chap 1 final
TRANSCRIPT
MATERIAL SCIENCE &
ENGINEERING
Material science 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.
CERAMIC SUPERCONDUCTORS
SEMICONDUCTING POLYMERS
STEEL SHEETS USED FOR MANUFACTURE OF CAR CHASSIS
Material Scientist is concerned with steel sheet’s
(1)Composition (2) Strength (3)Weight (4)Energy absorbing properties (5)Malleability(formability)
MATERIAL SPECIFICATION Chemical composition Mechanical properties – Strength,
hardness (under various conditions: temperature, humidity, pressure)
Physical properties – density, optical, electrical, magnetic
Environmental – green, recycling
METALS & ALLOYS 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.
METALS
Ferrous MetalsCast ironsSteels
Super alloysIron-basedNickel-basedCobalt-based
Non-ferrous metalsAluminum and its
alloysCopper and its alloysMagnesium and its
alloysNickel and its alloysTitanium and its alloysZinc and its alloysLead & TinRefractory metalsPrecious metals
GENERAL PROPERTIES AND APPLICATIONS OF FERROUS ALLOYS
• 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 AND ALLOY STEELSCarbon 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.
CARBON AND ALLOY STEELSAlloy 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 desired properties.
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 Ceramics are defined as inorganic
crystalline material. Advanced ceramics are made by
refining naturally occurring ceramics and other special processes.
CERAMICS Traditional ceramics
clays: kaolinitesilica: quartz, sandstonealuminasilicon carbide
New ceramicsoxide ceramics : aluminacarbides : 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.
CHARACTERISTICS 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 Glass products
window glasscontainers light bulb glass laboratory glassglass fibersoptical 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.
POLYMERS 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
POLYMERS 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
THERMOPLASTICSAcetalsAcrylics - PMMAAcrylonitrile-Butadiene-Styrene - ABSCellulosicsFluoropolymers - PTFE , TeflonPolyamides (PA) - Nylons, KevlarPolysters - PETPolyethylene (PE) - HDPE, LDPEPolypropylene (PP)Polystyrene (PS)Polyvinyl chloride (PVC)
THERMOSETS Amino resins Epoxies Phenolics Polyesters Polyurethanes Silicones
ELASTOMERS Natural rubber Synthetic rubbers
butadiene rubberbutyl rubberchloroprene rubberethylene-propylene rubber isoprene rubbernitrile rubberpolyurethanessiliconesstyrene-butadiene rubber thermoplastic elastomers
SEMICONDUCTORS 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.
COMPOSITES 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.
PROPERTIES 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
CLASSIFICATION OF COMPOSITE MATERIALS
Metal Matrix Composites
Ceramic Matrix Composites
Polymer Matrix Composites
COMPOSITE MATERIALS 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.
COMPOSITE MATERIALS
1D fibre
Woven fabric
Random fibre
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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 dampingCeramics and Glasses SiO2-Na2O-CaO Window glass Optically transparent, thermally insulatingPolymers Polyethylene Food packaging Easily formed into thin,
flexible, airtight film
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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)
Table 1.1 Continued
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rooks/Cole P
ublishing / Thom
son Learning™
Figure 1.4 Representative strengths of various categories of materials