Oct. 2008, Volume 2, No.10 (Serial No.11)
Journal of Materials Science and Engineering, ISSN1934-8959, USA
Study on microstructure and thermal parameters of CuTeSeFe alloy
ZHANG Rui-jun1, REN Yan-jun2, HE Miao1, LIU Jian-hua1
(1. State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, China;
2. Analysis and Measure Center, Hebei Normal University of Science & Technology, Qinhuangdao 066004, China)
Abstract: Microstructure of CuTeSeFe alloy was studied by
means of metallograph, SEM/EDS and XRD, and the thermal
diffusivity coefficient, thermal capacity and thermal
conductivity of CuTeSeFe alloy under 25-400℃ were measured
by TC-7000 thermal constant equipment. The results showed
that the CuTeSeFe alloy was composed of α(Cu) solid solution
and CuSeTe intermetallic compound appeared as irregular
particles, and with increasing heating temperature, the thermal
diffusivity coefficient decreased, the thermal capacity and
thermal conductivity showed fluctuation with a small fluctuation
margin.
Key words: CuTeSeFe alloy; microstructure; thermal
parameters; temperature
1. Introduction
Copper alloy has many advantages, such as high
strength, good electric conductivity and thermal
conductivity, so it has been widely used in fields of
electrode and electricity contact material etc. In recent
years, with the large scale integration and micromation
of electron circuitry, there are higher thermal
conductivity requirements to materials, and the heat
dissipation of conventional materials is not enough,
especially working at high temperature. Hence, the
research on producing copper alloy with high strength
and good thermal conductivity attracted many
researchers’ attention[1-4]. Some researches showed that
the addition of some microelement into copper alloy
was one of effective method to improve their
comprehensive properties[5-7]. Therefore, in this paper,
we choose self-made CuTeSeFe alloy as experimental
material and measure its thermal parameter in the
temperature range of 25-400℃, it provided fixed
reference data for the application of the copper alloy.
2. Experimental
The material is annealed CuTeSeFe alloy, with the
chemical composition (mass fraction, %) of 96.70Cu,
1.62Se, 1.09Te, 0.35Fe and 0.24 others. The material
was melted in the vacuum medium frequency induction
furnace and then cast to bar, and the bar was machined
to Φ10mm×1.75 mm. After grinding by 1200# sand
paper and then the thermal diffusion coefficient(K),
heat capacity(C) and thermal conductivity(λ) were
continuous measured at 25℃, 100℃, 200℃, 300℃
and 400℃, respectively. The microstructure were
observed and analyzed by Neophot21 type optical
microscope, KYKY-2800 type scanning electron
microscope and D/MAX-rB type X-ray diffraction
(with graphite monochramator, Kα radiation).
3. Results and discussion
3.1 Microstructure
Fig. 1 shows the microstructure of the CuTeSeFe
alloy. It can be seen that as-cast microstructure consists
of irregular granular and matrix, and it can be known
from the XRD analysis (Fig. 2) that the CuTeSeFe
alloy is mainly composed of α phase (Cu solid solution)
and Cu4SeTe intermetallic compound.
Corresponding author: ZHANG Rui-jun (1962- ), male,
Ph.D., professor; research field: metallic materials. E-mail:
Zhangrj@ysu.edu.cn.
31
Study on microstructure and thermal parameters of CuTeSeFe alloy
microstructure of the CuTeSeFe alloy after treatment at
25-400℃ and that before treatment, and the XRD
analysis indicate that there is no new phase formed in
the CuTeSeFe alloy after treatment at 25-400℃. It
means that during heating process at 25-400℃, the
microstructure of the CuTeSeFe alloy has little change.
Cu
Fig. 1 Microstructures of original CuTeSeFe alloy
20000
●
●——α(Cu)
15000
Intensity /counts
2500
(a) matrix
2000
1500
Cu
1000
▲——Cu4SeTe
Fe
Cu
CPS
500
10000
●
●
Fe
Fe
0
0
5000
●
Cu
Fe
keV
5
10
15
Energy/keV
●
▲
0
Cu
Cu
600
40
60
80
100
(b) granular
2θ/(º)
Fig. 2 X-ray diffraction pattern of original CuTeSeFe alloy
EDS analysis (Fig. 3) shows that the matrix is
mainly consist of Cu and Fe, and irregular granular is
compose of Cu, Se and Te (Table 1). It can be
concluded that the matrix is α phase, and irregular
granular is CuSeTe intermetallic compound (Such as
Cu4SeTe). From metallographic analysis, it can be also
observed that there is no difference between the
500
Intensity /counts
-5000
20
400
300
Se
Te
200
Cu
Se
100
Se
Te
Cu
Se
0
0
5
10
keV
15
Energy/keV
Fig. 3 EDS spectra of the CuTeSeFe alloy
Table 1 Data of EDS analysis (mass fraction, %)
Phase
Matrix
Granular
Cu
99.51-99.65
65.23-73.05
Fe
0.27-0.34
/
3.2 Thermal parameters
Fig. 4 shows the effect of heating temperature on
the thermal diffusivity coefficient of the CuTeSeFe
alloy. It can be seen that the thermal diffusivity
coefficient of the CuTeSeFe alloy decreases with
increasing temperature, and when temperature is
increased from 25℃ to 400℃, the thermal diffusivity
32
Se
/
14.18-17.72
Te
/
12.69-14.97
Others
0.16-0.21
/
coefficient is decreased from 0.8148 cm2.sec-1 to
0.6846 cm2.sec-1. Furthermore, the thermal diffusivity
coefficient at temperature from 25℃ to 200℃
decreases more greatly than that at temperature from
200℃ to 400℃. According to experimental data,
equation between the thermal diffusivity coefficient
Study on microstructure and thermal parameters of CuTeSeFe alloy
2.0
(K) and temperature (t) were gained as follows by
unitary linearity regression.
10
●—λ
1.6
8
0.84
K/cm2.sec-1
0.80
0.76
0.72
6
0.8
4
0.4
2
0.0
0.68
0.64
1.2
0
90
180
270
360
λ/W.cm-1.k-1
C/J.g-1.k-1
■—C
0
450
T/℃
0
100
200
300
400
500
Fig. 5 Relationship between the thermal capacity
or thermal conductivityof CuTeSeFe alloy
and heating temperature
T/℃
Fig. 4 Relationship between the thermal diffusivity
coefficient of CuTeSeFe alloy and heating temperature
K =-0.0005t+0.8298, t: 25-200℃;
K =-0.0002t+0.7641, t: 200-400℃.
Fig. 5 shows the relationship of the thermal
capacity or thermal conductivity of CuTeSeFe alloy
versus heating temperature. From Fig. 5, it can be
found that the thermal capacity and thermal
conductivity of the CuTeSeFe alloy show fluctuation
with a small fluctuation margin at 25-400℃, the
thermal conductivity and heat capacity varies from
0.7747 J.g-1.k- to 0.8899 J.g-1.k-1 and from 5.497
W.cm-1.k-1 to 5.898 W.cm-1.k-1 respectively in the
temperature range of 25-400℃. As a result, when
temperatures are 300℃ and 100℃, the highest value
and the lowest value of thermal capacity of the
CuTeSeFe alloy are 0.8899 g-1.k-1 and 0.7747 g-1.k-1,
respectively, and a difference of about 14.87 ％ in
thermal capacity between the highest value and the
lowest value. For the thermal conductivity of the
CuTeSeFe alloy, when temperatures are 25℃ and
200℃, the highest value and the lowest value of
thermal conductivity are 5.898 W.cm-1.k-1 and 5.497
W.cm-1.k-1, respectively, and a difference of about 6.79
％ in thermal conductivity between the highest value
and the lowest value,
3.3 Discussion
In general, in the process of the heat transfer, free
electron and phonon knock atom and molecule.
Meanwhile, the scattering of free electrons and
phonons are aggravated caused by interface and all
kinds of defects, resulting in thermal resistance
forms[8]. Therefore, the more integrated the metal
crystal is, the less of the defects of crystal distortion
and grain boundary caused by inhomogeneous atom,
the more easily electron passes, the better the thermal
conductivity of the metal. With the increase of the
heating temperature, on the one hand, the movement of
the atoms was speed up, the number of the collision
between the atoms was increased, heat vibrancy of the
crystal lattice was speed up, and the crystal defect was
manifold. In that case, the dispersion to the moving
electrons will be increased, the movement of the free
electron in the matrix will be restrained, and the heat
diffused coefficient of the atoms will be decreased,
thus, the thermal conductivity of the alloy was
decreased, while on the other hand, due to the increase
of the heating temperature, the internal stress in the
as-cast sample was cleared up, it is to say, that the
thermal wasting was eliminated[9], resulting in the
thermal conductivity of the alloy increases. Summing
up the function of the two above-mentioned aspects,
the thermal conductivity of the alloy may be fluctuated
with the increase of the temperature.
33
Study on microstructure and thermal parameters of CuTeSeFe alloy
The conduction of the CuTeSeFe alloy consisted
of the conduction of Cu matrix and irregular granular
intermetallic compound, the conduction of Cu matrix
was mainly depended on the free electron, and the
conduction of irregular granular intermetallic
compound was mainly depended on the free phonon[10].
Because Se and Te almost didn’t solid solution with
Cu, only formed a compound with higher melting
point, it could be confirmed that Se and Te didn’t affect
the microstructure of the CuTeSeFe alloy during the
heating in the experimental temperature range. Thus,
Se and Te affected very little to the thermal
conductivity of the alloy during the experiment
process, and the conduction of the Cu matrix played a
main role in the thermal conductivity change of the
CuTeSeFe alloy.
4. Conclusions
(1) The microstructure of the CuTeSeFe alloy is
consisted of α(Cu) solid solution and irregular granular
CuSe(Te) intermetallic compound.
(2) The thermal diffusion of the CuTeSeFe alloy
decreases with increasing heating temperature, in the
temperature ranges of 25-200℃ and 200-400℃, and
the relationship between thermal diffusion (K) and
temperature (t) can be explained as K=-0.0005t+0.8298
and K=-0.0002t+0.7641, respectively, The thermal
capacity and thermal conductivity of the CuTeSeFe
alloy show fluctuation with a small fluctuation margin
at 25-400℃.
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(Edited by Tsyung and Emily)