Phase relations in the Cu-poor part of the Ce-Al-Cu system at 503 K

Article abstract of DOI:10.1016/j.jallcom.2009.03.126

The phase relations of the ternary system Ce-Al-Cu in the Cu-poor part at 503 K were investigated by X-ray powder diffraction (XRD). The investigated composition region consists of 16 single-phase, 32 two-phase and 17 three-phase regions. At 503 K, the ma

Full text of DOI:10.1016/j.jallcom.2009.03.126

Journal of Alloys and Compounds 484 (2009) 86–89
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Journal of Alloys and Compounds
journal homepage: www.elsevier.com/locate/jallcom
Phase relations in the Cu-poor part of the Ce–Al–Cu system at 503 K
Q.R. Yaoa,∗, X.D. Hua,b, X.J. Chena, S.K. Pana, W. Zouc, H.L. Wanga, Y.C. Wangb, P.P. Wanga,
F. Liua, Z.M. Wanga, H.Y. Zhoua, C.Y. Tanga
a Department of Information Materials Science and Engineering, Guilin University of Electronic Technology, Guangxi 541004, PR China
b Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, PR China
c School of Application Science, Jiangxi University of Science and Technology, Ganzhou, Jiangxi 341000, China
a r t i c l e i n f o
a b s t r a c t
Article history:
The phase relations of the ternary system Ce–Al–Cu in the Cu-poor part at 503 K were investigated by X-ray
powder diffraction (XRD). The investigated composition region consists of 16 single-phase, 32 two-phase
and17three-phaseregions. At503 K, themaximumsolidsolubilitiesofCuinAl, ␣-Ce3Al11 , CeAl3 andCeAl2
are about 2.5 at.%, 1.6, 3.6 and 5.3, respectively, and Al in CeCu5 is about 39.2 at.%. The homogeneity ranges
of Al2Cu and AlCu phases extend from about 32.1 to 32.6 at.% Cu and 49.7 to 52.4 at.% Cu, respectively. Five
ternary compounds and their solid solutions have been observed in this work: CeAl12−xCux (4.0 ≤ x ≤ 4.52),
Ce2Al17−xCux (6.50 ≤ x ≤ 7.55), CeAl13−xCux (6.62 ≤ x ≤ 6.92), CeAl4−xCux (0.74 ≤ x ≤ 1.10) and CeAlCu.
© 2009 Published by Elsevier B.V.
Received 29 November 2008
Received in revised form 22 March 2009
Accepted 23 March 2009
Available online 31 March 2009
Keywords:
Ce–Al–Cu system
Rare earth compounds
Phase relations
Crystal structure
X-ray diffraction
1. Introduction
However, there is no report about the phase relationships in the
ternary Ce–Al–Cu system. In this work, we focus on the investiga-
Bulk metallic glasses (BMGs), as a new kind of materials, have
attracted extensive interests and gained rapid development in the
past decades. It is found that Ce-based amorphous metallic plas-
tics (AMPs) exhibited extremely low glass transition temperature
Tg down to about 68 ◦C, close to room temperature [1]. Ternary
Ce–Al–Cu AMPs showed good glass forming ability (GFA) and could
be easily fabricated in a wide composition range by conventional
copper mold cast technique. The Ce-based AMP is a model mate-
rial to investigate some basically important issues concerning the
glass transition and supercooled metallic liquid. A study on phase
relations of the ternary system Ce–Al–Cu can provide useful infor-
mation for better understanding the formation and performance of
the AMPs.
In Ref. [2], the phase diagram of binary Al–Ce system was
assessed. There are five intermetallic compounds in the Al–Ce sys-
tem, namely: Ce3Al11 , CeAl3, CeAl2, CeAl and Ce3Al. The phase
diagram of Al–Cu system was reported in Ref. [3], and the
existence of Al2Cu and AlCu was confirmed. In the reported
binary Ce–Cu system [4], the intermetallic compounds CeCu5
and CeCu were confirmed. Existence of ternary compounds:
CeAl12−xCux (4.0 ≤ x ≤ 4.55), CeAl4−xCux (0.75 ≤ x ≤ 1), Ce2Al17−xCux
(6.5 ≤ x ≤ 7.3), CeAl6.5Cu6.5 and CeAlCu, was reported in Refs. [5–9].
tion of the phase relations in the ternary Ce–Al–Cu system in the
Cu-poor part at 503 K.
2. Experimental
Two hundred and ten samples, each weighing 4 g, were prepared by arc melting
high purity cerium, aluminum and copper metal blocks (purity > 99.8 wt.%) in an
atmosphere of high purity argon. Then, the samples were turned and remelted eight
times to ensure homogeneity. Each ingot was enclosed in evacuated quartz tubes
and annealed for 5 months at 503 K. Finally, the samples were quenched into an ice-
cold mixture. Considering that the Ce-based alloys oxidize quickly in the air, these
samples were kept in the gasoline and every step of our experiment was carefully
treated. Possible oxidized surface of the sample was removed before grinding the
sample into powder for X-ray powder diffraction (XRD) experiments.
The powdered samples were investigated by XRD on a Rigaku D/Max-2500
diffractometer using Cu K␣ radiation (45 kV × 250 mA) and a graphite monochro-
mator for the diffracted beam in the range of 2ꢀ = 12 − 140◦. A continuous scanning
mode with rate of 4◦ (2ꢀ) min−1 was used for routine phase identification, and a step
scanning mode with a step width of 2ꢀ = 0.02◦ and a sampling time of 1 s was used
for accurate determination of lattice parameters and crystal structure refinements.
The structure and lattice parameters of the samples were refined by the Rietveld
refinement program Fullprof.2k (Version 2.40).
3. Results and discussion
3.1. Phase analysis
∗
In the Ce–Al–Cu ternary system (Cu-poor portion), nine
binary compounds, namely Ce3Al11 , CeAl3, CeAl2, CeAl, Ce3Al,
Corresponding author. Tel.: +86 773 5601517; fax: +86 773 5601517.
E-mail address: qingry96@guet.edu.cn (Q.R. Yao).
0925-8388/$ – see front matter © 2009 Published by Elsevier B.V.
doi:10.1016/j.jallcom.2009.03.126

Q.R. Yao et al. / Journal of Alloys and Compounds 484 (2009) 86–89
87
Table 1
Crystallographic data of the compounds in the Ce–Al–Cu system (Cu-poor portion) at 503 K.
Phase
Space group
Pearson symbol and prototype
Lattice parameter (Å)
Ref.
a
b
c
␤ (␣-Ce3Al11
␥(CeAl3)
)
Immm
oI28-␣La3Al11
hP8-Ni3Sn
4.3783(6)
4.3783(6)
6.5489(3)
6.547
8.0612(3)
8.061
12.9802(3)
13.02
–
–
–
–
10.0933(3)
10.09
4.6110(2)
4.61
–
–
This work
[2]
This work
[2]
This work
[2]
P63/mmc
¯
␦(CeAl2)
Fd3m
cF24-Cu2Mg
␧(CeAl)
␨(␣-Ce3Al)
␫(CeCu)
Cmcm
P63/mmc
Pnma
oC16-CeAl
hP8-Ni3Sn
oP8-FeB
9.269
7.042
7.370
6.0681(4)
6.067
7.680
–
4.623
–
5.761
5.451
5.648
4.8768(6)
4.877
[10]
[10]
[11]
This work
[3]
␪(Al2Cu)
I4/mcm
tI12-Al2Cu
–
␩2(AlCu)
C2/m
mC20-CuAl(r)
tI26-ThMn12
tI10-BaAl4
12.0606(3)
12.066
8.8223(2)
8.84
4.2633(4)
4.25
8.9501(3)
8.97
11.8754(1)
11.822
4.1047(2)
4.105
6.9123(6)
6.913
5.1557(3)
5.17
10.6852(6)
10.65
13.0452(3)
13.06
This work
[3]
This work
[5]
This work
[6]
This work
[7]
This work
[8]
This work
[15]
*␶1(CeAl8Cu4)
*␶4(CeAl3Cu)
I4/mmm
I4/mmm
–
–
–
–
–
–
–
–
–
–
–
¯
*␶2(Ce2Al10.2 Cu6.8
*␶2(Ce2Al10 Cu7)
*␶3(CeAl6.5Cu6.5
)
R3m
hR57-Th2Zn17
cF112-NaZn13
hP6-CaCu5
¯
)
Fm3c
–
–
␣(Ce(Al0.4Cu0.6)5)
*␶5(CeAlCu)
P6/mmm
5.2573(2)
5.25
7.176
4.1824(1)
4.17
4.201
p-62m
hP9-Fe2P
[9]
Table 1. The refinement result of the XRD data of *␶3(CeAl6.5Cu6.5
)
is shown in Fig. 1 as an example. The agreement between the
observed and calculated profiles is excellent. The refinement results
for *␶3(CeAl6.5Cu6.5) are Rwp (%) = 14.3, Rp (%) = 12.2, Rexp (%) = 10.7,
a = 11.8754(1) Å and V = 1674.73(4) Å3.
In addition to the phases observed in our investigated samples
and listed in Table 1, the compounds Al3Cu2 were reported in Ref.
[12]. However, under our experimental conditions, the XRD analysis
of the samples with the compositions close to “Al3Cu2” shows the
coexistence of Al2Cu and AlCu phases. Fig. 2 shows the XRD pattern
of the “Al3Cu2” alloy.
3.2. Solid solubility limit
Refs. [5–9] reported composition ranges of some solid solution
phases in the Ce–Al–Cu system. According to Refs. [13–14], the
single-phase composition ranges of Al2Cu and AlCu extend from
Fig. 1. The Rietveld refinement results of the XRD pattern of *␶3(CeAl6.5Cu6.5) com-
pound, including the calculated result, the observed result and difference intensities
between them (lower line). The vertical bars indicate the expected Bragg reflection
positions.
CeCu, CeCu5, Al2Cu, AlCu [2–4], and five ternary compounds:
CeAl12−xCux (4.0 ≤ x ≤ 4.55), CeAl4−xCux (0.75 ≤ x ≤ 1), Ce2Al17−xCux
(6.5 ≤ x ≤ 7.3), CeAl6.5Cu6.5 and CeAlCu [5–9] have been reported.
The crystal structure data derived from our Rietveld refinements
or reported in literature for the observed compounds are listed in
Fig. 3. XRD patterns of compound ␣(Ce0.167Cu0.833−xAlx) with different x.
Fig. 2. XRD pattern of the sample Al3Cu2 indicates the two phases: Al2Cu and AlCu.

88
Q.R. Yao et al. / Journal of Alloys and Compounds 484 (2009) 86–89
Fig. 6. XRD pattern of alloy Ce27Al66Cu7 situated in the three-phase region 9.
Fig. 4. The variation of lattice parameters of alloys ␣(Ce0.167Cu0.833−xAlx) on Al con-
tent x.
3.3. Phase relationships
By comparing the X-ray diffraction patterns and identifying
the phases in each sample, phase relationships of the Ce–Al–Cu
ternary system were determined (shown in Fig. 5). The XRD pattern
of the alloy Ce27Al66Cu7, which falls in the region 9 and cor-
responds to three phases *␶4(CeAl3.26Cu0.74) + ␥(Ce(Al0.95Cu0.05)3)
,+ ␦(Ce(Al0.92Cu0.08)2), is illustrated in Fig. 6.
Phase regions 15, 16 and 17 are of particular interest. The
reportedcompositionregionofthebulkglassalloysintheCe–Al–Cu
system [1] falls in this three phase regions. Among these BMGs,
Ce70Al10Cu20 exhibited the lowest glass transition temperature Tg
of341 K. TheXRDpatternsofthealloyMP001obtainedafteranneal-
ing or by suck-cast into a copper mold are illustrated in Fig. 7. The
annealed sample consists of three phases: ␥-Ce + ␣-Ce3Al + CeCu
and falls in the region 17.
According to all the results obtained, the phase relations
of the ternary system Ce–Al–Cu in the Cu-poor part at 503 K
were determined, as shown in Fig. 5. The investigated compo-
sition region consists of 16 single-phase, 32 two-phase and 17
three-phase regions. The 16 single-phase regions are: ␪(Al2Cu),
ꢁ2(AlCu), *␶1(CeAl12−xCux), *␶2(Ce2Al17−xCux), *␶3(CeAl13−xCux),
*␶4(CeAl4−xCux), *␶5(CeAlCu), ␣(CeCu5), ␤(␣-Ce3Al11 ), ␥(CeAl3),
␦(CeAl2), ␧(CeAl), ␨(␣-Ce3Al), ␫(CeCu), ␬(Al) and ␭(␥-Ce). The
32 two-phase regions are: ␬ + ␪, ␬ + *␶1, ␬ + *␶4, ␬ + ␤, ␪ + *␶1,
*␶1 + *␶2, *␶2 + *␶4, *␶1 + *␶4, *␶4 + ␤, *␶4 + ␥, ␤ + ␥, ␥ + ␦, *␶4 + ␦, ␣ + ␦,
*␶4 + ␣, ␣ + *␶2, *␶3 + ␣, *␶2 + *␶3, *␶1 + *␶3, ␪ + *␶3, ꢁ2 + *␶3, ␪ + ꢁ2,
␣ + *␶5, ␦ + *␶5, ␦ + ␧, ␧ + *␶5, ␧ + ␨, ␨ + *␶5, ␫ + *␶5, ␨ + ␫, ␭ + ␨, ␭ + ␫.
The 17 three-phase regions are: ␬ + ␪ + *␶1, ␬ + *␶1 + *␶4, ␬ + *␶4 + ␤,
␪ + ꢁ2 + *␶3, ␪ + *␶3 + *␶1, *␶3 + *␶1 + *␶2, *␶1 + *␶2 + *␶4, *␶4 + ␤ + ␥,
32.05 to 32.6 at.% Cu and 49.8 to 52.3 at.% Cu, respectively. The solid
solution of CeCu5 is reported in Ref. [15]: CeAl5−xCux (0 ≤ x ≤ 2.10).
Based on the variation of the derived unit cell dimensions with the
concentration of substituting component, we have determined that
the maximum solid solubilitiy of Al in CeCu5 is about 39.2 at.% Al, as
shown in Figs. 3 and 4 . Fig. 3 shows XRD patterns of alloys with dif-
ferent Al content from 0 to 46.6 at.% in ␣(Ce0.167Cu0.833−xAlx). The
reflections from *␶4(CeAl2.9Cu1.1 ) and *␶2(Ce2Al9.45Cu7.55) can be
observed when the Al content exceeds 39.2 at.%. The variation of lat-
tice parameters of alloys with Al contents in ␣(Ce0.167Cu0.833−xAlx)
is illustrated in Fig. 4. The lattice parameters a and c increase
with increasing Al content. Likewise, the maximum solid solu-
bilities of Cu in Al, ␣-Ce3Al11 , CeAl3 and CeAl2 are determined
to be about 2.5, 1.6, 3.6 and 5.3 at.%, respectively, and the homo-
geneity ranges of Al2Cu and AlCu extend from about 32.1 to
32.6 at.% Cu and 49.7 to 52.4 at.% Cu, respectively. We have deter-
mined the solid solubilities of the four ternary compounds in this
system: CeAl12−xCux (4.0 ≤ x ≤ 4.52), CeAl4−xCux (0.74 ≤ x ≤ 1.10),
Ce2Al17−xCux (6.50 ≤ x ≤ 7.55) and CeAl13−xCux (6.62 ≤ x ≤ 6.92).
However, no apparent solid solubility was detected in CeAl, CeAlCu,
␣-Ce3Al, CeCu and ␥-Ce under our experimental conditions.
Fig. 5. The phase relations of the ternary Ce–Al–Cu system in the Cu-poor part at
503 K. The reported composition region of the bulk glass alloys in the Ce–Al–Cu
system [1] falls in regions 15–17.
Fig. 7. XRD patterns of alloy Ce70Al10 Cu20 obtained after annealing (top) or by suck-
cast into a copper mold (bottom).

Q.R. Yao et al. / Journal of Alloys and Compounds 484 (2009) 86–89
89
Table 2
and ␫(CeCu), in the Ce–Al–Cu ternary system (Cu-poor portion)
are confirmed and their solid solubilities are determined.
(3) The reported composition region of the bulk glass alloys in the
Ce–Al–Cu system falls in regions 15–17. XRD shows that the
alloy of MP001, which could be easily fabricated by copper mold
cast technique as a metallic glass with Tg = 341 K, lies in phase
region 17 consisting of three phases Ce, Ce3Al and CeCu.
Identification of phase for the ternary alloy in each three-phase region in the
Ce–Al–Cu ternary system in the Cu-poor part at 503 K.
Phase regions
XRD identified phases
Ternary alloys
1
2
3
4
5
6
7
8
␬ + ␪ + *␶
Ce3Al72Cu25
Ce10 Al70Cu20
Ce15 Al79Cu6
Ce3Al52Cu45
Ce4.6Al60Cu35.4
Ce8Al51 Cu41
Ce12 Al58Cu30
Ce23Al72Cu5
Ce26Al67Cu7
Ce11 Al45Cu44
Ce15 Al49Cu36
Ce24Al56Cu20
Ce31 Al45Cu24
Ce40Al50Cu10
Ce60Al35Cu15
Ce65Al25Cu15
Ce70Al10 Cu20
1
␬ + *␶1 + *␶
4
␬ + *␶4 + ␤
␪ + ␩2 + *␶
3
␪ + *␶3 + *␶
1
Acknowledgements
*␶3 + *␶1 + *␶
2
*␶1 + *␶2 + *␶
4
*␶4 + ␤ + ␥
*␶4 + ␥ + ␦
*␶3 + *␶2 + ␣
The experimental assistance and discussion with J. Luo, J.R. Chen,
L.N. Ji and J. Yu are appreciated. The authors are grateful for the
financial support of the Natural Science Foundation of China (Grant
Nos. 50631040 and 50861006).
9
10
11
12
13
14
15
16
17
*␶2 + ␣ + *␶
4
␣ + *␶4 + ␦
␦ + ␣ + *␶
5
*␶5 + ␧ + ␦
*␶5 + ␧ + ␨
*␶5 + ␨ + ␫
␨ + ␫ + ␭
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we prepared are listed in Table 2.
4. Conclusions
(1) Based on XRD phase identification, the phase relations of the
ternary system Ce–Al–Cu in the Cu-poor part at 503 K have been
determined.
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