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On the phase transitions of the quasicrystalline phases in the Al–Cu–Fe–Co alloy
Journal of Alloys and Compounds 342 (2002) 246–250
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On the phase transitions of the quasicrystalline phases in the Al–Cu–Fe–Co alloy a, b c d a S.H. Kim *, B.H. Kim , S.M. Lee , W.T. Kim , D.H. Kim a
Center for Noncrystalline Materials, Yonsei University, Seoul 120 -749, South Korea b Korea Aerospace Industry, Changwon 641 -120, South Korea c Korea Institute of Industrial Technology, Inchon 404 -254, South Korea d Department of Physics, Chongju University, Chongju 360 -764, South Korea
Abstract Microstructural change with Co content together with heat treatment was studied in rapidly solidified Al–Cu–Fe–Co alloys using X-ray diffractometry and transmission electron microscopy. With an increase in Co content in the as-cast Al 65 Cu 20 Fe 152x Cox alloys, the relative amount of the icosahedral phase drastically decreased and that of the decagonal phase increased. In the as-melt spun alloys, effects of Co content are critically changed at around 5 at% Co. For the less Co containing alloys (below 5 at%), the icosahedral phase proved to be the major phase, while the 5 at% Co containing alloy showed the coexistence of the icosahedral and decagonal phases. The 8 at% containing alloy showed the monolithic decagonal phase in the as-melt spun state. Unlike as-cast alloys, all the as-melt spun alloys showed no trace of the l-phase. However, after heat treatment of ribbons, l-phase newly appeared in the Al 65 Cu 20 Fe 10 Co 3 and Al 65 Cu 20 Fe 10 Co 5 alloys. The l-phase showed orientation relationships with surrounding icosahedral or decagonal phases. 2002 Elsevier Science B.V. All rights reserved. Keywords: Quasicrystals; Liquid quenching; Scanning and transmission electron microscopy
1. Introduction Following the pioneering discovery by Shechtman et al. [1], quasicrystals have been reported in many alloy systems, including Al-, Ti-, Zr-, Mg-, Cd-based alloys [2]. Among them, the Al–Cu–Fe and Al–Cu–Co quasicrystals have been most widely studied, not only because of their thermodynamic stability and easy fabrication with relatively inexpensive elements, but also because of their scientific importance and possibility of industrial applications [3,4]. The compositional ranges for the stable quasicrystalline phases are very similar between the Al– Cu–Fe and Al–Cu–Co systems, but the resultant microstructures are different, typically icosahedral and decagonal, respectively. It has been reported that in the icosahedral forming Al–Cu–Fe alloys, the addition of a fourth element has resulted in various microstructures. For example, the addition of Si more than 8 at% encourages the formation of the 1 / 1 cubic approximant, while Be addition drastically enhances the formability and structural perfection of the *Corresponding author.
icosahedral phase [5,6]. Partial substitution of Fe by Co or Cr possibly leads to the formation of the decagonal phase, and the typical microstructure was reported to be a mixture of the icosahedral and decagonal phases in the as-cast Al 65 Cu 22 Co 6.5 Fe 6.5 alloy, for instance [7,8]. In this study, we report the effects of Fe replacement by Co on the comparative formation and structural variation between the icosahedral and decagonal quasicrystalline phases in the Al–Cu–Fe system. Phase selection and transition in the Al–Cu–Fe–Co systems with different Co contents were systematically investigated for as-melt spun and heat treatment conditions.
2. Experimental procedures The alloys with nominal compositions of Al 65 Cu 20 Fe 152x Co x (x50, 3, 5, 8 and 15) were fabricated by melt-spinning method using high purity (99.99%) elements of Al, Cu, Fe, and Co. Heat treatment for the ribbon specimens was carried out in vacuum sealed quartz tubes. X-Ray diffraction (XRD) and transmission electron
0925-8388 / 02 / $ – see front matter 2002 Elsevier Science B.V. All rights reserved. PII: S0925-8388( 02 )00185-8
S.H. Kim et al. / Journal of Alloys and Compounds 342 (2002) 246 – 250
microscopy (TEM) analyses were also employed to investigate the microstructure and crystallography.
3. Results and discussion Fig. 1 shows the XRD patterns obtained from the asmelt spun Al 65 Cu 20 Fe 152x Co x (x50, 3, 5, and 8) alloys. In the as-melt spun Al 65 Cu 20 Fe 15 and Al 65 Cu 20 Fe 12 Co 3 alloys, the icosahedral phase coexisted with a very small amount of the B2 phase. The partial replacement of Fe by Co below 3 at% has not significantly affected the microstructure of the alloy, leading to the same microstructure of the ternary Al–Cu–Fe alloy. Further replacement of Co up to 5 at%, however, dramatically changed the microstructure by forming the decagonal phase. The as-melt spun Al 65 Cu 20 Fe 10 Co 5 alloy showed the coexistence of the icosahedral, decagonal, and B2 phases. Note that the 2u angle of the strong diffraction peak for the decagonal phase coincides with that for the B2 phase. Detailed phase identification will be shown later. When the Co content reached 8 at%, the icosahedral phase has completely disappeared, showing a monolithic decagonal phase. Single decagonal phase was also obtained in the melt spun alloys containing Co contents above 8–15 at%. The melt-spun Al 65 Cu 20 Fe 15 and Al 65 Cu 20 Fe 12 Co 3 al-
Fig. 1. X-Ray diffraction patterns obtained from the as-melt spun Al 65 Cu 20 Fe 152x Co x alloys; (a) x50, (b) x53, (c) x55, and (d) x58.
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loys show dendritically grown icosahedral phase with a small amount of B2 phase located at the interdendritic region, indicating the icosahedral phase nucleated first from the undercooled liquid and the formation of the l-phase was effectively suppressed by rapid solidification. Fig. 2 shows the TEM image and diffraction patterns from the unchilled region of the as-melt spun Al 65 Cu 20 Fe 10 Co 5 ribbon (air-side surface of the ribbon) showing the coexistence of the icosahedral, decagonal, and B2 phases. Very small sized B2 phases exist in the interdendritic region of both the icosahedral and decagonal grains. Both quasicrystals have orientation relationships with the B2
Fig. 2. TEM image and diffraction patterns from the unchilled region of the as-melt spun Al 65 Cu 20 Fe 10 Co 5 ribbon showing the coexistence of the icosahedral, decagonal, and B2 phases; (a) bright field image, (b) twofold axis of the decagonal phase, (c) [110] of the B2 phase in the interdendritic region of the decagonal phase, (d) fivefold axis of the icosahedral, and (e) [110] of the B2 phase in the interdendritic region of the icosahedral phase. Both sets (b and c) and (d and e) show orientation relationships between the decagonal and B2 phase, and the icosahedral and B2 phase, respectively.
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phase, indicating heterogeneous nucleation of the B2 phase took place on growing quasicrystalline surface at a later stage of solidification. The twofold axis of the decagonal phase is parallel to [110] of the B2 phase, while the fivefold axis of the icosahedral phase is parallel to [110] of the B2 phase. However, no orientation relationship was found between the icosahedral and decagonal quasicrystals. Most icosahedral quasicrystalline grains were highly strained with a tweed structure in the as-melt spun alloys, which was further confirmed by irregular electron diffraction spots (Fig. 2(d)). Fig. 3 shows the TEM photographs taken from the chilled region of the as-melt spun Al 65 Cu 20 Fe 10 Co 5 ribbon (wheel-side surface of the ribbon), in which very fine sized (100–300 nm) equiaxed icosahedral and decagonal phases coexist without the B2 phase. The equiaxed icosahedral
and decagonal phases in the chilled region and dendritically grown icosahedral and decagonal phase in unchilled region indicated that both phases nucleated from the undercooled liquid independently during rapid solidification. In the chilled region, the decagonal phase was more dominantly observed than that of the icosahedral phase. Considering the formation of quasicrystalline phase by a peritectic reaction and the presence of several crystalline l-, b- and t-phases in as-cast alloys [5], it is noted that a higher cooling rate enhanced the formation of quasicrystalline phase, and depressed the formation of the crystalline phases. In order to investigate the thermal stability of the asmelt spun alloys, the Al 65 Cu 20 Fe 12 Co 3 and Al 65 Cu 20 Fe 10 Co 5 alloys were heat-treated in vacuumsealed quartz tubes. Fig. 4 shows the XRD patterns obtained from the Al 65 Cu 20 Fe 152x Co x (x53, 5) alloys annealed at 750 8C for 15 min. After heat treatment, both alloys showed completely different behavior. For the heattreated ribbons, the Al 65 Cu 20 Fe 12 Co 3 alloy consisted of the icosahedral and l-phases, while the Al 65 Cu 20 Fe 10 Co 5 alloy showed a mixture of icosahedral, decagonal, and l-phases. Comparing the XRD patterns for the as-melt spun alloy and heat-treated alloy, it can be found that the volume fraction of the decagonal phase in the Al 65 Cu 20 Fe 10 Co 5 alloy increased during annealing treatment. It is also interesting to note that the small amount of the monoclinic l-phase was newly detected in both alloys after annealing treatment. During conventional casting, generally the l-phase forms as a primary phase, followed by the formation of the icosahedral or decagonal phases through a peritectic reaction between the l- and liquid phases. However, in the present study of heat treatment, the l-phase was newly formed by a precipitation reaction from the icosahedral or decagonal phases. Details are discussed below. The formation of the l-phases in the annealed specimen indicates that the partial replacement of Fe by Co decreases the stability of icosahedral phase leading to the I1l two-phase region at the annealing temperature, otherwise it was within a single icosahedral phase region in Al 65 Cu 20 Fe 15 alloy [6]. Fig. 5 shows the TEM photographs showing the precipitation of the l-phase from the icosahedral phase in the Al 65 Cu 20 Fe 10 Co 5 ribbon annealed at 750 8C for 1 min. The l-phase nucleated on the twofold plane of the icosahedral phase, growing into the adjacent icosahedral grain with faceted interfaces. From the diffraction patterns (Fig. 5b,c), the orientation relationships can be obtained as follows I2 / / l[001], I2 / / l(310), I5 / / l(010), I5 / / l(3-10)
Fig. 3. TEM image and diffraction patterns from the chilled region of the as-melt spun Al 65 Cu 20 Fe 10 Co 5 ribbon showing the coexistence of the fine sized icosahedral and decagonal phases; (a) bright field image, (b and c) twofold axes of the decagonal phase, and (d and e) fivefold and threefold axes of the icosahedral phase.
Also the following orientation relationship between decagonal phase and l-phases were observed in the annealed specimen: D10 / / l[010], D2 / / l[001] and D29 / / l[104]
S.H. Kim et al. / Journal of Alloys and Compounds 342 (2002) 246 – 250
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Fig. 4. X-Ray diffraction patterns obtained from the Al 65 Cu 20 Fe 152x Co x ribbons heat-treated at 750 8C for 15 min; (a) x53 and (b) x55.
4. Conclusions With an increase in Co content in the as-cast Al 65 Cu 20 Fe 152x Co x alloys, the relative amount of the icosahedral phase drastically decreased and that of the decagonal phase increased. In the as-melt spun alloys, the effects of Co content are critically changed at around 5 at% Co. For the less Co containing alloys (below 5 at%), the icosahedral phase proved to be the major phase, while the 5 at% Co containing alloy showed the coexistence of the icosahedral and decagonal phases. The 8 at% containing alloy showed the monolithic decagonal phase in the as-melt spun state. Unlike as-cast alloys, all the as-melt spun alloys showed no trace of the l-phase. However, after heat treatment of the ribbons, the l-phase newly appeared in the Al 65 Cu 20 Fe 10 Co 3 and Al 65 Cu 20 Fe 10 Co 5 alloys. The l-phase showed orientation relationships with surrounding icosahedral or decagonal phases.
Acknowledgements This work was supported by the Creative Research Initiatives of the Korean Ministry of Science and Technology. One of the authors (S.H.K.) thanks the Korean Science and Engineering Foundation for financial support.
Fig. 5. TEM photographs showing the precipitation of the l-phase from the icosahedral phase in the Al 65 Cu 20 Fe 10 Co 5 ribbon annealed at 750 8C for 1 min; (a) bright field image, (b) twofold axis of the icosahedral phase, and (c) [001] axis of the l-phase (note that the l-phase is growing with a specific orientation relationship with the icosahedral phase).
References [1] D. Shechtman, I. Blech, D. Gratias, J.W. Cahn, Phys. Rev. Lett. 53 (1984) 1951.
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[2] C. Janot, Quasicrystals: A Primer, 2nd Edition, Oxford University Press, 1992. [3] A.P. Tsai, A. Inoue, T. Masumoto, Jpn. J. Appl. Phys. 26 (1987) L1505. [4] K. Hiraga, B.P. Zhang, M. Hirabashi, A. Inoue, T. Masumoto, Jpn. J. Appl. Phys. 27 (1988) L51. [5] S.M. Lee, B.H. Kim, S.H. Kim, E. Fleury, W.T. Kim, D.H. Kim, Mater. Sci. Eng. A 294 (2000) 93.
[6] S.M. Lee, B.H. Kim, S.H. Kim, W.T. Kim, D.H. Kim, Phil. Mag. Lett. 81 (7) (2001) 483. [7] R. Perez, J.A. Juarez-Islas, J.L. Albarran, Acta Metall. Mater. 40 (1992) 2423. [8] R. Perez, A. Arizmendi, J.A. Juarez-Islas, L. Martinez, J. Mater. Res. 8 (1993) 985.
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On the phase transitions of the quasicrystalline phases in the Al–Cu–Fe–Co alloy a, b c d a S.H. Kim *, B.H. Kim , S.M. Lee , W.T. Kim , D.H. Kim a
Center for Noncrystalline Materials, Yonsei University, Seoul 120 -749, South Korea b Korea Aerospace Industry, Changwon 641 -120, South Korea c Korea Institute of Industrial Technology, Inchon 404 -254, South Korea d Department of Physics, Chongju University, Chongju 360 -764, South Korea
Abstract Microstructural change with Co content together with heat treatment was studied in rapidly solidified Al–Cu–Fe–Co alloys using X-ray diffractometry and transmission electron microscopy. With an increase in Co content in the as-cast Al 65 Cu 20 Fe 152x Cox alloys, the relative amount of the icosahedral phase drastically decreased and that of the decagonal phase increased. In the as-melt spun alloys, effects of Co content are critically changed at around 5 at% Co. For the less Co containing alloys (below 5 at%), the icosahedral phase proved to be the major phase, while the 5 at% Co containing alloy showed the coexistence of the icosahedral and decagonal phases. The 8 at% containing alloy showed the monolithic decagonal phase in the as-melt spun state. Unlike as-cast alloys, all the as-melt spun alloys showed no trace of the l-phase. However, after heat treatment of ribbons, l-phase newly appeared in the Al 65 Cu 20 Fe 10 Co 3 and Al 65 Cu 20 Fe 10 Co 5 alloys. The l-phase showed orientation relationships with surrounding icosahedral or decagonal phases. 2002 Elsevier Science B.V. All rights reserved. Keywords: Quasicrystals; Liquid quenching; Scanning and transmission electron microscopy
1. Introduction Following the pioneering discovery by Shechtman et al. [1], quasicrystals have been reported in many alloy systems, including Al-, Ti-, Zr-, Mg-, Cd-based alloys [2]. Among them, the Al–Cu–Fe and Al–Cu–Co quasicrystals have been most widely studied, not only because of their thermodynamic stability and easy fabrication with relatively inexpensive elements, but also because of their scientific importance and possibility of industrial applications [3,4]. The compositional ranges for the stable quasicrystalline phases are very similar between the Al– Cu–Fe and Al–Cu–Co systems, but the resultant microstructures are different, typically icosahedral and decagonal, respectively. It has been reported that in the icosahedral forming Al–Cu–Fe alloys, the addition of a fourth element has resulted in various microstructures. For example, the addition of Si more than 8 at% encourages the formation of the 1 / 1 cubic approximant, while Be addition drastically enhances the formability and structural perfection of the *Corresponding author.
icosahedral phase [5,6]. Partial substitution of Fe by Co or Cr possibly leads to the formation of the decagonal phase, and the typical microstructure was reported to be a mixture of the icosahedral and decagonal phases in the as-cast Al 65 Cu 22 Co 6.5 Fe 6.5 alloy, for instance [7,8]. In this study, we report the effects of Fe replacement by Co on the comparative formation and structural variation between the icosahedral and decagonal quasicrystalline phases in the Al–Cu–Fe system. Phase selection and transition in the Al–Cu–Fe–Co systems with different Co contents were systematically investigated for as-melt spun and heat treatment conditions.
2. Experimental procedures The alloys with nominal compositions of Al 65 Cu 20 Fe 152x Co x (x50, 3, 5, 8 and 15) were fabricated by melt-spinning method using high purity (99.99%) elements of Al, Cu, Fe, and Co. Heat treatment for the ribbon specimens was carried out in vacuum sealed quartz tubes. X-Ray diffraction (XRD) and transmission electron
0925-8388 / 02 / $ – see front matter 2002 Elsevier Science B.V. All rights reserved. PII: S0925-8388( 02 )00185-8
S.H. Kim et al. / Journal of Alloys and Compounds 342 (2002) 246 – 250
microscopy (TEM) analyses were also employed to investigate the microstructure and crystallography.
3. Results and discussion Fig. 1 shows the XRD patterns obtained from the asmelt spun Al 65 Cu 20 Fe 152x Co x (x50, 3, 5, and 8) alloys. In the as-melt spun Al 65 Cu 20 Fe 15 and Al 65 Cu 20 Fe 12 Co 3 alloys, the icosahedral phase coexisted with a very small amount of the B2 phase. The partial replacement of Fe by Co below 3 at% has not significantly affected the microstructure of the alloy, leading to the same microstructure of the ternary Al–Cu–Fe alloy. Further replacement of Co up to 5 at%, however, dramatically changed the microstructure by forming the decagonal phase. The as-melt spun Al 65 Cu 20 Fe 10 Co 5 alloy showed the coexistence of the icosahedral, decagonal, and B2 phases. Note that the 2u angle of the strong diffraction peak for the decagonal phase coincides with that for the B2 phase. Detailed phase identification will be shown later. When the Co content reached 8 at%, the icosahedral phase has completely disappeared, showing a monolithic decagonal phase. Single decagonal phase was also obtained in the melt spun alloys containing Co contents above 8–15 at%. The melt-spun Al 65 Cu 20 Fe 15 and Al 65 Cu 20 Fe 12 Co 3 al-
Fig. 1. X-Ray diffraction patterns obtained from the as-melt spun Al 65 Cu 20 Fe 152x Co x alloys; (a) x50, (b) x53, (c) x55, and (d) x58.
247
loys show dendritically grown icosahedral phase with a small amount of B2 phase located at the interdendritic region, indicating the icosahedral phase nucleated first from the undercooled liquid and the formation of the l-phase was effectively suppressed by rapid solidification. Fig. 2 shows the TEM image and diffraction patterns from the unchilled region of the as-melt spun Al 65 Cu 20 Fe 10 Co 5 ribbon (air-side surface of the ribbon) showing the coexistence of the icosahedral, decagonal, and B2 phases. Very small sized B2 phases exist in the interdendritic region of both the icosahedral and decagonal grains. Both quasicrystals have orientation relationships with the B2
Fig. 2. TEM image and diffraction patterns from the unchilled region of the as-melt spun Al 65 Cu 20 Fe 10 Co 5 ribbon showing the coexistence of the icosahedral, decagonal, and B2 phases; (a) bright field image, (b) twofold axis of the decagonal phase, (c) [110] of the B2 phase in the interdendritic region of the decagonal phase, (d) fivefold axis of the icosahedral, and (e) [110] of the B2 phase in the interdendritic region of the icosahedral phase. Both sets (b and c) and (d and e) show orientation relationships between the decagonal and B2 phase, and the icosahedral and B2 phase, respectively.
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phase, indicating heterogeneous nucleation of the B2 phase took place on growing quasicrystalline surface at a later stage of solidification. The twofold axis of the decagonal phase is parallel to [110] of the B2 phase, while the fivefold axis of the icosahedral phase is parallel to [110] of the B2 phase. However, no orientation relationship was found between the icosahedral and decagonal quasicrystals. Most icosahedral quasicrystalline grains were highly strained with a tweed structure in the as-melt spun alloys, which was further confirmed by irregular electron diffraction spots (Fig. 2(d)). Fig. 3 shows the TEM photographs taken from the chilled region of the as-melt spun Al 65 Cu 20 Fe 10 Co 5 ribbon (wheel-side surface of the ribbon), in which very fine sized (100–300 nm) equiaxed icosahedral and decagonal phases coexist without the B2 phase. The equiaxed icosahedral
and decagonal phases in the chilled region and dendritically grown icosahedral and decagonal phase in unchilled region indicated that both phases nucleated from the undercooled liquid independently during rapid solidification. In the chilled region, the decagonal phase was more dominantly observed than that of the icosahedral phase. Considering the formation of quasicrystalline phase by a peritectic reaction and the presence of several crystalline l-, b- and t-phases in as-cast alloys [5], it is noted that a higher cooling rate enhanced the formation of quasicrystalline phase, and depressed the formation of the crystalline phases. In order to investigate the thermal stability of the asmelt spun alloys, the Al 65 Cu 20 Fe 12 Co 3 and Al 65 Cu 20 Fe 10 Co 5 alloys were heat-treated in vacuumsealed quartz tubes. Fig. 4 shows the XRD patterns obtained from the Al 65 Cu 20 Fe 152x Co x (x53, 5) alloys annealed at 750 8C for 15 min. After heat treatment, both alloys showed completely different behavior. For the heattreated ribbons, the Al 65 Cu 20 Fe 12 Co 3 alloy consisted of the icosahedral and l-phases, while the Al 65 Cu 20 Fe 10 Co 5 alloy showed a mixture of icosahedral, decagonal, and l-phases. Comparing the XRD patterns for the as-melt spun alloy and heat-treated alloy, it can be found that the volume fraction of the decagonal phase in the Al 65 Cu 20 Fe 10 Co 5 alloy increased during annealing treatment. It is also interesting to note that the small amount of the monoclinic l-phase was newly detected in both alloys after annealing treatment. During conventional casting, generally the l-phase forms as a primary phase, followed by the formation of the icosahedral or decagonal phases through a peritectic reaction between the l- and liquid phases. However, in the present study of heat treatment, the l-phase was newly formed by a precipitation reaction from the icosahedral or decagonal phases. Details are discussed below. The formation of the l-phases in the annealed specimen indicates that the partial replacement of Fe by Co decreases the stability of icosahedral phase leading to the I1l two-phase region at the annealing temperature, otherwise it was within a single icosahedral phase region in Al 65 Cu 20 Fe 15 alloy [6]. Fig. 5 shows the TEM photographs showing the precipitation of the l-phase from the icosahedral phase in the Al 65 Cu 20 Fe 10 Co 5 ribbon annealed at 750 8C for 1 min. The l-phase nucleated on the twofold plane of the icosahedral phase, growing into the adjacent icosahedral grain with faceted interfaces. From the diffraction patterns (Fig. 5b,c), the orientation relationships can be obtained as follows I2 / / l[001], I2 / / l(310), I5 / / l(010), I5 / / l(3-10)
Fig. 3. TEM image and diffraction patterns from the chilled region of the as-melt spun Al 65 Cu 20 Fe 10 Co 5 ribbon showing the coexistence of the fine sized icosahedral and decagonal phases; (a) bright field image, (b and c) twofold axes of the decagonal phase, and (d and e) fivefold and threefold axes of the icosahedral phase.
Also the following orientation relationship between decagonal phase and l-phases were observed in the annealed specimen: D10 / / l[010], D2 / / l[001] and D29 / / l[104]
S.H. Kim et al. / Journal of Alloys and Compounds 342 (2002) 246 – 250
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Fig. 4. X-Ray diffraction patterns obtained from the Al 65 Cu 20 Fe 152x Co x ribbons heat-treated at 750 8C for 15 min; (a) x53 and (b) x55.
4. Conclusions With an increase in Co content in the as-cast Al 65 Cu 20 Fe 152x Co x alloys, the relative amount of the icosahedral phase drastically decreased and that of the decagonal phase increased. In the as-melt spun alloys, the effects of Co content are critically changed at around 5 at% Co. For the less Co containing alloys (below 5 at%), the icosahedral phase proved to be the major phase, while the 5 at% Co containing alloy showed the coexistence of the icosahedral and decagonal phases. The 8 at% containing alloy showed the monolithic decagonal phase in the as-melt spun state. Unlike as-cast alloys, all the as-melt spun alloys showed no trace of the l-phase. However, after heat treatment of the ribbons, the l-phase newly appeared in the Al 65 Cu 20 Fe 10 Co 3 and Al 65 Cu 20 Fe 10 Co 5 alloys. The l-phase showed orientation relationships with surrounding icosahedral or decagonal phases.
Acknowledgements This work was supported by the Creative Research Initiatives of the Korean Ministry of Science and Technology. One of the authors (S.H.K.) thanks the Korean Science and Engineering Foundation for financial support.
Fig. 5. TEM photographs showing the precipitation of the l-phase from the icosahedral phase in the Al 65 Cu 20 Fe 10 Co 5 ribbon annealed at 750 8C for 1 min; (a) bright field image, (b) twofold axis of the icosahedral phase, and (c) [001] axis of the l-phase (note that the l-phase is growing with a specific orientation relationship with the icosahedral phase).
References [1] D. Shechtman, I. Blech, D. Gratias, J.W. Cahn, Phys. Rev. Lett. 53 (1984) 1951.
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[2] C. Janot, Quasicrystals: A Primer, 2nd Edition, Oxford University Press, 1992. [3] A.P. Tsai, A. Inoue, T. Masumoto, Jpn. J. Appl. Phys. 26 (1987) L1505. [4] K. Hiraga, B.P. Zhang, M. Hirabashi, A. Inoue, T. Masumoto, Jpn. J. Appl. Phys. 27 (1988) L51. [5] S.M. Lee, B.H. Kim, S.H. Kim, E. Fleury, W.T. Kim, D.H. Kim, Mater. Sci. Eng. A 294 (2000) 93.
[6] S.M. Lee, B.H. Kim, S.H. Kim, W.T. Kim, D.H. Kim, Phil. Mag. Lett. 81 (7) (2001) 483. [7] R. Perez, J.A. Juarez-Islas, J.L. Albarran, Acta Metall. Mater. 40 (1992) 2423. [8] R. Perez, A. Arizmendi, J.A. Juarez-Islas, L. Martinez, J. Mater. Res. 8 (1993) 985.