Ch-7 Compatibility Mode

8/22/2019 Ch-7 Compatibility Mode

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CHAPTER 7

Chapter 9-


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Contents of Todays Lecture

Introduction to phase change processes. Phase diagram.

Chapter 9-

conditions of solubilities.

Lever Rule.

Fe-C phase diagram.


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Introduction to phase diagrams

Most of the engineering materials are alloys. In a poly-phase material, the overall properties

depend upon Number of hases resent

Chapter 9-

Relative amount of each phase Composition and microstructure of each phase

Size and distribution of the phases in the microstructure.

In this topic we are going to develop theunderstanding of composition-structure-property relationship of materials.


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About Phase diagram

The phase diagram or Equilibrium diagram is the

graphical representation of number of phases that arepresent, their compositions and the relative amount ofeach phase as the functions of temperature and theoverall composition of the material.

Chapter 9-

The term equilibrium denotes a state of rest whichimplies that, for a given composition and temperature,there shall not be any change in the constituents withtime.


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Solid solution.

Solid Solution: When two elements dissolvein the solid state, the resulting phase iscalled as solid solution.

Chapter 9-

There are following possibilities The metals are completely soluble in solid

state.

The metals are completely insoluble in solidstate.

The metals are partially soluble in solid

state.


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System The universe or any part of it.

Phase A region in the system that has a distinct structure and/or

composition

Structure How the atoms or molecules of the components are physically

arranged in space

Composition The relative amounts of different components

Components Chemically distinct species, generally pure elements or

compounds

Phase Diagram Vocabulary

Chapter 9-

Phase Diagram A graphical representation of the influence of various factors,such as temperature, pressure, and composition on the phases

that exist in a system.

Unary System A system that has only one component

Binary System A system that has two components what this courseprimarily deals with

Ternary System A system that has three components

Quaternary System A system that has four components

A, B, C Generic names of componentsL, , , Generic names of phases


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Material Science & Engineering

Processing Structure Properties Performance

Chapter 9-


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What is materials science and

engineering?

Materials science is the investigation of therelationships that exist between the

structure and ro erties of materials.

Chapter 9-

Materials engineering uses the structure-

property relationships of materials to link

processing withperformance.

Processing Structure Properties Performance


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Whats meant by the structure of a

material?

Subatomic- Interactions of electrons with anucleus

Atomic- Arrangement of atoms relative to

Chapter 9-

each other Microscopic- Organization of large groups

of atoms (can be seen with a microscope)

Macroscopic- Structure that can beobserved with the naked eye.


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Example: Snow.

Chapter 9-

Individualmolecules arearranged into

crystals

Individualcrystals form

a solidstructure


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.is a lot like metal

Chapter 9-

Individualatoms are

arranged intograins

Individualgrains form

a solidstructure


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TerminologyTerminologyTerminologyTerminology

Chapter 9-


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SYSTEM

SYSTEM

Chapter 9-

SURROUNDING


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Components (C)Components (C)Components (C)Components (C)No. of Elements or Compounds thatNo. of Elements or Compounds thatNo. of Elements or Compounds thatNo. of Elements or Compounds that

constitute a systemconstitute a systemconstitute a systemconstitute a system

1-C

Chapter 9-

-

3-C

4-C

Multi-C


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PhasePhasePhasePhase Physically distinct,

Mechanically Separable &

Chemically homogeneous

Chapter 9-

Region of a system is called as phase.

Homogeneous portion of a system that has

uniform physical and chemical characteristics is

called as a PHASE


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Solid

Various phases [e.g. crystal structures (diamond; graphite)

Alloys (sometimes its difficult to tell this - microscopic

examination may be necessary {dispersions uniform onmacroscopic scale}) Miscible one phase (P=1)

Chapter 9-

Liquid Miscible liquids are one phase

Immiscible liquids are multiple phases (P>1)

Gas

Systems consisting of gases can have only one phase


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Definitions

Heterogeneous and homogeneous systems

Systems with one phase are homogeneous

Systems with more than one phase are heterogeneous

Constituent- a chemical species (ion or molecule which ispresent

Component (C) - chemically independent constituents of a

Chapter 9-

C = #of independent chemical constituents - # ofdistinct chemical reactions #of independent chemical constituents = total # of constituents

minus the number of any restrictive conditions (chargeneutrality, material balance etc.)


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(lighterphase)

Solid PhaseSolid PhaseSolid PhaseSolid PhaseCOMPONENTS AND PHASES

Chapter 9- 33

AlAlAlAl----CuCuCuCu

AlloyAlloyAlloyAlloy

ar er

phase)


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EquilibriumEquilibriumEquilibriumEquilibrium

State of a System at specified conditionswhen the system possesses minimum free

ener

Chapter 9-

Temperature, Pressure & Composition


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PHASE EQUILIBRIUMPHASE EQUILIBRIUMPHASE EQUILIBRIUMPHASE EQUILIBRIUM

Constancy with time in physicalcharacteristics

Chapter 9-


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Gibbs Phase RuleGibbs Phase RuleGibbs Phase RuleGibbs Phase Rule For a solid solution, the phase rule is

{P + F = C + N

}

P No. of Phases

Chapter 9-

F DOF

CNo. of Components

N Non-compositional variables


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Degree of Freedom (DOF)Degree of Freedom (DOF)Degree of Freedom (DOF)Degree of Freedom (DOF)

The number of independent variables

required to describe the state of a system is

called as the DOF

Chapter 9-

Externally controlled variables

(Temp, Pressure, Composition)


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Gibbs Phase RuleGibbs Phase RuleGibbs Phase RuleGibbs Phase Rule Ex. Ice + Water, heating at constant pressure

{P + F = C + N

}

P No. of PhasesP + F = 1 + 1

Chapter 9-

F DOF

CNo. of Components

N Non-compositional variables

F = 2 - P


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One Component Systems

Phase rule says that you can have at most 3 phasesF = C- P +2; C=1 so F=3-P

If P=3, F=0 system is invariant Specified by temperature and pressure and occurs at 1 point

(called the triple point)

If one phase is present, F = 2 that is P and T can be varied

Chapter 9-

n epen en y

This defines an area in a P,T diagram which only onephase is present

If two phases are present, F = 1 so only P or T can bevaried independently.

This defines a line in a P, T diagram


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Solubility LimitSolubility LimitSolubility LimitSolubility Limit

The elements or compounds which are

mixed

Chapter 9-

Solvent SoluteAt some specific temperature there is a maximum concentration

of solute atoms that may dissolve in the solvent to form a solid

solution this is called solubility limit


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erature

(C)

Lli uid solution

SolubilityLimit L

(liquid)+60

80

100

THE SOLUBILITY LIMIT

Chapter 9- 2

Pure

Sugar

Temp

0 20 40 60 80 100Co=Composition (wt% sugar)

i.e., syrup)

(solidsugar)

65

20

Pure

Water


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Changing T can change # of phases: path A to B.

Changing Co can change # of phases: path B to D.

)

B(100,70)1 phase

100

D(100,90)2 phases

EFFECT OF T & COMPOSITION (Co)

Chapter 9-

70 80 1006040200

Tem

perature(

Co=Composition (wt% sugar)

L(liquid solution

i.e., syrup)

A(70,20)2 phases

20

40

60

0

(liquid)+S

(solidsugar)


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PhasePhasePhasePhase----EquilibriumEquilibriumEquilibriumEquilibrium

Chapter 9-


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Phase DiagramsPhase DiagramsPhase DiagramsPhase Diagrams

1-Component

2-Components

3-Components

Chapter 9-

Unary P.D. (Binary P.D.) (Ternary P.D.)

Much of the information about the control of microstructure or

phase structure of a particular alloy system is conveniently and

concisely displayed in what is called a phase diagram, also

often termed as equilibrium or constitutional diagram.


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Unary Phase Diagram (Fe)

GAS

LIQUID

3000

1535

P + F = C + N

P + F = 1 + 2

F = 3 - P

Chapter 9-Pressure (GPa)

Temp (oC)

FCC ()

HCP ()

BCC ()

BCC ()

1410

910

For s ngle P,F = 2

For two P,

F = 1


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BINARY ISOMORPHOUS DIAGRAMBINARY ISOMORPHOUS DIAGRAMBINARY ISOMORPHOUS DIAGRAMBINARY ISOMORPHOUS DIAGRAM

Cu + NiCu + NiCu + NiCu + Ni

Chapter 9-

100 % Liquid solubility and100 % Liquid solubility and100 % Liquid solubility and100 % Liquid solubility and100 % Solid solubility100 % Solid solubility100 % Solid solubility100 % Solid solubility

PHASE DIAGRAM f C Ni


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1400

1500

1600

T(C)

L (liquid)

qu

idus

PHASE DIAGRAM for Cu-Ni

1453 C

Chapter 9- 5

20 40 60 80 10001000

1100

1200

(FCC solidsolution)

L

solidu

(Cu) (Ni)

1085 C

COMPOSITION WT %


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InterpretationInterpretationInterpretationInterpretationof Phase Diagramsof Phase Diagramsof Phase Diagramsof Phase Diagrams

1. Phases Present

Chapter 9-

2. Composition of Phases

3. Weight Fraction of Phases

T(C) Phases PresentPhases PresentPhases PresentPhases Present


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1400

1500

1600T(C)

L (liquid)

liquidu

s

solidus

1250,35)

Phases PresentPhases PresentPhases PresentPhases Present

Chapter 9- 6

wt% Ni20 40 60 80 1000

1000

1100

1200(FCC solidsolution)

L

A(1100,60)

B

composition of phasescomposition of phasescomposition of phasescomposition of phases


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1300

T(C)

L (liquid)liq

uidus

olidu

s

TAA

B

tie line

L+

composition of phasescomposition of phasescomposition of phasescomposition of phases

1280 C

1320C

Chapter 9- 7

wt% Ni

20

1200

(solid)L+

30 40 50

DTD

433532

CoCL C

weight fractions of phases


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1300

T(C)

L (liquid) liquid

us

solid

us

TA A

TBB

tie line

L+

weight fractions of phases

Chapter 9- 8

wt% Ni

20

1200

(solid)L+

30 40 50

DTD

433532C

oC

LC


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CoR S

CL C

THE LEVER RULE

Chapter 9- 9

WWL


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WL= S/(R+S) WL= (C-C0)/(C-CL)

Chapter 9-

W = (C0-CL)/(C-CL)


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Volume Fraction of Phases

Chapter 9-

Relation in between

Volume and Weight Fraction


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Equilibrium COOLING IN A Cu-Ni

Chapter 9-

COOLING IN A Cu Ni BINARY


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COOLING IN A Cu-Ni BINARY

Equilibrium Cooling

System is:Binaryi.e., 2 components:

Chapter 9-

u an .

Isomorphousi.e., complete solubility of one

component in another; phase

field extends from 0 to 100wt% Ni.

Extreme slow cooling of alloy

EX: COOLING IN A Cu-Ni BINARY


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1300

L (liquid)

L+

T(C)

A

D

B

L: 35wt%Ni

: 46wt%Ni

C

L: 35wt%Ni

4643

32

24

35

L: 32wt%Ni

EX: COOLING IN A Cu Ni BINARY

Chapter 9-10wt% Ni20

1200

30 40 501100

(solid)

L+

35Co

E : 43wt%NiL: 24wt%Ni

: 36wt%Ni



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Non-Equilibrium Cooling

System is:Binary

Chapter 9-

.e., componen s:

Cu and Ni.

Isomorphousi.e., complete solubility of one

component in another; phasefield extends from 0 to 100wt% Ni.


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Non-Equilibrium COOLING IN A

-

Chapter 9-


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Chapter 9-


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NonNonNonNon----Equilibrium CoolingEquilibrium CoolingEquilibrium CoolingEquilibrium Cooling

Consequences of Non-Equilibrium cooling

Chapter 9-


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C changes as we solidify.

Cu-Ni case:

Fast rate of cooling:Cored structure

Slow rate of cooling:Equilibrium structure

First to solidify has C = 46wt%Ni.Last to solidify has C = 35wt%Ni.

Uniform C:

CORED VS EQUILIBRIUM PHASES

Chapter 9-

46wt%Ni

35wt%Ni

Last to solidfy:

< 35wt%Ni

MECHANICAL PROPERTIES: Cu-Ni System


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Effect of solid solution strengthening

on:--Tensile strength (TS) --Ductility (%EL,%AR)

MECHANICAL PROPERTIES: Cu-Ni System

on(%EL)

50

60

%EL forpure Ni

%EL for pure Cu

ngth(MP

a)

400

TS for

Chapter 9-

Elong

at

Com osition, wt%Ni

Cu Ni0 20 40 60 80 100

20

30

TensileSt

re

Composition, wt%Ni

Cu Ni0 20 40 60 80 100

200

300pure

TS for pure Cu


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Binary Eutectic SystemsBinary Eutectic SystemsBinary Eutectic SystemsBinary Eutectic Systems

Chapter 9-


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Binary Eutectic System

Apply Modified Gibbs Phase Rule Phases present: L, and (P=3)

Components: Pb and Sn (C=2)

Chapter 9-

P+F=C+1

F=0 no degrees of freedom

Therefore, three phases can coexist in a binary system

only at a unique temperature and for unique

compositions of the three phases

Upon cooling, there is a temperature arrest during the

solidification process (eutectic reaction)

T(C)BINARY-EUTECTIC SYSTEMS


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L (liquid)

L + L+

1200( )

600

800

1000

TE 8.0 71.9 91.2779C

A

B E G

Solidus

line F

Chapter 9-13

+

Co, wt% Ag20 40 60 80 1000

200

400

CE

C

o vus ne

H

EX: Pb-Sn EUTECTIC SYSTEM


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L + L+ 200

T(C)

300

L (liquid)

represents a solid solution of tin in lead

For tin is a solvent and lead is a solute

Chapter 9-14

+

18.3

Co, wt% Sn

20 40 60 80 1000Co

100

61.9 97.8150

Wh d l k k ?


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What we wd like to know?

Microstructure Com osition

Chapter 9-

Weight Fraction

EX: Pb-Sn EUTECTIC SYSTEM


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L + L+ 200

T(C)

300

L (liquid)

183C

Chapter 9-15

+

18.3

Co, wt% Sn

20 40 60 80 1000Co

100

61.9 97.8150

11 99

R S


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Amounts of Phases at different temperatures

QP

PW

QP

QW

L+

=

+=

At Teutectic + T

( )

QP

PW

QP

QW

L

cproeutecti

+=

+=

Chapter 9-

eutectic -

( )

RQP

PW

RQP

RQW

total

++

=

++

+=

( ) ( ) ( )cproeutectitotaleutectic

WWW =

MICROSTRUCTURES IN EUTECTIC SYSTEMS


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L +

T(C)

300 L

L: Co

wt%Sn

L

400

solidus Liquidus

Chapter 9-16

Co, wt% Sn10

2

200Co

100

30

: Co

wt%Sn

+

(room T solubility limit)

TE-

System)

MICROSTRUCTURES IN EUTECTIC SYSTEMS


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2wt%Sn < Co < 18.3wt%Sn

Result:-- polycrystal with fine

crystals.

L +

T(C)

300

L

L: Cowt%Sn

400

L

d

Chapter 9-17

o

200

Co, wt% Sn10

18.3

200Co

100

30

+

(sol. limit at TE)

TE

2(sol. limit at Troom)

solvus

f

g

MICROSTRUCTURES


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T(C)

300

L: Cowt%Sn

Micrograph of Pb-Sneutecticmicrostructure

Co = CE Result: Eutectic microstructure

--alternating layers of and crystals.

IN EUTECTIC SYSTEMS

Chapter 9-18

L + 200

Co

, wt% Sn

20 400

100

60

+

TE

: 18.3wt%Sn

080 100

L +

CE18.3 97.8

61.9

183C

: 97.8wt%Sn 160m

Pb-Sn

system

MICROSTRUCTURES


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T(C)

300 L

L: Cowt%Sn

L

L

18.3wt%Sn < Co < 61.9wt%Sn

Result: crystals and a eutectic microstructure

Just above TE:C= 18.3wt%Sn

CL = 61.9wt%Sn

IN EUTECTIC SYSTEMS

Chapter 9-

L +

200

Co, wt% Sn

20 400

100

60

+

TE

080 100

L +

Co18.3 61.9

primary

97.8

S

S

R

R

eutectic eutectic

19

-

system WL= (1-W) =50wt%R+ S

W = =50wt%

Just below TE:

C = 18.3wt%Sn

C= 97.8wt%SnS

R+ SW = =73wt%

W= 27wt%

HYPOEUTECTIC & HYPEREUTECTIC


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T(C)

(Pb-Sn

System)

L + 200

Co, wt% Sn20 400

300

100

L

60

+

TE

080 100

L +

Cohypoeutectic

Cohypereutectic

HYPOEUTECTIC & HYPEREUTECTIC

Chapter 9-20

18.3

61.9

97.8eutectic

hypereutectic: (illustration only)

160m

eutectic: Co=61.9wt%Sn

175m

hypoeutectic: Co=50wt%Sn

eutectic micro-constituent

IRON-CARBON (Fe-C) PHASE DIAGRAM


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ite)

1600

1400

1200

L

(austenite)

+L L+Fe3C

1148C A

SR

Chapter 9-21

Fe3C

(ceme

n1000

800

600

4000 1 2 3 4 5 6 6.7

+Fe3C

+Fe3C

+

(Fe) C wt% C0.77 4.30

727C = TeutectoidB

R S

Important Points of to study Fe-C Diagram


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1. Pure Iron (0% C)

2. Cementite (Fe3C) (6.70% of C)

3. Alpha Ferrite4. Austenite

Chapter 9-

.

6. Cementite7. Reactions (Eutectic and Eutectoid)

8. Ferrous alloy

9. Eutectoid Alloy

10. Hypo-Eutectoid Alloy

11. Hyper-Eutectoid Alloy



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2 importantpoints

-Eutectic (A):

-Eutectoid (B):

L +Fe3C

+Fe3C

ementite)

1600

1400

1200

1000

L

(austenite)

+L

+Fe3C

L+Fe3C

1148C

T(C)

A

SR


Chapter 9-21

Result: Pearlite =

alternating layers of and Fe3C phases.

120m

Fe3C

(c

600

4000 1 2 3 4 5 6 6.7

+Fe3C

(Fe) Co, wt% C0.77 4.30

= eutectoid

R S

Fe3C (cementite-hard)

(ferrite-soft)

Ceutec

toid

Iron-Carbon System


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Reactions on

cooling

Peritectic

L +

Chapter 9-

Eutectic

L + Fe3C

Eutectoid

+ Fe3C

Steel Cast Iron

Iron-Carbon or Iron-Fe3C


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In principle, the components of the phase diagram should beiron (Fe) and carbon/graphite (C). Fe and C form an intermediate compound Fe3C, which is very stable

There isnt anything of interest at carbon contents greater than 25 at.%

or 6.7 wt.% C. Fe3C is considered to be a component, and the binary phase diagram is

drawn using Fe and Fe3C.

Chapter 9-

Ferrite iron bcc structure Austenite iron fcc structure

High temperature iron bcc structure

Cementite Fe3C

Steels have carbon contents


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Cabon ALLOYS

Chapter 9-

HYPOEUTECTOID STEEL


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HYPOEUTECTOID STEEL

Chapter 9-22

HYPEREUTECTOID STEEL


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HYPEREUTECTOID STEEL

Chapter 9-23

ALLOYING STEEL WITH MORE ELEMENTS


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tectoid(

C)

Ti

800

1000

1200

Mo

Si

W

Crtectoid(

wt%C)

Ni

0.4

0.6

0.8

Cr

Si

Teutectoid changes: Ceutectoid changes:

Chapter 9-

T

Eu

wt. % of alloying elements

Ni600

0 4 8 12

Mn

wt. % of alloying elements

C

eu

Ti

0 4 8 120

0.2 W

Mo

24

SUMMARY


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Phase diagrams are useful tools to determine:

--the number and types of phases,

--the wt% of each phase,--and the composition of each phase

for a given T and composition of the system.

Chapter 9-25

Alloying to produce a solid solution usually

--increases the tensile strength (TS)

--decreases the ductility.

Binary eutectics and binary eutectoids allow for

a range of microstructures.

Ch-7 Compatibility Mode

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