engineering

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Engineering Materials
Prof. Keyur P Hirpara
Assistant Professor
LD College of Engineering
hirparakp@gmail.com
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Mechanical Behavior of metals & their properties
Various characteristic of materials which describe their
behaviour under external loads are known as mechanical
properties of materials.
Study of such properties is important because the selection of
materials, design & manufacturing of various components of a
machine depends upon mechanical properties.
Mechanical properties
 Strength :
 it represents the ability of a material to resist the breaking under the action
of external loads.
 Varies according to types of loading. Like tensile, compressive, shearing
strength.
 Elasticity :
 The property by virtue of which a material regains its shape & size on
removal of external load is called elasticity.eg. Rubber, mild steel, copper
etc…
 the resistance of material to elastic deformation under external load is
called stiffness or rigidity.
 Plasticity:
 It is the property of a material due to which it undergo permanent deformation
without failure on application of load.
 E.g. this properties used for various processes of forging , shaping , rolling ,
stamping…….etc
 Malleability :
 It is the property of a material by virtue of which it can be flattened into sheets.
 Lead ,tin,aluminium,copper etc….are malleable material.
 Ductility :
 It is a property of the material by virtue of which enables it to be drawn into thin
wires on application of tensile force.
 E.g. gold ,platinum ,silver, iron ,zinc….
 Fatigue :
 It represent the property of material to determine its behavior when subjected to millions of
cyclic fluctuations of load in which the maximum stress developed in each cycle.
 Under these conditions a component may fail after certain number of load application . Such
type of failure is known as fatigue.
 Hardness :
 The ability of a material to resist against abrasion, scratching ,wear ,cutting, penetration etc..
Is called hardness.
 It is determined by various tests like brinell ,rockwell & vicker’s hardness test.
 Creep :
 Slow and progressive deformation of material with time under constant stress i.e. force per
area at high temp. is called creep.
 This property is useful in designing the machine components subjected to high tempreture
like boilers , i.c.engine etc…
Classification of Engineering materials
Engineering
materials
Metal
Ferrous
iron & steel & their alloy
Non-
ferrous
Copper , zinc , lead, tin
,etc. & their alloy
Non –
metal
Plastics, rubber,
timber, ceramic, glass

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FERROUS MATERIALS
 FERROUS MATERIALS contain iron, as a major element &
other as a minor element.
 They are the most important alloys in the metallurgical &
mechanical industries because of their extensive use.
 Ferrous metals commonly used in engineering practice are cast
iron, wrought iron, steel & alloy steel.
 The principal material for all ferrous metal is pig iron.
CAST IRON
 Pig iron is obtained by processing iron in blast furnace with coke
and limestone
 Cast Iron is obtained by remelting pig iron with coke and
limestone in cupola furnace
CAST IRON
 The cast iron is an alloy of iron & carbon.
 It Has melting point about 1200° C.
 This is good because it can be easily melted, requires less fuel
& it can be more easily handle in furnaces.
 So, this characteristics gives an inexpensive material & different
product design.
 Carbon content varies in cast iron from 2 to 4.5%.
 It also contains small amount of silicon, sulphur, manganese &
phosphorus.
 It is a brittle material, so it can not be used in those parts
which are subjected to shocks.
CAST IRON
 The properties of cast iron, which makes it valuable for
engineering purpose are:
1.Low cost.
2.Good casting characteristics.
3.High compressive strength.
4.Wear resistance.
5.Excellent Machinability.
CAST IRON
 The compressive strength>Tensile strength.
 Following are the values of ultimate strengths of cast iron.
Tensile = 100 to 200 MPa
Compressive=400 to 100 MPa
Shear =120 MPa
CLASSIFICATION OF CAST IRON
1. Grey cast iron
2. White cast iron
3. Chilled Cast iron
4. Molted cast iron
5. Malleable cast iron
6. Nodular cast iron
7. Alloy cast iron

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Application of CI
 Machine tool beds
 Cylinder blocks
 Piston rings
 Gears
GRAY CAST IRON
 It is low cost material that can be used
for many purpose.
 It is an alloy of carbon & silicon with
iron.
 It’s chemical compositions are given
below.
C: 2.5-3.8% Si:1.1-2.8%.
Mn:0.4-1% P: 0.15%
S: 0.10% Fe:Balance
 It is marked by the presence of flakes
of graphite in a matrix of ferrite
(Shown In Fig.).
GRAY CAST IRON
 Generally graphite flakes occupy about 10% of the metal volume.
 Length of the flakes is vary from 0.05mm-0.1mm.
 When a bar of gray cat iron fractured it gives gray appearance due to
presence of graphite in it.
 Low melting point.
 High Fluidity, It can be cast into complex shape & thin section.
 It has solidification Range of 2400(1093)-2000°F(1316°C)
GRAY CAST IRON
 Having a good machinability.
 High resistance to wear.
 It has high compressive strength & low tensile strength. Compare
to steel.
 It is a low cost material with good hardness.
 It has excellent casting qualities for producing simple & complex
shapes.
APPLICATIONS of GRAY CAST IRON
 Machine tool structures.
 Cylinder blocks & heads for I.C.Engine.
 Frames for electric motors.
 Piston Rings.
 Rolling mill & General Machinery Parts.
 Household Applications.
WHITE CAST IRON
 It is a particular variety of cast iron, which shows a white
fracture.
 The white color is due to that carbon is present in form of
carbide (Fe3C) also called cementite.
 It is cause by quick cooling of molten metal.
 High tensile strength & Low compressive strength.
 It cannot be machined.
 It is widely used as a coating material & it can be used as a raw
material for production of malleable cast iron.

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WHITE CAST IRON
 It’s name derives in that, if we
see the microstructure of the
freshly broken surface, bright
white fracture appears.
 It has carbide,so it is very hard
& brittle material.
 So, it has excellent wear
resistance.
 It is has very poor machinability.
 It is cause by quick cooling of
molten metal.
 High tensile strength & Low
compressive strength.
WHITE CAST IRON
 It has following chemical composition
C: 1.8-3.6% Si: 0.5-2.0%
Mn:0.2-0.8% P: 0.18%
S: 0.10% Fe: Balance
 Solidification Range:
2550(1398)-2065°F(1130°C)
 Applications:
1.Production in malleable cast iron.
2.For manufacturing those component parts which requires a hard surface.
MALLEABLE CAST IRON
 It can be obtained from white cast iron by suitable heat treatment
process (i.e. annealing).
 It is ductile & may be bent without breaking or fracturing section.
 It’s tensile strength is higher than grey cast iron.
 It is used in hubs of wagon wheels, brake supports, door hinges,
locks, etc.
MALLEABLE CAST IRON
 It is a cast iron which can be hammered & rolled to obtain
different shapes.
 It can be obtained from white cast iron through heat treatment
process.
 It has two types:
1.Ferritic malleable cast iron
2. Pearlitic malleable cast iron
MALLEABLE CAST IRON
 It has good vibration damping capacity.
 It has moderate cost.
 It has low coefficient of thermal expansion
 It has following composition:
C: 2-3% Si: 0.6-1.3%
Mn:0.2-0.6% P: 0.15%.
S: 0.10% Fe:Balance
 It has high young’s modulus.
 Solidification Range:
2550(1398)-2065°F(1130°C)
MALLEABLE CAST IRON
It has following application:
 Automotive Industries
 Rail Road.
 Electrical Line Hardware.
 Conveyor chain links.
 Gear Case.
 Crankshaft
 Crankshaft sprocket.

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Wrought Iron
 It is purest form of iron and is obtained by eliminating most of carbon
and impurities.
 Composition
C = 0.02% Si = 0.13%
Mn = 0.03% P = 0.1%
S = 0.02% Slag < 0.07%
Wrought Iron
Properties
 Tough, Malleable & Ductile material.
 It can withstand sudden and impact loads.
 Corrosion resistant and can be welded and forged
Applications
 Wire ropes, cranes, hooks, railway couplings, water and steam pipes, chains.
STEELS
 Steel is an alloy of iron & carbon.
 It has carbon maximum up to 1.5%.
 The carbon occurs in form of iron carbide, because of it’s
ability to increase the hardness & strength of steel.
 Other elements like silicon, phosphorus, & manganese are
also present to impart certain desired properties to it.
PLAIN CARBON STEEL
 It is an alloy of iron & carbon. It is malleable.
 It is different from cast iron as regards the amount of carbon
present.
 It contains 0.10-1.4% C whereas cast iron possesses 1.8-4.2%
C.
 It can be classified following.
1. Low carbon Steel
2. Medium Carbon Steel
3. High carbon steel
LOW CARBON STEEL
 These are also known as mild steel.
 They contain carbon upto 0.25%
 They show poor response to heat treatment .
 Cheapest among all steels.
 Possess good formability and can be easily welded.
 Relatively soft and weak but possess outstanding
ductility and toughness.
 Good Machinability.
 Surface hardness and wear resistance can be improved
by carburuzing.
LOW CARBON STEEL
 Applications
 Automobile and refrigerator bodies, structural shapes, girders
 Ship plates, boiler plates, pipelines, cams, shafts
 Drawbacks
 Poor corrosion resistance
 Hardenability is too low

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MEDIUM CARBON STEEL
• Carbon content – 0.25 to 0.65 %
• Better response to heat treatment than low carbon steels
• They are heat treated to improve their mechanical
properties.
Application : Railway wheel and tracks, railway couplings,
gears, crankshafts, axles, cylinders
HIGH CARBON STEEL
 Carbon content – 0.65% to 1.5%
 Hardest and strongest but least ductile among all plain
carbon steel.
 Possess good wear resistance
 Poor fabricability, formability , machinability and weldability
 Machinability and formability can be improved by annealing
 Application : Cutting tools, dies, shearing knives, razors,
hacksaw blades,chisels.
Copper
 Melting Point – 1083 C
 Highest electrical & thermal conductivity (except Silver)
 Good ductility and malleability
 High corrosion resistance
 Non Magnetic & reddish brown color
 Good Machinability and ease of fabrication
 Easily alloyed with other metals
 High scrap value
Applications of Copper
 Electrical application
 Heat conductors
 Telecommunication
 Components of turbo generators
 Pressure vessels
 Utensils
 Water heaters
 Refrigerators
 Heat exchanger
Copper Alloys
 Brass
 alloy of copper and zinc.
 They have higher strength but less expensive than copper.
 Application
 Cartridge casing, radiators, medals, coins, screws, musical
instruments, utensils , piston rods etc.
Copper Alloys
 Bronze
 Alloy of Copper, Tin, Al, Si, Ni
 Tin – 5 to 25%
 Tensile strength increases with increase in Tin content.
 Higher strength hardness, corrosion resistance than brass.
 Good fatigue resistance and bearing properties
 Application – bearings , bushes, springs, pump
castings, gears, dies, bell metals, utensils

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Aluminium
 Melting point – 660 C
 Lighter than all materials (except Be, mg)
 Possess good electrical and thermal conductivity
 High strength to weight ratio
 Good corrosion resistance.
 High ductility and malleability
 Non magnetic
 Very high reflectivity for heat and radiant energy
 Easily casted, rolled ,forged & machined
 Non toxic and suitable for food packaging.
Application of Al
 Electrical application such as cables wires, motor windings, generator
 Piston oil and fuel pumps.
 Airframes, enmgines, propellers and body parts in automobiles,
spacecrafts.
 Cooking utensils, food container, silver foils for packaging
 Used in place of copper as less costly
Aluminium Alloys
 Duralumin
 Contains Al-94% Cu-4%
Mg, Mn, Si, Fe – each 0.5%
 Can be easily casted, forged and stamped
 High tensile strength & high conductivity.
 Hardness between 60 to 100 BHN.
 Application
 Tubes, sheets, forging, rivets, nuts, bolts
 Used for making electrical cables
 Aircraft & automobile applications.
Alloys of Aluminium
 Hinduminium
 Alloy of AL & Cu with small amount of Ni, Mn, Ti,
Co, Zn, Sb
 Used in high temperature application up to 300 C.
 Hindalium
 Manufactured by Hindustan Aluminium Corp. Ltd.
 Alloy of Al, Mn, Si, Mg, Cr
 Used for anodized utensils.
Ceramic
 Inorganic, nonmetallic materials
 E.g – Glass, cements, concrete, abrasive, brick, tiles,
drain pipes, sanitary wares, refractory lining for furnaces
etc.
 Properties
 They are hard and brittle.
 Strong in Comp. but weak in tension.
 Poor conductor of heat & non conductor of electricity.
 Good corrosion resistance
 Chemically inert and poor machinability
Glass
 Ceramic material used for building construction,
automobiles, aeroplanes missiles, spacecraftt etc.
 Properties
 No specific crystalline structure.
 No specific melting point
 Can be easily shaped.
 Very good optical properties.
 Good rigidity, hardness and strength.
 Good electrical and thermal insulation
 Can be cleaned very easily
 Brittle and available in nice colors.

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Timber
 Used in building construction, furniture, wheels, carts
etc
 Advantages
 Easily available
 High strength to weight ratio
 Can be easily cut and shaped by ordinary carpentary
tools
 Good thermal and electrical insulation
 Suitable for use in hot cold and earthquake prone areas.
Plastic
 Plastic are composed of resin, catalyst, accelerator,
inhibitors, amd pigments
 Advantages
 Ease in fabricating a complex part as whole
 Expensive finishing processes not required.
 No lubrication required
 Noise of moving part is less
 Low weight so improves efficiency of m/c
 Can be produced transparent with low brittleness than
glass
Polymers & composite materials
 It is large molecule composed of repeating structural units connected by
covalent bonds e.g DNA & Proteins
 Crystalline in structure
 High tensile strength and melting point
 Degrades in front of heat and light.
 Applications – Synthetic fibres like silk, bullet proof vests, packaging and
coating materials, optical industry(lenses reflectors)
Diamond
 Carbon arranged in isometric hexoctahedral crystal lattice
 Hardest material and has property of high dispersion of
light.
 Diamonds make excellent abrasives
 Act as electrical insulator
 Blue diamonds are semiconductors
 High thermal conductivity, high refractive index and can cut
glass.
 Synthetic diamonds are manufactured by HTHP processes.
 Also produced by chemical vapor deposition process
Graphites
 Allotrope of carbon.
 Good electrical conductor & stable
 Used in pencils and drawings.
Thank You
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