Materials Sciences and Applications, 2010, 1, 310-316
doi:10.4236/msa.2010.15045 Published Online November 2010 (
Copyright © 2010 SciRes. MSA
Experimental Investigation on the Effect of
Reinforcement Particles on the Forgeability and
the Mechanical Properties of Aluminum Metal
Matrix Composites
S. Das, R. Behera, A. Datta, G. Majumdar, B. Oraon, G. Sutradhar*
Jadavpur University, Kolkata, West Bengal, India.
Received September 13th, 2010; revised November 1st, 2010; accepted November 6th, 2010.
The wide choice of materials, today’s engineers are posed with a big challenge for the right selection of a material and
as well as the right selection of a manufacturing process for an application. Aluminium Metal Matrix Composites is a
relatively new material among all the engineering materials. It has proved its position in automobile, aerospace, and
many other engineering applications due its wear resistance properties and due to its substantial hardness. One of the
most important criteria is forgeability by which the workability of the material can be determined. The nature of distri-
bution of reinforcing phase in the matrix greatly influenced the properties of Aluminum Metal Matrix Composites. The
forgeability of Aluminum Metal Matrix Composites, which are produced by powder metallurgy method, are greatly
depends on the size and percentage of reinforcement materials, compacting load, sintering temperature and soaking
time etc. In this present work, the forgeability of Aluminum Metal Matrix Composites reinforced with silicon carbide
(400 meshes) has investigated. A comparison have been made with different types of Aluminum Silicon Carbide Metal
Matrix Composite materials contains 0%5%,10%,15%&20% by weight of silicon carbide. The mechanical properties
like hardness of the different composites have also investigated. It is observed that the forgeabilty of the composites
decreases with increasing the wt% of SiC but the mechanical properties like hardness enhanced on increasing the wt%
of SiC.
Keywords: Aluminium Metal Matrix Composites, Sic, Forgeabilty, Mechanical Properties
1. Introduction
Particle reinforced aluminium matrix composites (MMCs)
have developed in the last few years, in order to reduce
the weight of components in structural applications and
to improve their mechanical properties and physical
properties. Metal matrix composites are a class of mate-
rial with the ability to blend the properties of ceramics
(high strength and high modulus) with those of metals or
alloys (ductility and toughness) to produce significant
improvements in the mechanical performance of the
composites over those of the monolithic metals or alloys
[1]. During the past two decades, a lot of research has
been devoted to controlling the size, shape, morphology,
and distribution of the grains in ceramics, in order to im-
prove the mechanical properties [2]. Metal-matrix com-
posites have been emerged as potential alternatives to
conventional alloys in high-strength and stiffness appli-
cations. Cost is the key factor for their wider application
in modern industry, although potential benefits in weight
saving, and increase component life, and improved recy-
clability is a vital factor [3,4]. The ever-increasing fuel
price has led to a renewed urgency of weight reduction in
the aerospace and automotive sectors. In recent years,
stringent requirements of material quality in automotive
and aerospace industries have necessitated the develop-
ment of lightweight aluminum alloys. Reinforcing of
aluminum alloys with discontinuous second phase parti-
cles offers high strength, high modulus, superior wear
resistance, good workability, desirable thermal expansion
and isotropy [5-9]. Al–SiCp composites meet most of the
requirements of automotive, electrical and aerospace
industry [10-13]. A wide range of production techniques
Experimental Investigation on the Effect of Reinforcement Particles on the Forgeability and the Mechanical Properties
of Aluminum Metal Matrix Composites
Copyright © 2010 SciRes. MSA
have developed for aluminum matrix composites. Metal
matrix composites have generally produced, either by
liquid metallurgy or powder metallurgy route. Of these
processes, forging is of high technical and economic in-
terest because it avoids problems such as the need for
special tools (expensive diamond-tipped inserts) during
machining, poor mechanical properties because of reac-
tions between some ceramic reinforcements and molten
metal in casting, and the porosity in P/M components. In
the liquid metallurgy, the particulate phases have me-
chanically dispersed in the liquid before solidification of
the melt. Among others, however, the powder metallurgy
(P/M) method has known as a very promising route,
which is most attractive due to several reasons. Firstly, in
P/M technique microstructural control of the phases is
possible (Figure 1). Secondly, the lower temperatures
employed during the process accounts for the strict con-
trol of interphase kinetics. In the P/M method, the start-
ing powders can be elemental or prealloyed. However, it
is difficult to take advantage of both these requirements
because they are prone to cause an inhomogeneous dis-
tribution. Poor distribution of reinforcement degrades the
composites in terms of its physical and mechanical prop-
erties and negates the attractiveness of reinforcement
additions. Using elemental powders are not only eco-
nomical, but also bring an extra advantage to modify the
matrix composition easily [14-17]. The presence of SiC
particles accelerated the aging process due to the in-
creased dislocation density, which provides more sites
for the nucleation of precipitates. Metal matrix compos-
ites reinforced by ceramic particles, with low density,
high strength and modulus and flexible fabricating tech-
niques, have received particular attention in the past
decades. Meanwhile, the particular preparation tech-
niques of the composites rely on these factors [18-20].
Fracture of the matrix between the clusters of reinforcing
particles, coupled with particle failure by cracking and
Figure 1. Various steps involved in synthesis of Al-SiCp
composites in P/M technique.
decohesion at the matrix/particle interfaces allows the
microscopic cracks to grow rapidly and link resulting in
macroscopic failure and resultant low tensile ductility.
However, little scientific evidence is available on the
forgeability P/M metal matrix composites. The present
paper explains the forgeability and mechanical properties
of P/M MMCs at different weight fraction of SiCp. The
forging conditions have chosen to be similar to those
necessary for mass production, and so a mechanical press
has used. In addition, the mechanical properties of the
unworked materials have also investigated because of
these. In the present study, the nature of changing density,
hardness and forgeability of Al-SiCp MMCs with chang-
ing of wt% of SiCp has been investigated.
2. Composite Production
2.1. Material
Air atomized aluminium powder (average particle size of
400 mesh) reinforced with SiC particulates (Figure 2)
(average size of 400 mesh) are used as the test material
along with commercially pure aluminium. Aluminium
matrix composites having 5, 10, 15 and 20 wt% fraction
of SiC particles were used as the test material along with
commercially pure aluminium. The above composites
and aluminium has fabricated by powder metallurgy
2.2. Blending
The metal and ceramic powders were blended in a drum
with a cylindrical mixer (diameter 40 mm, height 35
mm), at a constant speed of 1500 rpm for 1h. Blending is
one of the crucial processes in P/M where the metallic
powders have mixed with the ceramic reinforced parti-
cles. Good blending produces no agglomeration of both
the metallic and ceramic particle powders. To achieve
this, several parameters such as particle size, blending
speed and duration have taken into consideration to en-
sure the SiC particles distributing homogeneously in the
matrix powders. The powder blending parameters have
listed in listed in Table 1.
Figure 2. A schematic view of the evolution of distribution
of the SiC particulates in Al matrix.
Experimental Investigation on the Effect of Reinforcement Particles on the Forgeability and the Mechanical Properties
of Aluminum Metal Matrix Composites
Copyright © 2010 SciRes. MSA
Table 1. Powder blending parameters.
Mixture Filling of
mixer(vol.%) Operation R.P.M Time(min)
50 Blending 1500 10
75 Blending 1500 10
100 Blending 1500 10
Rest 15
400mesh pure
SiC and
Binder (Zinc
Stearate) Blending 1500 15
2.3. Compacting
A mixture of the particles and the binder (Zinc Stearate)
has poured into a cylindrical die with 110 mm high, 25
mm inner diameter and 75 mm outer diameter. After
pouring, the powder mixture was cold isopressed at 215
Kgf pressure with a hydraulic press (Manual Type, Ca-
pacity 800 Kgf. Ram stroke 300 mm.) for 5 min to obtain
green compacts. The hydraulic press and metallic die
with it’s punch are shown in Figures 3 and 4.
Figure3. Manual type hydraulic press.
Figure 4. Metallic die with punch.
2.4. Sintering
The green compacts are then subsequently baked at
300˚C and followed by sintering in a induction type floor
stand tube vacuum furnace (Figure 5) (dia of hot zone 75
mm length of hot zone 150 mm and maximum temp
1450˚C ). During processing, the matrix powders have
exposed to atmosphere, which contains oxygen and
moisture also, and it would oxidize at high temperature.
Moreover, the moisture would react chemically with the
oxide, and such reaction would reduce the bonding force
of Al-SiCp interface and further deteriorate the mechanical
properties of the composites. Thus, the degassing should
carry out in an environment of elevated temperatures and
high vacuum, where the dew point and the oxygen partial
pressure are low. The adsorbed compounds will evacuate
and further oxidation can suppressed effectively.
To avoid the oxidation of Al alloy powders at high
temperature and to abbreviate the preparation procedures,
the degassing and sintering procedures of the green
compacts have incorporated together. The stepped heat-
ing procedures of the degassing and sintering has intro-
duced into the experiment. The sintering parameters have
given in the Table 2
At the low temperature stages, the atmosphere and
moisture could extract out, while the crystallized water
would evaporate during sintering at the high temperature
stages. The sintering at a normal pressure usually has a
little influence on the Al-SiCp interfacial cohesion due to
the presence of an oxide layer on the Al powder surfaces.
Therefore, an advanced sintering has carried out at the
elevated temperature and high pressure to get the better
interfacial cohesion. As it is well known, the matrix alloy
will react with SiC particles or the interfacial layer will
become thicker at over-elevated temperatures because of
the intense atomic diffusion, and the matrix will lose its
strength at high temperatures, a suitable temperature for
the high pressure sintering should selected in this process.
3. Results and Discussion
3.1. Micro structural Examination and Phase
The samples (Figures 6 and 7) have prepared and examined
Table 2. Sintering parameters.
Operation From To
Heating Ambient (30˚C) 300˚C 40 min
Soaking 300˚C 300˚C 30 min
Heating 300˚C 500˚C 30 min
Soaking 500˚C 500˚C 30 min
Heating 500˚C 750˚C 30 min
Soaking 750˚C 750˚C 40 min
Cooling in furnace 750˚C Ambient (30˚C)
Experimental Investigation on the Effect of Reinforcement Particles on the Forgeability and the Mechanical Properties
of Aluminum Metal Matrix Composites
Copyright © 2010 SciRes. MSA
Figure 5.Induction type floor stand tube vacuum furnace.
Figure 6. Sample before sintering.
Figure 7. Sample after sintering.
by an optical microscopy. Samples for metallographic
examination has prepared by grinding through 320, 400,
600, 800, 1200 and 1500 grit papers followed by polish-
ing with 6-µm
diamond paste. Then the samples have etched with the
etchant (2.5 ml Nitric acid, 15.0 ml Hcl, 1.0 ml HF and
95.0 ml Water). The etched samples were dried and the
microstructure observed by using microscope (Olympus,
CK40M) at different magnification.
Figures 8-12(A) and (B) shows the fractograph and
metallograph of the cold isopressed green compacts and
followed by sintered Al-SiCp composites. So far, it indi-
cates that the plastic deformation is beneficial to improve
the homogeneity of the reinforcement. The presence of
SiC particles can be detrimental to the ultimate compres-
sive strength of the composite materials because of the
addition to the possible failure mechanisms of unrein-
forced aluminum alloy of particle cracking, particle ma-
Figure 8. A&B optical micrographs of the metal matrix
composites pure Al.
Figure 9. A&B Optical micrographs of the metal matrix composites
Al&5 wt% SiC.
Experimental Investigation on the Effect of Reinforcement Particles on the Forgeability and the Mechanical Properties
of Aluminum Metal Matrix Composites
Copyright © 2010 SciRes. MSA
Figure 10. A&B Optical micrographs of the metal matrix
composites Al&10-wt%SiC.
Figure 11. A&B Optical micrographs of the metal matrix
composites Al &15wt%SiC.
Figure 12. A&B Optical micrographs of the metal matrix
composites Al&20wt%SiC.
trix debonding and particle agglomerate decohesion. The
latter two mechanisms are of secondary importance when
the particles are well distributed and strongly bonded.
Particles enhance the relative density of the materials and
refine the metal matrix grains, which consequentially
result in the increase of mechanical properties of the
3.2. Mechanical Properties
3.2.1. Density Measurement
The density of the composites was obtained by the Ar-
chimedian principle of weighing the sample first in air
and then in water. Then, theoretical density of composite
and its alloy has calculated from the chemical analysis
data. The measured relative density of the compacts was
about 81.2%. The gain refinement of metal matrix-based
composites reinforced by tough particles can interpret by
the increased effective extrusion ratio with increasing
volume fraction of incompressible reinforcements. The
density of the composites has shown in Figure 13. Since
the density of SiC (3.215 gm/cm³) is higher than that of
the Aluminium (2.7 gm/cm³), the addition of SiC leads to
an increase in the density of the material as long as the
reinforcements are uniformly distributed in the matrix
and no SiC clusters are formed. Reinforcement concen-
Density vs Weight % of SiC
0 102030
Weight % of SiC
Density gm /
Figure 13. Relation between density and wt% of SiC in
Al-SiCp composites.
Experimental Investigation on the Effect of Reinforcement Particles on the Forgeability and the Mechanical Properties
of Aluminum Metal Matrix Composites
Copyright © 2010 SciRes. MSA
trations of about 5–10 wt.% of SiC and 10–15 wt.% of
SiC, leading to a decrease in the density despite the in-
crease in the SiC content in the composite
3.2.2. Hardness Measurement:
The hardness of the composites and matrix alloy has
measured after polishing to a 6-µm finish. In composites,
hardness increases proportionally by increasing the
weight percentage of reinforcement particle. The Figure
14 shows that, hardness value changed due to variation
of reinforcement ratio. Hardness of composites increases
proportionally with the increase of the weight percentage
of reinforcement particle.
Hardness vs Weight % of SiC
Weight % of SiC
Hardness in BHN
Figure 14. Relation between hardness and wt% of SiCp in
Al-SiC composites.
Figure 15. Forgeability test.
Figure 16. Photographs showing perform of before and
after deformation test.
4. Forgeability and Fracture Characteristics
The limit of forgeability is expressed as the critical re-
duction in height % crit, by the following equation [21]:
%Cirt H
where (HO) is the initial height of the sample and Initial
diameter is (DO ) in mm. After each interval of loading
dimensional changes in the specimen such as (HF) is the
final height of the sample in mm after deformation top
contact diameter (DTC), bottom contact diameter (DBC),
bulged diameter (DB).
Critical reductions under unlubricated conditions only
have compared to assess the forgeability of the experimen-
tal materials. The impact load was applied at room tem-
perature on samples of different section of as cast MMCs
reinforced with 5wt%, 10wt%, 15wt% and 20 wt%SiC.
At different load, the percentage of deformation inves-
tigated. These results have presented in Figure 17.
Thus, it is particle cracking that has a major influence
on the ultimate compressive strength of Al/SiCp com-
posite materials. The Figure 17 shows that on increasing
the weight percentage of silicon carbide particles in cast
composites the percentage of deformation decreases that
means the forgeability of cast composites decreases on
increasing the reinforcement ratios.
5. Conclusions
In this study, density, hardness, forgeability characteris-
tics of Aluminum reinforced with 5, 10, 15 and 20 wt.%
of SiC was examined .The effect of SiC reinforcement
ratio on the hardness and the forgeability of Al-SiCp
MMCs has been evaluated.
The microstructural study indicates that there is
uniform distribution of SiC in the metal matrix compos-
About 5–10 wt.% of SiC and 10–15 wt.% of SiC,
Load vs Deformation
0 102030
% of Deformation
Load in Kgf
Pure Al
5 w t% SiC
10 wt% SiC
15 wt% SiC
20 wt% SiC
Figure 17. Relation between load and % of deformation of
Al-SiCp composites.
Before deformation
After deformation Cracks
Experimental Investigation on the Effect of Reinforcement Particles on the Forgeability and the Mechanical Properties
of Aluminum Metal Matrix Composites
Copyright © 2010 SciRes. MSA
leading to a decrease in the density despite the increase
in the SiC content in the composite
Hardness increases with the increase of weight % of
SiC in the metal matrix composite.
Forgeability of metal matrix composite is remarka-
bly decreases with increase of weight % of SiC in metal
matrix composite.
6. Acknowledgements
Authors thankfully acknowledge the financial support pro-
vided by U.G.C, New Delhi under Major Research Project
Grant [F.No.–32-88/2006 (SR) dated 09.03.2007] without
which this work could not be attempted.
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