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Introduction:

Aluminum (Al) is an abundant element on
earth and has various applications in everyday life due to its longer life
span, lightweight and cost effectiveness. The properties of aluminum are
further enhanced by adding various elements creating durable alloys. These
alloys are further reinforced by metal matrix composites to enhance their
tribological properties.

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Metal-matrix composites have a lot of
commercial application due to their enhanced mechanical properties, wear
resistance and low coefficient of thermal expansion 1, 2. The application areas of Metal-matrix
composites include automotive and ballistic industries, infrastructure, space
and air vehicles, under-water vehicles and deep-ocean equipment.

 

Along with these properties,
metal-matrix composites also have other advantageous characteristics such as
good strength-to-weight ratio, high specific stiffness, high hardness, high
plastic-flow strength, good thermal expansion, thermal stability, creep
resistance, and good oxidation and corrosion resistance3, 4.

 

Wang and Rack 5 and Zhang and Alpas 6 have demonstrated that the rate-controlling wear
mechanisms may change abruptly at certain sliding velocities and contact loads,
leading to abrupt increases in wear rate. It is suggested that many of the
conflicting results in the wear literature can be explained by the three
regimes which have been identified, when the wear rate is considered as a
function of test load 3, 4.

 

Based on the above literature, Aluminum
6061 was taken for studies for calculation for study of wear for the following
conditions through pin on disc mechanism

Ø  Wear
effects with varying load conditions with constant velocity and distance

Ø  Wear
effects with varying velocity conditions with constant load and distance

Ø  Wear
effects with varying distance with constant load and velocity

 

Experiment
Details:

Material:

The composition of Al 6061 is as follows
5

Ø  Aluminum             :           97.9%

Ø  Silicon                   :           0.6%

Ø  Copper                  :           0.28

Ø  Magnesium            :           1.0%

Ø  Chromium             :           0.2%

The
tensile strength of Al6061 is 42 ksi and yield strength of 36 ksi 5. The microstructure of Al
6061 is given below  6

 

 

 

 

 

 

 

 

Fig
1: Microstructure of Al 6061

Al 6061 is used for the following
products manufacturing 5

Sheet; plate; foil; extruded rod, bar
and wire; extruded shapes; extruded tubes; cold finished rod, bar and wire;
drawn tube and forgings.

The major properties 5 of Al 6061 are

Ø  Good
formability,

Ø  Weldability,

Ø  Corrosion
resistance, and

Ø  Strength
in the T-tempers.

The major applications 7 of Al 6061 including structural
applications and welded assemblies are

 

Truck components, railroad cars, pipelines,
marine applications, furniture, agricultural applications, aircrafts,
architectural applications, automotive parts, building products, chemical equipment,
dump bodies, electrical and electronic applications, fasteners, fence wire, fan
blades, general sheet metal, highway signs, hospital and medical equipment,
kitchen equipment, machine parts, ordnance, recreation equipment, recreation vehicles,
and storage tanks

 

Experimental
Set Up:

The dry sliding wear test was conducted
on The Ducom Pin/Ball on Disk Tribometer as shown in Fig. 1. The specimen used
for the wear test is of 30 mm in length and 8 mm in diameter. They were machined
and polished as per ASTM standards. A radius of 5 mm was given to one end of
the specimen and the other side was made flat. The rounded end (pin) was made
in contact with the disc.

 

 

 

 

 

 

 

 

 

Figure
2: Experimental setup

The experiment was conducted by holding
the pin against a rotating disc (EN32 steel) and by adding weights on the left
arm of the apparatus. The track diameter was kept constant as 140 mm. The
experiment was then conducted by varying the applied load, sliding velocity and
sliding distance for three levels as shown in Table 1.

Tribological Parameters

Load (kg)

Velocity (m/s)

Sliding distance(mm)

1

2.5

1500

2

3

2

1.5

1500

2.0

2.5

2

2.5

1500

2000

2500

Table
1: Test conditions

The pin holding arm is monitored by a
Linear Variable Differential Transformer which determines wear at any given
point of time. When the pin gets out of contact with the sliding surface, a
signal is generated this induces the load to be pushed on the arm ensuring the
pin is in constant contact with the sliding surface. This generates a signal through
which the maximum wear on a continuous scale is monitored.

 

Experimental
Results:

Wear
test conditions

Pin Material                 :           Al 6061

Disc Material               :           EN52 Steel Disc

Pin Contact Area        :           64 mm2

Track Radius               :           120
mm

Sliding velocity           :           1.5, 2
& 2.5 m/s

Loads                          :           1,
2 & 3 kgs

Relative Humidity      :           85%

Temperature                :           Room
Temperature

Sliding Distance          :           3000 m

 

Effect
of load on wear rate:

The variation of wear rate with varying
loads of 1, 2 and 3 kgs over a sliding distance of 2000 m at a constant
velocity of 2.5 m/s is depicted in the figure 3.

 

 

 

 

 

 

 

 

 

Figure
3: Variation of Wear rate with varying load

The wear rate increases with the
increase of varying loads and the highest wear rate occurs for a load of 3 kg.
due to the monolithic nature of the alloy

The microstructure of the wear pattern
for varying load is depicted is shown in figure 4, 5 and 6

 

 

 

 

 

 

 

 

Figure
4: Wear pattern with 1kg load

 

 

 

 

 

 

 

 

Figure
5: Wear pattern with 2 kg load

 

 

 

 

 

 

 

 

Figure
6: Wear pattern with 3 kg load

 

Effect
of sliding velocities on wear rate

The variation of wear
rate with varying sliding velocity of 1.5 m/s, 2 m/s and 3m/s over a sliding
distance of 3000 m at a constant load of 2 kgs is depicted in the figure 7

 

 

 

 

 

 

 

 

 

 

Figure
7: Variation of Wear rate with varying sliding velocities

The wear rate increases with the
increase of varying sliding velocities and the highest wear rate occurs for a
sliding velocity of 2.5 m/s. From the graph it can be seen that the wear rate
increases at a higher rate as the sliding distance increases

 

Effect
of sliding distance on wear rate

The variation of wear
rate with varying sliding distance of 3000 m at a constant load of 2 kgs and
sliding velocity of 2.5 m/s is depicted in the figure 8

 

 

 

 

 

 

Figure
: Variation of Wear rate with varying sliding distance

The wear rate increases with the
increase of varying sliding distance and the highest wear rate occurs for a
sliding velocity of 3000 m. From the graph it can be seen that the wear rate
increases at a linear fashion.

 

Conclusion:

This research is intended to study the
rate of sliding wear of Al 6061 under different test cases like varying load, varying
sliding velocities and varying sliding distance.

The study indicates the effect of these
factors on the monolithic alloy. Based on the results it is proposed to study
the effect of wear rate on Al 6061 metal matrix composites with the following
composition

Compositions

Al 6061 85%
B4C 5%
Gr 10%

Al 6061 75%
B4C 10%
Gr 15%

Al 6061 65%
B4C 15%
Gr 20%

 

REFERENCES

1.   S.
Balasivanandha Prabu, L. Karunamoorthy, S. Kathiresan, B. Mohan, Journal of
Materials Processing Technology, 171 (2006), 268–273

2.   M.
Taya and R.J. Arsenault, Metal Matrix Composites—Thermo Mechanical Behavior,
New York, Pergamon Press, 1989

3.   A.
Ibrahim, F.A. Mohammed, and E.J. Lavernia, Metal Matrix Composites— A review,
J. Mater. Sci., (1991), 26, p 1137-1157

4.   A.
A. Cerit, M. B. Karamiº, F. Nair, K. Yildizli, Tribology in industry, 30 (2008),
3–4

5.   J.
Zhang and A.T. Alpas, Wear regimes and transitions in AIZO, particulate-reinforced
aluminium alloys, Mater. Sci. Eng., A161 (1993) 273-284.

6.   http://www.metallographic.com/Procedures/6061-Aluminum.html

7.   A.
Wang and H.J. Rack, Transition wear behaviour of Sic-particulate and
Sic-whisker reinforced 709lAI metal matrix composites, Mater. Sci. Eng.,  Al47 (1991),
21 l-224.

 

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