Preparation of the Al-Cu-Fe & Al-Fe-Si ternary intermetallic powders via a novel reaction ball milling technique

Article abstract of DOI:10.1016/j.jallcom.2003.12.019

The synthesis of elevated-temperature intermetallic powders such as the ternary Al-Cu-Fe and Al-Si-Fe alloy powders was carried out using a novel solid-liquid reaction milling technique. In comparison with that of high-energy ball milling, the phase formation law of ternary alloys by this technology was studied. Moreover, the reaction mechanism and advantages were discussed.

Full text of DOI:10.1016/j.jallcom.2003.12.019

Journal of Alloys and Compounds 376 (2004) 89–94
Preparation of the Al–Cu–Fe & Al–Fe–Si ternary intermetallic
powders via a novel reaction ball milling technique
Ding Chena, Zhenhua Chenb,∗, Jihua Chenb, Peiyun Huanga
a
School of Materials Science and Engineering, Central-south University, Changsha, Hunan 410083, PR China
b
School of Materials Science and Engineering, Hunan University, Changsha, Hunan 410082, PR China
Received 22 October 2003; received in revised form 12 December 2003; accepted 12 December 2003
Abstract
The synthesis of elevated-temperature intermetallic powders such as the ternary Al–Cu–Fe and Al–Si–Fe alloy powders was carried out
using a novel solid–liquid reaction milling technique. In comparison with that of high-energy ball milling, the phase formation law of ternary
alloys by this technology was studied. Moreover, the reaction mechanism and advantages were discussed.
© 2004 Elsevier B.V. All rights reserved.
Keywords: Ternary alloy; Intermetallics; Powder; Reaction ball milling; Mechanochemical field
1. Introduction
mechanical milling assisted by electrical discharge can re-
sult in quicker reactions and new synthesis and processing
routes [10]. However, there is still much work required for
the synthesis of high-purity elevated-temperature intermetal-
lic compounds by means of the mechanical milling route.
Recently, Chen et al. [11] have developed a novel
solid–liquid reaction milling technique and investigated the
effect of the mechanical force on the reaction between the
melt and the solid-state metal. Up to now, pure intermetallic
powders of the Fe–Sn, Ti–Al, Ni–Al, and Fe–Al systems
such as FeSn, Fe3Sn2, Ti3Al, Ni2Al3, and Fe3Al have been
successfully prepared via this novel route [12,13]. In this
contribution, the Al–Cu–Fe and Al–Si–Fe alloy systems
were selected for our present study and ternary intermetallic
powders were prepared.
The effects of external fields such as the magnetic field,
the electric field, and the force field induced by supersonic
waves or high pressure on the solidification behavior of
melts have attracted much attention in recent years [1–3].
As a result, much finer and more uniform solidification mi-
crostructures have been obtained. Mechanical alloying, as a
dry, high-energy ball milling technique, has been employed
to produce a variety of commercially useful and scientifi-
cally interesting materials such as supersaturated solid so-
lutions, crystalline and quasicrystalline intermediate phases,
and amorphous alloys [4,5]. In consideration of milling a
melt, the portion of melt in direct contact with the balls in-
volves high pressure and enhanced atomic reactivity, which
can induce mechanochemical reactions. It has been recog-
nized that this kind of reaction can occur at room tempera-
ture or lower temperatures than those normally required for
the preparation of pure metals, nanocomposites, and other
useful materials. The research performed by Peters [6] is
the most classic. A range of conventional and new milling
and attriting devices have been developed for initiating the
mechanochemical reactions [7–9]. It has been reported that
2. Experimental details
The solid–liquid reaction milling process was con-
ducted at the selected temperatures in a newly developed
solid–liquid reaction milling device (as shown in Fig. 1), in
which a sealed milling cylinder of Ø 300 mm in diameter
rotates in a resistance heated furnace equipped with the
thermostatic system. Both the balls and the milling cylin-
der were made of the same starting material to prevent the
melt from contamination. Moreover, the whole device can
be operated in vacuum or an inert gas atmosphere. Usually,
∗
Corresponding author. Tel.: +86-731-8821648;
fax: +86-731-8821648.
E-mail address: chenzhenhua45@hotmail.com (Z.H. Chen).
0925-8388/$ – see front matter © 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jallcom.2003.12.019

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D. Chen et al. / Journal of Alloys and Compounds 376 (2004) 89–94
binary alloy (200 g) and 20 wt.% Fe served as the starting
material for the conventional mechanical alloying.
The as-milled products were examined by X-ray diffrac-
tion (XRD), differential thermal analysis (DTA), scanning
electron microscopy (SEM) and transmission electron mi-
croscopy (TEM). For the X-ray diffraction we used Cu K␣
radiation.
3. Results
3.1. Al–Cu–Fe ternary alloy powders
Fig. 1. Schematic diagram for the solid–liquid reaction ball milling equip-
ment. (1) Thermoelectric couple; (2) thermostatic system; (3) electric
furnace; (4) milling cylinder; (5) vacuum valve; (6) shaft coupling; (7)
motor; and (8) milling ball.
3.1.1. Milling the eutectic Al–Cu melt
The as-milled products by milling the eutectic Al–Cu melt
(Al–33.2 wt.% Cu) blended with 20 wt.% Fe powders or not
for different hours at 923 K are shown in Table 1. Completely
solid-state powders were obtained after milling for 48 h in
the case of no iron powders. However, the milling time for
the solid-state product decreased to 12 h in the control group,
indicating that the addition of pure iron powders played
an important role in accelerating the reaction. However, it
became a common high-energy mechanical milling process
after the primitive liquid was exhausted.
the milling cylinder was evacuated first and then filled with
pure inert gas to avoid oxidation.
The metal with the higher melting point is termed as the
start material, while the metal with the lower melting point is
the reactant. In our work, the iron of the balls and the milling
cylinder acted as the start material, and pure binary alloy
ingots i.e. Al–33.2 wt.% Cu, Al–54 wt.% Cu, Al–7 wt.% Si,
and Al–30 wt.% Si (>99.5%) served as the reactants, re-
spectively. The rotational speed was controlled at 80 rpm.
The weight of the reactant was approximately 200 g. The
weight ratio of the balls to the reactant was 12:1. The milling
temperature was chosen higher than the melting point of
the reactant and thus it was in a molten state during the
milling process. Powdery iron with the same composition
as the milling balls and an average size of less than 74 ␮m
(20 wt.% Fe) was also added to investigate its effect on the
reaction rate during the solid–liquid milling process. In ad-
dition, conventional mechanical alloying of the Al–Cu–Fe
and Al–Si–Fe systems was carried out in a high-energy plan-
etary ball miller under similar conditions for comparison.
The weight ratio of ball-to-powder was maintained 12:1 and
the rotation speed was controlled at an angular velocity of
41.9 rad/s (i.e. 400 rpm). Blended powders of the original
3.1.2. Milling the Al2Cu melt
The as-milled products by milling the Al2Cu melt
(Al–54 wt.% Cu) blended with 20 wt.% Fe powders or not
for different hours at 943 K are shown in Table 2. Obviously,
iron powders also accelerated the reaction. As seen from
Fig. 2 Al7Cu2Fe was prepared by milling the Al–33.2 wt.%
Cu alloy melt blended with 20 wt.% Fe for 12 h at 923 K
while Al13Cu4Fe3 by milling the Al–54 wt.% Cu (Al2Cu)
alloy melt blended with 20 wt.% Fe for 12 h at 943 K.
3.2. Al–Fe–Si ternary alloy powders
3.2.1. Milling the hypoeutectic Al–7 wt.% Si melt
The as-milled products by milling the hypoeutectic
Al–7 wt.% Si melt blended with 20 wt.% Fe powders or not
Table 1
The as-milled products by milling the Al–33.2 wt.% Cu melt blended with 20 wt.% Fe powders or not for different hours at 923 K
State of the melt
Phase constituent of the as-milled products (h)
12
24
48
No iron powders
Blended with iron powders
Al7Cu2Fe, a little Al2Cu
Al7Cu2Fe
Al7Cu2Fe, Al13Cu4Fe3
Al7Cu2Fe, Al13Cu4Fe3
Al13Cu4Fe3
Al65Cu20Fe15
Table 2
The as-milled products by milling the Al–54 wt.% Cu melt blended with 20 wt.% Fe powders or not for different hours at 943 K
State of the melt
Phase constituents of the as-milled products (h)
12
24
48
No iron powders
Blended with iron powders
Al13Cu4Fe3, a little Al2Cu
Al13Cu4Fe3
Al13Cu4Fe3, Al65Cu20Fe15
Al13Cu4Fe3, Al65Cu20Fe15
Al13Cu4Fe3, Al65Cu20Fe15
Al65Cu20Fe15

D. Chen et al. / Journal of Alloys and Compounds 376 (2004) 89–94
91
Fig. 2. The XRD patterns of the as-milled products Al13Cu4Fe3 and Al7Cu2Fe. (a) Milling the Al–33.2 wt.% Cu melt blended with 20 wt.% Fe powders
at 923 K for 12 h and (b) milling the Al–54 wt.% Cu melt blended with 20 wt.% Fe powders at 943 K for 12 h.
Table 3
The as-milled products by milling the hypoeutectic Al–7 wt.% Si melt blended with 20 wt.% Fe powders or not for different hours at 963 K
State of the melt
Phase constituents of the as-milled products (h)
12
24
48
No iron powders
Blended with iron powders
Al8Fe2Si, Al, an unknown phase
Al8Fe2Si, Al, an unknown phase
Al8Fe2Si, a little Al, an unknown phase
Al8Fe2Si
Al8Fe2Si
Al8Fe2Si
for different hours at 963 K are shown in Table 3. Al8Fe2Si
was the final as-milled product. As seen from Fig. 3,
Al8Fe2Si was obtained after milling the Al–12.6 wt.% Si
alloy melt blended with the iron powders for 48 h at 963 K.
Similar to the Al–Cu–Fe system, iron powders also pro-
moted the reaction.
3.2.2. Milling the eutectic Al–12.6 wt.% Si melt
The as-milled products by milling the eutectic Al–
12.6 wt.% Si melt blended with 20 wt.% Fe powders or not
for different hours at 963 K are given in Table 4. The results
showed that iron powders not only accelerated the forma-
tion of Al8Fe2Si but also contributed to the formation of
Fig. 3. The XRD patterns of Al8Fe2Si, the mixture of Al8Fe2Si, Al3FeSi, and Al3FeSi. (a) Milling the Al–7 wt.% Si melt blended with 20 wt.% Fe
powders at 963 K for 24 h; (b) milling the Al–12.6 wt.% Si melt blended with 20 wt.% Fe powders at 963 K for 48 h; and (c) milling the Al–30 wt.% Si
melt blended with 20 wt.% Fe powders at 1133 K for 24 h.

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D. Chen et al. / Journal of Alloys and Compounds 376 (2004) 89–94
Table 4
Table 5
The as-milled products by milling the eutectic Al–12.6 wt.% Si melt
blended with 20 wt.% Fe powders or not for different hours at 963 K
The as-milled products by milling the hypereutectic Al–30 wt.% Si melt
blended with 20 wt.% Fe powders or not for different hours at 1133 K
State of the melt
Phase constituents of the as-milled products (h)
State of the melt
Phase constituents of the as-milled products (h)
12
24
48
12
24
48
No iron powders
Al8Fe2Si, Al, Si
Al8Fe2Si,
a little Al
Al8Fe2Si
Al8Fe2Si
No iron powders
Blended with iron
powders
Al3FeSi, Al, Si
Al3FeSi, a little Al
Al3FeSi
Al3FeSi
Al3FeSi
Al3FeSi
Blended with iron
powders
Al8Fe2Si, Al
Al8Fe2Si,
Al3FeSi
was finally obtained and iron powders also accelerated the
reaction. As seen from Fig. 3, Al3FeSi was obtained after
milling the Al–30 wt.% Si alloy melt blended with the iron
powders for 24 h at 1133 K.
Al3FeSi in the further solid-state high temperature milling
process. As seen from Fig. 3, the mixture of Al8Fe2Si and
Al3FeSi was obtained after milling the Al–12.6 wt.% Si
alloy melt blended with the iron powders for 48 h at 963 K.
3.3. Microstructures and DTA of the as-milled products
3.2.3. Milling the hypereutectic Al–30 wt.% Si melt
The as-milled products by milling the hypereutectic
Al–30 wt.% Si melt blended with 20 wt.% Fe powders or not
for different hours at 1133 K are listed in Table 5. Al5FeSi
The SEM and TEM images of the as-milled products
of the Al–Cu–Fe and Al–Si–Fe systems by solid–liquid
reaction milling (as shown in Figs. 4 and 5, respectively)
Fig. 4. (a) SEM and (b) TEM images of Al13Cu4Fe3 prepared by solid–liquid reaction milling.
Fig. 5. (a) SEM and (b) TEM images of Al8Fe2Si prepared by solid–liquid reaction milling.

D. Chen et al. / Journal of Alloys and Compounds 376 (2004) 89–94
93
4. Discussion
4.1. Mechanism of solid–liquid reaction milling
Generally, the metals must be heated to certain tempera-
tures above their respective melting points and then cooled
to prepare these intermetallics. But in the solid–liquid re-
action milling process, pure Al65Cu25Fe15, Al13Cu4Fe3,
Al7Cu2Fe15, Al3FeSi, and Al8Fe2Si intermetallics were
prepared at the temperatures much lower than their respec-
tive melting points in the ternary Al–Cu–Fe and Al–Fe–Si
alloy phase diagrams [14]. In this process, small amount
of ternary alloy may be generated on the surfaces of the
milling cylinder, milling balls or iron powders at the milling
temperature in a very short time by diffusion of the melt into
the solid-state component, then peel off and be deposited in
the melt. As the milling time increases, the solid-state par-
ticles react with the liquid metal until it is used up and thus
completely solid-state intermetallic powders are formed.
As far as the mechanochemistry effect is concerned, ball
milling can cause crystal lattice distortion, crystal defect
and emission of electrons, resulting in a large chemical
activity improvement and reaction speed increase. Thereby,
the activity of the start material i.e. iron in the solid–liquid
reaction milling process is high enough to accelerate the
reaction and shorten the milling time for the formation
of pure intermetallics. Additionally, the collision among
the milling balls leads to temperature rise in some local
Fig. 6. The DTA curves of the as-milled products in the Al–Cu–Fe and
Al–Si–Fe systems.
demonstrated that these intermetallic powders were com-
posed of agglomerated particles with an average grain size
of less than 100 nm. The DTA curves of the as-milled prod-
ucts in the Al–Cu–Fe and Al–Si–Fe systems are illustrated
in Fig. 6.
Fig. 7. The XRD patterns of the mechanically alloyed products. (a) Mechanical alloying of the blended powders of Al–54 wt.% Cu and 20 wt.% Fe and
(b) mechanical alloying of the blended powders of Al–12.6 wt.% Si and 20 wt.% Fe.

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D. Chen et al. / Journal of Alloys and Compounds 376 (2004) 89–94
areas above the melting point of the ternary alloy, which is
conducive to the formation of the intermetallics.
5. Conclusion
Pure Al7Cu2Fe, Al13Cu4Fe3, Al65Cu20Fe15, Al8Fe2Si,
and Al3FeSi ternary alloy powders, which can not be
obtained by conventional mechanical alloying under the
similar condition, were prepared via a novel solid–liquid
reaction ball milling route. This process involves a direct
reaction among three elements in the ternary alloy system,
different from knead and diffusion of powders in mechani-
cal alloying. It is a promising materials synthesis technique
and some new alloy phases which can not be obtained by
the traditional means are available in this way.
4.2. Phase formation law of ternary alloys
As mentioned above, the final ternary alloy product
is characteristic of the same elemental molar ratio as its
corresponding original binary alloy. As for the Al–Cu–Fe
systems, the as-milled products Al7Cu2Fe and Al13Cu4Fe3
correspond to the Al–33.2 wt.% Cu and Al–54 wt.% Cu al-
loys, respectively. Likewise, the as-milled products Al8Fe2Si
and Al3FeSi correspond to the Al–12.6 wt.% or Al–7 wt.%
Si, and Al–30 wt.% Si, respectively.
As for the Al–Si–Fe system, neither the Al–Fe nor the
Fe–Si binary alloy was observed though the Al–Si mechan-
ical mixture served as the reactant. Therefore, it can be con-
cluded that a direct reaction among the three elements oc-
curs during the solid–liquid milling process.
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4.3. Mechanically alloyed ternary alloy powders
The XRD patterns of the conventionally mechanically
alloyed products are shown in Fig. 7. Amorphous trans-
formation occurred after mechanical alloying 72 h for
the Al–Cu–Fe system and the ternary amorphous powder
formed for mechanical alloying times up to 200 h. But
for the Al–Fe–Si system, only grain refinement and solid
solution range extension were achieved after mechanical
alloying for 200 h. It is evident that there is a marked differ-
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alloying. The former involves a direct reaction, while the
latter involves kneading and diffusion of the powders [14].
Consequently, the solid liquid reaction ball milling involves
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