2.2 with the increase of SiC content. In addition,

2.2             
Aluminum Metal Matrix
Composite Reinforced with Silicon Carbide Particles (Al-SiCp)

SiCp
are one of the most used types of reinforcement to reinforce Aluminum (Al)
alloy in order to produce composite materials that have the desired properties.
SiC enhances the tensile strength, hardness, density and wear resistance of Al
alloy (Murty S. V. S. N. et al., 2003;  Iqbal
A. A.; 2016).

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T.
Ozben (2008) found that the increase in the ratio of SiCp in Al-SiCp composites
enhance the tensile strength, hardness and density whereas the impact toughness
decreased. In addition, particles clustering, particle cracking and weak
matrix-reinforcement bonding are the factors affecting the impact behavior of
SiC (Ozden S. et al., 2007; Iqbal A. A.; 2016).

P.
Zhang and L. Fuguo (2010) studied the impact of reinforcement particles agglomeration
on the flow behavior of SiCp reinforced AMMCs. They concluded that the particle
agglomeration has greater effects on the mechanical response of the matrix
during the tensile deformation compared to the elastic response. They also revealed
that the agglomeration region has higher number of fractured particles compared
to the particle random distribution region (Zhang P., & Fuguo L., 2010;
Iqbal A. A.; 2016).

K.
L. Meena et al. (2013) have studied the impact of SiCp volume in the Al-SiCp
composites. The study used 5%, 10%, 15% and 20% by weight of SiC to investigate
tensile strength, hardness, density and impact strength. In addition the study
found that all of these properties increase with the increase in the weight
percentage of SiCp.

Furthermore,
Srinivasa K. et al. (2014) fabricate Al LM6-SiCp composites using stir casting
method. They fabricated Al LM-6-SiCp with varying composition of 0%, 5%, 10%
and 15% by weight of SiC. They concluded that as the ratio of SiC content
increase the hardness of Al LM6-SiCp composite increases. However the wear
resistance decreases gradually with the increase of SiC content.

 In addition, N. S. Kalyankar et al. (2016) did
a study that was focusing on the change in the mechanical properties of Al LM25-SiCp
composites and fabricated by stir casting method. Al LM25 matrix material was reinforced
with 10%, 15% and 20% by weight of SiC. They found that wear resistance of the
fabricated composite increased with increasing SiC weight percentage and
hardness decreased with SiC content. Also they concluded that the tensile
strength, yield strength and percentage of elongation increased with the
increase in the weight percentage of SiC.

Different
studies have been conducted to study and understand the fatigue and fracture
behavior of Al-SiCp composites. A. A. Iqbal et al. found in two separate
studies on the hybrid AMMCs that the particle-matrix interface is the place
where the fatigue damage initiates. They also concluded that the fatigue damage
propagates by the particle fracture and interface de-bonding (Iqbal A. A.  et al., 2003; Iqbal A. A.  et al., 2004).  

G.G.
Hosamani et al. (2016) investigated the wear characteristics, microstructure
and the mechanical properties of SiC reinforced AMMCs. They fabricated AMMCs
with 0, 3, and 7 weight % of SiC content by stir casting process. They experimentally
concluded that the addition of SiC reinforcements in Al matrix increased wear
resistance, tensile strength and compressive strength. The maximum weight
percentage of SiC reinforcement at which the fabricated AMMCs showed maximum
wear resistance, tensile strength and compressive strength was 7%. They also
found from the microstructure analysis that clustering and non-homogeneous
distribution of SiC particles. They attributed this to the improper time given
for contact between SiC particle and Al matrix and the poor wetting of SiC
particle in molten Al.

2.3             
Aluminum Metal Matrix Composite
Reinforced with Aluminum Oxide Particles (Al-

p)

Al2O3p
are another type of reinforcement that is added to Aluminum (Al) alloy to
produce composite materials. It has strong ionic inter atomic bonding force
which help to enhance and increase the compressive strength and wear resistance
of the Aluminum alloy to which is added to as a reinforcement (Iqbal A. A.;
2016).

G.
Abouelmagd (2004) fabricated AMMC with Al2O3 reinforcement
by powder metallurgy in order to investigate the hot deformation and wear
resistance. He concluded that the hardness and compressive strength increased with
the addition of Al2O3 increased.

B.
G. Park et al. (2016) developed AMMCs samples that were reinforced with Al2O3.
The volume fraction of Al2O3 was varied from 5 to 10%.
They found that the fracture toughness of the AMMC decreased with the increase
in volume fraction of Al2O3. The reason was attributed to
the decrease in inter-particle spacing between nucleated micro voids (Park B.
G. et al., 2008; Iqbal A. A.; 2016).

Furthermore,
the elastic modulus and the tensile strength of Al-Al2O3 composite
increase when compared to Al alloy without reinforcement. Whereas the
elongation to fracture of Al- Al2O3  composite decreases when compared to
unreinforced Al alloy (Ceschini L. et al., 2006; A. A. Iqbal; 2016).

2.4             
Aluminum Oxide Reinforced AMMC
(Al-Al2O3p) and Silicon Carbide Reinforced AMMC (Al-SiCp) – Comparison

Different studies were conducted to
compare between the properties of Al- Al2O3p composites
and Al-SiCp composites. G. B. V. Kumar et al. (2010) and D. Sujan et al. (2012)
conducted two separated studies to compare between Al-SiCp composite and Al- Al2O3p
composites. In both investigations, the composites were reinforced with varying
content ratios of SiCp and Al2O3p. Both studies found
that the density of Al- Al2O3p composites were higher
that the density of Al-SiCp composites. They also concluded that Al-SiCp
composites had better wear resistance and tensile strength compared with Al-Al2O3
and the wear rate decrease with the increase in the content ratio of the
reinforcement in both Al-SiCp and Al-Al2O3p. In addition,
both studies found from SEM that the reinforcement particles are distributed
uniformly (Kumar G. B. V.  et al., 2010;
Sujan D. et al., 2012).

J. Lakshmipathy and B. Kulendran (2014)
studied the wear behavior, hardness and impact strength of Al7075-SiCp and
Al6061- Al2O3 composites. They used stir casting method
to fabricate the AMMCs with varying weight percentage of SiC and Al2O3
(10, 15, 20%). The experimental results showed that the hardness increases with
the increase in the weight percentage of the reinforcement. However, Al7075-SiCp
composites showed higher hardness than Al6061-Al2O3. They
also found that the wear resistance of Al7075-SiCp is better than the wear
resistance of Al6061-Al2O3. They analyzed that the
hardness and wear resistance increased with increasing the weight % of SiC and Al2O3
content. The study also concluded that the brittle property of the material
increases when the hardness increases which caused reduction of the impact
strength of the composites in both Al7075-SiCp and Al6061-Al2O3.
The impact strength of both Al7075-SiCp and Al6061-Al2O3
decreased with the weight percentage of the reinforcements.

 S. Dhanasekaran et al. (2016) carried out a
study to investigate the effects of different volume fractions of SiC and Al2O3
particles reinforcement on Al-SiCp composite and Al-Al2O3p
composites respectively on tensile strength, yield strength and hardness. In
contracts to base alloy (unreinforced alloy), tensile strength and yield
strength of 20% SiC reinforced composites increased by 16 % whereas 10 % Al2O3
reinforced composites showed 19 % increase in tensile strength and yield strength.
They also found that the main mechanism enhancing the mechanical properties of
Al-SiCp and Al-Al2O3p composites are dislocation density,
precipitation hardening and changes in grain size. Furthermore, it was found
that Al-20%SiCp and Al-10% Al2O3 composites are the
optimized composites for clutch pressure/face plate application.

2.5             
Hybrid Aluminum Metal Matrix
Composite

Hybrid Aluminum Metal Matrix Composites
(HAMMCs) are one of the newly developed type of MMCs. In contrast with AMMCs
with single reinforcement, it is being developed and recognized as material
that offers further optimized properties with potential of lower production
cost. HAMMCs can be classified in three types based on the combinations of
reinforcement used to reinforce HAMMCs. The three types are HAMMCs with two
synthetic ceramic reinforcements (SiC, Al2O3, B4C,
Gr), HAMMCs with synthetic ceramic and industrial waste as reinforcements (Fly
Ash, Red Mud) and HAMMCs with synthetic ceramic and agro waste derivatives as
reinforcements (Bodunrin M. O. et al., 2015). 

Different studies were done to study and
understand the microstructure mechanical properties of HAMMCs that are
reinforced with synthetic ceramic such as SiC, Al2O3, B4C
and Gr. For instance, AMMCs that are reinforced with SiC or Al2O3
have shown enhance strength and specific stiffness. However, this enhancement
is in the expense of ductility and fracture toughness. So, this made it necessary
to add reinforcement to AMMCs that are reinforced with single reinforcement
(Alaneme K. K. & Aluko A. O., 2012; Bhandakkar A., 2012; Alaneme K. K. &
M. O. Bodunrin M. O., 2013; Bodunrin M. O. et al., 2015). 

B. V. Ramnath et al. (2015) studied the
microstructure and mechanical properties of HAMMCs that was reinforced with Al2O3
and B4C and compared it with unreinforced Al alloy. They found that
HAMMCs exhibited better hardness and impact strength in comparison with
unreinforced Al alloy. On the other hand, he found that Al-Al2O3-B4C
HAMMCs slightly lower tensile strength and much better flexural properties than
the unreinforced Al alloy. In addition, the microstructure analysis showed an
acceptable distribution of the reinforcements in the matrix (Ramnath B. V. et
al., 2013; Bodunrin M. O. et al., 2015).

A. Deravaju et al. (2013) investigated
the wear resistance properties of two types of HAMMCs. They studied Al-SiC-Gr
HAMMC and Al-SiC-Al2O3 HAMMC that were fabricated by using
friction stir process. They found a uniform distribution of the reinforcement particles
in the nugget zone of both types of HAMMCs. In addition, the study reviled that
the HAMMCs have much better hardness and wear resistance in comparison with Al
alloy. Figure 2.5 shows the change in wear rate with sliding distance of
Al-SiC-Gr and Al-SiC-Al2O3 surface HAMMC. It can be seen that
Al-SiC-Gr HAMMC had lower hardness than that of Al-SiC-Al2O3
HAMMC. They attributed this to the combined pinning effect of SiC and Al2O3
and the higher hardness of Al2O3 than that of Gr. On the
other hand, Al-SiC-Al2O3 HAMMCs had lower wear resistance
in comparison with Al-SiC-Gr since Gr exhibits higher solid lubricating effect
than Al2O3 (A. Deravaju et al., 2013; M. O. Bodunrin et
al., 2015). The main reasons for the superior wear resistance of HAMMCs in
comparison with the unreinforced Al alloys were the load bearing capacity of
the SiC and the solid lubricating effect of Al2O3. (E. R.
I. Mahmoud et al., 2010; S. C. Tjong et al., 1999; M. O. Bodunrin et al., 2015).
Furthermore, the load bearing capacities and pinning effect of the hard ceramic
particulates and the solid lubricating effect are the main reasons of
improvement of tensile strength and hardness of HAMMCs (Bodunrin M. O. et al.,
2015).

A. Mali and S. A. Sonawane (2014)
conducted review on the effect of hybrid reinforcement on the mechanical
properties of AMMC. They found that tensile strength, yield strength and
hardness of HAMMCs are superior of those for the single reinforced AMMCs and
increasing with the increase in content ratio of the reinforcement. However,
the elongation decreased with the increase in the increase in content ratio of
the reinforcement. They also concluded from the optical micrographs that the
reinforcement particles are uniformly distributed in the Al matrix.

M. V. Achutha et al. (2014) fabricated
Al LM25-SiC-Gr HAMMC by gravity die casting technique to investigate its the
fatigue life. They concluded that Al LM25-SiC-Gr HAMMC has improved and longer
fatigue life.

K. Umanath et al. (2014) did a study to
investigate the dry sliding wear behavior of HAMMC that was reinforced with
SiCp and Al2O3p. They found that as the volume content of
SiCp and Al2O3p reinforcements increase the wear rate and
scratches width decrease whereas the hardness and scratches width increase.

Figure
2.5 Change
in wear rate with sliding distance of Al-SiC-Gr and Al-SiC-Al2O3
surface HAMMC. (Park S. J., & Seo M. K., 2011).