Materials Sciences and Applicatio ns, 2011, 2, 1471-1479
doi:10.4236/msa.2011.210198 Published Online October 2011 (http://www.SciRP.org/journal/msa)
1471
Discontinuous Precipitation and Dissolution in
Cu-4.6 at% In Alloy under the Effect of Plastic
Deformation and the Temperature
Said Bensaada, Hamoudi Mazouz, Mohamed Tewfik Bouziane
Laboratory LARHYSS Université Mohamed Khider, Biskra, Algeria.
Received January 19th, 2011; revised March 17th, 2011; accepted May 9th, 2011.
ABSTRACT
The study of the discontinuous precipitation reaction and the lamellar precipitate dissolution in the alloy Cu-In system
provoked a considerable benefit and has been the subject of many theoretical and experimental investigations. The aim
of this work is to make the evidence on the one hand the effect of the plastic deformation on the mechanism of the dis-
continuous precipitation reaction such as nucleation, growth and lamellar coarsening and in other hand the effect of
temperature on the characteristics and front behavior movement of the opposite reaction (discontinuous dissolution).
Different techniques of analysis have been used in this respect such as the optical microscopy, the differential thermal
analysis and the microhardness Vickers. The obtained results confirm various works achieved in this field.
Keywords: Cu-In Alloy, Discontinuous Precipitation, Dissolution, Plastic Deformation, Temperature
1. Introduction
1.1. Discontinuous Precipitation
The precipitation phenomena take a considerable place in
metal solutions, because it modifies the alloy properties,
sometimes in favourable way leading to the rise of hard-
ness and load breaking. The final state of the precipita-
tion process is of several phases.
Generally the reaction of precipitation consists of the
decomposition of a supersaturated solid solution α0
(mother phase) in a mixture of two phases of different
compositions [1], according to the following reaction:
α0 → α + δ
where α is the girl phase, depleted in alloy element and
has the same structure as α0 the mother phase and δ the
precipitated phase rich in alloy element and can be:
 A mixed crystal with the same structure, the case of
discontinuous precipitation in the alloy system Au-Ni
[2].
 A mixed crystal with a different structure, the case of
the alloy system Pb-Sn [3].
 An intermetallic phase, the case of the alloy system
Cu-Zn [4].
 A liquid phase, the case of the alloy system Pb-Bi [5].
Discontinuous precipitation in the alloy Cu-In system
has been the subject of many research tasks [6-8] and the
supersaturated solid solutions of this alloy system is de-
composed in continuous and discontinuous modes, ap-
pearing at high and low temperature respectively. The
favourable sites supporting the appearance of the cellular
precipitate are the grain boundaries of large orientation
[9,10]. The average size of the initial grains has also a
considerable influence on the precipitate morphology.
The mechanisms of discontinuous precipitation nu-
cleation suggested by Fournelle and Clark [11], then by
You and Turnbull [9] are most plausible in this alloy
system, i.e. it is a transformation related to the grain
boundary dynamics. The growth model in this alloy sys-
tem is that proposed by Frebel and Schenk [12] and of
which the speed growth of the precipitated lamellas de-
pends primarily on the speed of ageing annealing and the
solute content of this alloy system, Figure 1 [13].
Two types of cellular reactions were observed by
Spenger and Mack [14] in this alloy system, one fine and
the other coarse, in both cases the lamellas are uniformly
distributed. Predel and Gust [15] has shown also the
same observation Figure 2, where the formation of the
coarse lamella proceeds mainly between two fine lamellas
and in both cases the process is controlled by the diffusion
on the grain boundaries. The fine lamellas are uniform-

Discontinuous Precipitation and Dissolution in Cu-4.6 at% In Alloy under the Effect of Plastic Deformation 1472
and the Temperature
Figure 1. Growth speed of precipitate during annealing time
in the Cu-In alloy system [13].
ly distributed; in contrast the distribution of thick lamel-
las is disordered, so there is a competition between the
primary reaction of precipitation and the coalescence of
the lamellas.
In old work one could not observe the coarse lamellas,
because probably they appear only after long annealing
time. This sam
Figure 2. Morphology of lamellar precipitate in Cu-7, 5 at%
In alloy, homogenized, quenched and annealing during 3, 5
h at 392˚C [15].
issolution of the lamellate structure β + α (biphasic
carried out according
e phenomenon was observed in many al-
loys such as (Al-Ag [16], Al-Cu [17], Au-Fe [18], Cu-Ag
[19, 20], Fe-Zn [21], Fe-Ni-Ti [22], Ni-Sn [23], Pb-Na
[24], Cu-Ga [25], Cu-In [26] and Zn-Al [27]. The types
of precipitate in this alloy system have the shapes of hem
[28], quadratic and fissure [29]. Experimentally, it was
shown that a predeformation with the ageing annealing
affects considerably the mechanism and the kinetics of
precipitation [30]. D. B. Williams [31] affirmed that un-
der the influence of the deformation, the speed of con-
tinuous precipitation increases consequently, the degree
of supersaturation in solute atom decreases, which im-
plies a reduction in the driving force of the cellular reac-
tion.
1.2. Discontinuous Dissolution
The d
structure) formed after annealing is
to the reaction: β + α → α.
This can take place at any temperature higher from 20
to 50˚C at the solvus temperature (critical temperature of
solubility) corresponding to the alloy composition. Dis-
solution is easy and rapid if this critical temperature is
raised, and supported by diffusion of the addition ele-
ment in the matrix. The solid solution results after disap-
pearance of the precipitate, has however a uniform com-
position only if the dissolution heat treatment were suffi-
ciently prolonged (of about an hour) at a temperature
higher than the solvus temperature, to ensure by diffusion
a perfect homogenization (a complete dissolution).
The dissolution process is perhaps explained by Fig-
ures 3(a) and 3(b) represented on the one hand the dis-
continuous precipitation diagram on the grain boundary
with α0 is the mother phase (single-phase structure), the β
precipitate in the lamellate form and the new phase α,
and in other hand by the dissolution of precipitate with
grain boundary displacement (GB) according to the reac-
tion front (RF) [32].
According to a study made on several alloy systems
and among the Al-38 at %Ag alloy based on the micro-
hardness measure, the dissolved phase leads to the alloy
hardening, it increases the lattice tension due to the pre-
cipitate rich in solute by the introduction of this last into
the solid solution. In the same way, the fragmentation of
the lamellate of the β phase causes the same effect. The
mechanical properties of the alloy during the discon-

Discontinuous Precipitation and Dissolution in Cu-4.6 at% In Alloy under the Effect of Plastic Deformation
and the Temperature
1473
(a) (b)
Figure 3. Schetion (b) [32].
tinuous dissolu
es before dissolution.
y is of a discontinue-
ou
m diagram of the
Figure 4, which cor-
nduction melting under
in
cold rolling,
Table 1.
sed and on the same aged samples, see Table
2.
ermal analysis and the microhardness Vickers.
matic of discontinuous precipitation (a) and discontinuous dissolu
tion treatment depend on the alloy proper- ples, where two samples are deformed by
ti
S. P. Gupta [33] noticed that the dissolution of the la-
mellate precipitates in the same allo
s type. I. G. Solorzano and W. Gust [34] have shown
that an adequate heat treatment makes it possible to de-
velop two different mechanisms of dissolution, one at
480°C leading to a discontinuous dissolution where the
atoms diffusion is carried out through the reaction front
and the other at 580˚C leading after 60 seconds to a con-
tinues dissolution or the atoms diffusion is carried out in
volume, the latter is accomplished by a recrystallization
due to the presence of dislocations in the precipitated
lamella, which supports the formation of new grains. The
increase in the dislocations rate is due to the thermal cy-
cle. Schapiro and Kirkaldy [35] have observed the exis-
tence of twins inside the precipitated lamella which sup-
ports the process of recrystallization. S. P. Gupta and B
Prasard [36] found that the applied technique of the
thermal cycle to a Cu-In alloy causes a refinement of the
grain.
2. Experimental Methods
The significant part of the equilibriu
alloy Cu-In system is illustrated in
responds to the small percentage of Indium. The maxi-
mum solubility of the α phase is 18.1 at% In at 574˚C,
the δ precipitated phase (Cu9In4) from the supersaturated
phase with a composition of 29 to 30.6 at % In at all the
temperatures below 613˚C [37].
The alloy used for this investigation is the Cu-4.6 at%
In alloy obtained by vacuum i
ert atmosphere (Argon) from Copper (5N5Cu) and In-
dium (5N5In) very pure. The samples investigated in the
experimental study are homogenised for 27 days at T =
600˚C, quenched in water. For the effect of deformation
on the discontinuous precipitation, we have used 3 sam-
The ageing treatments were carried out at 400˚C to
cause only the discontinuous precipitation. For dissolu-
tion, three different temperatures of 460˚C, 500˚C and
600˚C are u
The structural evolution is of microhardness Vickers
(HV0,1). The structural morphology is followed by vari-
ous techniques such as optical microscopy, the different-
tial th
Figure 4. Part of equilibrium diagram of Cu-In alloy system
[37].
Table 1. The samples used in the precipitation study.
0,1
samples state HV
1 quenched 45
2 deformed, ε = 20% 52
3 deformed, ε2 = 70% 71
2

Discontinuous Precipitation and Dissolution in Cu-4.6 at% In Alloy under the Effect of Plastic Deformation 1474
and the Temperature
Table 2. Theples used in the disution stud
V0.1 Aged at T = 400˚C HV0.1 after ageing T˚C of dissolution
samsoly.
samples H
1. not deformed 600 42 for 97 hours 72
2. deform
0%
ed ε = 20% 48 for 67 hours 92 500
3. deformed ε = 767 for 53 hours 104 460
Figure 5. Structural evolution of Cu-4.6 at% In alloy, after homogenization during 27 days at 600˚C, quenched in water (a),
deformed of 20% (c) and of 70% (e) and annealing at 400˚C during 97 h (b), 67h (d) and 53h (f).

Discontinuous Precipitation and Dissolution in Cu-4.6 at% In Alloy under the Effect of Plastic Deformation 1475
and the Temperature
3. Results and Discussion
3.1. Discontinuous Precipitation
The temperature of ageing of 400˚C reveals only the
discontinuous precipitation (lamellate) and not of other
morphology precipitates whatever the deformation rate,
the precipitate are of the double hems type, Figures 5(b),
5(d) and 5(f) with the reaction front has a corrugated
pace. The mechanism of folding noticed by the authors
[9,11] was observed, i.e. in the early times of nucleation,
the grain would be folded locally to absorb the precipi-
tates, Figure 6, which confirms a precipitation with the
grain boundary dynamics.
However precipitation is much slower on a grain
boundary of small size than on a grain boundary of large
size, an average critical size of grains boundaries is de-
served to be in evidence for such cases.
The deformation does not have any effect on the pre-
cipitates growth, but however we have observed two
cellular reactions, one of fine lamellas and the other coa-
lesced, Figure 6, which implies a competition between
the primary reaction of precipitation and the coalescence
of the lamellas. The formation of the coalesced lamellas
is carried out mainly between two very close fine lamel-
las; this enlargement probably starts when the totality or
less most of the structure is precipitated. For the coa-
lesced lamellas it is always about the same phase as that
of discontinuous precipitation. The lamellas preserve
Figure 6. Structural evolution of Cu-4.6 at% In alloy, after
homogenization during 27 days at 600˚C, quenched in water,
deformed of 20% and annealing at 400˚C during 67 h.
tion during 27 days at 600˚C, quenched in water, of sample 1 Figure 7. D.T.A curves of Cu-4.6 at% in alloy, after homogen
not deformed.
iza

Discontinuous Precipitation and Dissolution in Cu-4.6 at% In Alloy under the Effect of Plastic Deformation 1476
and the Temperature
eir growth; the
gr
thermic peak confirms the precipitation of a new phase
which corresponds to the intermetallic phase Cu9In4. The
evolution of the microhardeness, Figure 8 clearly shows
the structural hardening of all the samples during discon-
tinuous precipitation; however this hardening is rela-
tively significant with the rise in the work hardening rate.
3.2. Discontinuous Dissolution
their morphology anisotropy during th
owth of the lamellas is observed in the deformed than
in the not deformed samples, it is a growth in width
leading to narrow hems. The differential thermal analysis,
Figure 7 which the curve is characterized by a variation
of energy during the rise in the temperature and the exo-
The various temperatures used during dissolution of pre-
cipitates lamellate have developed in two different me-
chanisms of dissolution. The temperatures of 600˚C and
500˚C led on the one hand to a dissolution of continues
type where the atoms diffusion is carried out in volume
(Figures 9(b) and 9(d)) and on the other hand supported
the formation of twins after dissolution of precipitates.
On the other hand the temperature of 460˚C has shown
a discontinuous dissolution of discontinuous type, Figure
9(f), with opposite migration of the reaction front (RF)
and where the atoms diffusion is carried out mainly
through the grain boundary. However the effect of the
temperature on the speed of dissolution is observed, be-
cause in comparison with the last two temperatures
(600˚C and 500˚C), the process of dissolution in the case
of the temperature of 460˚C is relatively slow. The dis-
solution of precipitates in the three cases has lead to a fall
of the microhardness, Figure 10 .
4. Conclusions
The results obtained by different technique of analysis
used in this respect are coherent between them and con-
firm several work devote to the study of the reaction of
precipitation and discontinuous dissolution in the alloy
Cu-In system. However the temperature of 400˚C sup-
ports only discontinuous precipitation and not other pre-
cipitates morphology was observed. The lamellas are of
double hems type with a corrugated pace. The presence
of the fine lamellas and coalescences confirms the exis-
tence of the competition between precipitation and the
coalescence of the lamellas. The grain boundary is char-
acterized by a crumpling to absorb the precipitate during
their movement. The effect of the deformation rate is
observed on the precipitation speed during the initial
stage; on the other hand no effect was observed on the
coalescence of the precipitate. Precipitation is carried out
mainly in the coarse grains zones, because the initial av-
erage size of th
Figure 8. Hardness evolution HV0,1 during annealing time
Cu-4.6 at% In alloy, after homogenization during 27 days
at 600˚C, quenched in water (a), deformed of 20% (c) and
of 70% (e) and annealing at 400˚C during.
nisms of precipitation. The appearance of the new inter-
metallic phase Cu9In4 led to the hardening of alloy. The
effect of the temperature on the mechanism of the disso-
lution of the lamellate precipitate has shown on the one
hand that dissolution is carried out into two different
e grains has an influence on the mecha-

Discontinuous Precipitation and Dissolution in Cu-4.6 at% In Alloy under the Effect of Plastic Deformation 1477
and the Temperature
Figure 9.Structural evolution of Cu-4.6 at% In alloy, after ho
nealing at 400˚C during 97 h (a), 67 h (c) and 53 h (e) and dis
und at 460˚C during 8 h (f).
mo
sol genization during 27 days at 600˚C, quenched in wate r, an- ution at 600˚C during 12 mn (b), at 500˚C during 25 mn (d)
mechanisms, one continuous for the temperatures of
600˚C and 500˚C where diffusion is carried out in vol-
discontinuous type in the case of the temperature of
460˚C with diffusion through the grain boundaries. In the
ume and accomplished by twin formation. The other is of other hand the dissolution p is relatively slow for rocess

Discontinuous Precipitation and Dissolution in Cu-4.6 at% In Alloy under the Effect of Plastic Deformation 1478
and the Temperature
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spheroidisation of the lamellate precipitate.
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1479
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