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face of slurry erosive specimens decreases wear loss by
forming protective layers against the impact of slurry.
Ramachandra and Radhakrishna also [8] analyzed the
slurry erosive wear behavior of Al-12wt%Si alloy rein-
forced with fly ash composites and it was noticed that the
flyash enhanced the slurry erosion wear resistance of the
developed composites. Li et al. [9] have investigated the
effect of time duration on slurry erosive wear of alumi-
num alloy and found that the wear rate increases with
increase in test time duration.
Setsuo et al. [10] discussed the effect of impact veloc-
ity and sand concentration on erosive wear of eutectic
alloys and observed that increase in sand concentration
and impact velocity increases the wear rate. Candan and
Bilgic [11] in their study reported that the addition of SiC
particles to Al-4wt%Mg could improve the corrosion
resistance of the composites over that of the base alloy in
3.5 wt% NaCl solution. On the other hand, Kiourtsidis
and Skolianos [12] noted that although SiC is not directly
responsible for the enhanced pitting corrosion of alumi-
num AA2024 composites in 3.5 wt% NaCl solutions,
intermetallic phases surrounding the particles initiated
pitting attack of the material.
Saxena et al. [13] explained the inferior seawater cor-
rosion resistance behaviour of a 4xx.x cast aluminum
alloy (LM-13 alloy), containing 3 wt% graphite particles,
to galvanic corrosion between the cathodic graphite par-
ticles and active aluminum matrix. However, the 4xx.x
cast aluminum-graphite composites displayed excellent
corrosion resistance in SAE-40 engine oil at 150˚C. Nath
and Namboodhiri [14] observed that Al-Mg and Al-Cu
composites exhibit superior corrosion resistance than the
composites reinforced with mica particles. The inferior
corrosion resistance of the mica-reinforced composites
was attributed to the distortion of the passive protective
films and provision of pit nucleation sites by the mica
particles. Nunes and Ramanathan [15] studied the corro-
sion behaviour of alumina-aluminium and SiC-Al in so-
dium chloride solution. Immersion and anodic polariza-
tion corrosion tests have been carried out and these
composites exhibit lower corrosion resistance when com-
pared to matrix alloy. The formations of pits in the ma-
trix near the particle matrix interface have been ob-
served by Paciej and Agarwala [16], which lead to the
pull out of the particle.
Mclnyre et al. [17] in their research reported that the
precipitation behavior and consequently the pitting sus-
ceptibility of heat treatable matrix alloys vary in the
presence of SiC particles. Ahmad and Aleem [18] de-
scribed the corrosion behavior of aluminum metal matrix
composites in salt water. Al6013-20%SiC composite
showed good resistance to corrosion in salt spray tests. It
was reported by Greene and Mansfield [19] that casting
defects, the particle size of the reinforcing phase, the
processing route, the amount of alloying element present
in the matrix alloy are the factors which determine the
pitting corrosion behavior of MMCs. Tazaskoma et al.
[20] found that the pitting susceptibility was same for the
composite and the matrix alloy except for the 2024 alloy.
The general corrosion of these alloys was affected more
by the presence of oxygen than by the silicon carbide
phase.
Although there are several studies reported in the lit-
eratures on wear behavior of aluminum metal matrix
composites, no published work has been seen on the ef-
fect of reinforcement on erosive wear of Al5000 series
MMCs. Hence, the present research work has been un-
dertaken, with an objective to explore the use of alumin-
ium oxide (Al2O3) with graphite (Gr) as reinforcing ma-
terials in Al5083 alloy.
2. Experimental Details
The base matrix is used in the present investigation is
Al5083 alloy; the chemical composition is presented in
Table 1. The base alloy was melted in the electric fur-
nace and different castings were taken. Aluminium oxide
(Al2O3) and graphite (Gr) are used as reinforcing materi-
als in Al5083 alloy. Aluminium oxide is chosen as rein-
forcement owing to its high hardness and low co-effi-
cient of thermal expansion, highly wear resistant, good
mechanical properties, high temperature strength and
thermal shock resistance. Graphite is a solid lubricant,
which permits high corrosion resistance and almost re-
duces the friction coefficient, disintegrates the wear prod-
ucts, accelerates heat abstraction and increases seizure
resistance. The properties of aluminium oxide (Al2O3)
and graphite (Gr) are summarized in Tables 2 and 3 re-
spectively. The different types of hybrid composites have
been prepared with three different compositions. The
designations of the proposed composites are given in
Table 4. The reinforcements aluminium oxide (Al2O3)
and graphite (Gr) of partical size in the range of 20 - 60
µm are varied in the range of 3 wt% to 6 wt% of base
alloy.
The synthesis of hybrid metal matrix composites used
in the present study has been carried out by stir casting
method. Al5083 alloys in the form of ingots were used
for the preparation of specimens. The cleaned metal in-
gots were then melted to the desired super heating tem-
perature of 800˚C in the graphite crucibles under a cover
of flux layer in order to minimize the oxidation of molten
metal. A three-phase electrical resistance furnace with
temperature controlling device was used for the melting
purpose. The graphite (Gr) and aluminum oxide (Al2O3)
particulates preheated to around 500˚C and added to
molten metal and then stirred continuously by a me-
chanical stirrer at 720˚C. The stirring time maintained in
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