Phase equilibria in the ternary Al-Zr-La system

Article abstract of DOI:10.1016/j.jallcom.2010.07.133

The phase relationships in the Al-Zr-La ternary system at 773 K have been investigated for the first time mainly by means of X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) equipped with energy dispersive analysis (EDX). The existenc

Full text of DOI:10.1016/j.jallcom.2010.07.133

Journal of Alloys and Compounds 507 (2010) 62–66
Contents lists available at ScienceDirect
Journal of Alloys and Compounds
journal homepage: www.elsevier.com/locate/jallcom
Phase equilibria in the ternary Al–Zr–La system
Dan Penga, Yongzhong Zhana,∗, Jia Shea, Mingjun Panga, Yong Dub
a Laboratory of Nonferrous Metal Materials and New Processing Technology, Ministry of Education, Guangxi University, Nanning, Guangxi 530004, PR China
b State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
The phase relationships in the Al–Zr–La ternary system at 773 K have been investigated for the first time
mainly by means of X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) equipped
with energy dispersive analysis (EDX). The existence of the Al4La5 and AlLa2 binary compounds has
been confirmed in this ternary system. The isothermal section consists of 18 single-phase regions, 33
two-phase regions and 16 three-phase regions. No ternary compound was observed in this work.
© 2010 Elsevier B.V. All rights reserved.
Received 5 July 2010
Accepted 10 July 2010
Available online 23 July 2010
Keywords:
Metals and alloys
Phase diagrams
X-ray diffraction
Scanning electron microscope
R3+ or R2+ states in Al-based alloys [10]. It means that the magnetic
moment per R-atom in the alloys is the same as that for pure R and
1. Introduction
Aluminum alloys are widely used in aerospace and automobile
industries due to their low density, good mechanical properties,
high corrosion and wear resistance, and lower thermal coefficient
of expansion [1–3]. Zirconium based alloys are used extensively in
the nuclear industry. They have distinct advantages of low neu-
tron absorption cross-section coupled with required mechanical
properties and good corrosion resistance, which makes them indis-
pensable as structural materials in thermal reactors. Formation of
Al3Zr precipitates in aluminum alloys has been used for a long time,
especially in alloys for aerospace applications (such as AA7000
series) [4]. The stronger covalence Al–Zr bond in Al3Zr is not eas-
ily to be broken down by dislocation cutting and thus can hinder
dislocation moving. In other words, the strong Al–Zr covalent bond
network can greatly strengthen the matrix of Al alloys [5].
Al–R (rare-earth) alloys have been investigated for a long time
due to their interesting physical properties and possibility of com-
mercial application. As the solubility of R in aluminum is very low,
the mixture of Al with Al3R (Al11R3) is always important for the
design of new materials [6]. These intermetallic compounds show
rather outstanding electrical and magnetic properties. For exam-
ple, Al3Ce and Al2Ce are considered to be model systems in the
investigations of “heavy fermions”. Kondo effect and peculiarities
in phase transitions of the second order were found for these and
similar Al–R compounds at low temperatures [7–9]. It is a com-
mon place for many works that rare-earth elements exist in the
4f-electrons which are not involved into chemical bonds formation.
However, this idea has to be checked experimentally, especially for
high temperatures.
In order to discover further application characteristics of the
aluminum and zirconium alloys, it is necessary to investigate the
phase relationships in the Al–Zr–RE ternary systems. However, up
to now very few information can be found on the ternary system of
the Al–Zr–La. This work was undertaken to experimentally inves-
tigate on the phase diagram of this ternary system and shed light
on the phase equilibrium information.
In Refs. [11–13], the binary phase diagrams of Al–Zr, Al–La and
Zr–La systems have been reported. Eight binary compounds, i.e.
Al3Zr, Al2Zr, Al3Zr2, AlZr, Al3Zr4, Al2Zr3, AlZr2 and AlZr3 are shown
in the Al–Zr binary phase diagram at 773 K. For the Al–La binary sys-
tem, five intermediate phases namely AlLa3, AlLa, AlLa2, Al3La and
Al11La3 have been reported in the previous binary phase diagram
at 773 K. In addition the existence of Al4La5 [14], a new compound
AlLa2 has been reported in the previous literature [15]. There is no
binary compound reported in the Zr–La system. Structural data for
the intermetallic compounds in the three binary systems are given
in Table 1.
2. Experimental procedure
Each sample was prepared with a total weight of 1.5 g by weighing appropriate
of the pure components (Al 99.9 wt.%, Zr 99.99 wt.% and La 99.99 wt.%). Sixty-one
alloy buttons were made in an electric arc furnace under an argon atmosphere and
a water-cooled copper crucible. Titanium was used as an oxygen getter during the
melting process. The alloys were re-melted four times in order to achieve complete
fusion and homogeneous composition. For most alloys, the weight loss is less than
1% after melting.
∗
Corresponding author. Tel.: +86 771 3272311; fax: +86 771 3233530.
E-mail address: zyzmatres@yahoo.com.cn (Y. Zhan).
0925-8388/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jallcom.2010.07.133

D. Peng et al. / Journal of Alloys and Compounds 507 (2010) 62–66
63
Table 1
Crystallographic data of the binary phases in the ternary Al–Zr–La system.
Compound
Conditions (◦C)
Space group
Lattice parameters (nm)
Reference
a
b
c
Al3Zr
Al2Zr
Al3Zr2
AlZr
<980
I4/mmm
P63/mmc
Fdd2
0.4005
–
1.7285
[16]
This work
[16]
This work
[16]
This work
[16]
This work
[16]
This work
[16]
This work
[16]
This work
[16]
This work
[17]
This work
[18]
0.400967
0.52824 (5)
0.528334
0.9601 (2)
0.95831
1.729368
0.87482 (5)
0.874973
0.5574 (2)
0.556662
0.4266
0.426421
−0.5390 (2)
0.534973
0.6998 (1)
0.703534
0.5928
<1250
<1480
<1275
<1030
<1275
<1595
<1490
<915
–
1.3906 (2)
1.386968
1.0866
1.08361
–
Cmcm
0.3353
0.33516
Al3Zr4
Al2Zr3
AlZr2
AlZr3
Al11La3
Al3La
Al2La
P6
0.5433 (2)
0.542897
0.7630 (1)
0.763362
0.4894
0.485921
0.43917 (1)
0.438000
0.4431
P42/mnm
P63/mmc
Pm3m
–
–
–
0.593844
–
Immm
P63/mmc
Fd3m
1.3142
1.31573
–
1.0132
1.013753
0.4616
0.462609
–
0.443219
0.6667
0.666098
<1170
<1405
This work
[19]
0.81489
–
0.814267
0.9531 (6)
0.9163
1.70942 (1)
0.5093
This work
[20]
[14]
[15]
[21]
AlLa
<873
–
–
Cmem
0.7734 (6)
0.5809 (5)
1.1231
0.53790 (3)
–
Al4La5
AlLa2
AlLa3
P62m
Tetragonal
Pm3m
–
–
–
520–400
0.510014
This work
The melted alloys were sealed in an evacuated quartz tube containing titanium
chips as an oxygen getter. The tube was placed in a resistance furnace for homog-
enization treatment and then annealed at different temperatures in order to attain
good homogenization. The heat treatment temperature of the alloys was determined
by differential thermal analysis (DTA) results of some typical ternary alloys or based
on previous works of the three binary phase diagrams. The alloys at the Al-rich cor-
ner or those contained AlLa3 phase were homogenized at 873 K for 960 h, and the
rest alloys were homogenized at 1173 K for 360 h. Then all of them were cooled
down to 773 K at a rate of 9 K/h and maintained for more than 240 h. Finally, all
these annealed alloys were quenched in liquid nitrogen.
Finally, the equilibrated samples in the Al–Zr–La system were determined from
X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) with
energy dispersive analysis (EDX). Samples for XRD analyses were firstly powdered
and then analyzed on a Rigaku D/Max-2500 V diffractometer with CuK␣ radiation
and graphite monochromator operated at 40 kV, 200 mA. The Materials Data Inc.
software Jade 5.0 and Powder Diffraction File (PDF release 2004) were used for phase
identification. Some typical alloys were analyzed by optical microscopy (OM) and
SEM.
work. As an example, the XRD pattern of the equilibrated alloy with
atomic proportion of 43 at.% Al, 23 at.% Zr and 34 at.% La shows the
existence of the Al4La5 phase, as shown in Fig. 2. This result is in
accordance with that reported in Refs. [14,15].
In the Zr–La system, it is confirmed here that no binary com-
pounds exists. This result is in good agreement with that reported
in Ref. [13]. Moreover, in the present work, no ternary compounds
have been found in the Al–Zr–La ternary system at 773 K.
Fig.
3 illustrates the XRD patterns of the equilibrated
Al86Zr10La4 alloy and Al85Zr5La10 alloy. The results indicate the
existence of three phases, i.e. Al11La3, Al3Zr and Al. It is clear from
Fig. 4 that the equilibrated alloys Al72Zr16La12 and Al70Zr5La25
consist of three phases, i.e. Al2La, Al3Zr and Al3La. From Fig. 5, it can
be observed that, at 773 K, there are three phases in the alloys of
Al55Zr40La5 and Al62Zr20La18, i.e. Al3Zr2, AlZr and Al2La. Another
two equilibrated alloys of Al54Zr22La24 and Al57Zr15La28 consist
of the patterns of three phases, i.e. AlZr, AlLa and Al2La, as shown
in Fig. 6.
3. Results and discussion
3.1. Phase analysis and solid solubility
In this work, the binary systems Al–Zr, Al–La and Zr–La at 773 K
have been studied to identify the binary compounds before the
analysis of the ternary system.
Eight binary compounds, i.e. Al3Zr, Al2Zr, Al3Zr2, AlZr, Al3Zr4,
Al2Zr3, AlZr2 and AlZr3, have been confirmed in the Al–Zr binary
system at 773 K, which agrees well with the other works [11,22].
In the present work, seven binary compounds, i.e. AlLa3, AlLa2,
Al4La5, AlLa3, AlLa, AlLa2, Al3La and Al11La3, have been confirmed
at 773 K in the Al–La system which agrees well with the previ-
ous works [12,14,15]. To our knowledge, two binary compounds
(i.e. AlLa2 and Al4La5) and their crystal structural data have been
reported [14,15]. The XRD pattern of the equilibrated sample which
contains 33.5 at.% Al and 66.5 at.% La clearly indicates the existence
of the AlLa2 phase. It is noted that there are some minor unknown
peaks (which has been labeled in the figure) exist, as illustrated
in Fig. 1. This unknown crystal structure needs additional study.
The existence of the Al4La5 compound was also confirmed in this
Fig. 1. The XRD patterns of the equilibrated sample with atomic proportion of
33.5 at.% Al and 66.5 at.% La showing the existence of AlLa2 single phase.

64
D. Peng et al. / Journal of Alloys and Compounds 507 (2010) 62–66
Fig. 5. The XRD patterns of two equilibrated Al–Zr–La ternary samples with com-
positions of (a) 55 at.% Al, 40 at.% Zr and 5 at.% La, and (b) 62 at.% Al, 20 at.% Zr and
18 at.% La.
Fig. 2. The XRD pattern of the equilibrated sample prepared with atomic proportion
of 43 at.% Al, 23 at.% Zr and 34 at.% La.
Fig. 3. The XRD patterns of two equilibrated Al–Zr–La ternary samples with compo-
sitions of (a) 86 at.% Al, 10 at.% Zr and 4 at.% La, and (b) 85 at.% Al, 5 at.% Zr and10 at.%
La.
Fig. 6. The XRD patterns of two equilibrated Al–Zr–La ternary samples with com-
positions of (a) 54 at.% Al, 22 at.% Zr and 24 at.% La, and (b) 57 at.% Al, 15 at.% Zr and
28 at.% La.
It is clear from Fig. 7 that the equilibrated alloy with composition
of 68 at.% Al, 22 at.% Zr and 10 at.% La consists of three phases, i.e.
Al3Zr, Al2Zr and Al2La. SEM result also clearly shows the existence
of these three phases (Fig. 8). EDX result indicates that the pale
phase is Al2La, the gray one is Al2Zr, and the rest is Al2Zr (which is
surrounded by the Al3Zr phase).
The solid solubility ranges of all of the single phases were deter-
mined using the phase-disappearing method and by comparing the
shift of the XRD patterns of the samples near to the compositions
of the binary phases have been employed to determine [23]. The
results showed that the diffraction patterns did not shift and the
diffraction patterns of the second phase could easily be detected
when the composition of the alloys deviated from its single-phases
region by 1.0 at.%. Therefore, none of these phases in this system
revealed a remarkable homogeneity range at 773 K.
3.2. Isothermal section
The isothermal section of the ternary Al–Zr–La system at
773 K was determined by XRD, SEM and optical microscopy.
Fig.
9 indicates a part of the investigated compositions
within the Al–Zr–La system in this work. The isothermal sec-
Fig. 4. The XRD patterns of two equilibrated Al–Zr–La ternary samples with com-
positions of (a) 72 at.% Al, 10 at.% Zr and 18 at.% La, and (b) 70 at.% Al, 5 at.% Zr and
25 at.% La.
Fig. 7. The XRD pattern of the equilibrated sample prepared with atomic proportion
of 68 at.% Al, 22 at.% Zr and 10 at.% La.

D. Peng et al. / Journal of Alloys and Compounds 507 (2010) 62–66
65
Fig. 8. The SEM micrograph of the equilibrated alloy containing 68 at.% Al, 22 at.%
Zr and 10 at.% La.
Fig. 10. The 773 K isothermal section of the Al–Zr–La ternary system.
Table 2
Details of the three-phase regions and compositions of the typical alloys in the
Al–Zr–La system at 773 K.
Phase region
Typical alloy composition (at.%)
Phase composition
Al
Zr
La
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
86
75
70
70
65
62
54
48
46
43
39
36
30
15
22
12
10
5
5
4
20
25
5
Al + Al11La3 + Al3Zr
Al3La + Al11La3 + Al3Zr
Al3La + Al2La + Al3Zr
Al2La + Al2Zr + Al3Zr
Al2La + Al2Zr + Al3Zr2
Al2La + Al3Zr2 + AlZr
AlLa + Al2La + AlZr
AlLa + AlZr + Al3Zr4
AlLa + Al4La5 + Al3Zr4
Al4La5 + Al2Zr3 + Al3Zr4
Al4La5 + AlLa2 + Al2Zr3
AlLa2 + AlZr2 + Al2Zr3
AlZr2 + AlLa3 + AlLa2
AlZr2 + AlLa3 + La
25
30
20
22
40
16
23
17
47
30
20
56
55
5
18
24
12
38
34
44
17
40
65
22
33
AlZr3 + AlZr2 + La
AlZr3 + La + Zr
Fig. 9. The compositions of the typical ternary Al–Zr–La samples annealed at 773 K.
system. The isothermal section consists of 18 single-phase regions,
33 two-phase regions and 16 three-phase regions. Remarkable
homogeneity range for all phases was not observed.
tion, shown in Fig. 10, consists of 18 single-phase regions,
33 binary-phase regions and 16 ternary-phase regions. The
following three-phase equilibria namely Al + Al11La3 + Al3Zr,
Al3La + Al11La3 + Al3Zr, Al3La + Al2La + Al3Zr, Al2La + Al2Zr + Al3Zr,
Acknowledgement
Al2La + Al2Zr + Al3Zr2,
Al2La + Al3Zr2 + AlZr,
AlLa + Al2La + AlZr,
AlLa + AlZr + Al3Zr4, AlLa + Al4La5 + Al3Zr4, Al4La5 + Al2Zr3 + Al3Zr4,
Al4La5 + AlLa2 + Al2Zr3, AlLa2 + AlZr2+ Al2Zr3, AlZr2 + AlLa3 + AlLa2,
AlZr2 + AlLa3 + La, AlZr3 + AlZr2 + La and AlZr3 + La + Zr, have been
determined at 773 K. Details of the three-phase regions and
compositions of the typical alloys are given in Table 2. No ternary
compounds were found in this system.
This work is supported by the National Natural Science Founda-
tion of China (Grant No. 50831007).
References
[1] D.L. McDanels, Metall. Trans. A 16 (1985) 1105–1115.
[2] B. Ralph, H.Y. Yuen, W.B. Lee, J. Mater. Process. Technol. 63 (1997) 339–353.
[3] M.K. Surappa, P.K. Rohatgi, J. Mater. Sci. 16 (1981) 983–993.
[4] A. Deschamps, L. Lae, P. Guyot, J. Acta Mater. 55 (2007) 2775–2783.
[5] Y.J. Gao, Q.F. Mo, J. Mater. Sci. 499 (2009) 299–303.
[6] N.P. Lyakishev (Ed.), Phase Diagrams for Binary Metallic Systems, vol. 1,
Moscow, Mashinostroenie, 1996, pp. 991 (in Russian).
[7] L. Degiorgi, Rev. Mod. Phys. 71 (3) (1999) 690.
[8] D.E. MacLaughlin, M.S. Rose, B.-L. Young, J. Phys. B: Condens. Mater. 326 (2003)
387–389.
[9] R.E. Majewski, A.S. Edelstein, A.E. Dwight, J. Appl. Phys. 50 (B3) (1979) 2336.
[10] K.N.R. Taylor, Adv. Phys. 20 (1971) 551.
4. Conclusions
In this work, 15 binary compounds, i.e. Al3Zr, Al2Zr, Al3Zr2, AlZr,
Al3Zr4, Al2Zr3, AlZr2, AlZr3, AlLa3, AlLa, AlLa2, Al3La, Al11La3, Al4La5
and AlLa2, were confirmed. The phase equilibria of the ternary
Al–Zr–La system at 773 K have been determined. The existence of
the two binary compounds Al4La5 and AlLa2 was confirmed in the
isothermal section. No ternary compound is found in the ternary

66
D. Peng et al. / Journal of Alloys and Compounds 507 (2010) 62–66
[11] H. Okamoto, J. Phase Equilibria 23 (2002) 455–456.
[12] T.B. Massalski, H. Okamoto, P.R. Subramanian, L. Kacprzak (Eds.), Alloy Phase
Diagrams 2 (1990) 1718–1719.
[18] E.E. Havinga, J. Less-Common Met. 41 (1975) 241–254.
[19] B. Appa Rao, P. Kistaiak, N. Rajasekhar Reddy, K. Satyanarayana, J. Mater. Sci.
Lett. 1 (1982) 432–434.
[13] H. Okamoto, J. Phase Equilibria 3 (1992) 162.
[14] N.M. Belyavina, V.Ya. Markiv, V.V. Zavodyanny, J. Alloy Compd. 367 (2004)
132–136.
[15] Y. Chen, Q. Feng, L. Zeng, J. Alloy Compd. 492 (2010) 208–212.
[16] P. Villars, Pearson’s Handbook of Crystallographic Data, ASM International,
Materials Park, OH, 1997, pp. 488–489.
[20] K.H.J. Buschow, Philips Res. Rep. 20 (1965) 337–348.
[21] A. Iandelli, Natl. Phys. Lab. 1 (9) (1959), 3F-2–3F-11.
[22] Z. Hu, Y. Zhan, J. She, J Alloy Compd. 491 (2010) 200–202.
[23] Y. Zhan, Y. Du, Y. Zhuang, Determination of phase diagrams using equili-
brated alloys, in: J.-C. Zhao (Ed.), Methods for Phase Diagram Determination,
first ed., Elsevier Science Press, Amsterdam, The Netherlands, 2007, pp.
108–150.
[17] A.H. Gomes de Mesquita, K.H.J. Buschow, Acta Cryst. 22 (1967) 497–501.