17. a review on electrical, thermal and wear behaviour of al6061 ag composite

Dogo Rangsang Research Journal UGC Care Group I Journal
ISSN : 2347-7180 Vol-10 Issue-08 No. 15 August 2020
Page | 219 Copyright @ 2020 Authors
A Review on Electrical, Thermal and Wear Behaviour of AL6061-Ag Composite
Rumaisa Farooq1
, Er. Neeraj Kumar2
1,PG SCHOLAR,DEPARTMENT OF MECHANICAL ENGINEERING, R N COLLEGE OF
ENGINEERING & TECHNOLOGY, MADLAUDA, PANIPAT
2,ASSISTANT PROFESSOR, DEPARTMENT OF MECHANICAL ENGINEERING, R N COLLEGE
OF ENGINEERING & TECHNOLOGY, MADLAUDA, PANIPAT
Email id :- rumisafarooq96@gmail.com
Abstract
The review work focuses on the mechanical, electrical and thermal behavior of cast
aluminum6061 with different content of silver, 3,6,9 & 12% by weight basis. Al6061 composite
were produced by means of stir casting. Stir casting have numerous advantages over the other
traditional production methods such as increased die life, less porosity and better mechanical
properties in addition to tribological behavior. The optical microscopy was used to study the
microstructure of Al6061 composite as well as the distribution of silver particles. The density of
cast samples were determined by using Archimedes Principle as per ASTM (B962-13) standard.
Electrical resistivity of Al6061 composite was determined by using the four point probe tester.
The thermal behavior of Al6061-Ag composite was determined by using the Differential Scanning
Calorimetry (DSC) analysis having a heat rate of 20o
C/min at nitrogen atmosphere.
Keywords:- cast Aluminum 6061, stir casting, tribology behavior, DSC.,
1. INTRODUCTION
Metals have an important role from household utensils to manufacturing applications which include chemical and
electronic industries as well as production sectors and oil fields. In the past period, the requirement of minimal cost,
better accomplishment as well as an elevated quality material has brought a transformation in research from a phase
of monolithic materials to materials, which are composites. By a composite material we mean a system of material,
which compromise of a properly sequenced joining of at least two contents, having a separating interface them, such
that in form, difference occur, as well as in chemical constituents and are effectively not capable of dissolving in
each other. Materials referred to as composites are employed to offer particular kinds of material characteristics, for
instance, their better strength as well as stiffness, resistance to friction, wear resistance, non, matching resistance to
composing, elevated electrical conductivity, thermal conductivity as well as elevated temperature mechanical
characteristic. The metal matrix composites can be grouped by fortification of constituents into fibers, particulates,
whiskers as well as wires. These fortifications are postponed in matrices of magnesium, copper, aluminum,
titanium, nickel-noted super alloys, nickel, as well as iron alloys.Aluminum metal matrix composite because of its
low cost, elevated strength-to-weight index, elevated wear resistance, is utilised in structural uses together with the
aerospace as well as the automobile industry. A method, which is cost- effective as well as simple for composite
manufacturing is necessary for increasing its use. Aluminum metal matrix composites had turned to be an industry
standard due to the benefaction in cost when weighted against the majority of other metal matrix composites.
Aluminum-rooted composites as well as provide added advantages such as, elevated shear strength, outstanding

resistance to abrasion and excellent thermal conductivity, and they can be operational in high temperature and
formed and treated using conventional equipment.
A. Aluminum metal matrix composites
In automobile manufacturing, lower weight as well as increased efficiency of engines has been acknowledged as an
immense contributor to enhanced economy of fuel with the present power trains. Evidently, this has stimulated a
growth in the employment of aluminum alloys for engines as well as chassis parts. Castings of aluminum as well as
magnesium in the automobile area have soared in the last half-a-decade to assist engineers in the design as well as
production of extra fuel -proficient cars.
The small density as well as elevated specific mechanical properties of aluminum metal matrix composites
(AMMC’s) projects these alloys as a largely appealing material option to produce lightweight components for
various vehicular kinds. Having wear resistance as well as strength identical to cast iron, as well as 67% lesser
density and three times the value of the thermal conductivity, the aluminum MMC alloys are the ultimate materials to
produce manufacture of lightweight automotive as well as other commercial components.
AMMC’s enviable characteristics are the outcome of the occurrence of little, elevated strength ceramics
particulates, fibers or whiskers that spread uniformly in the whole of the aluminum alloy matrix. The AMMC
castings compete economically competitive , having iron as well as steel castings in several situations. Nevertheless,
the occurrence of wear-resistant particulates substantially lessens the machinability of the alloys, promoting the
machining costs to be elevated because of grown tool wear. Consequently, the use of cast AMMCs to parts
necessitating a significant quantity of auxiliary machining has been in a way stifled.
B. Aluminum metal matrix composite fabrication methods
There are generally two methods employed for the fabrication of Aluminum metal matrix composites:-
a) Liquid State Fabrication Process
In general, there exist three liquid route fabrication techniques or casting routes to casting that are presently in use
for practice: the stir casting, the liquid metal infiltration method as well as the squeeze casting. Poor meltability as
well as an elevated propensity for reactions to chemicals of the fortification with the liquid (metal) are two main
issues that restricts the use of this elevated temperature procedural technique. Nevertheless, there exits several
methods applied in the control of this phenomenon. Usually, this kind of method of fabrication is conducted in the
circumstance of vacuum. Alternatively an inert gas atmosphere may be employed to lessen the liquid metal
oxidation. For the stir casting technique, incorporation of the particulates of ceramics is done in a molten matrix by
employing several methods, subsequently pressing or mixing. This is followed by casting of the final MMC. A
matrix-reinforcement strong bond is attained in this procedure through the employment of elevated temperatures, and
frequently, alloying the matrix using an interactive element with the fortification to create a moved stage that
enhances the melting occurring in-between the matrix as well as the fortification material. Variations exist in the stir
casting approaches. Two forms of variations are expressed as follows. In a variation, stirring of the liquid metal is
actualized for a complete liquid state , for instance, through the vortex approach. The second form is a state of partial
solidification with the example being the compocasting approach. For the vortex approach, the production of the
fortification is made into a vortex that is produced by stirring the liquid metal ( Balasivanahaprabu 2006).
Figure 1.1 showcases the diagram of the vortex approach from a schematic perspective.

Figure 1:- Schematic diagram of producing MMC slurry using vortex method
Squeeze infiltration is the most successful form for MMC production (Sree Manu et al. 2015). In this technique, the
molten metal is forced-infiltrated into fibre bundles or preformed, expelling all absorbed and trapped gases. This
method involves placing a preheated preform of reinforcement into a preheated die, filling the die with molten matrix
metal, squeezing the molten metal into the preform using a hydraulic press with a preheated ram, holding the
pressure during solidification, releasing the pressure and ejecting the resulting composite. Figure 1.2 shows squeeze
casting schematically.
Figure 2:- Squeeze casting process

b) Solid State Fabrication Process
Solid state processes are generally used to obtain the highest mechanical properties in MMCs, particularly in
discontinuous AMMCs. This is because segregation effects and brittle reaction product formation are at a minimum
for these processes, especially when compared with liquid state processes.
Powder Metallurgy
Powder Metallurgy (PM) is the common method for fabricating discontinuously reinforced AMMC. In this process,
after blending the matrix alloy powder with reinforcement material and binder, the resulting mixture is fed into a
mould of the desired shape. Cold isostatic pressing is utilized to obtain a green compact. The main difficulties
encountered in this process are the removal of the binder used to hold the powder particles together.
The organic binders often leave residual contamination that causes deterioration of the mechanical properties of the
composites.To ease the bonding of powder particles, the compact is heated to less than the melting point temperature
but high enough to develop significant solid state diffusion (sintering) Sometimes, it becomes necessary to maintain
the consolidation temperature slightly above the solidus to minimize deformation stress and to avoid the damage of
particles or whiskers. The consolidated composites are subsequently extruded or forged into the desired shape.
Figure 1.3 shows a schematic diagram of powder metallurgy technique (Radha et al. 2015)
Figure 3:- The flow chart of the powder metallurgy process

Spray Casting
Another method of manufacturing AMMCs are spray casting or spray deposition method. This method also can be
used on unreinforced materials. In this process, a controlled stream of molten metal is produced. The stream is
converted to a spray of molten droplets in an inert atmosphere, for example in nitrogen gas. The size of the droplets
is approximately 205-40µm in diameter. The droplets are impacted onto a collecting surface, and allowed to
coalesce. It is possible to add solid particles such as metal and ceramic to the atomised metal stream. The advantage
of this process is the short contact time between the liquid matrix and reinforcement that will reduce chemical
reactions. However, the production cost of this process is very high.
C. Electrical conductivity
Electrical conductivity is a very useful property since values are affected by such things as a substance’s chemical
composition and the stress state of crystalline structures. Therefore, electrical conductivity information can be used
for measuring the purity of water, sorting materials, checking for proper heat treatment of metals, and inspecting heat
damage in some materials. It is a measure of how well a material accommodates the movement of an electric charge.
It is the ratio of the current density to the electric field strength. Its SI - derived unit is the Siemens per meter, but
conductivity values are often reported as percent International Annealed Copper Standard (IACS), which was
established by the 1913 International Electrochemical Commission.
Four-Probe Conductivity Tester
The four-probe assembly consists of four spring loaded probes arranged in a line with equal spacing between
adjacent probes. These probes rest on a metal plate on which thin slices of samples (whose resistivity is to be
determined) can be mounted by insulating their bottom surface using a mica sheet. Different colored leads are
provided for carrying current and for voltages measurements. The sample, usually, is brittle, hence the sample should
not be mounted. This assembly is mounted on the lid of an oven so that the four probes and the sample can be kept
inside the oven and the sample can be heated up to a temperature of 200°C. The temperature inside the oven can be
measured by inserting a thermometer through a hole in the lid.
Figure 4:- Schematic diagram of Four-probe conductivity tester
The sample is, normally, germanium crystal in the form of a chip. It is brittle and costly. Therefore, the setup should
be handled only after fully understanding the management of probe settings. Contacts of the probes with the crystal
should be done very carefully using gentle up /down motion of the screw provided for the purpose. There exists
provision for varying the temperature of the oven (up to a maximum of 200o
C). Suitable voltage for the oven is
obtained through a stepdown transformer with a provision for low and high rates of heating.

The conductivity of the annealed copper (5.8001 x 107 S/m) is defined to be 100% IACS at 20°C. All other
conductivity values are related back to this conductivity of annealed copper. Conductivity values are reported in
micro Siemens/centimeter, the conductivity value is multiplied by 172.41 to convert to the % IACS value.
D. Thermal analysis
The thermal methods usually employed are Differential Scanning Calorimetry (DSC), Differential Thermal Analysis
(DTA) and thermo gravimetric analysis (TGA). For comparative study of thermal behavior of related polymer or
simple molecules, each molecule is analyzed by any one or more of these methods of analysis under identical
experimental conditions. For example, TGA is carried out in air and in oxygen- free nitrogen. It is carried out at
different heating rates. It may be a method that the result of thermal analysis of a given sample by a given method
depends on various aspects. The amount and particle size of the material examined, influence the nature of the
thermogram. The speed of the recorder noting the change in weight and the shape of the sample container also
influence the thermo-gravimetric results. The rate of heating the sample and the ambient atmosphere during analysis
are very important factors to be controlled during thermal analysis. The information furnished by TGA, DTA and
DGA are to some extent complementary. From the results of DTA and TGA, it is noted that the temperature up to the
material does not lose weight. It is also possible to know the temperature at which the material starts decomposing. It
is possible to know whether the decomposition occurs in one or more stages.
Figure 5:- Photograph of thermal gravimetric analysis
The thermogravimetric analyses of sample have been carried out by using PERKIN ELMER PYRIS in a slow
stream of air. The boat prepared from platinum foil would hold the sample for analysis. It is properly washed and
dried. It was suspended on the quartz rod in the TG balance. The powdered sample (about 5 mg) was placed in the
boat. The sample in the boat was covered by a quartz tube in which the flow of air was maintained. The weight of the
sample was noted on TGA balance. The whole assembly was brought down in the furnace. It was ascertained that the
boat was hanging on quartz rod. The experiment was started by the heating the system at a constant rate of 10°C/min.
Simultaneously change in the weight was recorded automatically with time (temperature). This will reveal
percentage weight loss of materials which is a function of the time and also of temperature. The experiment was
stopped at about 650°C, when there was no further decrease in weight. The thermogram was analyzed to obtain
information about percentage weight loss at different temperatures.
E. Tribology
Tribology (derived from two greek words ‘tribos’ meaning rubbing, and ‘logos’ meaning study) the collective name
given to the science and technology of interacting surfaces in relative motion, is indeed one of the most basic
concepts of engineering, especially of engineering design.
Tribology is a science which concerns, production engineering, mechanical engineering, chemistry and chemical
engineering, fluid dynamics and material science and other related topics. There is no mechanism, no machine and

no equipment that are not affected by tribological factors. Tribology is estimated that with reference to 70% of failure
in mechanical equipment are owing to tribological causes (friction and wear) and most of these result in wear. So, it
is of prime importance to study the wear behavior of materials. Tribology encompasses three classical subjects.
(i) Friction
(ii) Wear
(iii) Lubrication
Figure6:- Tribology
In material science, wear is the removal of material from a solid surface as a result of the mechanical action exerted
by another solid. It is a slow but continuous process of removal of materials from one or more elements. Like
friction, wear is also not an intrinsic material property. The four basic types of wear mechanisms are :
 Adhesive
 Abrasive
 Corrosive
 Surface-fatigue
Figure 7:- Different types of wear

2. RELATED WORK
A review of the literature relevant to the present study. For easiness and lucidity of arrangement, the literature review
is separated into the subsequent sections.
 Aluminium Matrix Composites
 Stir casting
 Tribological behaviour of AMMCs
A. Aluminium matrix composites
Caton et al. (1999) have investigated the fabrication of Al–Si7–Mg (A356) alloy and it is commonly used as
cylinder head and engine block materials. However, the use of these cast alloys is still limited for structure critical
applications in comparison with wrought alloy even though casting would be a more economical production method.
Among several series of Al-alloys, heat treatable Al6061 is much researched. The peculiar properties of Al6061
alloys are highly corrosion resistant, excellent extractability in nature, moderate strength and numerous application
potentials in the areas of building and highway constructions, automotive industries and marine engineering
(Kaufman 2002). Li et al. (2004) analyzed the effect of various alloying elements and different heat treatments in
A319-type alloys by means of instrumented impact test; in particular, they have found that impact tests can give a
measure of the capability of the material to resist crash, providing a useful estimation of the ductility of an alloy
under conditions of rapid loading. Aluminium 2024 alloy metal matrix composites reinforced with diverse sizes
(16,32and66μm) and weight fractions of Al2O3 particles up to30wt.% produced through a vortex method and
subsequent applied pressure were studied for the effects of Al2O3 particle and size on the mechanical properties of
the composites viz. tensile strength and hardness by Kok et al.(2005). The density of the composites was directly
proportional to the weight percentage and particles size of Al2O3, while the porosity was indirectly and directly
proportional to the particles size and weight percentage respectively. The bonding between Al alloy and Al2O3
particles was improved by the applied pressure after the casting hence the porosity was also decreased because of this
pressure. The hardness and tensile strength of the composites were increased however their elongation decreased
with increasing weight percentage and decreasing size of Al2O3 particles. Mahmudi et al. (2006) studied the effects
of 0.15 wt.% Zr addition on the mechanical properties and wear resistance of an A319 Al casting alloy. They found
no evidence of Al3Zr particles in the as-cast structure. Because of the similarity of the hardness of the alloys with
and without the Zr addition, they concluded that no Zr-rich precipitates were formed during the solidification of the
alloy. They found a 15% difference between the hardness of the two alloys after a 24 hour solution treatment at
503°C and attributed this difference to the formation of Al3Zr particles. However, they offered no other evidences
for this conclusion.
Aigbodion et al.(2007) have synthesized Al–Si–Fe alloy with silicon carbide addition using double stirring casting
method and concluded that addition of silicon carbide particles using this method to Al–Si–Fe alloy increased both
the yield strength, ultimate tensile strength and hardness values up to maximum values of 79.98, 106.12N/mm2 and
67.0HRB respectively, at 20% SiC addition. There is a slight increase in the apparent porosity of the composites with
percentage SiC addition that is still lower than the recommended values. For optimum service performances of this
alloy, silicon carbide addition should be between 15 and 20% and not exceed 20% in order to develop better
necessary properties. Singh & Balasubramanian (2009) prepared aluminium alloy matrix composites with copper
coated carbon fibre reinforcement by stir casting process to eliminate any interfacial reactions. An electroless
technique was employed towards achieving fairly uniform and continuous coating of copper on carbon fibres.
Among the composites containing different amounts of carbon fibres, the fibres were distributed quite
homogeneously with negligible agglomeration in the composites having up to 4wt% carbon fibres. The tensile
strength of the coating increased up to 4wt% fibre with the decrease of elongation and hardness increased initially to
some extent and then decreases. Pradeep et al. (2014) investigated the mechanical properties of Al-red mud and
silicon carbide metal matrix composite of aluminium alloy (7075) by adding different weight percentage
compositions, viz. SiC (8%) + Al7075, SiC (6%) + red mud (2%) + Al7075, SiC (4%) + red mud (4%) + Al7075,
SiC (2%)+ red mud (6%) + Al7075, red mud (8%) + Al7075 by stir casting technique. The experimental results
disclosed that the composite containing matrix material with reinforcement materials (SiC and red mud) improved
mechanical properties strength (tensile, compressive and yield) and hardness.
B. Stir casting
Davis (1993) explained the broad ranging employment of aluminum silicon (Al–Si) casting alloys in the diverse
application fields, for instance, aerospace, military, automobile as well as in standard engineering practice
organizations as a result of some specific advantages. These advantages among others, are outstanding castability,

wear resistance at elevated levels, minimal specific gravity, fluidity, lessened thermal expansion due to the addition
of silicon as well as proper mechanical as well as physical properties at superior temperatures.
Hashim et al.(1999) suggested the necessary parameters to study the influences on mechanical properties. These
parameters, referred to as processing variables, include the stirring speed, the impeller’s position in the melt, as well
as the holding temperature. Consequently, through the control of procedural situations and the comparative quantity
of the fortification material, a composite having a wide span of mechanical properties is possibly function of a
pleasant resolution of the technical difficulties showcased.
Jian et al.(2006) explained mainly four defect types in SiCp/A356 composites provided that an inappropriate
process of stir casting is employed. The defects are called black inclusions (i.e. SiC Agglomerates), silver spots ( i.e.
SiC particles sticking to Al2O3) as well as the pores (caused through gas bubbles as well as agglomerated SiC
particles). An enhanced process of stir casting is determined to fabricate SiCp/A356 composites having high quality
mechanical properties as well as lower defects. The A384-SiC metal matrix composites were developed using stir
casting approach by changing the processing conditions of the stirring speed (500,600and700rpm) and the stirring
time (5, 10 and 15 min).The microstructural examination disclosed that in a minimum stirring speeds and minimum
stirring time, the particle clustering increased. The growth in the stirring speed as well as stirring time brought about
homogeneous spreading of the SiC in the Al matrix. Better composite’s hardness was obtained at superior stirring
speed and stirring time. The constant value of hardness was attained at 600 rpm and 10 min stirring, however above
particular stirring speeds the properties declined (Prabu et al.2006).
Rajan et al. (2007) has described the several manufacturing procedures for producing alloying elements and ceramic
particle fortified metal matrix composites, such as using stir casting, mechanical alloying, powder metallurgy,
squeeze casting, disintegrated melt deposition, infiltration and selfpropagating elevated temperature synthesis
methods. Powder metallurgy and stir casting practices have been widely used in manufacturing aluminum and its
alloys. Stir casting procedure is the best and easily employed method, used in the production of large size composite
casting due to its cheapness which is as little as a third to a tenth of the complete mass production when compared to
various methods.
Unlu (2008) presented that the mass production and accurate shape at a lower cost processing to be the advantages
of stir casting. Also, it indicates the better bonding of matrix and reinforcement, due to the mechanical stirring action
with the optimum selection of casting process parameters like temperature of molten material, speed of rotation,
stirring time, and preheating temperature of the mold. Aluminium metal matrix composites were fabricated through
stir casting approach using material referred to as commercially pure aluminium as well as the matrix material and
different percentages of 30μm SiC particulates (5 and 10 vol.%) as the reinforcement material. The composites were
treated under severe plastic deformation, and it was observed that no changes in the particle spreading occurred,
however, it had led to refinement in the grain size of matrix material. In the Al-5 vol.% SiC particulates, the
composite grain size lessened to 8μm from 45μm with greater than two equal channel angular pressing passes, but in
Al-10vol.% SiC particulates, the composite grain size was refined to 16μm from 45μm after the first equal channel
angular pressing pass. Both the composites showed improved mechanical properties after equal channel angular
pressing (Ramu et al. 2009).
Jayaseelan et al.(2010) declared that the stir casting samples exhibit elevated hardness values in relation to the
sample form the powder metallurgy route. It was observed that the microstructures of the samples through stir
casting route were of finer grain quality in comparison with those samples from the powder metallurgy route.
However, the attractive properties of lessened porosity, clusters elimination, enhanced ductility, expanded strength,
grain refinement, increased constant particle spreading were common to the samples processed from the two routes.
Nevertheless, the necessary extrusion load was lower in the powder metallurgy route weighted against the stir casting
procedure. Overall, the author concluded, based on the results, the samples from the stir casting route had superior
strength weighted against the powder metallurgy samples.
Anilkumar et al. (2011) used stir casting method to prepare fly ash reinforced aluminum alloy (Al6061)
composites. Three fly-ash particle group with size ranges of 4-25, 45-50 as well as 75-100μm were employed to
prepare the composites. The mechanical properties of the composites such as tensile strength, compression strength
and hardness grew while increasing the fortified fly ash’s weight fraction as well as lessened through particle size
growth of the fly- ash. A decrease in the composite’s ductility was experienced while increasing the fortified fly
ash’s weight fraction as well as reduced with growth in the fly- ash’s particle size. The improvement of mechanical
properties could be ascribed to the elevated density of dislocation. Nevertheless, composites exhibiting 15% fly-ash
particle’s weight fraction, the tensile strength was found to decrease.
.Su et al. (2012) prepared Al2O3/2024 nanocomposites via solid–liquid mixed casting method in association with the
ultrasonic treatment. The resultant nanocomposites showcased fine grain microstructure, appropriate Al2O3
nanoparticles spreading in the host matrix as well as lessened porosity. The use of ultrasonic vibration on the

composite’s liquefied form in the course of solidification refined the microstructure of the grain of the matrix as well
as enhanced the spreading of the nano-sized reinforcement. The yield strength and the 1wt.% Al2O3 /2024
composite’s ultimate tensile strength were improved by 81 and 37%, correspondingly, than those of the pure matrix.
Liquid metallurgy method was adopted to reinforce the diverse particle size (50–75, 75–100 and 100–150μm) and
contents (3, 6, 9, and 12 wt.%) of rice husk ash with aluminum alloy (AlSi10Mg). The dry sliding wear behavior of
the composites was examined by using the pin-on-disc tribo-testing machine at various loads and sliding velocities.
The results disclosed that the composite fortified with coarse rice husk ash particles held better wear resistance
property over fine rice husk ash particles. Composite’s wear rate was reduced while increasing the rice husk ash
particles weight percentage for all ranges of size. The frictional coefficient was indirectly proportional to the weight
fraction of reinforcement, sliding speed as well as load (Saravanan et al. 2013).
.Moses et al. (2014) used stir casting method to reinforce aluminum alloy Al6061 with SiC particles of diverse wt.%
(0, 5, 10 and 15). The Al6061 alloy matrix was initially melted in a furnace and stirred to form a vortex, in which the
SiC particles were added and the formed composite melt was solidified in a permanent mold. The SEM and optical
imaging analysis of the composite revealed fairly homogeneous distribution of SiC in the Al6061 matrix and proper
bonding of SiC particles with the Al6061 matrix. Absence of any impurities, pores and voids was noticed in the
interface of SiC particle and aluminium matrix. The composites exhibited improved hardness and ultimate tensile
strength as a consequence of the presence of SiC particles.
Amouri et al. (2016) produced composites of A356- nanoSiC (0.5and1.5 wt%) and A356-5 wt% of micro SiC
fabricated by stir casting method and found that the mechanical strength of A356 increased substantially by
combining the T6 heat treatment along with the addition of nanoSiC particles.The effects of graphite particles on
Al6082 metal matrix composite with varying percentages of graphite (0 to 12% in a step of 3%) manufactured by
conventional stir casting process were studied by Sharma et al. (2016). The micro structural analysis of all the
composites disclosed the presence of substantial impurities having a non-constant spreading of graphite particles
along with the agglomeration of graphite particles at some locations. The density of graphite particles was found out
to be low over pristine Al6082, and as a consequence, the graphite particles were floating in the aluminium melt that
resulted in non-uniform distribution. When the weight percentage of graphite was increased from 0 to 12%, the
hardness of the composites was reduced by 11.1%. This could be associated with the increased brittle kind of
graphite reinforcement particles that caused the composites to deform plastically more easily with increased content
of graphite.
C. Tribological behavior of AMMCS
Sanjeevdas et al.(2006) concluded that wear behavior of Aluminium with 4.5wt % Cu alloy enhances much after
alumina and zircon particles are added. Reduction in particle size results in improving wear resistance quality for
both alumina, and zircon reinforced composites because smaller particle reinforced composite has more hardness and
is additional effective in blunting SiC abrading surfaces. The Zircon fortified composite exhibits more resistance to
wear than the alumina fortified composite because of its greater bonding in the particle–matrix interface.
Basavarajappa et al.(2007) noted that the wear resistance properties of the composites increases with the addition
of reinforcement content SiCp to aluminium 2219 alloy. The addition of SiCp in aluminium alloy additionally
increases the resistance to wear at every sliding speeds as well as effectively evades the presence of intensive wear.
Suresha et al.(2010) carried out experiments on the hybrid composite Al–SiC–Gr that contains joint fortification till
10% Al–Gr as well as Al–SiC composites having fortification till 10% employing the equipment referred to as pin-
on-disc ,the fortification amount, the speed at sliding, and the load as well as the sliding distance influence all
composite’s wear. The author reported the existence of interaction among the parameters of speed of sliding, sliding
distance and load in Al–SiC–Gr hybrid composites. The occurrence of such interface could not be found Al–SiC
composites. It was reported that the growth of the speed causes a decline in a wear through the support of the
tribolayer that is mechanically mixed. It was reported that the growth of the load causes growth in wear through the
reduction of the function of the tribolayer. It was further stated the wear grow with the sliding distance (because of
the non-stablity of the tribolayer).This is the major parameter influencing wear of all composites.
Radhika et al. (2011) produced composites of aluminium alloy (AlSi10Mg) fortified with 9% alumina as well as
3% of graphite that have been fabricated using the stir casting method. The authors investigated its tribological
behavior of the composities. The outcome shows that the component rate of wear was highly affected by the sliding
distance (46.8%), which was trailed by the applied load (31.5%) as well as the sliding speed (14.1%). Similarly, the
frictional coefficient was considerably affected by sliding distance (50%),subsequently the applied load (35.7%) as
well as sliding speed (7.3%).Aluminium alloy (Al-6061) was fortified with silicon carbide particles (10 and 15 wt.%)
as well as the stir casting process, and the tribological behavior of resultant composites was investigated by Mishra
et al. (2012). For Al-6061/10% SiC composite, sliding distance exhibited the most superior effect (62.5%) on the

wear rate, which was then followed by the sliding speed (37.5%) and the applied load (1.25%) as well as for the
frictional coefficient, the contribution of the applied load and the sliding distance was 85.5 and 13.4% respectively.
For Al-6061/15% SiC composite, applied load showed the highest influence (57.2%) on the wear rate, which was
followed by the sliding distance (7.1%) and sliding speed (7.1%) and for the friction coefficient, the contribution of
the applied load and the sliding as a result of increasing the proportion of SiC, which created a protective layer
between pin and counter face is reflected.
The mechanical and tribological properties of Al6061–silicon carbide (SiC) composites fabricated by employing the
liquid metallurgy technique by altering the proportion of SiC in the composite from 2to 6 wt%, was investigated by
Kumar et al. (2012). The outcome exposed the density of the composite which was directly proportional to the SiC
content. The homogeneous distribution of the SiC by the Al6061matrix was assessed by microstructural
characterization. The hardness and ultimate tensile strength of the composites were also directly proportional to the
SiC content, except for the reduced ductility. The wear property was better in the presence of SiC in the composites
when compared to the pure matrix material. Higher volumetric wear losses were found when the composites were
subjected (with the SiC content)to increased applied load and sliding distances. After a detailed study of different
composites, the Al6061- 6wt% SiC composite showed better mechanical and tribological properties. Elango &
Raghunath (2013) reported on the wear behavior of aluminium alloy LM25 fortified with SiC and TiO2 particles,
prepared through the stir casting process. The reinforcement of metal matrix using SiC and TiO2 particles minimized
the wear rate at room temperature. Moreover, by increasing the TiO2 percentage by keeping SiC percentage constant,
the resultant composites also exhibited reduced wear rate. The wear of the test specimens grew while increasing the
load as well as sliding distance. The frictional coefficient was decreased with load upon an increase in the volumetric
content of reinforcement. The study also proved that the lubricating nature of reinforcement material improved the
wear resistance, and this property could be considered as a factor in the design of new material for different
applications Hariprasad et al. (2014) examined the wear characteristics of hybrid aluminium metal matrix
composite created by reinforcing Al2O3 and B4C particles with Al 5083 alloy matrix through the stir casting method.
The hybrid composites having 5 wt.% of Al2O3 and different weight percentages (3, 5 and7%) of B4C reinforcements
were taken to study the wear behavior. They inferred that the wear rate of Al2O3- B4C 8% was roughly 10% below
Al2O3- B4C 10% and the Al2O3-B4C 12% composites.
Baradeswaran et al. (2014) stated the wear performance of Al6061 reinforced with 5, 10 and 15 wt.% graphite
composite made by the casting process ,and found that 5wt.% graphite reinforcement yielded in lesser wear rate
(0.006–0.008 mm2 /m) as compared to unreinforced Al6061alloy (0.008 - 0.012mm2 /m) because of its self-
lubricating behavior. Baradeswaran & Elayaperumal (2015) evaluated the characteristics of graphite particulates
on the dry sliding wear behavior of aluminum alloy 7075 with graphite composites prepared through the liquid
casting technique with diverse proportions (5–20 wt%) of graphite employing a pin-on-disc setup. The results of the
study disclosed that the wear rate of the composites reduced while increasing the graphite composition and attained
the lower value at graphite composition of 5 wt%. In contrast, the frictional coefficient decreased while increasing
the graphite content and reached a minimum value at graphite content of 5 wt%. The hardness and tensile strength
were reduced with an increase in graphite content up to 5 wt%.
3. MATERIAL SELECTION
As the intention of this research work,the base alloy 6XXX series (Al6061) has been selected because the aluminium
alloy 6061is a precipitation hardened alloy, having silicon and magnesium as the major alloying elements.
Aluminium alloy are generally popular because of this elevated high strength to weight, outstanding corrosion
resistance, elevated strength, excellent machinability, formability and weld-ability properties. On the other hand ,the
aluminium alloys used are limited because of minimal resistance to wear .To enhance its physical features, the metal
matrix composites are broadly employed. AMMCs are offered to produce light-weight equipment because of their
mechanical qualities and denseness. The AMMCs are offered in elevated class structural and purposeful uses like
sports, aerospace region, defence, automotive and thermal areas (Radhika et al. 2011).
The reinforcement particle used in the current research is silver (Ag) because it has exclusive properties that project
it a most useful and valuable metal. It has properties (thermal, optical and electrical) and is being joined with
products in the array of sensors, (photovoltaic , biological and chemical) (Auld1986& Min SONG et al. 2006).
The base alloy selected for the present study is the Al6061 aluminium alloy. This alloy is the most appropriate for
the mass production of metal castings (i.e lightweights). Al6061 alloy has copious reimbursement like formability,
weldability, wear resistance, corrosion resistance and less cost. The chemical composition of Al6061 alloy is given in
Table(Source from ASM Hand book).

Table 1: Chemical Composition of Al6061 by weight percentage
Chemical Composition Al6061
Si 0.62
Fe 0.23
Cu 0.22
Mn 0.03
Mg 0.84
Cr 0.22
Zn 0.1
Ti 0.1
Al Bal
Table 2: Properties
Properties Al6061 Ag
Elastic modulus (GPa) 70-80 72-76
Density (g/cc) 2.7 10.49
Poisson’s ratio 0.33 0.37
Hardness (500HB) 91 206
Tensile strength (MPa) 310 360
Boiling point (o
C) 652 962
Melting point (o
C) 2519 2212
4. CONCLUSION
Aluminum play a major role in engineering applications because of its moldability, low density, corrosion
resistance, low melting point, better machinability and deformable properties etc. But at the same time has certain
limitations such as low hardness, low strength and low wear resistance etc. if these limitations are overcome by
tailoring them by suitable fabrication processes, then these tailor-made materials find wider applications in various
fields. So, it is necessary to develop the Aluminum based materials that could have all combinational properties
satisfying all our engineering requirements. Carbon nanotubes can be considered as ideal reinforcements, due to
their high strength, high aspect ratio and thermo-mechanic properties. The mechanical, electrical, thermal and wear
behavior studies on Al6061- Ag composites are carried out.

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