and W, used in the annealing furnace. The present paper concentrates on the phase identification and microstructure analysis in Fe-10 at% Zr alloys. Resolution of these questions will contribute to clarification of long-standing questions in the literature concerning the Fe-Zr phase diagram. Experimental The Fe-10 at% Zr alloy was prepared by arc melting. The annealing samples were encapsulated in a high vacuum of 10m4Pa to prevent oxidation, and were annealed at 700,900 and 1190 OC for 4,24 and 48 hours, at each temperature. To avoid the influence of the reaction of the material with furnace crucible and quartz, the samples used for the study were cut from the inner part of the annealed bulk alloy. To prepare TEM and STEM samples, sections approximately 0.4 mm thick were cut using a diamond saw, then ground to a thickness of about 0.1 mm and electropolished in a solution of 10 ~01% perchloric acid-90 ~01% methanol. The electron microscopy work was performed using JEOL 200 CX and EM-002B transmission electron microscopes operating at an accelerating voltage of 200kV. A Vg HB5 scanning transmission electron microscope with a minimum probe size of 0.5 nm was used in the composition micro-analysis. X-ray diffraction analysis on slice specimens were performed on an RU-300 diffractometer with Cu-Ka radiation and a rotating mode. The samples for metallographic examination were etched using a solution of 1 ~01% HF, 9 ~01% HNO, and 90 ~01% distilled H,O. Quantitative metallography was also carried out on an optical microscope. The volume fraction of a phasewas measured by point-counting method at a magnification of 1600 X using 600 grid points. The number of counting points assured that the 95 percent confidence limit was within 0.1 of the mean values for all the measured data.
1129
1130
Fe&r PHASE
Vol. 32. No. 8
Observations and Dicussion The phases observed in the Fe- 10 at% Zr alloy were a-Fe, Fe3Zr and the Laves phase Fe2Zr. The dominant structures in as-cast alloy are proeutectic Fe2Zr and eutectic cr-Fe and Fe2Zr. The eutectic structure has two forms: Cell lamellar and long linear lamellar structures. The former coarsens quickly and the latter is relatively stable during annealing. The microstructure and the transformation of the Laves phase Fe,Zr has been discussed in detail in another paper[7]. The results of TEM micrographs, electron diffraction, optical micrographs and STEM micro-analysis in the research provide sufficient evidence confirming the existence of a small volume fraction of Fe3Zr in the as-cast samples and the samples annealed at 700. 900 and 1190 OC. In the as-cast samples, Fe,Zr has a cubic shape size of 3-10 micrometers. The cross sections cut on the optical microscopy and TEM samples show some concentric squares and triangles, as shown in a TEM micrograph, Fig.1. During annealing, Fe3Zr cubes dissolved gradually. Some residual Fe,Zr cubes still remain in the 1190 OC, 4 hour annealed samples, but they completely disappear in the samples annealed for longer times. Meanwhile, new Fe3Zr particles of different shape began to nucleate and grow during the annealing. Their deeper-etched character and flower-like shape make them easy to recognize in the optical microscope. In TEM micrographs, Fe3Zr can also be distinguished easily from the Laves phase in cl-Fe matrix, as the latter contains dense faults. In these samples, some Fe3Zr regions have a very large size of about 20-30 microns and are polycrystalline. It is reasonable to think they are the product of the direct change and growth of the cubic Fe3Zr in as-cast samples. Others have smaller size of about 3-5 micrometers, consisting of only one or several grains. They are thought to be the products of the phase transformation: Fe,Zr + Fe = FegZr. Careful observation on the smaller size Fe,Zr revealed that they usually connected to Fe+ phase. This is shown in Fig.2. A preferred nucleation site for Fe3Zr seems to be the long lamellar structure. Many polycrystalline Fe3Zr particles grew from and interrupt the long lamellar phases, as shown in Fig.3. It is interesting that, in the center of the polycrystalline Fe3Zr, there usually is a small “island” remaining untransformed, which still has the same lamellar structure as the surrounding lamellae. This makes the Fe+ phase more “flower-like”. Multiple-point micro-analysis by STEM on both as-cast and annealed samples showed the composition of the Fe,Zr phase was in the range of 23-25 at% Zr (the error of the composition determination is less than la), which is the equilibrium composition with a-Fe. In the energy dispersive analysis in STEM, the crucible material and furnace winding elements, such as Si, MO, W, Al, C, 0, were not found in either the cubic shape or the flower-like phase, eliminating the possibility that the phases were produced in the reaction of Fe and Zr with crucible material in the annealing, as suggested by [3] and [5]. The selected-area diffraction patterns of some typical crystallographic planes are given in Fig.4, showing some characteristics of fee type structure. From these patterns, we may determine if the structure belongs to Ti,Ni type or ThgMn23 typ e easily. A distinctive difference between the general reflection conditions of Fd?m-0; (Ti,Ni type) and Fm?m-0: (TheMn23 typ e ) is that the former has a reflection condition of h = 4n in hO0, whereas the latter has a condition of h = 2n in hOO[8]. The orientations of the patterns in Fig.4 were chosen to be suitable to show the ho0 reflections. It should be noted from the index that the [ 200) reflections are present in both the patterns. When the sample is moved to a thin area, which is the case in figure (a), the relative intensity of (2001 reflections has no obvious change. This implies a low possibility of double diffraction, so the crystal structure of Fe+ is more likely to belong to Th,Mn,, type, as concluded by [4], rather than Ti,Ni structure[3]. The lattice parameter determined from the selected-area diffraction patterns is a, = 1.166 nm. The phase rule limits the number of equilibrium phases in a two-component system at constant temperature and pressure to two. Since the samples characterized in the study contain three phases, one of the high Zr phases must not be an equilibrium phase. The appearance of newly formed Fe,Zr particles and their growth in long time annealing indicate that the equilibrium phase is Fe3Zr rather than Fe,Zr. The presence of a large amount of Fe.+ in the alloy may result from either of the following causes: First, possibly the Fe3Zr peritectoid temperature is much lower than 1480 OC, so that the 10 at% alloy can enter this region before the peritectoid reaction Fe2Zr + Fe(a) = Fe+ occurs in the cooling. Secondly, and more likely, the formation of Fe,Zr is the result of non-equilibrium cooling. In this case, a possible free energy plot is shown in Fig.5 When the 10 at% alloy is cooled to a temperature below the liquidus line in a noneqilibrium condition, the driving force for the transformation to Fe,Zr (A,G*-~z~ is larger than that to Fe+ (AGl-&a’), even if the free energy of FegZr is lower than that of Fe,Zr. So Fe,Zr may come out first to form a me&stable proeutectic phase, and also reaches the eutectic point first in the cooling. These are illustrated clearly in the figure. Even though Fe3Zr is a stable phase in the temperature range, its precipitation is quite slow. Fig.6 gives the variation of measured volume fraction x of Fe,Zr with annealing time t at 1190 OC, which can be described in the equation x = kt”
Fe&r PHASE
Vol. 32. No. 8
1131
with m = 517. The very small exponent is consistent with the observed low growth rate of the phase. The reaction FezZr + a-Fe = Fe& in the long time annealing is very similar to a peritecroid reaction in this non-equilibrium sohdified alloy. Fe,Zr must nucieate on the surface of Fe,Zr particles. The growing Fe,Zr then gradually surrounds some parts of a Fe?Zr particle completely. Later transformation of the surrounded part of Fe,Zr relies on the slow diffusion of Fe atoms through the outer layer of Fe,Zr to the interface between Fe3Zr and Fe+. An incomplete transformation usually leaves an untransformed Fe2Zr core in the center of a Fe3Zr particle. This is what we have seen in Fig.3, a Fe2Zr “island” in the “flower-like” Fe-& particle. The slow diffusion rate of Fe atoms limits the rate of the transformation. It can be seen in Fig.6 that the volume fraction of Fe,Zr is still less than 4% after 48 hour annealing, making it very difficult to be detected by X-ray diffraction or Mossbauer measurement. This may explain why so many investigators failed to find the phase in their experiments. To reduce the diffusion distance, Fe,Zr particles prefer to form in the fine lamellar region, especially the long lamellar lines which have a low coarsening rate in the annealing, as shown in Fig.3.
The existence o’f the controversial Fe,Zr is confirmed in this study by optical and TEM imaging, electron diffraction and STEM composition analysis. Fe,Zr has a cubic morphology in the as-cast alloy and a polycrystalline morphology in the annealed alloy. Electron diffraction patterns indicate its crystal structure belongs to Th,Mn,, type rather than Ti,Ni type. Fe3Zr and a-.Fe should be equilibrium phases in the alloy in the temperatures. The presence of the metastable phase Fe,Zr may be the result of a larger driving force for its formation and the extremely slow growth rate of Fe,Zr. Fe3Zr particles are a product of a reaction similar to a peritectoid reaction: Fe,Zr + Fe(a) = Fe,Zr. Its growth rate in most cases depends on the diffusion of Fe atoms through the Fe,Zr outer layer to the Fe2Zr core. The volume fraction of FegZr is less than 4% after a 48 hour annealing at 119O’C. Acknowledgement Financial support from the Department of Energy, Division of Basic Energy Sciences, Grant No. DEFGO2-90ER45426, is greatly appreciated. We also acknowledge the helpful discussions with Professor John B. Vander Sande, Professor Bemhardt J. Wuensch and Kathy Chen. References [ 11. Q. Kubaschewski, Iron-Binary Phase Diagrams, 1982. [2]. W. G. Moffatt, The Handbook of Binary Phase Diagrams, 1984. [3]. V. N. Svechnikov, V. M. Pan and A. Ts. Spector, Russ. J. Inorg. Chem., Vol. IO, No. I, Sep. 1963, pp. 1106. [4]. P. I. Kripyakevich, V. S. Protasov and E. E. Cherkashin, Russ. J. Inorg. Chem., Vol. 10, No. 1, Jan 1965, nn. 151. [5]. F. Aubertin, IJ. Gonser, S. J. Campbell and H. Wagner, Z. Metallkunde, Vol. 76, 1985, pp.237. [6]. Z. M. Alekseeva and N. V. Korotkova, Russ. Met. R., No. 4, 1989, pp. 197. [7]. Yaping Liu, James D. Livingston, and Samuel M. Allen: Met. Trans. A, Dec. 1992, Vol. 23A, No 12, pp, 3303-3308. 181. T. Hahn, International Tables for Crystallography, Vol. A, Second, Revised Edition, D. Reidel Publishing Company, 1987.
Fig. 1. Concentric cubes of Fe+
in as-cast alloy.
Fig.2. Polycrystalline Fr,Zr connecting Fe2Zr in annealed samples (annealed at 1190OC for 48 hours).
1132
Fe& PHASE
Vol. 32. No. 8
(b) Fig.3. “Flower-like” Polycrystalline Fe,Zr grown from long straight Inmellar Fe,%
I
,
I
I
I
,
Fig.4. Electron diffraction patterns of Fe,Zr phase. (a) B=[OOll. (b)B=[Ol 11.' '
.^
Fig.5. Free energy curves of the phases in Fe- IO at% Zr alloy at cooling.
Fig.6. Change of volume fraction of Fe,Zr ph:isc vs. time in the annealing (I 190 T).