Development of ex-situ Aluminium metal matrix
composites with re-inforcement of Iron Oxide and
multi-wall Carbon nanotubes
Asst Prof. R.G. Vani
Sana S Rai, Sushant S Rai, Zabiulla,
Department of Mechanical Engineering, PESIT-BSC
Zuhaib Nissar
Asst Prof. Azharuddin Kazi
Department of Mechanical Engineering, PESIT-BSC,
Department of Mechanical Engineering, PESIT-BSC
Bangalore, India
Abstract
This project aims to develop new aluminum metal matrix
composites using MWCNT and iron oxide as reinforcements.
The casting was prepared using conventional sand casting
after which impact strength, wear resistance, hardness, density
were calculated.
In this project, Aluminium composite is prepared with the
different combination of reinforcement using ex-situ method.
The different combination that were used are “Aluminium
with iron oxide” and “Aluminium with iron oxide and
MWCNT”.
It was observed that the wear, impact and hardness improves.
Based on the observations, the materials can be used for high
impact and wear applications. However since MWCNT being
brittle in nature at low temperatures infers that the composites
cannot be used for high strength applications.
KEYWORDS
FE3O4, EX-SITU, MECHANICAL PROPERTIES, Aluminium alloy, LM6,
MULTIWALL CARBON NANOTUBE
INTRODUCTION
In aviation, automobile and other structural applications, the
demand for materials possessing superior properties like
higher strength to weight ratio, high modulus and high
temperature stability along with good damping ability is
continuously increases.
However, it is difficult to achieve all these properties in a
single material. This is one of the driving force for the
development of composite materials [1]. Aluminium (Al) and
its alloys have emerged as one of the most governing metal
matrix materials in the 21st century [2]. This is because of
their attractive mechanical properties [3, 4]. Among the Al
alloys, Aluminium-Silicon (Al-Si) alloys in particular have
been utilized considerably for engineering applications due to
their better mechanical and physical properties. They also
possess good manufacturing ability and lower density than Al
[5]. This reduces weight and results in energy savings in
automotive and aerospace applications. Aluminum matrix
composites (AMCs) are the competent material in the
industrial world. Due to its excellent mechanical properties,
AMCs is broadly used in aerospace, automobiles, marine etc
[6 - 8]. Researchers, particularly in the defense application, are
continuously striving hard to find the materials that suit their
specific requirements.
Metal matrix composite (MMC) is engineered combination of
the metal (Matrix) and hard Particle/ceramic (Reinforcement)
to get tailored properties. Like all composites, aluminummatrix composites are not a single material but a family of
materials whose stiffness, strength, density, thermal and
electrical properties can be tailored. The matrix alloy,
reinforcement material, volume and shape of the
reinforcement, location of the reinforcement and fabrication
method can all be varied to achieve required properties.
Research in the field of carbon was revolutionized by the
discovery of carbon nanotubes (CNTs) by Iijima6 in 1991.
Although CNTs might have been synthesized in 1960 by
Bacon, it took the genius of Iijima to realize that they are tubes
made by rolling a graphene sheet onto itself. A multiwalled
carbon nanotube (MWCNT) is made up of many single walled
Carbon nanotubes (SWCNT) arranged in a concentric manner.
Unless otherwise specified, CNT in this work refers to
MWCNTs. Experiments and simulations showed that CNTs
have extraordinary mechanical properties over carbon fibers,
e.g. stiffness up to 1000 GPa, strength of the order of 100 GPa
and thermal conductivity of up to 6000 W m-1 K-1. These
investigations showed that CNTs were the strongest fibers
known to mankind that possess exceptional properties. Since
the last decade, a number of investigations have been carried
out using CNT as reinforcement in different materials, namely
polymer, ceramic and metals [9]. Major works have been
carried out on polymer and ceramic based CNT reinforced
composites [10].
The aim involved in designing metal matrix composite
materials is to combine the desirable attributes of metals and
reinforcements. The addition of high strength, high modulus
refractory particles to a ductile metal matrix produce a
material whose mechanical properties are intermediate
between the matrix alloy and the reinforcement. Metals have a
useful combination of properties such as high strength,
ductility and high temperature resistance, but sometimes have
low stiffness, which can be improved by the addition of
reinforcements.
Casting is generally accepted as a particularly promising route,
currently practiced commercially. Its advantages lie in its
simplicity, flexibility and applicability to large quantity
production. It is also attractive because, in principle, it allows
a conventional metal processing route to be used, and hence
minimizes the final cost of the product.
Present study is carried out on physical and mechanical
characterization of multiwall carbon nanotubes reinforced
Aluminium LM6 to know the density, hardness, impact
strength and wear properties of the prepared materials.
Aluminium LM6 alloys are suitable for Marine 'on deck'
castings, water-cooled manifolds and jackets, motor car and
road transport fittings, thin section and intricate castings such
as housing, meter cases and switchboxes, for very large
castings, e.g cast doors and panels where ease of casting is
essential; for chemical and dye industry castings, e.g pump
parts; for paint industry and food and domestic castings. The
general use where marine atmospheres or service conditions
make corrosion resistance a matter of major importance.
Especially suitable for castings that are to be welded.
The ductility of LM6 alloy enable castings easily to be
rectified or even modified in shape, e.g simple components
may be cast straight and later bent to the required contour.
Equally adaptable for sand and permanent mould castings. In
general, the binary alloys are not heat treated; at elevated
temperatures their strength falls rapidly. Although of medium
strength their hardness and elastic limit are low but they
possess excellent ductility.
0.2% Proof Stress
(N/mm2)
Tensile
Stress
(N/mm2)
Elogation (%)
Impact Resistance.
Izod (Nm)
Brinell
Hardness
Number
Endurance
Limit
(5×107 cycles +/N/mm2)
Modulus of Elasticity
(×103 N/mm2)
Sand cast
60-70
Chill cast
70-80
Die Cast
120
160-190
190-230
280
5-10
6.0
7-15
9.0
2-5
-
50-55
55-60
55-60
51
68
-
71
71
71
Strength at Elevated Temperatures
Tensile strength and hardness decrease fairly regularly with
increasing temperature and become relatively poor at
temperatures of the order of 250 ̊C.
Physical Properties
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Coefficient of Thermal Expansion (per ̊C at 20100 ̊C)
0.000020
Thermal Conductivity (cal/cm2/cm/ ̊C / at 25 ̊C)
0.24
Electrical Conductivity (% copper standard at 20 ̊C)
37
Solidification Shrinkage (approx. %)
3.7
Specific Gravity
2.65
Freezing Range (̊C) approx.
575-565
Machinability
Materials and Methods
Chemical Composition of Al-(LM6)
Copper
Magnesium
Silicon
Iron
Manganese
Nickel
Zinc
Lead
Tin
Titanium
Aluminium
Mechanical Properties of Al (LM6)
%
0.1 Max
0.1 Max
10.0-13.0
.6 Max
0.5 Max
0.1Max
0.1Max
0.1Max
0.05Max
0.2Max
Remainder
Alloys of this and similar compositions are rather difficult to
machine. This is due firstly to their tendency to drag and
secondly to the rapid tool wear caused by the high silicon
content. Carbide tipped tools with large rake angles and
relatively low cutting speeds give comparatively good results.
A cutting lubricant and coolant should be employed.
Corrosion Resistance
LM6 exhibits excellent resistance to corrosion under both
ordinary atmospheric and marine conditions. For the severest
conditions this property can be further enhanced by anodic
treatment.
Anodising
LM6 can be anodised by any of the common processes, the
resulting protective film ranging in colour from grey to dark
brown.
Casting Characteristics
Fluidity - Can be cast into thinner and more intricate sections
than any of the other types of casting alloys.
Pressure Tightness - Especially suitable for leak tight castings.
Hot Tearing - Castings in sand or chill moulds exhibit
complete freedom for hot tearing.
Typical Pouring Temperature - A typical temperature for sand
and chill castings is 725 ̊C but in practice it may range
considerably above or below this value according to the
dimensions of the casting.
Pouring Temperatures for die castings depend very largely on
the particular casting and the machine and vary too widely for
a typical temperature to provide useful guidance. The melt
should not, however, be allowed to stand at temperatures only
a little above the freezing range or the bottom of the melt may
become enriched in such elements as iron and manganese.
Notes - For sand castings and medium and heavy section chill
castings the alloy must be modified before pouring (by
treatment with sodium or sodium salts. If the maximum
mechanical properties are to be realized. An alternative
modifying process is the treatment of the melt with strontium
as an aluminium-silicon-strontium hardener. A more persistant
state of modification is achieved by this method.
Heat Treatment
Ductility can be improved slightly by heating at 250-300°C,
but apart from stress relieving, the heat treatment of LM6 is of
little industrial interest.
Properties of Fe3O4
Molar mass
Density
Melting Point
Appearance
231.533 g/mol
5 g/cm3
1,538 °C
Red powder
Properties of MWCNTs
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Tensile Strength of 63 GPa
Density is 1.3-1.4 g/cm3
Specific strength of up to 48,000 kN·m·kg−1
Specific surface area 330 m2/g
Appearance in the form of black powder
Fabrication
The fabrication methods were adopted from the literature
survey [11], the Fe3O4 and MWCNT is not synthesized
within the matrix Aluminium LM6, rather they are directly
incorporated as reinforcement, the procedure is said to be ExSitu.
Fabrication of Aluminium (LM 6) and Fe3O4 composite
Fabrication of Aluminium (LM6) and Fe3O4 composite.
Aluminium (10kg) was heated in a graphite crucible using
coke powder as a fuel. The melting point of Aluminium is
660.3°C and that of iron oxide is 1460°C .Iron oxide (1kg)
was taken in pockets and dipped in the molten aluminium
when it reached the temperature of 700°C and the mixture was
stirred mechanically to achieve uniform dispersion. This was
done in a time span of 5 mins. The mixture was taken in a
ladle and then poured in the mould. The pouring temperature
was 690°C. Sand casting method was used to produce moulds.
One mould fetched 4 standard specimens. It took the mixture
10 minutes to harden in the moulds. For degasification
100gms of coveroll and 2 chlorine tablets were used. For the
purpose of machining clearance has been kept in a mould
cylinder specimen has a diameter of 30mm and length of
160mm. The composition of Fe3O4 by weight is 10%.2.2
Fabrication of Aluminium-Iron Oxide and MWCNT castings.
First an emulsion of MWCNT was prepared. In a beaker, 15
gms of MWCNT and 160 ml of acetone was stirred using
magnetic stirrer for 20 mins at 1320 rpm at room temperature.
In another beaker 2gm of Sodium Lauryl sulphate, 2 gm of
Tween 80 and 30 ml of Acetone was stirred using magnetic
stirrer for 15 mins at 400 rpm at room temperature.The
contents of both the beakers were poured into another beaker
and it was magnetically stirred for 30 mins at1250 rpm at
room temperature. Acetone was used as a dispersion medium,
Sodium Lauryl Sulphate was used to disperse nanotubes and
Tween 80 was used as an emulsifier. Aluminium (10 kg) was
heated in a graphite crucible using coke powder as a fuel. The
melting point of Aluminium is 660.3°C and that of iron oxide
is 1460°C .Iron oxide (1kg) was taken in pockets and dipped
in the molten aluminium and the emulsion of MWCNT was
poured into the molten aluminium when it reached 700°C and
the mixture was stirred mechanically to achieve uniform
dispersion. This was done in a time span of 5 mins. The
mixture was taken in a ladle and then poured in the mould.
The pouring temperature was 690°C. Sand casting method was
used to produce moulds. One mould fetched 4 standard
specimens. It took the mixture 10 minutes to harden in the
moulds. For degasification 100gms of coveroll and 2 chlorine
tablets were used.
For the purpose of machining clearance has been kept in a
mould cylinder specimen has a diameter of 30mm and length
of 160mm. The composition of Fe3O4 by weight is 10% and
that of MWCNT is 0.15 %.
Fabrication of Aluminium-Iron Oxide and MWCNT castings.
First an emulsion of MWCNT was prepared. In a beaker, 15
gms of MWCNT and 160 ml of acetone was stirred using
magnetic stirrer for 20 mins at 1320 rpm at room temperature.
In another beaker 2gm of Sodium Lauryl sulphate, 2 gm of
Tween 80 and 30 ml of Acetone was stirred using magnetic
stirrer for 15 mins at 400 rpm at room temperature. The
contents of both the beakers were poured into another beaker
and it was magnetically stirred for 30 mins at 1250 rpm at
room temperature.
Acetone was used as a dispersion medium, Sodium Lauryl
Sulphate was used to disperse nanotubes and Tween 80 was
used as an emulsifier.
Aluminium (10 kg) was heated in a graphite crucible using
coke powder as a fuel. The melting point of Aluminium is
660.3°C and that of iron oxide is 1460°C .Iron oxide (1kg)
was taken in pockets and dipped in the molten aluminium and
the emulsion of MWCNT was poured into the molten
aluminium when it reached 700°C and the mixture was stirred
mechanically to achieve uniform dispersion. This was done in
a time span of 5 mins.
The mixture was taken in a ladle and then poured in the
mould. The pouring temperature was 690°C. Sand casting
method was used to produce moulds. One mould fetched 4
standard specimens. It took the mixture 10 minutes to harden
in the moulds. For degasification 100gms of coveroll and 2
chlorine tablets were used.
For the purpose of machining clearance has been kept in a
mould, cylinder specimen has a diameter of 30mm and length
of 160mm. The composition of Fe3O4 by weight is 10% and
that of MWCNT is 0.15 %.
Impact Test
Charpy impact test was performed upon the specimens.
Charpy test is a standardized high strain-rate test which
determines the amount of energy absorbed by a material
during fracture. This absorbed energy is a measure of a given
material's notch toughness .The specimens taken had the cross
section area as 10mm X 10 mm. The notch was a U-notch.
The impact energy is calculated by using the formula
Energy absorbed = Average Energy / Area
During impact test results for “Aluminium and iron oxide”
average energy was found to be 3J and energy absorbed was
60J/m2 while that of “Aluminium- iron oxide-MWCNT”
average energy is 3J and energy absorbed=60J/m2
Density
Density of Aluminium-Iron oxide-MWCNT=2550 kg/m3
Density of Aluminium-Iron oxide=2632 kg/m3
Wear test
Wear is a process of material removal phenomenon. The
specimens were subjected to wear using pin on disc apparatus.
Test Procedures
Hardness Test
Hardness is generally considered as resistance to penetration.
The harder the materials, the greater the resistance to
penetration.
The hardness of both the compositions were evaluated using
Brinells Hardness Number. A standard specimen of 27.8mm
diameter and 10 thickness was used. The ball indenter
diameter is 1.5mm. The hardness is calculated by the formula
Brinell hardness number for the composition containing
“Aluminium-iron oxide” was found to be 62.806, while that of
the composition containing “Aluminium-iron oxide and
MWCNT” 58.7.
For the composition of Aluminium –Iron oxide, 3 specimens
were taken with the lengths 30mm, 34.2mm and 35.1mm and
3.27 g.3.4 g, 3.5 g respectively.
Sample
Load
Speed
Time
(kg)
(rpm)
(min)
1
1
600
5
2
1
600
5
3
1
600
5
Average wear co-efficient = 9.26x10-13 kg/mm3
For the composition of Aluminium -Iron oxide-MWCNT,3
specimens were taken with the weights 3.8108g,3.9205 g and
3.8605 g .
Sample
Load
Speed
Time
(kg)
(rpm)
(min)
1
1
600
5
2
1
600
5
3
1
600
5
Average wear co-efficient = 3.169x10-12 kg/mm3
Conclusions
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The hardness in the composition of Aluminium -iron
oxide is better than that of Aluminium –iron oxideMWCNTs
The Impact resistance in both the compositions is the
same
The wear rate is better in Aluminium-iron oxide
composition than that of Aluminium-iron oxide and
MWCNTs
The density of the composition of Aluminium-iron
Oxide-MWCNTs is lesser than that of Aluminiumiron oxide
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