NOTES
[
1ü4]
interfacial reaction
meters; for example, the control of fabrication temper-
. ξ) Control of processing para-
Interfacial reaction between
the oxidized SiC particles and
Al-Mg alloys
ature and holding time can limit the extent of the
[
5]
interfacial reaction and affect the reaction dynamics . ο)
Reinforcement surface modification; for instance, coating,
electroplating or passive oxidation have been successful to
some extent in preventing the deleterious interfacial
1
SHI Zhongliang , GU Mingyuan , LIU Junyou ,
1
2
[
6,7]
2
3
LIU Guoquan , LEE Jae-chul , ZHANG Di
1
reaction and enhancing the materials wettabilities . The
passive oxidation of SiC particles is known as one of the
most simple and easy approaches. However, the matrix of
aluminum-based composites consists of not only alumi-
num itself but also the reactive element Mg, such as 2xxx
and 6xxx Al alloys series. Mg is prone to react with oxi-
1
&
WU Renjie
1
2
3
. State Key Lab of Metal Matrix Composites, Shanghai Jiao Tong Uni-
versity, Shanghai 200030, China;
. School of Materials Science and Engineering, University of Science
and Technology Beijing, Beijing 100083, China;
. Division of Materials Science and Engineering, Korea Institute of
Sciecne and Technology, P. O. Box 131, Cheongryang, Seoul, Korea
[
8]
2
dized layer SiO at surface of SiC particles. Zhong et al.
characterized the interfacial reaction products of oxi-
dized-SiCp/Al-Mg (5083Al) composite by X-ray diffrac-
tion and TEM, from which the crystal boundaries of the
MgO (or MgAl O ) reaction products were believed to be
Correspondence should be addressed to Shi Zhongliang or Gu Mingyuan
e-mail: zlshi325@hotmail.com, mygu@mail.sjtu.edu.cn)
(
Abstract The interfacial reactions of oxidized SiC parti-
cles reinforced Al-Mg matrix composites were investigated
by the field emission-scanning electron microscopy (FE-
SEM), TEM and X-ray diffraction. It was found that the
nanoscale MgO forms initially due to the interfacial reaction,
then whether it reacts with molten Al continuously or not
depends on the content of Mg in the matrix and its covering
densification at the surface of particles. When there is not
enough Mg in the matrix for the formation of dense MgO
2
4
the diffusion channels during the interfacial reaction. Gu
[
12]
et al. found a concentration of aluminum within the
interface of oxidized SiC by parallel electron energy loss
spectrometer (PEELS), the result indicated that the reac-
tion between the oxidized layer of SiC particles and pure
aluminum could take place. There are a few of reports on
the interfacial characteristics and their corresponding re-
action products in oxidized SiCp/Al-Mg matrix compo-
layer, MgO will transform into MgAl
continuous reaction with SiO and molten Al. When dense
2 4
O crystal owing to the
[
8ü15]
2
sites
. However, from the available reports it is not
MgO layer forms at the surface of the particles due to the
affluence of Mg for the initial reaction, it will protect the
inner SiC from the attack of molten Al. However, the reac-
clear how the interfacial reaction takes place in the oxi-
dized-SiCp/Al-Mg composite systematically, as their re-
action routes are important to the composite engineering
application. The purposes of the present work are to char-
acterize the microstructure evolution between Mg con-
tained aluminum matrix and oxidized SiC particles as
reinforcement for the composites and to illustrate the in-
terfacial reaction in order to get the significant data for the
control of the interfacial reactions by means of FE-SEM,
X-ray diffraction and TEM.
2 4
tion products of both MgO and MgAl O are thermo-stable
phases at the surface of the particles under high temperature.
The results clarify the interfacial reaction route and they are
of great value to the control of the interfacial reactions and
their interfacial design of the composites.
Keywords: oxidized SiC particle, Al-Mg matrix composite, interfa-
2 4
cial reaction, FE-SEM, nanoscale MgO, MgAl O .
SiC reinforced Al-matrix composite is one of the
materials that have been frequently studied. It has wide
potential applications. However, it is a little bit difficult to
control the interfacial reaction between SiC and Al at ele-
vated temperature during its fabrication, no matter what
kind of SiC such as fiber, whisker and particle is used as a
reinforcement substance in the Al-matrix composite. The
1
Experimental
(ν) Preparation of the composites. SiC particles
used in the study were the hexagonal D-SiC (6+) with an
average size of 5 Pm. The oxidation of SiC particles was
carried out at 1100qC for two or six hours using alumina
crucibles in an electric-resistance furnace in dry air at an
atmospheric pressure. After oxidation, these oxidized
powders were pestled, ground artificially, and sifted using
reaction product Al
ronments such as water and methanol. Meanwhile the
formation of Al will degrade the surface of the SiC and
4 3
C is an unstable phase in some envi-
4 3
C
7
0 Pm grid sifting screen at room temperature in order to
results in composites with poor mechanical properties.
Thus, three primary techniques have been adopted for
controlling the deleterious interfacial reactions as follows:
make them distribute well during the composites fabrica-
tion. In order to facilitate an easier penetration of the
molten Al-alloys (2014Al (Al-3.9%Cu-0.54%Si-0.32%-
Mg-0.56%Mn, weight percent), Al-2.0%Mg, Al-4.0%Mg
and Al-8.0%Mg) through the particles, the tool steel die
with an inner diameter of 25 mm, wall thickness of 30
mm, and length of 100 mm loaded with the particles were
ν) Utility of some aluminum alloys containing proper
silicon, such as A356, A357 and A359. On the basis of the
reaction equation 4Al + 3SiC o Al
4 3
C + 3Si, an addition
of Si into the aluminum alloy matrix can suppress the
1948
Chinese Science Bulletin Vol. 46 No. 23 December 2001