Chap 1 final

 Materialscience and engineering is an
interdisciplinary field concerned with
inventing new materials and improving
previously known materials by developing
deeper understanding of microstructure-
composition-synthesis processing
relationships.

 Structure means description of arrangement
of atoms.
 Synthesis refers to how material are being
made from naturally occurring or man made
chemicals
 Processesing refers to how material are
shaped into useful component to cause
changes in properties of different material.

 In MATERIAL SCIENCE the emphasis is on
underlying relation ships between synthesis
and processesing, structure and properties of
materials.
 In MATERIALS ENGINEERING the focus is on
how to translate or transform materials into
useful devices or structures.

 PERFORMANCE:
 What is Strength to density ratio?
 What is formability?
 How does this relate to the crash worthiness of the vehicle?
 What is the cost of fabrication?
 A COMPOSITION
 Iron Based ?
 Aluminium based?
 What alloying elements should be added?
 What quantities?
 B MICROSTRUCTURE:
 (a)What features of the structure limit the strength and formability?
 (b) What controls the strength?
 C SNYTHESIS & PROCESSESING
 (a)How can steel making be controlled so as to provide high level of
toughness and formability
 (b)How can aerodynamic car chassis be formed.

 Material Scientist is concerned with steel
sheet’s
 (1)Composition
 (2) Strength
 (3)Weight
 (4)Energy absorbing properties
 (5)Malleability(formability)

 Chemical composition
 Mechanical properties – Strength, hardness
(under various conditions:
temperature, humidity, pressure)
 Physical properties –
density, optical, electrical, magnetic
 Environmental – green, recycling

 These materials are inorganic substances
that are composed of one or more metallic
elements .
 Eg:Fe,Ni,Cu,Al
 Non metallic elements as C,N may also be
included in metallic materials
 Metals have crystalline structure in which
atoms are arranged in orderly fashion
 Many metals are strong and hard even at high
temperature.

 Ferrous Metals  Non-ferrous metals
 Cast irons  Aluminum and its alloys
 Steels  Copper and its alloys
 Super alloys  Magnesium and its alloys
 Iron-based  Nickel and its alloys
 Nickel-based  Titanium and its alloys
 Cobalt-based  Zinc and its alloys
 Lead & Tin
 Refractory metals
 Precious metals

• Ferrous alloys are useful metals in
terms of mechanical, physical and
chemical properties.
• Alloys contain iron as their base metal.
• Carbon steels are least expensive of all
metals while stainless steels is costly.

Carbon steels
• Classified as low, medium and high:
1. Low-carbon steel or mild steel, <
0.3%C, bolts, nuts and sheet plates.
2. Medium-carbon steel, 0.3% ~
0.6%C, machinery, automotive and
agricultural equipment.
3. High-carbon steel, > 0.60%
C, springs, cutlery, cable.

Alloy steels
• Steels containing significant amounts of
alloying elements.
• Structural-grade alloy steels used for
construction industries due to high
strength.
• Other alloy steels are used for its
strength, hardness, resistance to creep
and fatigue, and toughness.
• It may heat treated to obtain the

 New and improved Ni-based,Fe-Ni-Co based
SUPERALLOYS are available for use in high
pressure turbine airfoils in aircraft gas
turbines.
 The term SUPER ALLOY is used because of
their improved performance at elevated
temperature of 5400Cand high stress levels

 Ceramics are defined as inorganic crystalline
material.
 Advanced ceramics are made by refining
naturally occurring ceramics and other
special processes.

 Traditional ceramics
 clays: kaolinite
 silica: quartz, sandstone
 alumina
 silicon carbide
 New ceramics
 oxide ceramics : alumina
 carbides : silicon carbide, titanium carbide, etc.
 nitrides : silicon nitride, boron nitiride, etc.

 Advanced Ceramics are used in substrate that
house computer chips,sensers and
actuators,capacitors,wirless communication, spark
plug,inductor,and electrical insulation.
 They are used as barrier coating to protect the
substrate in turbine engines.
 Used in consumer product like paints, plastics and
tires, and for industrial application as tiles for
space shuttle, a catalyst support and oxygen
sensors used in car.
 Traditional Ceramics are used to make brick,table
ware,sanitary ware,refractories and abrasives.

 1. Due to presence of porosity(small holes)
ceramics do not conduct heat well and must
be heated to very high temperature before
melting
 2.Ceramics are strong and hard but also very
brittle
 3. Fine powders of ceramics are prepared
and then converted to useful shapes.

 Glass products
 window glass
 containers
 light bulb glass
 laboratory glass
 glass fibers
 optical glass
 Glass ceramics - polycrystalline structure

 Glasses are Amorphous materials which do not have
regular periodic arrangement of atoms
 Fiber optic system uses optical fiber based on high
purity silica glass.
 Glasses can be thermally treated (tempered ) to
make them stronger.
 Forming glasses and nucleating(forming)small
crystal within them by special thermal process
creates material that are known as GLASS
CERAMICS”
 ZERODUR is the glass ceramic material that is used
for making mirror substrate for large telescope.

 They are inorganic materials
 Processed by Polymeraistaion
 Properties:
1. Good thermal insulation
 2.Good electrical resistivity
 3.Lower strenth but high strength to weight
ratio.
 4. Not suitable for high temperature application
 5.Good corrosion resistance
 Application:
Bullet proof vests ,compact disc,and liquid
crystal displays

 Thermoplastics - reversible in phase by heating and
cooling. Solid phase at room temperature and liquid
phase at elevated temperature.
 Thermosets - irreversible in phase by heating and
cooling. Change to liquid phase when heated, then
follow with an irreversible exothermic chemical
reaction. Remain in solid phase subsequently.
 Elastomers - Rubbers

 Acetals
 Acrylics - PMMA
 Acrylonitrile-Butadiene-Styrene - ABS
 Cellulosics
 Fluoropolymers - PTFE , Teflon
 Polyamides (PA) - Nylons, Kevlar
 Polysters - PET
 Polyethylene (PE) - HDPE, LDPE
 Polypropylene (PP)
 Polystyrene (PS)
 Polyvinyl chloride (PVC)

 Amino resins
 Epoxies
 Phenolics
 Polyesters
 Polyurethanes
 Silicones

 Natural rubber
 Synthetic rubbers
 butadiene rubber
 butyl rubber
 chloroprene rubber
 ethylene-propylene rubber
 isoprene rubber
 nitrile rubber
 polyurethanes
 silicones
 styrene-butadiene rubber
 thermoplastic elastomers

 Si,Ge and gallium arsenide based semiconductors
such as those used in computers and electronics
are part of Electronic materials.
 The electrical conductivity of semiconductors is
material is between metal conductor and
ceramic insulator.
 In some semiconductor the level of conductivity
can be controlled to enable electronic devices
such as transistor, diodes etc that are used to
build integrated circuits.
 Thin films of semiconducting materials are also
made by specialization processes.

 Main idea in developing COMPOSITE is to
blend the properties of different material
 These are formed from two or more
materials, producing properties not found in
single material.
 Concrete, plywood and fiberglass are
example of composite material
 Fiberglass is obtained by dispersing glass
fibers in polymer matrix. Fiber make it
stiffer without increasing density.

 With composite we can produce structure:
 1. Light Weight
 2. strong
 3. ductile
 4.high temperature resistant
 5. Shock resistant
 Advanced Aircraft and aerospace vehicles
rely heavily on composites as carbon fiber
reinforced composites

 Metal Matrix Composites

 Ceramic Matrix Composites

 Polymer Matrix Composites

 Metal Matrix Composites (MMC)
Mixture of ceramics and metals reinforced by strong, high-
stiffness fibers
 Ceramic Matrix Composites (CMC)
Ceramics such as aluminum oxide and silicon carbide
embedded with fibers for improved properties, especially
high temperature applications.
 Polymer Matrix Composites (PMC)
Thermosets or thermoplastics mixed with fiber
reinforcement or powder.

1D fibre

Woven fabric

Random fibre

Table 1.1 Representative
examples, applications, and properties for
each category of materials

Example of Applications Properties

Metals and Alloys
Gray cast iron Automobile engine blocks Castable, machinable,
vibration damping
Ceramics and
Glasses SiO2-Na2O-CaO Window glass Optically transparent,
thermally insulating
Polymers
Polyethylene Food packaging Easily formed into thin,
flexible, airtight film

37

Table 1.1 Continued

Example of Applications Properties

Semiconductors
Silicon Transistors and integrated Unique electrical
circuits behavior

Composites Carbide cutting tools for High hardness, yet
Tungsten carbide machining good shock resistance
-cobalt (WC-Co)

38

© 2003 Brooks/Cole Publishing / Thomson Learning™
Figure 1.4 Representative strengths of various categories of materials

39

Chap 1 final

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Chap 1 final