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ENGINEERING MATERIALS AND
METALLURGY
AUTONOMOUS
For fourth SEMESTER(II YEAR)
PREPARED BY
S.ARAVINDHA BALAJI
ASSISTANT PROFESSOR
DEPARTMENT OF MECHANICAL
ENGINEERING
SONA COLLEGE OF TECHNOLOGY
SALEM:636005
ENGINEERING MATERIALS AND
METALLURGY
1/5/2013
SAB-AP/MECH SONACT
Application of EMAM(In Industry):
 Steel industry( e.g. steel plants, (SAIL) Essar
steels, jindal steel ltd.(JSW))
 Pipe maufacturing industry, Plastic
industry.
 Some jewelry industry(Grades of the gold)
 Manufacturing industry.
2
ENGINEERING MATERIALS AND
METALLURGY
1/5/2013
OBJECTIVE




SAB-AP/MECH SONACT

Knowledge on the structure
Properties of the materials
Treatment
Testing and applications of metals and non-metallic
materials
Suitable materials for various engineering application
3
ENGINEERING MATERIALS AND
METALLURGY
Review (Not for Exam)

Crystal structure

BCC, (Body cubic centre) structure

FCC, (Face cubic centre) structure and

HCP, (Hexagonal close packing)structure

Unit cell

Crystallographic planes and directions

Miller indices

Crystal imperfections for point, line, planar and
volume defects.
ENGINEERING MATERIALS AND
METALLURGY
1/5/2013
SAB-AP/MECH SONACT
Review (Not for Exam)
 Grain size
 ASTM grain size number
5
ENGINEERING MATERIALS AND
METALLURGY
1/5/2013
UNIT:I CONSTITUTION OF ALLOYS AND
PHASE DIAGRAMS
Constitution of alloys-Solid solution,
substitutional
and interstitial-Phase
diagrams,
Isomorphous,
eutectic,
peritectic,
and peritectroid reactions,
Iron-Iron carbon equilibrium diagram.
of steel and cast Iron,
Microstructure,
Properties
and
applications.
SAB-AP/MECH SONACT

 Classification
6
ENGINEERING MATERIALS AND
METALLURGY
1/5/2013
UNIT:II
HEAT TREATMENT
SAB-AP/MECH SONACT
Definition-Full annealing, stress relief,
recrystallisation
and
spheroidizingnormalising, hardening and tempering of
steel.
Isothermal
transformation
diagrams-cooling curves superimposed on
I.T.diagram, CCR-Hardenability, Jominy
and
quench
testAustempering,
Martempering-case
hardeningcarburising,
nitriding,
cyaniding,
carbonitriding, flame and induction
hardening .
7
ENGINEERING MATERIALS AND
METALLURGY
1/5/2013
SAB-AP/MECH SONACT
UNIT:III
MECHANICAL PROPERTIES AND TESTING
Mechanism of plastic deformation, slip and
twinning-types of fracture-testing of materials
under tension, compression and shear loadsHardness tests (Brinell, Vickers and Rockwell),
Impact test-Izod and charpy, Fatigue and creep
tests, fracture toughness tests.
8
ENGINEERING MATERIALS AND
METALLURGY
1/5/2013
UNIT:IV
FERROUS AND NON FERROUS METALS
SAB-AP/MECH SONACT
Effect of alloying elements on steel(Mn, Si,
Cr, Mo, V, Ti & W) –Stainless and tool steels
–HSLA-maraging steels-Cast irons-Grey,
White malleable, spheroidal-Graphite, Alloy
cast irons,
Copper and copper alloys-Brass, Bronze and
Cupronickel-Aluminum and Al-Cu alloyPrecipitation hardening-Bearing alloys.
9
ENGINEERING MATERIALS AND
METALLURGY
1/5/2013
SAB-AP/MECH SONACT
UNIT V
NON-METALLIC MATERIALS
Polymers-Types of polymer, commodity and
Engineering polymers-properties and
applications of PE, PP, PS, PVC, PMMA, PET,
PC, PA, ABS, PI, PAI, PPO, PPS, PEEK, PTFE
Polymer-Urea and Phenol formaldehydesEngineering ceramics-Introduction to fiber
reinforced plastics.
10
ENGINEERING MATERIALS AND
METALLURGY
1/5/2013
Each category of engineering application requires material from any or all of
these three group of materials
Ceramics and
glasses
Polymers
Engineering Materials
SAB-AP/MECH SONACT
Metals and alloys
Application
Structures
Machines
Devices
11
Ceramic and
glasses
Mgo, cds,
Al2O3,
S iC, BaTio3,Silica,
soda-time-glass,
Concrete, cement
ferrites and garnets
ceramic
superconductors
Organic polymers
Plastics,
Pvc,PTFE,
polyethylene
SAB-AP/MECH SONACT
Metals and alloys
Steels, aluminum,
copper, silver
,gold, Brasses,,
bronze s, maganin
invar, super alloys
boron rare earth
magnetic alloys
Metalreinforce
d plastics
Si, Ge, GaAs,
Boridereinforced steel
ENGINEERING MATERIALS AND
METALLURGY
Fibers:Terylene,nylo
n,cotton,
natural, and
synthetic
rubbers ,
leathers
Glass fiber- reinforced
plastics
1/5/2013
12
ENGINEERING MATERIALS AND
METALLURGY
1/5/2013
SAB-AP/MECH SONACT
Structure:
The internal structure of a material,
simply called the structure.
13
NON-METALLIC MATERIALS:







SAB-AP/MECH SONACT

PE (polyethylene)
PP (Polypropylene)
PS(Polystyrene)
PMMA(Polymethyl methacrylate)
PET(Polyethylene teraphthalate)
PC(Polycarbonates)
PA(Polyamides)
ABS(Acryknitrile-Butadiene-styrene)
PI(Polyimide)
1/5/2013

14
NON-METALLIC MATERIALS:



SAB-AP/MECH SONACT

PAI( Polyamideimide)
PPO(Polyphenylene oxide)
PPS(Polyphenylene sulphide)
PEEK(Polyether ether ketone)
PTFE(Polytetra fluoro ethylene)
1/5/2013

15
ENGINEERING MATERIALS AND
METALLURGY
1/5/2013
SAB-AP/MECH SONACT
UNIT:I CONSTITUTION OF ALLOYS AND
PHASE DIAGRAMS
Constitution of alloys-Solid solution, substitutional
and interstitial-Phase diagrams Isomorphous,
eutectic, peritectic, and peritectroid reactions,
Iron-Iron carbon equilibrium diagram.
Classification of steel and cast Iron,
Microstructure, Properties and applications.
16
CONSTITUTION- establishment, foundation,
creation, formation, structure, organization,
charter, bill.
SAB-AP/MECH SONACT

1/5/2013
UNIT:I
CONSTITUTION OF ALLOYS
AND PHASE DIAGRAMS
17
1.SYSTEM: It is a combination of phases of one or
more components.
SAB-AP/MECH SONACT
SOME TECHNICAL TERMS AND
DEFINITIONS:
1/5/2013
UNIT:I
CONSTITUTION OF ALLOYS
AND PHASE DIAGRAMS
2.PHASE: It is a Physically and chemically
homogenous part of a system under study, one
phase is different from the other in structure or
composition
18
3.COMPONENTS:
system are called component. A system may
consist of two or more components.
SAB-AP/MECH SONACT
The elements present in the
1/5/2013
UNIT:I
CONSTITUTION OF ALLOYS AND
PHASE DIAGRAMS
19
CONSTITUTION OF ALLOYS
AND PHASE DIAGRAMS
An alloy is defined as a combination of two or
more elements, of which one of the element should be
a metal in major proportion.

SAB-AP/MECH SONACT

1/5/2013
CONSTITUTION OF ALLOYS:
4.ALLOY:
The others could be metals or non-metals, for eg:
Brass (CU-Zn), Steel (Fe-C)
20
UNIT:I
CONSTITUTION OF ALLOYS AND
PHASE DIAGRAMS

Uses of pure metals
1. High electrical conductivity
2. High ductility
SAB-AP/MECH SONACT
Alloy find very wide application in the industry than pure metals.
1/5/2013

3. Corrosion resistance are required.
These properties are generally at a maximum value in pure metals.
21
UNIT:I
CONSTITUTION OF ALLOYS AND
PHASE DIAGRAMS
Mechanical properties
2. Yield point
SAB-AP/MECH SONACT
1. Tensile strength
1/5/2013

3. Hardness are
improved by alloying.
22
UNIT:I
CONSTITUTION OF ALLOYS AND PHASE
DIAGRAMS
Pure metals
Solid
Solution
SAB-AP/MECH SONACT
CLASSIFICATION OF
ALLOYS
1/5/2013
CLASSIFICATION OF ALLOYS
Intermedia
te phase
23
UNIT:I
CONSTITUTION OF ALLOYS AND
PHASE DIAGRAMS
Alloy can be either a single phase or a mixture

A phases is anything which is homogeneous and
SAB-AP/MECH SONACT
of phases.
1/5/2013

physically distinct.

In solid state alloys of three are three possible
phase.
24
UNIT:I
CONSTITUTION OF ALLOYS AND
PHASE DIAGRAMS
If an alloy has a single phase, it could be either

If the alloy is a mixture it could be composed of
any combination of the above three phases.
SAB-AP/MECH SONACT
a solid solution or an intermediate phase.
1/5/2013

25
UNIT:I
CONSTITUTION OF ALLOYS AND
PHASE DIAGRAMS
SAB-AP/MECH SONACT
major element which is large in
amount is called base metal or parent
metal or solvent.
 The other element that is lesser in
amount is called the alloying element or
solute, it is the minor part (such as salt or
sugar which is less in amount, being
mixed in water- solvent).
1/5/2013
 The
26
UNIT:I
CONSTITUTION OF ALLOYS AND
PHASE DIAGRAMS
1/5/2013
SAB-AP/MECH SONACT
5. MIXTURE:
It is a material more than one phase.
27
UNIT:I
CONSTITUTION OF ALLOYS AND
PHASE DIAGRAMS
Disordered
(or) Random
Ordered
(or) regular
Interstitial
solid solution
SAB-AP/MECH SONACT
Substitutinal
Solid solution
1/5/2013
SOLID SOLUTION
28
UNIT:I
CONSTITUTION OF ALLOYS AND
PHASE DIAGRAMS

A solid solution is the simplest type of alloys.
A Solution can be defined as a homogeneous mixture
in which the atoms or molecules of one substance are
SAB-AP/MECH SONACT

solutions:
1/5/2013
 Solid
dispersed at random into another substance.
29
UNIT:I
CONSTITUTION OF ALLOYS AND
PHASE DIAGRAMS
SAB-AP/MECH SONACT
1 . Solute: A solute is the minor part of
the solution or the material which is
dissolved.
1/5/2013
A solid solution may be defined as a solid
that consist of two or more elements
atomically dispersed in a single-phase
structure.
 A solid solution is composed of two parts.

30
UNIT:I
CONSTITUTION OF ALLOYS AND
PHASE DIAGRAMS
Both the solute and the solvent can be solid,
SAB-AP/MECH SONACT
the solution.
1/5/2013
2. Solvent: Solvent constitutes the major portion of
liquid or gas.
31
UNIT:I
CONSTITUTION OF ALLOYS AND
PHASE DIAGRAMS
Solid solution:
Solid solution may be defined as a
solution In the solid state which consists of two
kinds of atoms combined in one type of space
SAB-AP/MECH SONACT
Simply a solution in the solid state.
1/5/2013

lattice.
32
UNIT:I
CONSTITUTION OF ALLOYS AND
PHASE DIAGRAMS
space lattice:
points in three dimensions in which every point
has surroundings identical to that every other
SAB-AP/MECH SONACT
Space lattice is defined as an array of
1/5/2013

point in the array.
33
SOLID SOLUTION


In certain cases, the solidification of an
alloy results in the formation of one kind of
crystal.
In which both metals are present, but they
cannot be detected by the microscope
Although properties of the crystals are
profoundly( deeply,strongly) changed.
SAB-AP/MECH SONACT

Case:
1/5/2013

34
SOLID SOLUTION
In such a case we have a solid metal in which the
has been persevered after solidification, and it is
known as a solid solution.

SAB-AP/MECH SONACT
interatomic state which existed in the liquid solution
1/5/2013

In a solid solution the atom occur in a definite
geometrical pattern, which is usually a slightly
distorted form of one of the constituent metals.
35
SOLID SOLUTION
1/5/2013
SAB-AP/MECH SONACT
Soildsolution are conductors, but not so good as
the pure metals on which they are based.
Some examples of solid solutions are:
 Cu-Zn alloys (Brasses)
 Ni-Cu alloys (Monel metal)

Au-Ag alloys(Sterling silver)
 Fe-Cr-Ni alloys (Certain stainless steels)
 Fe-C alloys (Steels)

36
SUBSTITUTIONAL SOLID SOLUTION
solute-Atom of Metal-B Solvent-Atoms of zinc Metal-A
zinc(Solute)
Copper(Solvent)
Disordered substitutinal solid solution(random,)
SAB-AP/MECH SONACT
SOLVENT OR
MATRIX ATOMS
1/5/2013
Solute Atoms
37
SUBSTITUTIONAL SOLID SOLUTION
Ordered subsitutional solid solution
Solute
Atoms
SAB-AP/MECH SONACT
SOLVENT OR
MATRIX ATOMS
1/5/2013

38
SUBSTITUTIONAL SOLID SOLUTION
In substitutional solid solution, there is a direct

so that solute atoms(cu) enter the crystal to take
positions normally occupied by solvent atoms (e.g.,
SAB-AP/MECH SONACT
substitution of one type of atom for another.
1/5/2013

Nickel atoms);
39
SUBSTITUTIONAL SOLID SOLUTION
The alloy is said to be in a disordered condition if
solution, the solute atoms do not occupy any
specific position but are distributed at random in
SAB-AP/MECH SONACT
in the formation of a substitutional solid
1/5/2013

the lattice structure of the solvent.
40
SUBSTITUTIONAL SOLID SOLUTION
An ordered subsititutional solid solution is shown
ordered structures.
SAB-AP/MECH SONACT
fig Cu-Zn, Al-Cu, α-Brass are some examples of
1/5/2013

41
INTERSTITIAL SOLID SOLUTION
The four elements hydrogen, carbon, nitrogen,
can occupy the empty spaces (Interstices) in the
crystal lattices of many metals.
SAB-AP/MECH SONACT
and boron have such small diameters that they
1/5/2013

42
INTERSTITIAL SOLID SOLUTION
Solute atoms
(solute)
SAB-AP/MECH SONACT
CARBON
1/5/2013
Solvent or
matrix atoms
IRON
( SOLVENT)
INTERSTITIAL SOLID SOLUTION
43
INTERSTITIAL SOLID SOLUTION
Interstitial solid solution usually have a limited
of secondary importance, but there are a few
instances worthy of special attention.
SAB-AP/MECH SONACT
composition range and are generally considered
1/5/2013

44
INTERSTITIAL SOLID SOLUTION
The interstitial solution of carbon in iron

Very small amount of hydrogen introduced into
SAB-AP/MECH SONACT
constitutes the basis of steel hardening.
1/5/2013

steels during acid pickling(cleaning), plating, or
welding operations causes a Sharpe decrease in
ductility, known as hydrogen embrittlement.
45
INTERSTITIAL SOLID SOLUTION
Interstitial nitrogen is useful not only in
in maintaining 18Cr-8Ni
SAB-AP/MECH SONACT
nirtriding process but also as an important factor
1/5/2013

Stainless steel in the austenitic condition.
46
HUME - ROTHERY’S RULES OF SOLID
SOLUBILITY
1/5/2013
SAB-AP/MECH SONACT
Hume - Rothery’s Rules of solid solubility
47
HUME - ROTHERY’S RULES OF
SOLID SOLUBILITY
1/5/2013
SAB-AP/MECH SONACT
Hume - Rothery’s Rules of solid solubility
48
INTERSTITIAL SOLID SOLUTION
various factors. These were stated by Hume-rothery
and are as follows:
1.
SAB-AP/MECH SONACT
The solubility limit of solute in solvents depends on
1/5/2013
HUME –ROTHERY’S RULES OF SOLID SOLUBILITY
Critical structure factor (or) Crystal structure:
Metals that have the same crystal stucture (Lattice
structure) have a greater solubility.
49
INTERSTITIAL SOLID SOLUTION
difference in size of solute and solvent is less than
15%.

If the difference is greater than 15% formation of
SAB-AP/MECH SONACT
The solid solution will tend to form if the

1/5/2013
2. Relative atomic size factor(or) size factor:
solid solution will be limited.

For good solid solubility the difference should be less
than 8%
50
INTERSTITIAL SOLID SOLUTION
favoured for metals that have less chemical affinity
is more, then a compound is formed instead of a solid
solution.

SAB-AP/MECH SONACT
Formulation of solid solution is

1/5/2013
3. Chemical affinity factor (or) Electronegativity:
The metal which are separated in widely in the
periodic table are not suitable for making alloys
because of their high affinity.
51
INTERSTITIAL SOLID SOLUTION
disslove only a small amount of a lower valency
metal, where as the metal with low valency
SAB-AP/MECH SONACT
A metal that has a higher valency will
1/5/2013
4. Relative valency factor(or)valence:
will have good solubility for the higher valency
metal.
52
INTERSTITIAL SOLID SOLUTION
In some alloys both interstitial and
appreciable extent.

SAB-AP/MECH SONACT
substitutional solid solution are formed to an
1/5/2013

For Eg: A Cr-Ni steel contains interstitially
dissolved carbon and substitution ally dissolved
chromium, nickel, and minor elements.
53
POSSIBILITIES OF SOLID SOLUTIONS
There are three possible solid solutions based on
1.Unsaturated solid solution: In the solvent is
SAB-AP/MECH SONACT
the amount of their elements. They are:
1/5/2013
•
dissolving small amount of solute as well as at a
given temperature and pressure, it is called
unsaturated solid solution.
54
POSSIBILITIES OF SOLID SOLUTIONS
limiting amount of solute, it is called saturated
solid solution.
SAB-AP/MECH SONACT
If the solvent is dissolving
1/5/2013
2. Saturated solid solution:
55
POSSIBILITIES OF SOLID SOLUTIONS
should, under equilibrium, it is called
supersaturated solid solution.
SAB-AP/MECH SONACT
If the solvent is dissolving more of solute that it
1/5/2013
3. Supersaturated solid solution:
56
PHASE DIAGRAM
2. Eutectoid system
SAB-AP/MECH SONACT
1. Isomorphous
1/5/2013
Types of phase diagram
3. Eutectic system
4.Peritectic system
5. Peritectroid reactions
57
PHASE DIAGRAM
Phase Diagrams
representation of what phases are present in an
SAB-AP/MECH SONACT
Phase diagrams are graphical
1/5/2013

alloy system at various
Temperatures, pressures, and compositions.
58
PHASE DIAGRAM

Phase diagrams are also known as equilibrium
SAB-AP/MECH SONACT
A phase diagram is a map showing the
structure or phase present as the
temperature and overall composition of
the material are varied.
1/5/2013
(or)
diagrams or constitutional diagrams.
59
WHY SHOULD PHASE DIAGRAMS BE
STUDIED?
The phase diagrams can answer the following

What condition is the material in?

Is the composition uniform throughout?
SAB-AP/MECH SONACT
important questions:
1/5/2013

If not, how much of each component is present?
60
WHY SHOULD PHASE DIAGRAMS BE
STUDIED?
Is something present that may give undesired

What will happen if temperature is increased or
SAB-AP/MECH SONACT
properties?
1/5/2013

decreased; pressure is changed or composition is
varied?
61
WHY SHOULD PHASE DIAGRAMS BE
STUDIED?
Phase diagrams are used by engineers and
aspects of the behavior of materials.
SAB-AP/MECH SONACT
scientists to understand and to predict many
1/5/2013

62
TERMINOLOGY USED IN PHASE DIAGRAMS
Components
System
3.
Alloy
4.
Solid solution
5.
Solute Solution
SAB-AP/MECH SONACT
2.
1/5/2013
1.
63
TERMINOLOGY USED IN PHASE DIAGRAMS
8. Equilibrium
SAB-AP/MECH SONACT
7. Phase
1/5/2013
6. Solvent
9. Solubility limit
10.Degrees of freedom
64
TERMINOLOGY USED IN PHASE DIAGRAMS
The various terms used in the study of phase
1. COMPONENT: Component are pure metals
SAB-AP/MECH SONACT
diagrams have been explained below:
1/5/2013

and or compounds of which an alloy is composed.
Eg: In a copper-zinc brass, the components are
CU and Zn.
65
TERMINOLOGY USED IN PHASE DIAGRAMS
i. System: May refer to a specific body of
material under consideration. For Eg: A
SAB-AP/MECH SONACT
context
1/5/2013
2. SYSTEM: The system has two meanings in this
ladle of molten steel is referred as a system.
66
TERMINOLOGY USED IN PHASE DIAGRAMS
(ii)system: May also refer to the series of possible
example, the Iron-Carbon system.
SAB-AP/MECH SONACT
alloys consisting of the same components. For
1/5/2013

67
TERMINOLOGY USED IN PHASE DIAGRAMS
A system having one components is called a
and four components are known as Binary,
ternary and quaternary systems, respectively.
SAB-AP/MECH SONACT
Unary system, and the system having two, three
1/5/2013

68
TERMINOLOGY USED IN PHASE DIAGRAMS
or a metal (metals) and a non-metal (non-metals).
SAB-AP/MECH SONACT
An alloy is a mixture of two or more metals
1/5/2013
3. ALLOY:
69
TERMINOLOGY USED IN PHASE DIAGRAMS
more elements atomically dispersed in a singlephase structure.
SAB-AP/MECH SONACT
It is a solid that consist of two or
1/5/2013
4.SOLID SOLUTION:
70
TERMINOLOGY USED IN PHASE DIAGRAMS
solution or the material which is dissolved.
SAB-AP/MECH SONACT
It is the minor part of the
1/5/2013
5. SOLUTE SOLUTION:
71
TERMINOLOGY USED IN PHASE DIAGRAMS
major portion of the solution.
SAB-AP/MECH SONACT
The material which contributes the
1/5/2013
6. SOLVENT:
72
TERMINOLOGY USED IN PHASE DIAGRAMS
portion of a system that has uniform physical
SAB-AP/MECH SONACT
A phase may be defined as a homogenous
1/5/2013
7. PHASE:
and chemical characteristics.
73
TERMINOLOGY USED IN PHASE DIAGRAMS
enough time is allowed for all possible reactions
SAB-AP/MECH SONACT
Equilibrium is said to exit when
1/5/2013
8. EQUILIBRIUM:
to be completed.
74
TERMINOLOGY USED IN PHASE DIAGRAMS
The equilibrium state refers to the
constant indefinitely. Equilibrium occurs when
SAB-AP/MECH SONACT
characteristics of the system that remain
1/5/2013

the free energy of the system is at its minimum
value.
75
TERMINOLOGY USED IN PHASE DIAGRAMS
The term phase equilibrium refers to
more than one phase may exist.
SAB-AP/MECH SONACT
equilibrium as it applies to systems in which
1/5/2013

76
TERMINOLOGY USED IN PHASE DIAGRAMS
solute that may be added without forming a new
phase.
SAB-AP/MECH SONACT
It is the maximum concentration of

1/5/2013
9. SOLUBILITY LIMIT:
77
TERMINOLOGY USED IN PHASE DIAGRAMS
NOTE:
The addition of solution in excess
another solid solution or compound.
SAB-AP/MECH SONACT
of the solubility limit results in the formation of
1/5/2013

78
TERMINOLOGY USED IN PHASE DIAGRAMS
independent variables ( such as temperature,
pressure, and composition).
SAB-AP/MECH SONACT
It is the number of
1/5/2013
10. DEGREES OF FREEDOM:
That can be changed independently without
changing the phase or phases of the system.
79
WHAT IS MEANT BY THE TERM PHASE?
A phase may be a portion of matter which is

A phase may be defined as any physical distinct
SAB-AP/MECH SONACT
homogenous
1/5/2013

homogenous and mechanically separable portion
of a substance.
80
WHAT IS MEANT BY THE TERM PHASE?
In Layman’s term, a phase requires a unique
boundaries or interfaces
SAB-AP/MECH SONACT
structure, uniform composition, and well-defined
1/5/2013

Examples: A pure substance such as water is a
single phase.
81
WHAT IS MEANT BY THE TERM PHASE?
The pure substance water can exist in solid,
single phase, as shown in fig (a)

SAB-AP/MECH SONACT
liquid and vapour, each of these states being a
1/5/2013

Now consider the effect of adding salt(Nacl) to
water. Salt will dissolve in water to give a
homogeneous solution.
82
WHAT IS MEANT BY THE TERM PHASE?
Thus the salt- water solution forms a single

If more salt is added into water, then we have
SAB-AP/MECH SONACT
phase as shown if fig(b)
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
two different phases as shown if fig(c)
83
WHAT IS MEANT BY THE TERM PHASE?
A Single phase system is also termed as
SAB-AP/MECH SONACT
“homogeneous system”
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
84
WHAT IS MEANT BY THE TERM PHASE?
System composed of two or more phases are
Fig (d)

SAB-AP/MECH SONACT
termed as mixtures or heterogeneous systems’.
1/5/2013

Most metallic alloys, ceramic, polymers, and
composite are heterogenous.
85
ILLUSTRATION OF PHASES
WATER(2)
SAB-AP/MECH SONACT
ICE (1)
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WATER VAPOUR(3)
WATER
ILLUSTRATION OF PHASES:
(A) Three
forms of water: 1) Ice 2)water 3)
86
water vapour are each a phase.
ILLUSTRATION OF PHASES
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salt
SAB-AP/MECH SONACT
•
(b) Salt and water have unlimited solubility
(Homogeneous solution)- from a single phase
87
ILLUSTRATION OF PHASES
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Saturated brine
SAB-AP/MECH SONACT
Excess salt
(C) Salt and water have limited solubility
(Heterogenous solution)-from two distinct phases
88
ILLUSTRATION OF PHASES
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SAB-AP/MECH SONACT
OIL
WATER
OIL AND WATER HAVE VIRTUALLY NO SOLUBILITY FROM TWO
DISTINCT PHASES
89
PHASE DIAGRAM OF PURE
SUBSTANCE
One- Component Phase diagram
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
SAB-AP/MECH SONACT
90
PHASE DIAGRAM OF PURE
SUBSTANCE
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SAB-AP/MECH SONACT
91
PHASE DIAGRAM OF PURE
SUBSTANCE
A pure substance such as water can exist in
condition of temperature and pressure
SAB-AP/MECH SONACT
solid, liquid, or vapour phases, depending on the
1/5/2013

92
PHASE DIAGRAM OF PURE
SUBSTANCE
The phase relationships may be represented on
a one-component (or unary) phase diagram, for
the H2O System.
SAB-AP/MECH SONACT
a pressure- temperature (PT) diagram, known as
1/5/2013

93
PHASE DIAGRAM OF PURE
SUBSTANCE
The phase diagram is composed of regions of
phase is stable.

SAB-AP/MECH SONACT
pressure and temperature where only a single
1/5/2013

The line OA indicates the vapourisation line
and the line OB indicates the freezing line.
94
PHASE DIAGRAM OF PURE
SUBSTANCE
Liquid and vapour phase exist along the
along the freezing line, shows in figure. These
lines are also known as Two phase equilibrium
SAB-AP/MECH SONACT
vapourisation line and liquid and solid phases
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
lines.
95
PHASE DIAGRAM OF PURE
SUBSTANCE
The point “O” is know as Triple point.
(Solid, liquid, and vapour phases(gas)).
SAB-AP/MECH SONACT
Triple point is the point at which three phases
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
of a single material coexit. This triple point of
water exists at temperature 0.00980C
and at pressure 4.58 mm of Hg.
96
PHASE DIAGRAMS
The properties of an alloy depend on nature,
phases.

SAB-AP/MECH SONACT
amount, size, distribution and orientation of the
1/5/2013

A phase is the chemically and structurally
homogeneous portion of the microstructure.
97
PHASE DIAGRAMS
It has the following characteristics
2. Roughly the same composition and
properties throughout.
SAB-AP/MECH SONACT
1. Same structure throughout.
1/5/2013

3. Definite interface between the phase
and surrounding.
98
1/5/2013
J.W. GIBBS
( JOSIAH WILLARD GIBBS)
SAB-AP/MECH SONACT
99
J.W. GIBBS( JOSIAH WILLARD
GIBBS)
(OR)
(OR)
GIBB’S PHASE RULE
(or)
SAB-AP/MECH SONACT
J.W. GIBBS LAW
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JOSIAH WILLARD GIBBS PROPOSAL
PHASE RULE
100
GIBBS PHASE RULE
J.W. Gibbs, American physicist derived an
system between the number of phases,

SAB-AP/MECH SONACT
equation which established relationship in a
1/5/2013

The number of degree of freedom and the
number of components.
101
GIBB’S PHASE RULE
The phase rule indicates the phases that exists

The Gibb’s phase rule satisfies the following
relation:
SAB-AP/MECH SONACT
at equilibrium.
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
P+F=C+n
102
GIBB’S PHASE RULE
P- Number of phases that exist in a
C-Number of components in the system.
SAB-AP/MECH SONACT
system under certain conditions.
1/5/2013

n- It represents the number of variables,
examples: Temperature, pressure and
concentration.
103
GIBB’S PHASE RULE
pressure or concentration which can
be change independently without
SAB-AP/MECH SONACT
variables such as temperature or
1/5/2013
F- Degree of freedom. It is the number of
changing the number of phases that
are present in the system.
104
GIBB’S PHASE RULE

i.e., 1 atmospheric pressure and hence pressure
is not considered a variable.
Usually the only variable under consideration is
temperature and hence the Gibb’s phase rule
becomes;
SAB-AP/MECH SONACT

In most studies the pressure is constant
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
P+F=C+1
105
USES OF PHASE RULE
The phase rule predicts maximum number of
conditions at any point of diagram.

If the number of phases are known, one can
determine the degree of freedom using phase
SAB-AP/MECH SONACT
phases present in the alloy under equilibrium
1/5/2013

rule.
106
USES OF PHASE RULE
Thus the phase rule is useful to know whether
can be changed without changing the structure of
the alloy.
SAB-AP/MECH SONACT
the temperature or pressure or both variables
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
107
ILLUSTRATION OF THE USE OF THE
PHASE RULE
Let us consider the application of gibbs phase rule


Case 1 : Consider a triple point in the diagram.
At the triple point, three phases coexist in
equilibrium .
SAB-AP/MECH SONACT
to the phase diagram of water system
1/5/2013

P=3. Since there is one component (water) in the
system C= 1
108
THE USE OF THE PHASE RULE
The number of degree of freedom can be

F=1- 3+2
F=0 (Zero degree of freedom)

SAB-AP/MECH SONACT
calculated using the Gibbs phase rule as,
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
This means that one of the variables
(Temperature or pressure) can be changed
at the triple point.
109
THE USE OF THE PHASE RULE
Note: Since the variables temperature or
three phases of coexistence.

SAB-AP/MECH SONACT
pressure cannot be changed and still keep the
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
The triple point is called an invariant point.
110
THE USE OF THE PHASE RULE
liquid-
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SAB-AP/MECH SONACT
Case 2: Next consider a point along
solid freezing curve
P=2
Then for water system
C=1
Applying the phase rule, we get:
F=1- 2+ 2
F=1 (one degree of freedom)

111
THE USE OF THE PHASE RULE
( Temperature or pressure) can be changed
independently and still maintain a system
SAB-AP/MECH SONACT

This means that one variable
1/5/2013

with two coexisting phases.
112
THE USE OF THE PHASE RULE
Case:3
SAB-AP/MECH SONACT
Now consider a point on the phase
diagram of water inside a single phase in this
case there will be only one phase present.
P=1 ,
Then for water system, C=1
Now the phase rule gives
1/5/2013

113
THE USE OF THE PHASE RULE
F=1-1+2
This means that two variables ( Temperature
and pressure) can be varied independently and
SAB-AP/MECH SONACT
F=2 ( two degree of freedom)
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
the system will still remain in a single phase.
114
THE USE OF THE PHASE RULE
Note: In many application (especially for most
atmosphere.

In this case Gibbs phase rule is modified as
SAB-AP/MECH SONACT
binary alloy) the pressure is kept constant at 1
1/5/2013

F=C-P+1
115
THE USE OF THE PHASE RULE
The above equation is known as condensed phase

This equation can be applied to most of
SAB-AP/MECH SONACT
rule.
1/5/2013

the binary phase diagram.
116
OBJECTIVE TYPE QUESTIONS
of a small group of atoms oriented into one of the
common crystal patterns.
SAB-AP/MECH SONACT
centre of freezing, or nucleus, which is composed
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1. -----------May be visualized as forming from a
Crystal
117
OBJECTIVE TYPE QUESTIONS
conditions
SAB-AP/MECH SONACT
obtained only if crystallisation develops under
1/5/2013
2.Perfect crystal of proper external shape can be
when degree of ----------------is very slight and the
metal has a very high purity.
118
MICRO-CONSTITUENTS OF IRON-CARBON
ALLOYS
There are different micorscope constituents of

The study of these micro-constituents is
SAB-AP/MECH SONACT
Iron-Carbon alloys exit.
1/5/2013

essential in order to understand iron-iron
carbide (Fe-Fe3C) equilibrium phase diagram.
119
VARIOUS MICRO-CONSTITUENTS OF IRONCARBON ALLOYS ARE:
3.Cementite
SAB-AP/MECH SONACT
2.Austenite
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1.Ferrite
4.Pearlite
5.Ledeburite
6.Martensite
120
VARIOUS MICRO-CONSTITUENTS OF IRONCARBON ALLOYS ARE:
9.Bainite
SAB-AP/MECH SONACT
8. Sorbite, and
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7. Troosite
121
VARIOUS MICRO-CONSTITUENTS OF IRONCARBON ALLOYS ARE:
Ferrite is a primary solid solution based on α iron
having BCC structure.

SAB-AP/MECH SONACT

Ferrite (or α-Iron)
1/5/2013
1.
It is Nothing but the interstitial solid solution of
carbon in iron.
122
FERRITE
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SAB-AP/MECH SONACT
123
VARIOUS MICRO-CONSTITUENTS OF IRONCARBON ALLOYS ARE:
Maximum solubility of carbon in iron is 0.025% carbon
only 0.008%.

SAB-AP/MECH SONACT
at 723°C, While its solubility at room temperature is
1/5/2013

Ferrite is soft, ductile, and highly
Magnetic.

It can undergo extensive cold working
124
VARIOUS MICRO-CONSTITUENTS OF IRONCARBON ALLOYS ARE:
Austenite is a primary solid solution based on γ
iron having FCC structure.

SAB-AP/MECH SONACT

1/5/2013
2. Austenite(or γ-Iron)
This is also an interstitial solid solution of
carbon in iron

125
AUSTENITE
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SAB-AP/MECH SONACT
126
AUSTENITE

Austentite has a greater electrical resistance
and coefficient of expansion than ferrite.
SAB-AP/MECH SONACT
It is also a non-magnetic (paramagnetic)
1/5/2013

127
CEMENTITE
Cementite is the name given to the carbide of

It is the hard, brittle, intermetallic compound of
SAB-AP/MECH SONACT
iron(Fe3c).
1/5/2013

iron with 6.69% of carbon.
128
CEMENTITE
The hardness and brittleness of cast iron is
cementite.

SAB-AP/MECH SONACT
believed to be due to the presence of the
1/5/2013

It is Magnetic below 250°c
129
CEMENTITE
1/5/2013
SAB-AP/MECH SONACT
130
PEARLITE
Pearlite is the eutectoid mixture of ferrite

It is formed when austenite decomposes
SAB-AP/MECH SONACT
(87.5%) and cementite (12.5%).
1/5/2013

during cooling. It contains 0.8% of carbon
131
PEARLITE
1/5/2013
SAB-AP/MECH SONACT
132
1/5/2013
PEARLITE
LAMELLAR-PEARLITE BEADED BAG
SAB-AP/MECH SONACT
133
PEARLITE
It consist of alternate thin layers (or lamellae) of

The name derives from its lustrous apperance
SAB-AP/MECH SONACT
ferrite and cementite shown in fig.
1/5/2013

(similar to mother of pearl) when viewed in
white light under a microscope.
134
PEARLITE
The properties of pearlite is midway between
and ductile.
SAB-AP/MECH SONACT
ferrite and cementite. It is relatively strong, hard
1/5/2013

135
LEDEBURITE
Ledeburite is the eutectic mixture of austenite(γ-Iron) and

In pure iron-carbon alloy, it forms at 1140 °C.
Most of the engineering alloy materials belong to
SAB-AP/MECH SONACT
cementite (Fe3C) Containing 4.3% carbon.
1/5/2013

this range of alloy.
136
LEDEBURITE
Pig iron, the most important engineering
SAB-AP/MECH SONACT
material, is ledeburite.
1/5/2013

137
LEDEBURITE
1/5/2013
SAB-AP/MECH SONACT
138
LEDEBURITE
1/5/2013
SAB-AP/MECH SONACT
139
MARTENSITE
Martensite is the super saturated solid solution

It is formed when steel is very rapidly cooled from the
SAB-AP/MECH SONACT
of carbon in α-Iron.
1/5/2013

austenitic state.

It exhibits a characteristic acicular or needle like
structure.
140
MARTENSITE
It is very hard more brittle and low ductility

There is an increase in specific volume during
SAB-AP/MECH SONACT
properties.
1/5/2013

formation of martensite from austenite.
141
MARTENSITE
As a result internal stresses are set up in the
cracks.
SAB-AP/MECH SONACT
materials leading to the formation of minute
1/5/2013

142
MARTENSITE (RED AND YELLOW
MARTENSITE. GREEN: AUSTENITE)
1/5/2013
SAB-AP/MECH SONACT
143
TROOSTITE
Troosite is the mixture of radial lamella of
pearlite only in the degree of fitness.

SAB-AP/MECH SONACT
ferrite and cementite. In fact, it differs from
1/5/2013

This constituents is also known as troostite
pearlite.
144
TROOSTITE
It is the microstructure consisting ferrite and
martensite below 450 °C
SAB-AP/MECH SONACT
finely divided cementite, produced on tempering
1/5/2013

145
TROOSTITE
It is formed by the decomposition of austenite
will yield a martensitic structure and faster than
that which will produce a sorbitic structure.
SAB-AP/MECH SONACT
when cooled at a rate slower than that which
1/5/2013

146
TROOSTITE
It has hardness intermediate between
SAB-AP/MECH SONACT
martensite and sorbite.
1/5/2013

147
TROOSTITE
1/5/2013
SAB-AP/MECH SONACT
148
SORBITE
Sorbite is the microstructure consisting ferrite,
tempering martensite above 450°C
SAB-AP/MECH SONACT
and finely divided cementite, produced on
1/5/2013

149
SORBITE
This constituents is also known as sorbitic

It is formed by the decomposition of austenite
SAB-AP/MECH SONACT
pearlite.
1/5/2013

when cooled at a rate slower than that which
will produce a pearlitic structure
150
SORBITE
Though sorbitic steel is slightly less ductile than
high.

SAB-AP/MECH SONACT
pearlite steel, its tensile and yield strength are
1/5/2013

The sorbite steels are often known as Toughened
steels.
151
SORBITE
1/5/2013
SAB-AP/MECH SONACT
152
SORBITE
1/5/2013
Note:
All the pearlite, troosite and sorbite are ferritecementite mixtures having lamellar structure.

However they are distinguished by their degree of
SAB-AP/MECH SONACT

dispersion.

Pearlite has corase pearlite.
153
SORBITE
And sorbite has medium pearlite
SAB-AP/MECH SONACT

Troosite has fine pearlite
1/5/2013

154
BAINITE
Bainite is a decomposition product of austenite,

Bainite is obtained by transformation of pearlite
SAB-AP/MECH SONACT
consisting of an aggregate of ferrite and carbide.
1/5/2013

higher temperature ( has a feathery structure) is
called upper bainite.
155
BAINITE
Lower bainite provides high mechanical
used for components of machine and structures.

SAB-AP/MECH SONACT
properties and that is why it is extensively
1/5/2013

Bainite has hardness in between the hardness
of pearlite and martensite.
156
BAINITE
1/5/2013
SAB-AP/MECH SONACT
157
IRON/CARBON ALLOY PHASE DIAGRAM
1/5/2013
SAB-AP/MECH SONACT
158
1/5/2013
SAB-AP/MECH SONACT
159
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