Inroduction to Engineering materials

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


METALLURGY

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.

1/5

/20

13

2

SA

B-A

P/M

EC

H S

ON

AC

T


METALLURGY

OBJECTIVE

Knowledge on the structure

Properties of the materials

Treatment

Testing and applications of metals and non-metallic

materials

Suitable materials for various engineering application

1/5

/20

13

3

SA

B-A

P/M

EC

H S

ON

AC

T


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.


METALLURGY

Review (Not for Exam)

Grain size

ASTM grain size number

1/5

/20

13

5

SA

B-A

P/M

EC

H S

ON

AC

T


METALLURGY

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.

1/5

/20

13

6

SA

B-A

P/M

EC

H S

ON

AC

T


METALLURGY

UNIT:II HEAT TREATMENT

Definition-Full annealing, stress relief, recrystallisation and spheroidizing-normalising, hardening and tempering of steel. Isothermal transformation diagrams-cooling curves superimposed on I.T.diagram, CCR-Hardenability, Jominy and quench test- Austempering, Martempering-case hardening- carburising, nitriding, cyaniding, carbonitriding, flame and induction hardening .

1/5

/20

13

7

SA

B-A

P/M

EC

H S

ON

AC

T


METALLURGY

UNIT:III

MECHANICAL PROPERTIES AND TESTING

Mechanism of plastic deformation, slip and

twinning-types of fracture-testing of materials

under tension, compression and shear loads-

Hardness tests (Brinell, Vickers and Rockwell),

Impact test-Izod and charpy, Fatigue and creep

tests, fracture toughness tests.

1/5

/20

13

8

SA

B-A

P/M

EC

H S

ON

AC

T


METALLURGY

UNIT:IV

FERROUS AND NON FERROUS METALS

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 alloy-

Precipitation hardening-Bearing alloys.

1/5

/20

13

9

SA

B-A

P/M

EC

H S

ON

AC

T


METALLURGY

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 formaldehydes-

Engineering ceramics-Introduction to fiber

reinforced plastics.

1/5

/20

13

10

SA

B-A

P/M

EC

H S

ON

AC

T


METALLURGY

1/5

/20

13

11

SA

B-A

P/M

EC

H S

ON

AC

T

Metals and alloys Ceramics and

glasses Polymers

Engineering Materials

Application

Structures Machines Devices

Each category of engineering application requires material from any or all of

these three group of materials


METALLURGY

Organic polymers Plastics, Pvc,PTFE, polyethylene

Fibers:Terylene,nylon,cotton, natural, and synthetic rubbers , leathers

1/5/2013

12

SA

B-A

P/M

EC

H S

ON

AC

T

Metals and alloys

Steels, aluminum,

copper, silver

,gold, Brasses,,

bronze s, maganin

invar, super alloys

boron rare earth

magnetic alloys

Ceramic and

glasses

Mgo, cds,

Al2O3,

S iC, BaTio3,Silica,

soda-time-glass,

Concrete, cement

ferrites and garnets

ceramic

superconductors

Glass fiber- reinforced

plastics

Si, G

e, G

aAs,

Bori

de-

rein

forc

ed s

teel M

etal-

rein

force

d p

lastics


METALLURGY

Structure:

The internal structure of a material,

simply called the structure.

1/5

/20

13

13

SA

B-A

P/M

EC

H S

ON

AC

T

NON-METALLIC MATERIALS:

PE (polyethylene)

PP (Polypropylene)

PS(Polystyrene)

PMMA(Polymethyl methacrylate)

PET(Polyethylene teraphthalate)

PC(Polycarbonates)

PA(Polyamides)

ABS(Acryknitrile-Butadiene-styrene)

PI(Polyimide)

1/5

/20

13

14

SA

B-A

P/M

EC

H S

ON

AC

T

NON-METALLIC MATERIALS:

PAI( Polyamideimide)

PPO(Polyphenylene oxide)

PPS(Polyphenylene sulphide)

PEEK(Polyether ether ketone)

PTFE(Polytetra fluoro ethylene)

1/5

/20

13

15

SA

B-A

P/M

EC

H S

ON

AC

T


METALLURGY

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.

1/5

/20

13

16

SA

B-A

P/M

EC

H S

ON

AC

T

UNIT:I

CONSTITUTION OF ALLOYS

AND PHASE DIAGRAMS

CONSTITUTION- establishment, foundation,

creation, formation, structure, organization,

charter, bill.

1/5

/20

13

17

SA

B-A

P/M

EC

H S

ON

AC

T

UNIT:I


AND PHASE DIAGRAMS

SOME TECHNICAL TERMS AND

DEFINITIONS:

1.SYSTEM: It is a combination of phases of one or

more components.

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

1/5

/20

13

18

SA

B-A

P/M

EC

H S

ON

AC

T

UNIT:I

CONSTITUTION OF ALLOYS AND

PHASE DIAGRAMS

3.COMPONENTS:

The elements present in the

system are called component. A system may

consist of two or more components.

1/5

/20

13

19

SA

B-A

P/M

EC

H S

ON

AC

T

UNIT:I


AND PHASE DIAGRAMS

CONSTITUTION OF ALLOYS:

4.ALLOY:

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.

The others could be metals or non-metals, for eg:

Brass (CU-Zn), Steel (Fe-C)

1/5

/20

13

20

SA

B-A

P/M

EC

H S

ON

AC

T

UNIT:I


PHASE DIAGRAMS

Alloy find very wide application in the industry than pure metals.

Uses of pure metals

1. High electrical conductivity

2. High ductility

3. Corrosion resistance are required.

These properties are generally at a maximum value in pure metals.

1/5

/20

13

21

SA

B-A

P/M

EC

H S

ON

AC

T

UNIT:I


PHASE DIAGRAMS

Mechanical properties

1. Tensile strength

2. Yield point

3. Hardness are

improved by alloying.

1/5

/20

13

22

SA

B-A

P/M

EC

H S

ON

AC

T

UNIT:I

CONSTITUTION OF ALLOYS AND PHASE

DIAGRAMS

CLASSIFICATION OF ALLOYS

1/5

/20

13

23

SA

B-A

P/M

EC

H S

ON

AC

T

CLASSIFICATION OF

ALLOYS

Pure metals Solid

Solution Intermedia

te phase

UNIT:I


PHASE DIAGRAMS

Alloy can be either a single phase or a mixture

of phases.

A phases is anything which is homogeneous and

physically distinct.

In solid state alloys of three are three possible

phase.

1/5

/20

13

24

SA

B-A

P/M

EC

H S

ON

AC

T

UNIT:I


PHASE DIAGRAMS

If an alloy has a single phase, it could be either

a solid solution or an intermediate phase.

If the alloy is a mixture it could be composed of

any combination of the above three phases.

1/5

/20

13

25

SA

B-A

P/M

EC

H S

ON

AC

T

UNIT:I


PHASE DIAGRAMS

The 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

/20

13

26

SA

B-A

P/M

EC

H S

ON

AC

T

UNIT:I


PHASE DIAGRAMS

5. MIXTURE:

It is a material more than one phase.

1/5

/20

13

27

SA

B-A

P/M

EC

H S

ON

AC

T

UNIT:I


PHASE DIAGRAMS

1/5

/20

13

28

SA

B-A

P/M

EC

H S

ON

AC

T

SOLID SOLUTION

Substitutinal

Solid solution Interstitial

solid solution

Disordered

(or) Random

Ordered

(or) regular

UNIT:I


PHASE DIAGRAMS

Solid solutions:

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

dispersed at random into another substance.

1/5

/20

13

29

SA

B-A

P/M

EC

H S

ON

AC

T

UNIT:I


PHASE DIAGRAMS

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.

1 . Solute: A solute is the minor part of

the solution or the material which is

dissolved.

1/5

/20

13

30

SA

B-A

P/M

EC

H S

ON

AC

T

UNIT:I


PHASE DIAGRAMS

2. Solvent: Solvent constitutes the major portion of

the solution.

Both the solute and the solvent can be solid,

liquid or gas.

1/5

/20

13

31

SA

B-A

P/M

EC

H S

ON

AC

T

UNIT:I


PHASE DIAGRAMS

Solid solution:

Simply a solution in the solid state.

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

lattice.

1/5

/20

13

32

SA

B-A

P/M

EC

H S

ON

AC

T

UNIT:I


PHASE DIAGRAMS

space lattice:

Space lattice is defined as an array of

points in three dimensions in which every point

has surroundings identical to that every other

point in the array.

1/5

/20

13

33

SA

B-A

P/M

EC

H S

ON

AC

T

SOLID SOLUTION

Case:

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.

1/5

/20

13

34

SA

B-A

P/M

EC

H S

ON

AC

T

SOLID SOLUTION

In such a case we have a solid metal in which the

interatomic state which existed in the liquid solution

has been persevered after solidification, and it is

known as a solid solution.

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.

1/5

/20

13

35

SA

B-A

P/M

EC

H S

ON

AC

T

SOLID SOLUTION

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)

1/5

/20

13

36

SA

B-A

P/M

EC

H S

ON

AC

T

SUBSTITUTIONAL SOLID SOLUTION

1/5

/20

13

37

SA

B-A

P/M

EC

H S

ON

AC

T

Solute Atoms

SOLVENT OR

MATRIX ATOMS

solute-Atom of Metal-B Solvent-Atoms of zinc Metal-A

zinc(Solute) Copper(Solvent)

Disordered substitutinal solid solution(random,)


Ordered subsitutional solid solution

1/5

/20

13

38

SA

B-A

P/M

EC

H S

ON

AC

T

Solute

Atoms

SOLVENT OR

MATRIX ATOMS


In substitutional solid solution, there is a direct

substitution of one type of atom for another.

so that solute atoms(cu) enter the crystal to take

positions normally occupied by solvent atoms (e.g.,

Nickel atoms);

1/5

/20

13

39

SA

B-A

P/M

EC

H S

ON

AC

T


The alloy is said to be in a disordered condition if

in the formation of a substitutional solid

solution, the solute atoms do not occupy any

specific position but are distributed at random in

the lattice structure of the solvent.

1/5

/20

13

40

SA

B-A

P/M

EC

H S

ON

AC

T


An ordered subsititutional solid solution is shown

fig Cu-Zn, Al-Cu, α-Brass are some examples of

ordered structures.

1/5

/20

13

41

SA

B-A

P/M

EC

H S

ON

AC

T

INTERSTITIAL SOLID SOLUTION

The four elements hydrogen, carbon, nitrogen,

and boron have such small diameters that they

can occupy the empty spaces (Interstices) in the

crystal lattices of many metals.

1/5

/20

13

42

SA

B-A

P/M

EC

H S

ON

AC

T


1/5

/20

13

43

SA

B-A

P/M

EC

H S

ON

AC

T

Solvent or

matrix atoms Solute atoms


CARBON

(solute)

IRON

( SOLVENT)


Interstitial solid solution usually have a limited

composition range and are generally considered

of secondary importance, but there are a few

instances worthy of special attention.

1/5

/20

13

44

SA

B-A

P/M

EC

H S

ON

AC

T


The interstitial solution of carbon in iron

constitutes the basis of steel hardening.

Very small amount of hydrogen introduced into

steels during acid pickling(cleaning), plating, or

welding operations causes a Sharpe decrease in

ductility, known as hydrogen embrittlement.

1/5

/20

13

45

SA

B-A

P/M

EC

H S

ON

AC

T


Interstitial nitrogen is useful not only in

nirtriding process but also as an important factor

in maintaining 18Cr-8Ni

Stainless steel in the austenitic condition.

1/5

/20

13

46

SA

B-A

P/M

EC

H S

ON

AC

T

HUME - ROTHERY’S RULES OF SOLID

SOLUBILITY

1/5

/20

13

47

SA

B-A

P/M

EC

H S

ON

AC

T

Hume - Rothery’s Rules of solid solubility

HUME - ROTHERY’S RULES OF

SOLID SOLUBILITY

1/5

/20

13

48

SA

B-A

P/M

EC

H S

ON

AC

T

Hume - Rothery’s Rules of solid solubility


HUME –ROTHERY’S RULES OF SOLID SOLUBILITY

The solubility limit of solute in solvents depends on

various factors. These were stated by Hume-rothery

and are as follows:

1. Critical structure factor (or) Crystal structure:

Metals that have the same crystal stucture (Lattice

structure) have a greater solubility.

1/5

/20

13

49

SA

B-A

P/M

EC

H S

ON

AC

T


2. Relative atomic size factor(or) size factor:

The solid solution will tend to form if the

difference in size of solute and solvent is less than

15%.

If the difference is greater than 15% formation of

solid solution will be limited.

For good solid solubility the difference should be less

than 8%

1/5

/20

13

50

SA

B-A

P/M

EC

H S

ON

AC

T


3. Chemical affinity factor (or) Electronegativity:

Formulation of solid solution is

favoured for metals that have less chemical affinity

is more, then a compound is formed instead of a solid

solution.

The metal which are separated in widely in the

periodic table are not suitable for making alloys

because of their high affinity.

1/5

/20

13

51

SA

B-A

P/M

EC

H S

ON

AC

T


4. Relative valency factor(or)valence:

A metal that has a higher valency will

disslove only a small amount of a lower valency

metal, where as the metal with low valency

will have good solubility for the higher valency

metal.

1/5

/20

13

52

SA

B-A

P/M

EC

H S

ON

AC

T


In some alloys both interstitial and

substitutional solid solution are formed to an

appreciable extent.

For Eg: A Cr-Ni steel contains interstitially

dissolved carbon and substitution ally dissolved

chromium, nickel, and minor elements.

1/5

/20

13

53

SA

B-A

P/M

EC

H S

ON

AC

T

POSSIBILITIES OF SOLID SOLUTIONS

• There are three possible solid solutions based on

the amount of their elements. They are:

1.Unsaturated solid solution: In the solvent is

dissolving small amount of solute as well as at a

given temperature and pressure, it is called

unsaturated solid solution.

1/5

/20

13

54

SA

B-A

P/M

EC

H S

ON

AC

T


2. Saturated solid solution:

If the solvent is dissolving

limiting amount of solute, it is called saturated

solid solution.

1/5

/20

13

55

SA

B-A

P/M

EC

H S

ON

AC

T


3. Supersaturated solid solution:

If the solvent is dissolving more of solute that it

should, under equilibrium, it is called

supersaturated solid solution.

1/5

/20

13

56

SA

B-A

P/M

EC

H S

ON

AC

T

PHASE DIAGRAM

Types of phase diagram

1. Isomorphous

2. Eutectoid system

3. Eutectic system

4.Peritectic system

5. Peritectroid reactions

1/5

/20

13

57

SA

B-A

P/M

EC

H S

ON

AC

T

PHASE DIAGRAM

Phase Diagrams

Phase diagrams are graphical

representation of what phases are present in an

alloy system at various

Temperatures, pressures, and compositions.

1/5

/20

13

58

SA

B-A

P/M

EC

H S

ON

AC

T

PHASE DIAGRAM

(or)

A phase diagram is a map showing the

structure or phase present as the

temperature and overall composition of

the material are varied.

Phase diagrams are also known as equilibrium

diagrams or constitutional diagrams.

1/5

/20

13

59

SA

B-A

P/M

EC

H S

ON

AC

T

WHY SHOULD PHASE DIAGRAMS BE

STUDIED?

The phase diagrams can answer the following

important questions:

What condition is the material in?

Is the composition uniform throughout?

If not, how much of each component is present?

1/5

/20

13

60

SA

B-A

P/M

EC

H S

ON

AC

T


STUDIED?

Is something present that may give undesired

properties?

What will happen if temperature is increased or

decreased; pressure is changed or composition is

varied?

1/5

/20

13

61

SA

B-A

P/M

EC

H S

ON

AC

T


STUDIED?

Phase diagrams are used by engineers and

scientists to understand and to predict many

aspects of the behavior of materials.

1/5

/20

13

62

SA

B-A

P/M

EC

H S

ON

AC

T

TERMINOLOGY USED IN PHASE DIAGRAMS

1. Components

2. System

3. Alloy

4. Solid solution

5. Solute Solution

1/5

/20

13

63

SA

B-A

P/M

EC

H S

ON

AC

T


6. Solvent

7. Phase

8. Equilibrium

9. Solubility limit

10.Degrees of freedom

1/5

/20

13

64

SA

B-A

P/M

EC

H S

ON

AC

T


The various terms used in the study of phase

diagrams have been explained below:

1. COMPONENT: Component are pure metals

and or compounds of which an alloy is composed.

Eg: In a copper-zinc brass, the components are

CU and Zn.

1/5

/20

13

65

SA

B-A

P/M

EC

H S

ON

AC

T


2. SYSTEM: The system has two meanings in this

context

i. System: May refer to a specific body of

material under consideration. For Eg: A

ladle of molten steel is referred as a system.

1/5

/20

13

66

SA

B-A

P/M

EC

H S

ON

AC

T


(ii)system: May also refer to the series of possible

alloys consisting of the same components. For

example, the Iron-Carbon system.

1/5

/20

13

67

SA

B-A

P/M

EC

H S

ON

AC

T


A system having one components is called a

Unary system, and the system having two, three

and four components are known as Binary,

ternary and quaternary systems, respectively.

1/5

/20

13

68

SA

B-A

P/M

EC

H S

ON

AC

T


3. ALLOY:

An alloy is a mixture of two or more metals

or a metal (metals) and a non-metal (non-metals).

1/5

/20

13

69

SA

B-A

P/M

EC

H S

ON

AC

T


4.SOLID SOLUTION:

It is a solid that consist of two or

more elements atomically dispersed in a single-

phase structure.

1/5

/20

13

70

SA

B-A

P/M

EC

H S

ON

AC

T


5. SOLUTE SOLUTION:

It is the minor part of the

solution or the material which is dissolved.

1/5

/20

13

71

SA

B-A

P/M

EC

H S

ON

AC

T


6. SOLVENT:

The material which contributes the

major portion of the solution.

1/5

/20

13

72

SA

B-A

P/M

EC

H S

ON

AC

T


7. PHASE:

A phase may be defined as a homogenous

portion of a system that has uniform physical

and chemical characteristics.

1/5

/20

13

73

SA

B-A

P/M

EC

H S

ON

AC

T


8. EQUILIBRIUM:

Equilibrium is said to exit when

enough time is allowed for all possible reactions

to be completed.

1/5

/20

13

74

SA

B-A

P/M

EC

H S

ON

AC

T


The equilibrium state refers to the

characteristics of the system that remain

constant indefinitely. Equilibrium occurs when

the free energy of the system is at its minimum

value.

1/5

/20

13

75

SA

B-A

P/M

EC

H S

ON

AC

T


The term phase equilibrium refers to

equilibrium as it applies to systems in which

more than one phase may exist.

1/5

/20

13

76

SA

B-A

P/M

EC

H S

ON

AC

T


9. SOLUBILITY LIMIT:

It is the maximum concentration of

solute that may be added without forming a new

phase.

1/5

/20

13

77

SA

B-A

P/M

EC

H S

ON

AC

T


NOTE: The addition of solution in excess

of the solubility limit results in the formation of

another solid solution or compound.

1/5

/20

13

78

SA

B-A

P/M

EC

H S

ON

AC

T


10. DEGREES OF FREEDOM:

It is the number of

independent variables ( such as temperature,

pressure, and composition).

That can be changed independently without

changing the phase or phases of the system.

1/5

/20

13

79

SA

B-A

P/M

EC

H S

ON

AC

T

WHAT IS MEANT BY THE TERM PHASE?

A phase may be a portion of matter which is

homogenous

A phase may be defined as any physical distinct

homogenous and mechanically separable portion

of a substance.

1/5

/20

13

80

SA

B-A

P/M

EC

H S

ON

AC

T


In Layman’s term, a phase requires a unique

structure, uniform composition, and well-defined

boundaries or interfaces

Examples: A pure substance such as water is a

single phase.

1/5

/20

13

81

SA

B-A

P/M

EC

H S

ON

AC

T


The pure substance water can exist in solid,

liquid and vapour, each of these states being a

single phase, as shown in fig (a)

Now consider the effect of adding salt(Nacl) to

water. Salt will dissolve in water to give a

homogeneous solution.

1/5

/20

13

82

SA

B-A

P/M

EC

H S

ON

AC

T


Thus the salt- water solution forms a single

phase as shown if fig(b)

If more salt is added into water, then we have

two different phases as shown if fig(c)

1/5

/20

13

83

SA

B-A

P/M

EC

H S

ON

AC

T


A Single phase system is also termed as

“homogeneous system”

1/5

/20

13

84

SA

B-A

P/M

EC

H S

ON

AC

T


System composed of two or more phases are

termed as mixtures or heterogeneous systems’.

Fig (d)

Most metallic alloys, ceramic, polymers, and

composite are heterogenous.

1/5

/20

13

85

SA

B-A

P/M

EC

H S

ON

AC

T

ILLUSTRATION OF PHASES

WATER(2)

ILLUSTRATION OF PHASES:

(A) Three forms of water: 1) Ice 2)water 3)

water vapour are each a phase.

1/5

/20

13

86

SA

B-A

P/M

EC

H S

ON

AC

T

WATER

ICE (1)

WATER VAPOUR(3)


salt

(b) Salt and water have unlimited solubility

(Homogeneous solution)- from a single phase

1/5

/20

13

87

SA

B-A

P/M

EC

H S

ON

AC

T

•


(C) Salt and water have limited solubility

(Heterogenous solution)-from two distinct phases

1/5

/20

13

88

SA

B-A

P/M

EC

H S

ON

AC

T

Saturated brine

Excess salt

ILLUSTRATION OF PHASES 1

/5/2

013

89

SA

B-A

P/M

EC

H S

ON

AC

T

OIL

WATER

OIL AND WATER HAVE VIRTUALLY NO SOLUBILITY FROM TWO

DISTINCT PHASES

PHASE DIAGRAM OF PURE

SUBSTANCE

One- Component Phase diagram

1/5

/20

13

90

SA

B-A

P/M

EC

H S

ON

AC

T


SUBSTANCE

1/5

/20

13

91

SA

B-A

P/M

EC

H S

ON

AC

T


SUBSTANCE

A pure substance such as water can exist in

solid, liquid, or vapour phases, depending on the

condition of temperature and pressure

1/5

/20

13

92

SA

B-A

P/M

EC

H S

ON

AC

T


SUBSTANCE

The phase relationships may be represented on

a pressure- temperature (PT) diagram, known as

a one-component (or unary) phase diagram, for

the H2O System.

1/5

/20

13

93

SA

B-A

P/M

EC

H S

ON

AC

T


SUBSTANCE

The phase diagram is composed of regions of

pressure and temperature where only a single

phase is stable.

The line OA indicates the vapourisation line

and the line OB indicates the freezing line.

1/5

/20

13

94

SA

B-A

P/M

EC

H S

ON

AC

T


SUBSTANCE

Liquid and vapour phase exist along the

vapourisation line and liquid and solid phases

along the freezing line, shows in figure. These

lines are also known as Two phase equilibrium

lines.

1/5

/20

13

95

SA

B-A

P/M

EC

H S

ON

AC

T


SUBSTANCE

The point “O” is know as Triple point.

Triple point is the point at which three phases

(Solid, liquid, and vapour phases(gas)).

of a single material coexit. This triple point of

water exists at temperature 0.00980C

and at pressure 4.58 mm of Hg.

1/5

/20

13

96

SA

B-A

P/M

EC

H S

ON

AC

T

PHASE DIAGRAMS

The properties of an alloy depend on nature,

amount, size, distribution and orientation of the

phases.

A phase is the chemically and structurally

homogeneous portion of the microstructure.

1/5

/20

13

97

SA

B-A

P/M

EC

H S

ON

AC

T

PHASE DIAGRAMS

It has the following characteristics

1. Same structure throughout.

2. Roughly the same composition and

properties throughout.

3. Definite interface between the phase

and surrounding.

1/5

/20

13

98

SA

B-A

P/M

EC

H S

ON

AC

T

J.W. GIBBS

( JOSIAH WILLARD GIBBS) 1/5

/20

13

99

SA

B-A

P/M

EC

H S

ON

AC

T

J.W. GIBBS( JOSIAH WILLARD

GIBBS)

JOSIAH WILLARD GIBBS PROPOSAL

(OR)

J.W. GIBBS LAW

(OR)

GIBB’S PHASE RULE

(or)

PHASE RULE

1/5

/20

13

100

SA

B-A

P/M

EC

H S

ON

AC

T

GIBBS PHASE RULE

J.W. Gibbs, American physicist derived an

equation which established relationship in a

system between the number of phases,

The number of degree of freedom and the

number of components.

1/5

/20

13

101

SA

B-A

P/M

EC

H S

ON

AC

T

GIBB’S PHASE RULE

The phase rule indicates the phases that exists

at equilibrium.

The Gibb’s phase rule satisfies the following

relation:

P+F=C+n

1/5

/20

13

102

SA

B-A

P/M

EC

H S

ON

AC

T

GIBB’S PHASE RULE

P- Number of phases that exist in a

system under certain conditions.

C-Number of components in the system.

n- It represents the number of variables,

examples: Temperature, pressure and

concentration.

1/5

/20

13

103

SA

B-A

P/M

EC

H S

ON

AC

T

GIBB’S PHASE RULE

F- Degree of freedom. It is the number of

variables such as temperature or

pressure or concentration which can

be change independently without

changing the number of phases that

are present in the system.

1/5

/20

13

104

SA

B-A

P/M

EC

H S

ON

AC

T

GIBB’S PHASE RULE

In most studies the pressure is constant

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;

P+F=C+1

1/5

/20

13

105

SA

B-A

P/M

EC

H S

ON

AC

T

USES OF PHASE RULE

The phase rule predicts maximum number of

phases present in the alloy under equilibrium

conditions at any point of diagram.

If the number of phases are known, one can

determine the degree of freedom using phase

rule.

1/5

/20

13

106

SA

B-A

P/M

EC

H S

ON

AC

T

USES OF PHASE RULE

Thus the phase rule is useful to know whether

the temperature or pressure or both variables

can be changed without changing the structure of

the alloy.

1/5

/20

13

107

SA

B-A

P/M

EC

H S

ON

AC

T

ILLUSTRATION OF THE USE OF THE

PHASE RULE

Let us consider the application of gibbs phase rule

to the phase diagram of water system

Case 1 : Consider a triple point in the diagram.

At the triple point, three phases coexist in

equilibrium .

P=3. Since there is one component (water) in the

system C= 1

1/5

/20

13

108

SA

B-A

P/M

EC

H S

ON

AC

T

THE USE OF THE PHASE RULE

The number of degree of freedom can be

calculated using the Gibbs phase rule as,

F=1- 3+2

F=0 (Zero degree of freedom)

This means that one of the variables

(Temperature or pressure) can be changed

at the triple point.

1/5

/20

13

109

SA

B-A

P/M

EC

H S

ON

AC

T


Note: Since the variables temperature or

pressure cannot be changed and still keep the

three phases of coexistence.

The triple point is called an invariant point.

1/5

/20

13

110

SA

B-A

P/M

EC

H S

ON

AC

T


Case 2: Next consider a point along liquid-

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)

1/5

/20

13

111

SA

B-A

P/M

EC

H S

ON

AC

T


This means that one variable

( Temperature or pressure) can be changed

independently and still maintain a system

with two coexisting phases.

1/5

/20

13

112

SA

B-A

P/M

EC

H S

ON

AC

T


Case:3

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

/20

13

113

SA

B-A

P/M

EC

H S

ON

AC

T


F=1-1+2

F=2 ( two degree of freedom)

This means that two variables ( Temperature

and pressure) can be varied independently and

the system will still remain in a single phase.

1/5

/20

13

114

SA

B-A

P/M

EC

H S

ON

AC

T


Note: In many application (especially for most

binary alloy) the pressure is kept constant at 1

atmosphere.

In this case Gibbs phase rule is modified as

F=C-P+1

1/5

/20

13

115

SA

B-A

P/M

EC

H S

ON

AC

T


The above equation is known as condensed phase

rule.

This equation can be applied to most of

the binary phase diagram.

1/5

/20

13

116

SA

B-A

P/M

EC

H S

ON

AC

T

OBJECTIVE TYPE QUESTIONS

1. -----------May be visualized as forming from a

centre of freezing, or nucleus, which is composed

of a small group of atoms oriented into one of the

common crystal patterns.

Crystal

1/5

/20

13

117

SA

B-A

P/M

EC

H S

ON

AC

T

OBJECTIVE TYPE QUESTIONS

2.Perfect crystal of proper external shape can be

obtained only if crystallisation develops under

conditions

when degree of ----------------is very slight and the

metal has a very high purity.

1/5

/20

13

118

SA

B-A

P/M

EC

H S

ON

AC

T

MICRO-CONSTITUENTS OF IRON-CARBON

ALLOYS

There are different micorscope constituents of

Iron-Carbon alloys exit.

The study of these micro-constituents is

essential in order to understand iron-iron

carbide (Fe-Fe3C) equilibrium phase diagram.

1/5

/20

13

119

SA

B-A

P/M

EC

H S

ON

AC

T

VARIOUS MICRO-CONSTITUENTS OF IRON-

CARBON ALLOYS ARE:

1.Ferrite

2.Austenite

3.Cementite

4.Pearlite

5.Ledeburite

6.Martensite

1/5

/20

13

120

SA

B-A

P/M

EC

H S

ON

AC

T


CARBON ALLOYS ARE:

7. Troosite

8. Sorbite, and

9.Bainite

1/5

/20

13

121

SA

B-A

P/M

EC

H S

ON

AC

T


CARBON ALLOYS ARE:

1. Ferrite (or α-Iron)

Ferrite is a primary solid solution based on α iron

having BCC structure.

It is Nothing but the interstitial solid solution of

carbon in iron.

1/5

/20

13

122

SA

B-A

P/M

EC

H S

ON

AC

T

FERRITE

1/5

/20

13

123

SA

B-A

P/M

EC

H S

ON

AC

T


CARBON ALLOYS ARE:

Maximum solubility of carbon in iron is 0.025% carbon

at 723°C, While its solubility at room temperature is

only 0.008%.

Ferrite is soft, ductile, and highly

Magnetic.

It can undergo extensive cold working

1/5

/20

13

124

SA

B-A

P/M

EC

H S

ON

AC

T


CARBON ALLOYS ARE:

2. Austenite(or γ-Iron)

Austenite is a primary solid solution based on γ

iron having FCC structure.

This is also an interstitial solid solution of

carbon in iron

1/5

/20

13

125

SA

B-A

P/M

EC

H S

ON

AC

T

AUSTENITE

1/5

/20

13

126

SA

B-A

P/M

EC

H S

ON

AC

T

AUSTENITE

It is also a non-magnetic (paramagnetic)

Austentite has a greater electrical resistance

and coefficient of expansion than ferrite.

1/5

/20

13

127

SA

B-A

P/M

EC

H S

ON

AC

T

CEMENTITE

Cementite is the name given to the carbide of

iron(Fe3c).

It is the hard, brittle, intermetallic compound of

iron with 6.69% of carbon.

1/5

/20

13

128

SA

B-A

P/M

EC

H S

ON

AC

T

CEMENTITE

The hardness and brittleness of cast iron is

believed to be due to the presence of the

cementite.

It is Magnetic below 250°c

1/5

/20

13

129

SA

B-A

P/M

EC

H S

ON

AC

T

CEMENTITE

1/5

/20

13

130

SA

B-A

P/M

EC

H S

ON

AC

T

PEARLITE

Pearlite is the eutectoid mixture of ferrite

(87.5%) and cementite (12.5%).

It is formed when austenite decomposes

during cooling. It contains 0.8% of carbon

1/5

/20

13

131

SA

B-A

P/M

EC

H S

ON

AC

T

PEARLITE

1/5

/20

13

132

SA

B-A

P/M

EC

H S

ON

AC

T

PEARLITE

LAMELLAR-PEARLITE BEADED BAG

1/5

/20

13

133

SA

B-A

P/M

EC

H S

ON

AC

T

PEARLITE

It consist of alternate thin layers (or lamellae) of

ferrite and cementite shown in fig.

The name derives from its lustrous apperance

(similar to mother of pearl) when viewed in

white light under a microscope.

1/5

/20

13

134

SA

B-A

P/M

EC

H S

ON

AC

T

PEARLITE

The properties of pearlite is midway between

ferrite and cementite. It is relatively strong, hard

and ductile.

1/5

/20

13

135

SA

B-A

P/M

EC

H S

ON

AC

T

LEDEBURITE

Ledeburite is the eutectic mixture of austenite(γ-Iron) and

cementite (Fe3C) Containing 4.3% carbon.

In pure iron-carbon alloy, it forms at 1140 °C.

Most of the engineering alloy materials belong to

this range of alloy.

1/5

/20

13

136

SA

B-A

P/M

EC

H S

ON

AC

T

LEDEBURITE

Pig iron, the most important engineering

material, is ledeburite.

1/5

/20

13

137

SA

B-A

P/M

EC

H S

ON

AC

T

LEDEBURITE

1/5

/20

13

138

SA

B-A

P/M

EC

H S

ON

AC

T

LEDEBURITE

1/5

/20

13

139

SA

B-A

P/M

EC

H S

ON

AC

T

MARTENSITE

Martensite is the super saturated solid solution

of carbon in α-Iron.

It is formed when steel is very rapidly cooled from the

austenitic state.

It exhibits a characteristic acicular or needle like

structure.

1/5

/20

13

140

SA

B-A

P/M

EC

H S

ON

AC

T

MARTENSITE

It is very hard more brittle and low ductility

properties.

There is an increase in specific volume during

formation of martensite from austenite.

1/5

/20

13

141

SA

B-A

P/M

EC

H S

ON

AC

T

MARTENSITE

As a result internal stresses are set up in the

materials leading to the formation of minute

cracks.

1/5

/20

13

142

SA

B-A

P/M

EC

H S

ON

AC

T

MARTENSITE (RED AND YELLOW

MARTENSITE. GREEN: AUSTENITE)

1/5

/20

13

143

SA

B-A

P/M

EC

H S

ON

AC

T

TROOSTITE

Troosite is the mixture of radial lamella of

ferrite and cementite. In fact, it differs from

pearlite only in the degree of fitness.

This constituents is also known as troostite

pearlite.

1/5

/20

13

144

SA

B-A

P/M

EC

H S

ON

AC

T

TROOSTITE

It is the microstructure consisting ferrite and

finely divided cementite, produced on tempering

martensite below 450 °C

1/5

/20

13

145

SA

B-A

P/M

EC

H S

ON

AC

T

TROOSTITE

It is formed by the decomposition of austenite

when cooled at a rate slower than that which

will yield a martensitic structure and faster than

that which will produce a sorbitic structure.

1/5

/20

13

146

SA

B-A

P/M

EC

H S

ON

AC

T

TROOSTITE

It has hardness intermediate between

martensite and sorbite.

1/5

/20

13

147

SA

B-A

P/M

EC

H S

ON

AC

T

TROOSTITE

1/5

/20

13

148

SA

B-A

P/M

EC

H S

ON

AC

T

SORBITE

Sorbite is the microstructure consisting ferrite,

and finely divided cementite, produced on

tempering martensite above 450°C

1/5

/20

13

149

SA

B-A

P/M

EC

H S

ON

AC

T

SORBITE

This constituents is also known as sorbitic

pearlite.

It is formed by the decomposition of austenite

when cooled at a rate slower than that which

will produce a pearlitic structure

1/5

/20

13

150

SA

B-A

P/M

EC

H S

ON

AC

T

SORBITE

Though sorbitic steel is slightly less ductile than

pearlite steel, its tensile and yield strength are

high.

The sorbite steels are often known as Toughened

steels.

1/5

/20

13

151

SA

B-A

P/M

EC

H S

ON

AC

T

SORBITE 1

/5/2

013

152

SA

B-A

P/M

EC

H S

ON

AC

T

SORBITE

Note:

All the pearlite, troosite and sorbite are ferrite-

cementite mixtures having lamellar structure.

However they are distinguished by their degree of

dispersion.

Pearlite has corase pearlite.

1/5

/20

13

153

SA

B-A

P/M

EC

H S

ON

AC

T

SORBITE

Troosite has fine pearlite

And sorbite has medium pearlite

1/5

/20

13

154

SA

B-A

P/M

EC

H S

ON

AC

T

BAINITE

Bainite is a decomposition product of austenite,

consisting of an aggregate of ferrite and carbide.

Bainite is obtained by transformation of pearlite

higher temperature ( has a feathery structure) is

called upper bainite.

1/5

/20

13

155

SA

B-A

P/M

EC

H S

ON

AC

T

BAINITE

Lower bainite provides high mechanical

properties and that is why it is extensively

used for components of machine and structures.

Bainite has hardness in between the hardness

of pearlite and martensite.

1/5

/20

13

156

SA

B-A

P/M

EC

H S

ON

AC

T

BAINITE 1

/5/2

013

157

SA

B-A

P/M

EC

H S

ON

AC

T

IRON/CARBON ALLOY PHASE DIAGRAM 1

/5/2

013

158

SA

B-A

P/M

EC

H S

ON

AC

T

1/5

/20

13

159

SA

B-A

P/M

EC

H S

ON

AC

T

Documents

Inroduction to Engineering materials