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FABRICATION AND COLD UPSETTING BEHAVIOUR OF AL-5.4ZN ALLOY/COAL ASH/SIC PARTICLES REINFORCED COMPOSITES

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International Journal of Mechanical Engineering and Technology (IJMET)
Volume 10, Issue 03, March 2019, pp. 298-303. Article ID: IJMET_10_03_031
Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=10&IType=3
ISSN Print: 0976-6340 and ISSN Online: 0976-6359
© IAEME Publication
Scopus Indexed
FABRICATION AND COLD UPSETTING
BEHAVIOUR OF AL-5.4ZN ALLOY/COAL
ASH/SIC PARTICLES REINFORCED
COMPOSITES
Ramesh Jami
Research Scholar, Dept of Mechanical Engineering, Acharya Nagarjuna University
M. Gopi Krishna
Assistant Professor, Dept of Mechanical Engineering, Acharya Nagarjuna University
ABSTRACT
Experiments on cold deformation behaviour are conceded out on as cast and
homogenized Al-5.4Zn /coal ash/ Silicon carbide composite billets. The study was
intended to evaluate the effect of reinforcement percentage on the deformation
behaviour. The mechanical properties like hardness, tensile behavior, modulus of
elasticity, yield stress have been carried out. The microstructures were taken from
SEM to examine the distribution of ash and SiC particulates in the matrix. The
deformation process is carried out between two flat platens and sample at the center
to envisage the metal flow at room temperature. To observe the changes in hardness
after deformation the hardness measurements were carried out to examine the
changes after the forging. It is observed from the experimentation that the
circumferential stress σθ has positive values (tensile) with unremitting deformation. As
the barreling initiates, the axial stress, σz will get compressive values. The effect of
strength coefficient and strain hardening behaviour with the sample deformation and
barreling effects have been calculated.
Key words: Friction, cold upsetting, coal ash, strain hardening behavior
Cite this Article Ramesh Jami and M.Gopi Krishna, Fabrication and Cold Upsetting
Behaviour of Al-5.4zn Alloy/Coal Ash/Sic Particles Reinforced Composites,
International Journal of Mechanical Engineering and Technology, 10(3), 2019, pp.
298-303.
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Fabrication and Cold Upsetting Behaviour of Al-5.4zn Alloy/Coal Ash/Sic Particles Reinforced
Composites
1. INTRODUCTION
Lightweight materials are suitable for advanced aerospace and automobile industries.
Aluminium Metal Matrix composites (AMMCs) are used to fulfill the needs of the industries
which can be customized throughout the addition of preferred reinforcements to enhance the
mechanical properties [1, 2]. Due to the high specific stiffness and strength at room or high
temperatures the particle reinforced metal matrix composites are used. Normally micron sized
ceramic particles are used as reinforcement to improve the properties of the MMCs. Flyash is
the most l o w d e n s i t y a n d economical reinforcement obtainable in bulk quantities as
waste byproduct after incineration of coal in power plants. Chawla et al. [3] studied the
characterization and SEM examination of SiC as reinforcement in metal matrix composites
which are fabricated by secondary processing methods like extrusion and identified higher
strain to failure values for the extruded material also sinter forged test showed the higher
value of elastic modulus and Ultimate tensile strength because of failure in particle due to
fracture. The lower strains were observed for inferior bonding among the matrix and
reinforcing particles when compared to deform one.
V. Sethi [4] reported that incorporating ceramic particles in A356 matrix weakens the
interfacial bonding and in due course resulting in the pull-out of the SiC particle. The lattice
straining in the adjacent areas of the particles will reduce the extent of plastic deformation that
these areas can undergo, which will make them more vulnerable to cracking. These cracks
will result in the removal of the matrix from adjoining areas of the particles, thus decreasing
the strength of interfacial bond
2. MATERIALS AND METHODS
2.1. Matrix alloy
In the present research Al-5.4Zn alloy is chosen as matrix which is prepared in the laboratory.
2.2. Composite fabrication
Investigation on aluminium based hybrid metal matrix composites is carried out with 5, 10
and 15wt% SiC and coal ash particulates of 53µm were effectively casted by eddy method.
Al-5.4Zn alloy is used as matrix alloy.
The fabrication is carried out using vortex (stir casting) method. Al-5.4Zn alloy is melted
in a graphite crucible which is placed inside a muffle furnace. Once the required temperature
is attained i.e. (750 0C) a pool was created. The preheated particulates of SiC and coal ash at
were poured into the melt. To ensure the smooth and continuous flow of the particles, a
conical shaped object made of tin is used so that the particles will be added exactly in the
vortex. Argon gas is to be shielded around the melt to prevent oxidation.
3. DEFORMATION TESTS
Deformation tests were conceded out on specimens made in cylindrical shape for the alloy
and composites with height to diameter ratio of 1.0. The samples were prepared using CNC
lathe for accuracy as shown in figure 1. The ends of the specimens were chamfered to
minimize the folding. In order to attain low friction between die and samples concentric
grooves were made on the top flat surfaces. The prepared samples were compacted by placing
them between the dies (platens) at a constant speed of 0.4mm/minute in unlubricated
condition, using an advanced universal testing machine.
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Ramesh Jami and M.Gopi Krishna
Figure 1 Deformed samples
3.1.1. Friction and Ring Compression test
In metal working processes the friction arises from sliding of the work piece in opposition to
the die [5]. In the interest of clarity, friction forces are often neglected. In many real metal
working processes friction is the predominant factor [5]. J.P Avery et al. [6] reported the
implication of compression and the properties of materials to estimate forming boundaries up
to plastic unsteadiness and rupture. Substantial consideration has been dedicated to the
investigation of platen forces and distribution of pressures in upsetting, particularly for discs
made in thin size [7-10].
The compression test (ring) technique was started by Kunogi [11], developed further by
Cockroft and Male [12] for measuring friction beneath regular processing circumstances.
Before satisfactory mathematical solution for the compression of a ring was available, a
pioneering independent calibration was made by experimentation [13]. Subsequent theoretical
analyses [14, 15] have made possible more accurate and less laborious calibration of the ring
test by mathematical computation.
Avitzur [16], conducted the first satisfactory analysis of the compression of a flat ring
through an optimum upper bound mathematical solution and verified by Hawkyard and
Johnson [17] using a stress analysis approach.
4. RESULT AND DISCUSSION
4.1. Microstructural analysis and EDS of alloy and composites
The SEM pictures of reinforcements and hybrid composites varying with wt. percentages of 5
to 15% is shown in figure 2 (a-d), it is observed that, coal ash and SiC additions in the alloy
fig (b) shows the microstructure of the matrix alloy whereas figures c and d shows the
addition of the coal ash and SiC to the alloy, difference in the microstructures was noticed
clearly.
b
a
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Fabrication and Cold Upsetting Behaviour of Al-5.4zn Alloy/Coal Ash/Sic Particles Reinforced
Composites
d
c
Figure 2 (a) Scanning electron microscope of coal ash particles (b)Al-5.4Zn (c) Al-5.4Zn –5%
Composite (e) SiC Particle in matrix
4.1.2: Compressive Properties of the coal ash /SiC hybrid Composites
Load displacement curves for deformation properties of both the alloy and the composites
were shown in figure 3.
4.1.3. Strength coefficient and Strain Hardening
As the Coal ash and silicon carbide content increases, the strength coefficient, K found to be
increased as depicted in figure 5 .A rise in „K‟ value was observed from 410 MPa for Al5.4Zn alloy to 900 MPa for 10% composite. The obtained values were at 50% deformation by
cold upsetting process.
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% Increment
Ramesh Jami and M.Gopi Krishna
Strength Coefficient (K)
Strain Hardening Exponent (n)
% of Reinforcement
Figure 5 strength coefficient
By the addition of ceramic particles in solid form, the strength of the matrix was
predictable to increase due to the escalation possessions occurred in particulate reinforced
composites. Also the occurrence of second phase particles in the continuous metal matrix
phase the plastic properties have been modified due to localized internal stresses. Hence,
presence of the hard Coal ash /SiC particles made the composites high strength subsequently
increase in strain hardening exponent „n‟ values for larger Coal ash /SiC particulates
content.Strain hardening exponent „n‟ is increasing with increase in reinforcements Coal ash
and silicon carbide) as shown in figure 5. The strengthening occurs due to the dislocations
within the structure of the material which make improvements in the plastic properties to an
enormous extent. Hence, presence of the hard Coal ash /SiC particles made the composites
high strength subsequently increase in strain hardening exponent „n‟ values for larger Coal
ash /SiC particulates content.
During metal forming the dislocation density increased by several orders of magnitude.
By this, higher dislocation zones of density will appear which represent an obstruction for
moving dislocations.
5. CONCLUSIONS
1. Al- 5.4Zn /Coal ash/SiC Hybrid composites were fabricated by vortex method successfully.
2. The distribution of Coal ash and silicon carbide particles are uniform throughout in the matrix
phase.
3. A good interfacial bonding is observed from the SEM figures, which clearly shows that there
were no discontinuities and voids in the composites.
4. For the given set of compression dies in dry condition, the friction factor „m‟ was found to be
0.37.
5. Irrespective of alloy composition the friction factor values were found to be same for a given
set of dies.
6. Load requirement increased with decrease in aspect ratio for given frictional condition.
7. Strength coefficient (K) increased with increase in Coal ash /SiC particulates content for all
the composites compare to Al- 5.4Zn alloy.
8. Strain hardening exponent (n) increased with in Coal ash /SiC particulates content for all the
composites compare to Al- 5.4Zn alloy
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Fabrication and Cold Upsetting Behaviour of Al-5.4zn Alloy/Coal Ash/Sic Particles Reinforced
Composites
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