Journal of Minerals and Materials Characterization and Engineering, 2012, 11, 1126-1131
Published Online November 2012 (http://www.SciRP.org/journal/jmmce)
Processing of 5083 Aluminum Alloy Reinforced with
Alumina through Microwave Sintering
Jagesvar Verma1, Anil Kumar2, Rituraj Chandrakar3, Rajesh Kumar4
1Department of Mechanical Engineering at SSIPMT, Raipur, India
2Department of Mechanical Engineering at BIT, Durg, India
3Department of Mechanical Engineering at CSIT, Durg, India
4Department in Mechatronics Engineering at CSIT, Durg, India
Received July 7, 2012; revised August 13, 2012; accepted August 28, 2012
ABSTRACT
Today, there is an increasing demand worldwide for the advanced materials in order to obtain the desired properties.
This is because a single material generally cannot meet the requirement of harsh engineering environment that is why
the need for composites arises. Metal matrix composite is an importan t class of materials with high potential for struc-
tural applications requiring high specific modulus, strength and toughness. Metal matrix composites with unique pro-
perties are growing every day and widely used in different industries because of their high mechanical properties and
wear resistance.
Keywords: Microstructure; Powder Metallurgy; Composite Materials
1. Introduction
Aluminium MMC has been of interest in the recent li-
terature because of its lower density, high toughness and
corrosion resistance in the environmental condition [1].
Aluminium MMC shows poor strength which can be im-
proved by adding some alloying elements like Cu, Mg, Si
and Zn. The alloying elements improves strength but
shows poor wear resistance properties which is the main
drawback of aluminium which can be improved by ad-
ding ceramic particle such as Al2O3 and also using such
reinforcement makes the control of microstructure, tri-
bology and mechanical properties through controlling
volume fraction, size and distribution of constituents.
Among the ceramic particles Al2O3 is favorable since it
does not react with the matrix at high temperature and
does not create undesired phases [1]. Alloy and compo-
site have been prepared i.e. Al5083 alloy and alumina as
reinforcement in various weight percentages by powder
metallurgy route (e.g . high energ y ball milling), ho t com-
paction, and microwave heating. Powder metallurgy me-
thod is the most suitable method for making metal matrix
composites. In comparison with the melting methods, it’s
most important advantage is low processing temperature.
That is why undesired phases between the matrix phase
and the reinforcement are prevented. Moreover, rein-
forcement particles are also suitably distributed in the
matrix [2]. Another significant feature is the production
of near net-shape parts, which is cost-effective. Hardness
and Wear resistance of the composite is improved by
proper addition of the reinforcement. However, elonga-
tion of the composite may be reduced [3,4]. By addition
of the hard phase particles, greatly improves the streng th
which in turn depends on the manipulation method [5].
Microwave energy is being utilized as an alternative en-
ergy source for the processing of materials to ensure ra-
pid, volumetric heating, finer microstructure and better
properties [6,7]. Researchers have established that metal
powder can be efficiently heated by microwave energy.
Where in the dielectric loss and eddy current loss have
important roles.
In addition, multiple scattering in the powdered sam-
ple also leads to the absorption of the microwave energy.
The main aim of the present work is to develop alumi-
num alloy matrix Al2O3 particulate composite and their
structure property correlation. The experimental work
has been classified into three parts: 1) Development of
5083Al-Al2O3 composite. 2) Thermal behavior analyses.
3) Characterization of 5083Al/Al2O3 composite.
2. Methodology
2.1. Development of 5083Al/Al2O3 Composite
2.1.1. R aw Materials
Aluminum 5083Al alloy was chosen for this study and
alumina (Al2O3) particulates were reinforced with this
5083Al alloy matrix. The raw materials are shown in the

J. VERMA ET AL. 1127
following table.
The alumina (Al2O3) powders were mixed in different
composition with 5083Al by four point planetary ball
mill. Four different sets of metal matrix composites were
prepared given in the Table 1. Initia lly all elemen tal pow-
ders were taken as its weight percentage and it was al-
loyed by ball mill. Then mechanically shaken powder of
10 gram mass is compacted in a rigid tool steel die using
a single action hydraulic press at a pressure of 240 MPa.
Graphite was used as a die wall lubricant during compac-
tion. Sintering was done in a microwave furnace at 535˚C.
After the definite holding time they were allowed to cool
in the furnace itself. Sintered density is the major factor
influencing the mechanical properties of the material
processed through powder metallurgy. The sintered den-
sities were calculated by rule of mixture; the samples
were weighed using a Sartorius electronic balance to an
accuracy of 0.001 g. The microstructure was character-
rized by using an optical microscope. Micro structural
characterization was conducted in the etched conditions.
Optical micrographs of selected specimens were obtained
following the standard metallographic preparation. Kel-
ler’s reagent (0.5HF-1.5HCl-2.5HNO3-95.5H2O) was used
as a reagent. The therma l stability of alloy and composite,
decomposing temperature, exothermic and endothermic
properties of materials at specific heat rate, temperature
and atmosphere. The analysis has been done with alu-
mina as a reference material with gas flow rate at 20˚C/
min, temperature range 700˚C in argon atmosphere by
DSC scanning. After ball milling the elemental powder
was sent for XRD study because it is one of the better
tools to understand the new phase evolution, structural
transformation, particle refinement and alloying forma-
tion, etc. Alloys and composites hardness were also ob-
tained by Vickers micro hardness using a 1000 g load.
Pin on disc wear tests were done at different sliding dis-
tance of 1000 m, 2000 m, 3000 m, 4000 m and 5000 m at
10 N and 20 N l oad.
2.1.2. Dat a Analysis
Structure Evolution of Milled Powders and Sintered
Body from XRD
XRD data of Al5083 alloy and composite powder and
microwave treated sample with varying weight percent
(5%, 10% and 15%) are shown in Figure 1, different phases
such as Al2O3, Al, Al3Mg2, Si, Mg and some oxides are
Table 1. Composition of 5083Al/Al2O3 alloy and composite.
sample Mg Mn Cr Si FeZn Cu Ti Al2O3Al
5083 4.4 0.7 0.15 0.4 0.4 0.25 0.1 0.15 - Bal.
5%Al2O3 4.4 0.7 0.15 0.4 0.4 0.25 0.1 0.15 2.5Bal.
10%Al2O3 4.4 0.7 0.15 0.4 0.4 0.25 0.1 0.15 5 Bal.
15%Al2O3 4.4 0.7 0.15 0.4 0.4 0.25 0.1 0.15 7.5Bal.
20 40 60 80
0
500
1000
1500
2000
2500
Al2o3
si
Al
Al
inte n sity (cps)
2 theta(degree)
(a)
20 40 60 80
0
200
400
600
800
1000
Mg
Al
Al
Intensity (cp s)
2Theta (deg.)
(b)
10 20 30 40 5060 70 80 90
0
200
400
600
800
1000
Al
Intensity (cp s )
2the ta (deg r ee )
Al
Al
Al
(c)
10 20 30 40 50607080 90
0
100
200
300
400
500
600
700
800
sio2
cu5zn
Al203
Al3mg2
Intensity (c p s)
2 theta(degree)
(d)
Figure 1. XRD patterns of mechanically alloyed powder and
sintered sample (a) Al5083 sintered sample; (b) Al5083
powder; (c) Al5083-Al2O3 Composite (10 wt%) powder; (d)
Al5083-Al2O3 Composite (10 wt %) sintered sample.

J. VERMA ET AL.
1128
of Al5083/Al2O3 composite having weight percent 10%
slightly shifted to higher temperature range that is 653.26˚C
the phenomenon may be due to inhibiting effect of alu-
mina in rearrangement of the particles .The other reason
may be that the addition of alumina in aluminum matrix
reduces the grain size and particle distribution increases
the sintering temperature.
confirmed, having seen both the figure of alloy powder
and microwave treated sample are slightly differ, in pow-
der alloy there is no formation of such kind of oxide lay-
ers and also peaks are somewhat broad compare to mi-
crowave treated sample the aluminums are slight shifted
towards low angle. Al peaks predominantly because of
initial consideration amount is very high. Oxide is formed
because of temperature rise. Some inter-metallics are also
formed during the mechanical alloying of Al5083 and
composite Mg atom substituted in matrix which gives sub-
stitutional so lid solution.
2.2.1. Density Measurements
Sintered density is the major factor influencing the me-
chanical properties of the material processed through
powder metallurgy. Sinter densities of th e compacts were
determined by the rule of mixture. Powder metallurgy
products are prone to porosity. Since, the composites
developed in this work are focused for structural applica-
tions, the porosity estimation as well as reduction of po-
rosity is essential. Technically, porosity is inversely pro-
portional to density, i.e. higher porosity and lower den-
sity leads to poor mechanical and chemical property.
Therefore, it is necessary to obtain good density P/M
components by adopting newer consolidation technique
like hot compaction and microwave sintering. Figure 3
shows the density values of sintered materials at different
composition. In fact, density of the conventional P/M
alloy is dependent on many variables such as powder
morphology, particle distribution, compaction parameters,
sintering parameters, etc. The density obtained in this
work is around 97% of the theoretical density of alumi-
num/composites with the remaining 3% porosity density
2.2. Differential Thermal Analysis (DTA)
The occurrence of amorphous phase is generally inferred
by observing the presence of broad peak in the X-ray
diffraction patterns. By observing broad peaks alone, it is
not possible to distinguish amongst materials in which
very small crystals are embedded in an amorphous ma-
trix. So, it is desirable that the X-ray diffraction observ a-
tion be confirmed by other technique as well. Thermal
stability and nano-crystalline microstructures are ob-
tained by ball milling. The analysis has been done with
alumina as a reference material with gas flow rate at
20˚C/min, temperature range 700˚C in argon atmosphere.
After DSC scan at heating rate 20˚C/min of 5083 alloy a
peak was observed at 631.84˚C .This temperature shows
the decomposition temperature of alloy. Figure 2(a),
shows DSC measurements of 5083Al alloy powder. But
in Figure 2(b), can see that decomposition temperature
Figure 2. DSC scan at heating rate 20˚C/min of 5083 alloy and 10 wt% composite.

J. VERMA ET AL. 1129
051015
94.5
95.0
95.5
96.0
96.5
97.0
97.5
98.0
98.5
99.0
99.5
100.0
15wt%-96.7
10wt%-97.2
5wt%-97.7
Al5083-98.9
Relative density (%)
A lu mina c o n te n t (wt%)
Figure 3. Relative density V/s Alumina content.
increasing due to hot compaction and microwave effect.
Hot compaction gives better densification. Volumetric and
rapid heating of material through microwave results in
high shrinkage and less porosity. The relative density of
the composite decreases compares to alloy. Due to higher
hardness of alumina it decreases the pressing capacity of
the sample. The result is lower density of the sample.
Another reason for this phenomena is the preventive ef-
fect of alumina particles on the sintering mechanism be-
cause of high melting point of alumina (2054˚C) having
low tendency to make bonds with alloy leading to weak
network.
2.3. Micro-Structural Characterization
Micro-structural characterization was done using image
analyzer. The micrographs are shown in Figure 4 with-
out etched and Figure 5 etched and without etched con-
ditions. The particles are reasonably well distributed
within 5083 aluminum matrix. The interface between
matrix and reinforcement could not be detected at this
magnification. Metallograph y is one of the better tools to
correlate the properties of the alloy. In our work, optical
microscopy was used to understand the structural evolu-
tion, Al2O3 distribution in the matrix, porosity, etc. The
microstructure of aluminum/composites prepared at dif-
ferent amounts of Al2O3 dispersion were studied by me-
tallography. The structures are also observed under etched
condition to study the structural changes. The micro-
structure revealed the respective structure with fine grain
size this may be because of ball milling and microwave
sintering.
2.3.1. Hardness Test
The hardness value increases with increasing alumina
Figure 4. Micrographs of Al2O3 (10 and 15 wt%) particles
dispersed in 5083 matrix (without Etched).
content. The maximum value obtained for Al5083/Al2O3
composite at 15 wt%, shows that as the alumina content
increases, the hardness value increases. The minimum
value of micro hardness obtained for alloy Al5083, are
shown in Figure 6. The composites show higher hard-
ness than Al5083 alloy. The reason is because of disper-
sion of very fine and hard alumina particles the specific
surface area is more and the dislocation cannot move
easily, as the reinforcement in aluminum matrix gives
higher hardness. It will provide better wear resistance.
2.3.2. Wear Behavior
It shows that the composite wear loss strongly depends
on reinforcement loading in the composite. As the rein-
forcing phase content increases from 5 to 15 wt%, the
wear loss decreases. Figure 7 shows the variation of wear
rate with sliding distance of 1000 m to 5000 m for the

J. VERMA ET AL.
1130
.
Figure 5. Micrographs of Al2O3 (5, 10 and 15 wt%) parti-
cles dispersed in 5083 matrix (with etched).
Figure 6. Hardness V/s Alumina content.
Al5083 alloy and composite alumina reinforced with 5,
10 and 15 wt% tested under an applied load of 10 N - 20
N at 500 r.p.m. From Figure 7, it can be shown that in-
crease in the applied load from 10 N to 20 N sharply in-
creases the wear rate and with the increase in the rein-
forcement the wear rate is decreased. The co mposites with
high hardness abraded at lower rates. The Al2O3 rein-
forcement phases impeded the indentation and removal
by scratching of material from the surface by the abrasive
particles; this resulted in the lower wear rates. It is ap-
parent from Figure 6 that with the increase in the rein-
forcement, the wear rate decreases. Moreover; the wear
Figure 7. Wear rate vs. sliding distance at constant load 10 N
and 20 N respectively.
loss of the composites increases rapidly with increasing
sliding distance indicating that the counter body (En 32
steel) can deform and remove the material from compo-
sites progressively. However, a much slower increase in
wear loss is observed at lower load (10 N) whereas, the
wear loss varies almost linear with the sliding distance
under specific loading conditions. The wear loss increases
with the sliding distan ce and applied load. At higher load
(20 N) the wear loss of the composite is high. The hard-
ness of the counter body is 55 HRC, which is higher than
the hardness of the microwave sintered Al5083 and com-
posites. The Al5083 alloy and composites are removed
by the hard counter body and this removal is faster at 20 N
load. Since, at lower load the wear loss is very small, the
mechanism operative at 10 N is the polishing wear. As
the load is increased to 20 N the wear loss increases due
to the plastic ploughing and grooving of alloy and com-
posite with the higher sliding distances. At higher load
and longer sliding distances the polishing wear mecha-
nism is accompanied by the plastic ploughing and groo-
ving wear mechanisms and cause more wear loss from
the composite surface. At higher loads and less rein-
forcement loading (5% Al2O3) the matr ix deformation and
removal is inevitable.
3. Conclusions
1) Solid solution of solute in Al during mechanically

J. VERMA ET AL.
1131
alloying was determined by XRD.
2) Powder morphology and size become uniform i.e.
all powder partials were regular shape with narrow size
distribution.
3) Microwave sintering of mechanically alloyed
Al5083 alloy and composites resulted in good density, i.e.
97% of theoretical density.
4) The effect of alumina in 5083 alloy was studied
with respect to hardness value .There was a trend that
hardness value increased with increase alumina content.
5) The wear rate was low with increasing alumina con-
tent.
Aluminium 5083 alloy and composite give good re-
sponse to microwave.
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