Studies On Microstructure And Mechanical Properties Of Flyash Reinforced Al2024 Composites

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Technology & Research
Volume 1, Issue 3, Mar 2017 Available at: www.dbpublications.org
International e-Journal For Technology And Research-2017
IDL - International Digital Library 1 | P a g e Copyright@IDL-2017
Studies On Microstructure And Mechanical
Properties Of Flyash Reinforced Al2024
Composites
Sathisha N 1
, Tejas G2
, Praveen kumar R A 3
, Manjunath Vajjaramatti4
, Avinash L5
UG student, Department of Mechanical Engineering, NMIT Bengaluru, Karnataka, India1, 2, 3, 4
Assistant professor, Department of Mechanical Engineering, NMIT, Bengaluru, Karnataka, India5
Abstract:
The aim is to study the mechanical property and
Tribological behavior of Al2024/flyash composite
with various weight fractions (3%, 6%, 9%) were
prepared by squeeze casting method. The average
particle size of flyash is 45-50 μm. In addition, Al2024
alloys were cast for comparison purposes.
Microstructure, hardness and tensile properties of
these composites were evaluated and compared with
as-cast alloy and the composites. In addition,
tribological properties of these composites were
evaluated using a Pin-on-Disc apparatus with different
parameters of varying loads of 10N and 50N and(with
constant parameters such as time of 10 minutes,
sliding velocity of 3 m/s, track diameter of
150mm).The microstructure of the composites shows
homogenous distribution of flyash particles in the Al
matrix composite. The wear and mechanical properties
of composites improve with increasing the weight
fraction of flyash. The aim of present study is to
evaluate the effect of microstructure, mechanical and
tribological properties of aluminium alloy
Al2024/flyash metal matrix composites
Keywords: Al2024 alloy, Flyash, microstructure,
Hardness, Wear.
1. INTRODUCTION
Conventional monolithic materials have
limitations in achieving good combination of strength,
stiffness, toughness and density. To overcome these
shortcomings and to meet the ever increasing demand
of modern day technology, composites are most
promising materials of recent interest. Metal matrix
composites (MMCs) possess significantly improved
properties including high specific strength; specific
modulus, damping capacity and good wear resistance
compared to unreinforced alloys. There has been an
increasing interest in composites containing low
density and low cost reinforcements. Among various
discontinuous dispersoids used, fly ash is one of the
most inexpensive and low density reinforcement
available in large quantities as solid waste by-product
during combustion of coal in thermal power plants.
Hence, composites with fly ash as reinforcement are
likely to overcome the cost barrier for wide spread
applications in automotive and small engine
applications. It is therefore expected that the
incorporation of fly ash particles in aluminium alloy
will promote yet another use of this low-cost waste by-
product and, at the same time, has the potential for
conserving energy intensive aluminium and thereby,
reducing the cost of aluminium products [1-3].
Now a days the particulate reinforced aluminium
matrix composite are gaining importance because of
their low cost with advantages like isotropic properties
and the possibility of secondary processing facilitating
fabrication of secondary components. Cast aluminium
matrix particle reinforced composites have higher
specific strength, specific modulus and good wear
resistance as compared to unreinforced alloys [4-
6].While investigating the opportunity of using fly-ash
as reinforcing element in the aluminium melt,
R.Q.Guo and P.K.Rohatagi [7-8] observed that the
high electrical resistivity, low thermal conductivity
and low density of fly-ash may be helpful for making a
light weight insulating composites. The particulate

composite can be prepared by injecting the reinforcing
particles into liquid matrix through liquid metallurgy
route by casting [9-10]. Casting route is preferred as it
is less expensive and amenable to mass production.
Among the entire liquid state production routes, stir
casting is the simplest and cheapest one. The only
problem associated with this process is the non
uniform distribution of the particulate due to poor wet
ability and gravity regulated segregation. Mechanical
properties of composites are affected by the size,
shape and volume fraction of the reinforcement,
matrix material and reaction at the interface. These
aspects have been discussed by many researchers.
Rohatgi [1] reports that with the increase in volume
percentages of fly ash, hardness value increases in Al–
fly ash (precipitator type) composites. He also reports
that the tensile elastic modulus of the ash alloy
increases with increase in volume percent (3–10) of fly
ash. Aghajanian et al. [11] have studied the Al2O3
particle reinforced Al MMCs, with varying particulate
volume percentages (25, 36, 46, 52 and 56) and report
improvement in elastic modulus, tensile strength,
compressive strength and fracture properties with an
increase in the reinforcement content. The interface
between the matrix and reinforcement plays a critical
role in determining the properties of MMCs.
Stiffening and strengthening rely on load transfer
across the interface. Toughness is influenced by the
crack deflection at the interface and ductility is
affected by the relaxation of peak stress near the
interface [12-14]. Extensive studies on the tribological
characteristics of Al MMCs containing reinforcements
such as SiC and Al2O3 is available in the literatures
[15-18]. However, reports on friction and wear
characteristics of fly ash reinforced AMCs are very
limited. Rohatgi has reported that the addition of fly
ash particles to the aluminium alloy significantly
increases its abrasive wear resistance. He attributed the
improvement in wear resistance to the hard
aluminosilicate constituent present in fly ash particles.
In the present work, fly-ash which mainly consists of
refractory oxides like silica, alumina, and iron oxides
is used as reinforcing phase. Composite was produced
with 10% fly-ash as reinforcing phase. Commercially
pure aluminium was also melted and casted. Then
particle size and chemical composition analysis for
fly-ash was done. Mechanical, physical and wear
properties of the composite were evaluated and
compared with the commercially pure aluminium.
Moreover, the composite was characterized with the
help optical microscope, hardness test and tensile
tester.
2. OBJECTIVES
The need of a systematic study of various mechanical
properties of fly ash reinforced Al2024 composites.
This study can lead one to explore the possibility of
identifying the use of these composites as
tribomaterials especially for automobile applications.
Therefore the work taken up had the following
objectives:
1. Fabrication of Al2024/ fly ash composites by
Liquid metallurgy route.
2. Microstructure characterization of the
composites using optical microscopes.
3. Evaluation of mechanical properties of the
composites.
4. Comparing the results of mechanical
properties of as-cast alloy with composites.
5. Validating the experimental results with
Design of Experiments
6. Drawing Conclusion based on the obtained
result.
The present study is thus aimed at producing MMCs
with Al2024 as the matrix material with fly ash as
reinforcement processed by stir casting route of these
composites in order to obtain mechanical properties
suitable for a wide range of engineering applications.
3. METHODOLOGY

Fig. Flow Chart of Experimental Work
4. IMPLEMENTATION
2024 is typically used in:
1. Architectural applications
2. Extrusions
3. Window frames
4. Doors
5. Shop fittings
6. Irrigation tubing
7. In balustrading the rails and posts are
normally in the T6 temper and formed elbows
and bends are T4. T4 temper 2024 aluminium
is also finding applications in hydro formed
tube for chassis.
5. OUTCOMES
1. It is widely used in aircraft structures.
2. The material is susceptible to thermal shock.
3. Good improvement in mechanical properties.
4. High strength to weight ratio.
 Optical Microstructural Characterization
Figure(a),(b),(c),(d)shows the micro photographs
of both the matrix alloy Al2024 and its composites
system. Figure (b). (c), (d) revealed that presence of
fly ash particles in Al2024 alloy matrix and further
confirms that there was a uniform distribution of fly
ash particles in the base matrix of Al2024 alloy .The
images clearly shows that there were no voids and
discontinuities in the composite and also there was a
good interfacial bonding between the fly ash particles
and matrix materials.
Hardness Test Result:

Fig: Hardness values of Al2024 alloy and its
composites
From above Figure it is found that hardness increase
with increasing Flyash content in the material. As
compared to as-cast (AL2024 alloy), 3% Flyash
addition shows an increase of 5.56 BHN (11.44%).
In contrast 6% and 9% Flyash addition shows an
increase of 17.35 BHN (35.72%) and 26.32 BHN
(54.20%) respectively. The improvement in hardness
in casted composites may be ascribed to uniform
distribution of reinforcement (Flyash) in the matrix
material
TENSILE TEST RESULTS:
UTS of Al2024 alloy and its Composites
Fig: UTS values of Al2024 alloy and its Composites
From above Figure it is found that Ultimate tensile
strength increase with increasing Flyash content in the
material. As compared to as-cast (AL2024 alloy), 3%
Flyash addition shows an increase of 30.16 MPa
(24.45%). In contrast 6% and 9% Flyash addition
shows an increase of 39.32 MPa (31.88%) and 45.95
MPa (37.25%) respectively. The improvement in
strength in casted composites may be ascribed to
uniform distribution of reinforcement (Flyash) in the
matrix material. The fly ash particles help in
strengthening the matrix, acting as barriers to the
dislocations when taking up the load applied.
Table : YTS of Al2024 alloy and its Composites
Fig: YTS values of Al2024 alloy and its Composites
From Figure it is found that Yield tensile
strength increase with increasing Flyash content in the
material. As compared to as-cast (AL2024 alloy), 3%
Flyash addition shows an increase of 30.16 MPa
(28.34%). In contrast 6% and 9% Flyash addition

shows an increase of 39.32 MPa (35.31%) and 45.95
MPa (39.24%) respectively. The improvement in
strength in casted composites may be ascribed to
uniform distribution of reinforcement (Flyash) in the
matrix material. The fly ash particles help in
strengthening the matrix, acting as barriers to the
dislocations when taking up the load applied.
Table : Ductility of Al2024 alloy and its
Composites
Fig: Ductility values of Al2024 alloy and its
Composites
The results of the ductility test carried out on
all the MMCs taken up for investigations are shown in
Table The percentage decrease in ductility with
different weight fractions of reinforcements is also
given. Figure shows the effect of the weight fraction of
fly ash on the ductility of Al2024 alloy matrix by
reinforcements. Figure shows that the ductility of the
composite decreased with the increase in weight
fraction of the fly ash. This may be due to the hardness
of the fly ash particles or clustering of the particles.
 WEAR STUDIES
Dry sliding wear tests were conducted as per
ASTM-G99 norms. The wear rate was based on the
average value of 3 tests. Two loads of 10N and 50N at
a sliding velocity of 3.0m/sec and sliding distance of
1800m. During the test the following specifications
were used:
Table : Specifications used in wear studies
 CALCULATIONS:
1. SlidingVelocity(V)=
3.= ……..(i)
Where, D is track diameter in mm, N is speed in rpm
From Equation (i) N=382 rpm
2. SlidingDistance(S)
= = ……..(ii)
Where, T is time in minutes.
From Equation (ii) S=1800meters

Table: Wear behavior of Al2024 alloy and its Composites
Fig(a): Wear graphs of Al2024 alloy and its
AL2024 alloy +3% Flyash Composites
respectively at 10N and 50N respectively
Fig(b): Wear graphs of Al2024 alloy +6% Flyash
and AL2024 alloy +9% Flyash Composites
respectively at 10N and 50N respectively
Fig(c): Effect of load on wear (µm) of the Al2024
alloy and its Flyash composites
(Sliding Velocity : 3.0m/s, Sliding distance: 1800m,
load: 10 and 50N)
From the above figs it can be see that as the
load increases the wear rate increases. Maximum wear
rate can be observed in Al2024 alloy and least wear
rate is observed in As-cast alloy with 9% alumina. The
decrease in wear rate may be attributed to the Flyash
particles which act as load bearing in the Al2024
matrix and resist wear. Due to the absence of Flyash
particle as reinforcement in as-cast alloy it has a
maximum wear rate. The wear rate in composites is
less due to the fact that ploughing of the fly ash
becomes difficult as the particle size increases.
 CONCLUSION
From the test conducted I order to determine the
mechanical properties of flyash reinforced Al2024
composites of different weight fractions of the
reinforcement, it was found that
i. flyash particles as reinforcements helped in
increase of UTS of Al2024 from 110.02 MPa
as per the following
 3%flyash141.20MPa(46%
increases)
 6% flyash-148.87MPa(46% increases)
 9% flyash-153.20MPa(46% increases)
It can be noted that UTS of the composite
increased with increase in weight fraction of flyash
ii. flyash particles as reinforcement helped in the
increasing the hardness of Al2024 from
48.6BHN as per the following
 3%flyash54.12BHN (21% increase).

iii. The increase in weight fraction of the flyash
reinforcement had a significant increase in
hardness and wear resistance further.
From the tribological tests carried out on Al2024 and
its composites, it was observed that:
i. F
Flyash particles as a reinforcement helped in
decreasing the wear rate of Al2024
ii. t
he percentage of reinforcement of flyash was
increased, wear rate was found to reduce and
hence wear resistance of specimen improved.
From the optical micrographs of polished specimen,
the following was observed:
i. T
The distribution of reinforcement
particles (flyash) is found to be uniform
ii. T
The flyash particles are not trapped in the
grain boundaries
iii. T
The majority of the Flyash particles are
located inside the matrix itself which
indicates that it has wetted better due to
the addition of Mg as a wetting agent.
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