Al-Cr (Aluminum-Chromium)
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Section III: Supplemental Literature Review
Al-Cr (Aluminum-Chromium) H. Okamoto
The Al-Cr phase diagram in [Massalski2] was as assessed by [1998Mur]. Figure 1 shows the updated Al-Cr phase diagram. The [1998Mur] phase diagram and Fig. 1 differ in the following features.
•
•
Table 1
AlCr: The existence of the second-order transition from bcc (Cr) to CsCl-type AlCr was found by [1999Hel].
Table 1 shows Al-Cr crystal structure data. Two other phases, Al13Cr2 and Al5Cr, reported earlier are the same
Al11Cr2: According to [1998Mur], Al11Cr2 is stable at least down to 200 C. [2000Mah] found that Al11Cr2 decomposes eutectoidally at 785 C. • Al11Cr4: [2006Gru] discovered Al11Cr4 at about Al3Cr composition. It forms from Al4Cr and aAl8 Cr5 by a peritectoid reaction at a temperature between 700 and 800 C. • Al8Cr5: According to [1998Mur], cAl9 Cr4 ; bAl9 Cr4 ; aAl9 Cr4 ; bAl8 Cr5 ; and aAl8 Cr5 exist in the range covered by aAl9 Cr4 ; bAl8 Cr5 ; and aAl8 Cr5 in Fig. 1. [2000Mah] could not find any phase separation between Al9Cr4 and Al8Cr5 and questioned the phase relation shown in [Massalski2]. In agreement with [2000Mah], [2005Gru] found only bAl8 Cr5 and aAl8 Cr5 in this range (22-55 at.% Cr). The result of [2005Gru] is shown in Fig. 1. The existence of aAl9 Cr4 was not examined by [2005Gru]. Therefore, it is still shown in Fig. 1 in the same way as in [Massalski2]. Its existence must be reexamined.
Al-Cr crystal structure data Composition, Pearson at.% Cr symbol
Phase (Al) Al7Cr Al11Cr2 Al4Cr Al11Cr4 aAl9 Cr4 bAl8 Cr5 aAl8 Cr5 AlCr AlCr2 X (Cr)
0 12.5-14 15.2-17 18.5-20 25 30-34 30-42 30-42 60.5-63 65.5-71.4 75 54.5-100
cF4 mC104 mP48 mP180 aP30 cI52 hR26 cP2 tI6 cI2
Space group
Strukturbericht designation Prototype
Fm3m C2/m P2 P2/m P1 I 43m R3m Pm3m I4/mmm Im3m
A1 D810 B2 C11b A2
Weight Percent Chromium 0
10
20
30
40
50
60
70
80
90
100
2000 1863°C 1800
L
1600
1400
1200
(Cr)
Al11Cr2
799°C
800
785 656°C
700
Al7Cr
Al4Cr
(Al) 400
62
AlCr
αAl9Cr4
660.452°C 600
910°C 882°C
AlCr2
1040°C 895°C
αAl8Cr5
1060°C 1000
βAl8Cr5
1140°C
Al11Cr4
Temperature, °C
1320°C
350°C
Tc
X
200 0
Al
10
20
30
40
50
60
70
80
90
Atomic Percent Chromium
Fig. 1 Al-Cr phase diagram
112
Journal of Phase Equilibria and Diffusion Vol. 29 No. 1 2008
100
Cr
Cu Al45V7 Al8Cr5 CsCl MoSi2 W
Supplemental Literature Review: Section III phases as Al7 Cr and Al11Cr2, respectively, according to [1998Mur]. References 1998Mur: J.L. Murray, The Al-Cr (Aluminum-Chromium) System, J. Phase Equilibria, 1998, 19(4), p 368-375 1999Hel: T. Helander and O. Tolochko, An Experimental Investigation of Possible B2-Ordering in the Al-Cr System, J. Phase Equilibria, 1999, 20(1), p 57-60
2000Mah: K. Mahdouk and J.C. Gachon, Thermodynamic Investigation of the Aluminum-Chromium System, J. Phase Equilibria, 2000, 21(2), p 157-166 2005Gru: B. Grushko, E. Kowalska-Strze˛ ciwilk, B. Przepio´rzyn´ski, and M. Surowiec, Investigation of the A
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