by

SHAIK JABBAR (1604-13-736-323 )

MOHAMMED FAHED (1604-13-736-318 )

SYED MUQSEEDUDDIN (1604-13-736-315 )

MOHAMMED SHAREEF (1604-13-736-317 )

Under the guidance

Of

Mr . M. A. Hakeemuddin Ahmed Associate Professor (Mechanical Eng.. Dept.)

Objectives

To fabricate Aluminium Metal Matrix Composite (Al SiC MMC).

To characterize its mechanical properties such as tensile strength and

hardness.

To obtain optimum machining parameters in order to get good

surface finish.

Introduction

Composites

“A materials system composed of two or more physically distinct

phases whose combination produces aggregate properties that are

different from those of its constituents”.

Composite = Matrix + Reinforcement + Additives

Examples

Cemented carbides (WC with Co binder)

Plastic molding compounds containing fillers

Rubber mixed with carbon black

Wood (a natural composite as distinguished from a synthesized

composite)

Importance of composites

Composites can be very strong and stiff, yet very light in weight, so

ratios of strength-to-weight and stiffness-to-weight are several times

greater than steel or aluminum.

Fatigue properties are generally better than for common engineering

metals.

Toughness is greater than other materials

Composites can be designed to be corrosion resistive.

It is possible to achieve combinations of properties not attainable

with metals, ceramics, or polymers alone.

Matrix

A Matrix is a material into which the

reinforcement is embedded & is completely

continuous..

Transfer Stresses to phases.

When a load is applied, the matrix shares the

load with reinforcement.

Nylon, epoxy, polyester, aluminium,

magnesium, titanium, etc., are some of the

matrix elements.

Reinforcement • The reinforcement material is embedded into a matrix. It used to

change physical properties such as wear resistance, friction

coefficient, or thermal conductivity.

• They support the matrix, they are principal load bearing members.

Carbon Nanotubes

Classification

Natural Composites – composite materials that occur in nature or

have been produced by civilizations for many years

Examples: wood, concrete, asphalt

Synthetic composites - modern material systems normally

associated with the manufacturing industries, in which the

components are first produced separately and then combined in a

controlled way to achieve the desired structure, properties, and part

geometry.

Natural composites

• Wood is a combination of cellulose fibre

and lignin. Cellulose provides strength and

lignin is the glue that bonds and stabilizes

the fibres.

• In bone, collagen protein

fibres form the matrix phase,

which is reinforced with

small rod like crystals of

hydroxyapatite about 5nm x

5nm x 50nm size.

Synthetic Composites

• Based on Matrices Composites

Polymer Metal Ceramic

• Most plastic molding

compounds.

• Rubber reinforced

with carbon.

• Fiber-reinforced

polymers

• Carbon Reinforced Al

• Aluminium SiC.

• Magniesium

• Silicon carbide

• Silicon nitride

• Aluminium oxide

Metal Matrix Composite

Definition A metal matrix composite (MMC) is composite material with at least

two constituent parts, one being a metal necessarily, the other material

may be a different metal or another material, such as a ceramic or

organic compound.

Examples: Aluminium SiC, Magnesium Graphite, Copper reinforced

with Boron.

Aluminium

• Density: 2.70 g/cm 3

• Density in liquid state: 2.375 g/cm3

• Lighter in weight.

• It has a tensile strength of 270 Mpa

.

• It is the property of the material to

resist deformation under tension.

• It has a thermal conductivity of 237 W/mK

• Rapid heat dissipation takes place.

• Hardness is resistance to scratch and indentation.

• Hardness of Aluminium is Rockwell number 40

• It is very soft.

• It is the increase in length per unit rise in

temperature.

• Its value for aluminium is 22.2 e-6 m/(mK)

Silicon Carbide

• Density : 3.1gm/cc

• It has a tensile strength of 1625Mpa ..

• Hardness of Silicon carbide is Rockwell number 2800

Kg/mm2

• Melting temperature 2730 C

• Coefficient of Thermal expansion 2.7 e-6 m/(mK)

Aluminium Silicon Carbide

Property SiC- 5% SiC- 10% SiC-15% SiC-20%

Density

(g/cm3)

2.4660 2.3125 N/A N/A

Yield strength

(N/mm2)

236 257 N/A N/A

Hardness

(BHN)

85.3 87.2 N/A N/A

Tensile

strength

(N/mm2)

248 265 N/A N/A

Coefficient of

thermal

expansion

N/A N/A N/A N/A

Advantages Of Al MMC

Higher specific strength and modulus over metals.

Lower coefficients of thermal expansion.

Maintenance of high strength properties at high temperatures.

No moisture absorption.

High thermal conductivity.

Higher operating temperatures.

Fatigue resistance.

Limitations Material cost is higher than the conventional metals.

Higher manufacturing cost.

Non visible impact damage.

Repairs are different than those of conventional metals.

Complex fabrication methods.

Applications

Fabrication of Aluminium MMC

Diffusion Bonding

Diffusion bonding process: (a) apply metal foil and cut to shape, (b) lay up desired

plies, (c) vacuum encapsulate and heat to fabrication temperature, (d) apply

pressure and hold for consolidation cycle, and (e) cool, remove, and clean part.

• Used to fabricate carbon

fiber reinforced aluminum,

boron, beryllium and steel

fibers in aluminum alloy

matrix.

Powder Metallurgy Process

• Used to produce composites

such as boron, carbon and

boric fibers with aluminum

alloy, SiC fibers with

chromium alloys, boron and

Al2O3 fibers with titanium

alloy, tungsten and

molybdenum fibers with

nickel alloy.

Stir Casting Process Stir casting process parameters

Stirring speed – 200 rpm to 400 rpm

Stirring temperature – 630 C

Stirring time – 10 min @ 100rpm

Pouring temperature – Sufficiently

high to avoid coarse structure.

Specifications:

Power of motor – 0.5 Hp

Stirrer material – High carbon Steel

Sand mould

Components to be casted:

Two rods of 200 mm length

and 30mm diameter.

A disc of 40mm diameter

and 15mm thick.

Non pressurized Parting gating system

Characterization

Tensile Test

A test in which fabricated Al MMC is subjected to a controlled

tension until failure.

Properties that are directly measured via tensile test are

Tensile strength

Maximum elongation under tension.

Reduction in cross section area.

Young’s Modulus of elasticity

Yield strength

• According to ASME standard a dog bone shape test specimen is

produced by machining operation.

• Tensile test is to be carried out on universal testing machine.

Hardness Test

Hardness is the property of a material that enables it to resist

indentation, scratching, bending, abrasion and cutting.

Hardness Test Methods:

• Rockwell Hardness Test

• Rockwell Superficial Hardness Test

• Brinell Hardness Test

• Vickers Hardness Test

• Micro hardness Test

• Moh's Hardness Test

• Scleroscope and other hardness test

methods

Rockwell hardness test

Rockwell hardness test method consists of indenting the test material

with a diamond cone or hardened steel ball indenter.

The Rockwell hardness number can be calculated by

HR = E - e

E = a constant depending on form of indenter: 100 units for diamond indenter,

130 units for steel ball indenter.

e = permanent increase in depth of penetration due to major load F1 measured

in units of 0.002 mm

Machining Test

Speed (rpm) Feed

(mm/min)

Depth of cut

(mm)

150 10 0.2

250 20 0.3

300 30 0.4

The machining variables which effect the

surface roughness value include

a) cutting speed

b) feed, and

c) depth of cut.

Literature Review Pradeep R et.al observed the study of mechanical properties of Al- Red

Mud and Silicon Carbide Metal Matrix Composite (MMC) of Aluminum

alloy of grade 7075 with addition of varying SiC weight percentage such as

6%, 4%, 2%. The experimental result reveals that the combination of a

matrix material improves mechanical properties like tensile strength,

compressive strength, hardness and yield strength.

H. Izadi et.al investigated through FSP and has observed improvement in

the micro hardness of Al–SiC composites produced by traditional powder

metallurgy and sintering methods. The material flow in the stir zone during

FSP was successful in uniformly distributing the SiC particles. However,

when samples with 16% SiC (by volume) were processed, there were

residual pores and lack of consolidation. An increase in hardness of all

samples was observed after friction stir processing which was attributed to

the improvement in particle distribution and elimination of porosity.

Thank You