- Email: [email protected]
Complex intermetallics in Al–Cu–Cr system
Journal of Alloys and Compounds 442 (2007) 114–116
Complex intermetallics in Al–Cu–Cr system B. Grushko a,∗ , B. Przepi´orzy´nski a,b , D. Pavlyuchkov a,c , S. Mi a , E. Kowalska-Strz˛eciwilk a,b , M. Surowiec b a
Institut f¨ur Festk¨orperforschung, Forschungszentrum J¨ulich, D-52425 J¨ulich, Germany b Institute of Materials Science, University of Silesia, 40007 Katowice, Poland c I.N. Frantsevich Institute for Problems of Materials Science, 03680 Kiev 142, Ukraine
Received 24 April 2006; received in revised form 20 November 2006; accepted 8 December 2006 Available online 30 January 2007
Abstract We present a revised version of the Al-rich part of the Al–Cr phase diagram. The Al-rich range of the Al–Cu–Cr alloy system was investigated at 900 ◦ C and below. The Al–Cr ␥-range extends up to 18 at.% Cu, while extensions of other Al–Cr phases are below 3 at.% of Cu. The formation of at least six ternary phases was observed. © 2007 Elsevier B.V. All rights reserved. PACS: 81.30.Bx; 61.66−f Keywords: Phase diagrams; Intermetallics
1. Introduction
2. Results
The Al–Cr alloy system, and based on it ternary systems with Cu, Ni, Co, Fe, Mn and other transition elements, has evoked interest because of the observation there of quasicrystals and a great number of related complex periodic intermetallics. Investigation of the corresponding alloys revealed numerous discrepancies not only in ternary systems but also in the extensively studied Al–Cr. The Al–Cu–Cr system was studied earlier in Ref. [1] and its Al-rich part was recently reinvestigated in Ref. [2] at 800–1000 ◦ C. In this contribution, we present additional results on the Alrich part of the Al–Cu–Cr alloy system. The Al–Cr binary phase diagram is accepted according to the recent updates included in Refs. [3–5]. For the convenience of the reader the relevant part of the updated Al–Cr phase diagram is reproduced in Fig. 1 and the crystallographic data of the Al–Cr phases are presented in Table 1. The experimental procedures were as in Refs. [2–5].
Recent investigation of the Al–Cr phase diagram revealed several differences from the diagram presented in Ref. [6] and subsequently in popular reference sources. Experiments in Ref. [3] point to the existence of only one high-temperature and one low-temperature phase extending in the compositional range between about 30 and 42 at.% Cr. The low-temperature phase (␥2 ) has a rhombohedrally distorted ␥-brass structure with α < 90◦ (see Table 1). The -phase is formed by a peritectic reaction from ␥2 and the liquid at 1040 ◦ C and composition of Al78.7 Cr21.3 . This phase was found to exist in a compositional range from Al78.7 Cr21.3 to Al81.3 Cr18.7 [5]. At about 865 ◦ C and Al83.5 Cr16.5 composition the other, -phase, is formed by a peritectic reaction of the -phase with the liquid [5]. The highest-Al monoclinic -phase is formed by a peritectic reaction of the -phase with the liquid at 795 ◦ C and about Al87.0 Cr13.0 composition. Finally, there is a eutectic reaction between the -phase, (Al) and the liquid at a composition very close to pure Al. The -phase revealed in Ref. [4] is formed by solid-state reaction ↔ + ␥2 . The temperature of the latter reaction has not yet been specified. The powder XRD pattern of the -phase is shown in Fig. 2a and that of the -phase in Fig. 2b. An orthorhombic structure
∗
Corresponding author. Tel.: +49 2461 612399; fax: +49 2461 616444. E-mail address: [email protected] (B. Grushko).
0925-8388/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2006.12.154
B. Grushko et al. / Journal of Alloys and Compounds 442 (2007) 114–116
115
Fig. 1. Partial Al–Cr constitutional diagram.
with a ≈ 1.25, b ≈ 3.47 and c ≈ 2.02 nm associated in Ref. [7] with Al7 Cr (-phase), in Ref. [8] with Al5 Cr (-phase) and in Ref. [9] with Al4 Cr was not observed in our experiments in the binary Al–Cr alloy system. Using the structural model published in Ref. [9], we calculated the powder diffraction pattern of the assumed -Al4 Cr. It appeared to be very similar to our experimental pattern of the -phase and also to that of the phase (see Fig. 2). A systematic reinvestigation of the Al–Ni–Cr alloy system revealed an orthorhombic structure matching that of -Al4 Cr in a single-phase sample of Al76.5 Ni2 Cr21.5 . Our results concerning Al–Ni–Cr will be published in more detail elsewhere. According to Ref. [2], the Al–Cr ␥-range was found to extend up to 18 at.% Cu in its high-Cr limit. The ␥2 ↔ ␥1 transition temperatures decrease with increasing Cu concentration, together with a significant decrease of the melting temperatures. Thus, Table 1 Crystallographic data of the phases in the relevant part of the Al–Cr and Al–Cu–Cr alloy systems Phase
S.G. or symmetry
Lattice parameters a (nm)
b (nm)
c (nm)
α, β, γ (◦ )
(Al45 Cr7 ) (Al11 Cr2 ) (Al4 Cr) (Al11 Cr4 )
C2/m C2/c (?) P63 /mmc P 1¯
2.5196 1.76 2.00 0.5089
0.7574 3.05 – 0.9033
1.0949 1.76 2.46 0.5044
␥1 a (63:8:29) ␥2 a (62:–:38) a (72:13:15) a (63:18.8:18.2) a (47:33:20)
I43m R3m P63 /m ¯ F 43m ¯ Pm3m ? Cubic fcc
0.9066 1.2733 1.7653 1.8109 0.2980 ? 1.2616 0.5828
– – – – – ? – –
– 0.7947 1.2575 – – ? – –
β = 128.72 β ≈ 90 – α = 91.84 β = 100.77 γ = 107.59 – – – – – ? – –
a Wide compositional range, the lattice parameters are for the given compositions (Al:Cu:Cr).
Fig. 2. Powder XRD patterns (Cu K␣1 radiation) of the binary: (a) -phase, (b) -phase, (c) calculated pattern of the suggested -Al4 Cr phase, and of the ternary: (d) -phase, (e) -phase, (f) -phase, (g) -phase and (h) -phase.
at ternary compositions the ␥1 and ␥2 phases could coexist at the same temperature. The -phase and -phase dissolve only a little of the Cu. The partial 900 ◦ C section of the Al–Cu–Cr phase diagram presented in Ref. [2] was corrected according to the Al–Cr phase diagram specified above (see Fig. 3a, the ––L equilibrium shown in Fig. 4 of Ref. [2] by broken lines was removed). Close to the compositions of the -phase and -phase a ternary -phase is formed between about Al82 Cu2 Cr16 , Al75 Cu4 Cr21 and Al71 Cu11 Cr18 . The high-temperature -phase exists around Al46 Cu36 Cr18 between ∼906 and ∼815 ◦ C. Below 842 ◦ C a cubic -phase was observed between about Al65 Cu15 Cr20 and Al58 Cu26 Cr16 (also present in the 700 ◦ C section in Fig. 3b).
116
B. Grushko et al. / Journal of Alloys and Compounds 442 (2007) 114–116
from the -phase and -phase, at least two other ternary phases were found (see Table 1): the -phase around Al70.5 Cu18 Cr11.5 and the -phase around Al65 Cu25 Cr10 . The range of the -phase is extended to higher Cu. In the Cu-rich part of this range metallography revealed a contrast which could indicate the existence of an additional phase, but this was not confirmed by powder XRD. Only one range and the corresponding equilibria are shown in Fig. 3b. Below 638 ◦ C another phase (-phase, see Table 1) was revealed around the Al61 Cu35.5 Cr3.5 composition. The corresponding phase equilibria have not yet been reliably determined. Acknowledgements We thank W. Reichert and M. Schmidt for technical contributions. References
Fig. 3. Partial isothermal sections of the Al–Cu–Cr alloy system at 900 ◦ C (a) and 700 ◦ C (b). Provisional equilibria are shown by broken lines. L is the liquid.
The typical powder XRD patterns of the -phase and -phase are shown in Fig. 2d and e and the crystallographic data are included in Table 1. At 700 ◦ C the Al–Cr -phase exhibits visible solubility of Cu. The Al–Cr -phase was not observed in ternary samples. Apart
[1] A.P. Prevarskiy, R.V. Skolozdra, Russ. Metal. 1 (1972) 137. [2] B. Grushko, E. Kowalska-Strz˛eciwilk, B. Przepi´orzy´nski, M. Surowiec, J. Alloys Compd. 417 (2006) 121. [3] B. Grushko, E. Kowalska-Strz˛eciwilk, B. Przepi´orzy´nski, M. Surowiec, J. Alloys Compd. 402 (2005) 98. [4] B. Grushko, B. Przepi´orzy´nski, E. Kowalska-Strz˛eciwilk, M. Surowiec, J. Alloys Compd. 420 (2006) L1. [5] B. Grushko, B. Przepi´orzy´nski, D. Pavlyuchkov, J. Alloys Compd., 2007, doi:10.1016/j.jallcom.2007.01.001. [6] W. K¨oster, E. Wachtel, K. Grube, Z. Metalkde. 54 (1963) 393 (in German). [7] A.J. Bradley, S.S. Lu, J. Inst. Metal. 60 (1937) 319. [8] M. Audier, M. Durand-Charre, E. Laclau, H. Klein, J. Alloys Compd. 220 (1995) 225. [9] X.Z. Li, R. Sugiyama, K. Hiraga, A. Sato, A. Yamamoto, H.X. Sui, K.H. Kuo, Z. Kristallogr. 212 (1997) 628.
Complex intermetallics in Al–Cu–Cr system B. Grushko a,∗ , B. Przepi´orzy´nski a,b , D. Pavlyuchkov a,c , S. Mi a , E. Kowalska-Strz˛eciwilk a,b , M. Surowiec b a
Institut f¨ur Festk¨orperforschung, Forschungszentrum J¨ulich, D-52425 J¨ulich, Germany b Institute of Materials Science, University of Silesia, 40007 Katowice, Poland c I.N. Frantsevich Institute for Problems of Materials Science, 03680 Kiev 142, Ukraine
Received 24 April 2006; received in revised form 20 November 2006; accepted 8 December 2006 Available online 30 January 2007
Abstract We present a revised version of the Al-rich part of the Al–Cr phase diagram. The Al-rich range of the Al–Cu–Cr alloy system was investigated at 900 ◦ C and below. The Al–Cr ␥-range extends up to 18 at.% Cu, while extensions of other Al–Cr phases are below 3 at.% of Cu. The formation of at least six ternary phases was observed. © 2007 Elsevier B.V. All rights reserved. PACS: 81.30.Bx; 61.66−f Keywords: Phase diagrams; Intermetallics
1. Introduction
2. Results
The Al–Cr alloy system, and based on it ternary systems with Cu, Ni, Co, Fe, Mn and other transition elements, has evoked interest because of the observation there of quasicrystals and a great number of related complex periodic intermetallics. Investigation of the corresponding alloys revealed numerous discrepancies not only in ternary systems but also in the extensively studied Al–Cr. The Al–Cu–Cr system was studied earlier in Ref. [1] and its Al-rich part was recently reinvestigated in Ref. [2] at 800–1000 ◦ C. In this contribution, we present additional results on the Alrich part of the Al–Cu–Cr alloy system. The Al–Cr binary phase diagram is accepted according to the recent updates included in Refs. [3–5]. For the convenience of the reader the relevant part of the updated Al–Cr phase diagram is reproduced in Fig. 1 and the crystallographic data of the Al–Cr phases are presented in Table 1. The experimental procedures were as in Refs. [2–5].
Recent investigation of the Al–Cr phase diagram revealed several differences from the diagram presented in Ref. [6] and subsequently in popular reference sources. Experiments in Ref. [3] point to the existence of only one high-temperature and one low-temperature phase extending in the compositional range between about 30 and 42 at.% Cr. The low-temperature phase (␥2 ) has a rhombohedrally distorted ␥-brass structure with α < 90◦ (see Table 1). The -phase is formed by a peritectic reaction from ␥2 and the liquid at 1040 ◦ C and composition of Al78.7 Cr21.3 . This phase was found to exist in a compositional range from Al78.7 Cr21.3 to Al81.3 Cr18.7 [5]. At about 865 ◦ C and Al83.5 Cr16.5 composition the other, -phase, is formed by a peritectic reaction of the -phase with the liquid [5]. The highest-Al monoclinic -phase is formed by a peritectic reaction of the -phase with the liquid at 795 ◦ C and about Al87.0 Cr13.0 composition. Finally, there is a eutectic reaction between the -phase, (Al) and the liquid at a composition very close to pure Al. The -phase revealed in Ref. [4] is formed by solid-state reaction ↔ + ␥2 . The temperature of the latter reaction has not yet been specified. The powder XRD pattern of the -phase is shown in Fig. 2a and that of the -phase in Fig. 2b. An orthorhombic structure
∗
Corresponding author. Tel.: +49 2461 612399; fax: +49 2461 616444. E-mail address: [email protected] (B. Grushko).
0925-8388/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2006.12.154
B. Grushko et al. / Journal of Alloys and Compounds 442 (2007) 114–116
115
Fig. 1. Partial Al–Cr constitutional diagram.
with a ≈ 1.25, b ≈ 3.47 and c ≈ 2.02 nm associated in Ref. [7] with Al7 Cr (-phase), in Ref. [8] with Al5 Cr (-phase) and in Ref. [9] with Al4 Cr was not observed in our experiments in the binary Al–Cr alloy system. Using the structural model published in Ref. [9], we calculated the powder diffraction pattern of the assumed -Al4 Cr. It appeared to be very similar to our experimental pattern of the -phase and also to that of the phase (see Fig. 2). A systematic reinvestigation of the Al–Ni–Cr alloy system revealed an orthorhombic structure matching that of -Al4 Cr in a single-phase sample of Al76.5 Ni2 Cr21.5 . Our results concerning Al–Ni–Cr will be published in more detail elsewhere. According to Ref. [2], the Al–Cr ␥-range was found to extend up to 18 at.% Cu in its high-Cr limit. The ␥2 ↔ ␥1 transition temperatures decrease with increasing Cu concentration, together with a significant decrease of the melting temperatures. Thus, Table 1 Crystallographic data of the phases in the relevant part of the Al–Cr and Al–Cu–Cr alloy systems Phase
S.G. or symmetry
Lattice parameters a (nm)
b (nm)
c (nm)
α, β, γ (◦ )
(Al45 Cr7 ) (Al11 Cr2 ) (Al4 Cr) (Al11 Cr4 )
C2/m C2/c (?) P63 /mmc P 1¯
2.5196 1.76 2.00 0.5089
0.7574 3.05 – 0.9033
1.0949 1.76 2.46 0.5044
␥1 a (63:8:29) ␥2 a (62:–:38) a (72:13:15) a (63:18.8:18.2) a (47:33:20)
I43m R3m P63 /m ¯ F 43m ¯ Pm3m ? Cubic fcc
0.9066 1.2733 1.7653 1.8109 0.2980 ? 1.2616 0.5828
– – – – – ? – –
– 0.7947 1.2575 – – ? – –
β = 128.72 β ≈ 90 – α = 91.84 β = 100.77 γ = 107.59 – – – – – ? – –
a Wide compositional range, the lattice parameters are for the given compositions (Al:Cu:Cr).
Fig. 2. Powder XRD patterns (Cu K␣1 radiation) of the binary: (a) -phase, (b) -phase, (c) calculated pattern of the suggested -Al4 Cr phase, and of the ternary: (d) -phase, (e) -phase, (f) -phase, (g) -phase and (h) -phase.
at ternary compositions the ␥1 and ␥2 phases could coexist at the same temperature. The -phase and -phase dissolve only a little of the Cu. The partial 900 ◦ C section of the Al–Cu–Cr phase diagram presented in Ref. [2] was corrected according to the Al–Cr phase diagram specified above (see Fig. 3a, the ––L equilibrium shown in Fig. 4 of Ref. [2] by broken lines was removed). Close to the compositions of the -phase and -phase a ternary -phase is formed between about Al82 Cu2 Cr16 , Al75 Cu4 Cr21 and Al71 Cu11 Cr18 . The high-temperature -phase exists around Al46 Cu36 Cr18 between ∼906 and ∼815 ◦ C. Below 842 ◦ C a cubic -phase was observed between about Al65 Cu15 Cr20 and Al58 Cu26 Cr16 (also present in the 700 ◦ C section in Fig. 3b).
116
B. Grushko et al. / Journal of Alloys and Compounds 442 (2007) 114–116
from the -phase and -phase, at least two other ternary phases were found (see Table 1): the -phase around Al70.5 Cu18 Cr11.5 and the -phase around Al65 Cu25 Cr10 . The range of the -phase is extended to higher Cu. In the Cu-rich part of this range metallography revealed a contrast which could indicate the existence of an additional phase, but this was not confirmed by powder XRD. Only one range and the corresponding equilibria are shown in Fig. 3b. Below 638 ◦ C another phase (-phase, see Table 1) was revealed around the Al61 Cu35.5 Cr3.5 composition. The corresponding phase equilibria have not yet been reliably determined. Acknowledgements We thank W. Reichert and M. Schmidt for technical contributions. References
Fig. 3. Partial isothermal sections of the Al–Cu–Cr alloy system at 900 ◦ C (a) and 700 ◦ C (b). Provisional equilibria are shown by broken lines. L is the liquid.
The typical powder XRD patterns of the -phase and -phase are shown in Fig. 2d and e and the crystallographic data are included in Table 1. At 700 ◦ C the Al–Cr -phase exhibits visible solubility of Cu. The Al–Cr -phase was not observed in ternary samples. Apart
[1] A.P. Prevarskiy, R.V. Skolozdra, Russ. Metal. 1 (1972) 137. [2] B. Grushko, E. Kowalska-Strz˛eciwilk, B. Przepi´orzy´nski, M. Surowiec, J. Alloys Compd. 417 (2006) 121. [3] B. Grushko, E. Kowalska-Strz˛eciwilk, B. Przepi´orzy´nski, M. Surowiec, J. Alloys Compd. 402 (2005) 98. [4] B. Grushko, B. Przepi´orzy´nski, E. Kowalska-Strz˛eciwilk, M. Surowiec, J. Alloys Compd. 420 (2006) L1. [5] B. Grushko, B. Przepi´orzy´nski, D. Pavlyuchkov, J. Alloys Compd., 2007, doi:10.1016/j.jallcom.2007.01.001. [6] W. K¨oster, E. Wachtel, K. Grube, Z. Metalkde. 54 (1963) 393 (in German). [7] A.J. Bradley, S.S. Lu, J. Inst. Metal. 60 (1937) 319. [8] M. Audier, M. Durand-Charre, E. Laclau, H. Klein, J. Alloys Compd. 220 (1995) 225. [9] X.Z. Li, R. Sugiyama, K. Hiraga, A. Sato, A. Yamamoto, H.X. Sui, K.H. Kuo, Z. Kristallogr. 212 (1997) 628.