lec2 - ch10 ppts callister7ebbb

7/17/2019 Lec2 - Ch10 Ppts Callister7ebbb

1/30

Chapter 10 -1

ISSUES TO ADDRESS... Transforming one phase into another takes time.

How does the rate of transformation depend on

time and T? How can we slow down the transformation so that we can engineering non-equilibrium structures? re the mechanical properties of non-equilibrium structures better?

!e

"ustenite#

$utectoidtransformation

C !CC

!e%C"cementite#

"ferrite#

&

"'CC#

Chapter 10:

Phase Transformations


2/30

Chapter 10 -2

Phase Transformations

(ucleation) nuclei "seeds# act as template to grow cr*stals

) for nucleus to form rate of addition of atoms tonucleus must be faster than rate of loss

) once nucleated+ grow until reach equilibrium,riing force to nucleate increases as we increase T

) supercooling "eutectic+ eutectoid#) superheating "peritectic#

mall supercoolingfew nuclei - large cr*stals

/arge supercoolingrapid nucleation - man* nuclei+small cr*stals


3/30

Chapter 10 -3

olidification (ucleation rocesses

Homogeneous nucleation) nuclei form in the bulk of liquid metal

) requires supercooling "t*picall* 20-%003C ma4#

Heterogeneous nucleation) much easier since stable 5nucleus6 is alread*present

Could be wall of mold or impurities in the liquidphase

) allows solidification with onl* 0.1-107Csupercooling


4/30

Chapter 10 -4

r8 9 critical nucleus nuclei : r8 shrink; nuclei


5/30

Chapter 10 -5

olidification

TH

Tr

S

m

=

2*

(oteHS 9 strong function of T 9weak function ofT

r8 decreases asTincreases

!or t*picalT r8 ca. 100A

H9 latent heat of solidification

Tm9 melting temperature

9 surface free energ*

T9 Tm- T9 supercooling

r*9 critical radius


6/30

Chapter 10 -6

Rate of Phase Transformations

Binetics- measure approach to equilibrium s.time

Hold temperature constant measureconersion s. time

sound waes ) one sample

electrical conductiit* ) follow one sample

D-ra* diffraction ) hae to do man* samples

How is conersion measured?


7/30

Chapter 10 -7

Rate of Phase Transformation

rami rate equation 9< y9 1- e4p "-ktn#

) k nfit for specific sample

All out of material -done

log t!rac

tiontransformed+y

!i4ed T

fra!tiontransforme%

time

0.E

'* conention r9 1 F t0.E

dapted from!ig. 10.10+Callister 7e.

maximum rate reached nowamount

unconverted decreases so rateslows

t0.&

rate increases as surface area

increases& nuclei grow


8/30

Chapter 10 -8

Rate of Phase Transformations

Gn general+ rate increases as T

r9 1Ft0.E9Ae -QFRT

) R9 gas constant) T9 temperature "B#) A9 pree4ponential factor) Q9 actiation energ*

rrheniuse4pression

roften smallequilibrium not possible

dapted from !ig.

10.11+ Callister 7e."!ig. 10.11 adaptedfrom '.!. ,ecker and,. Harker+IJecr*stalli>ation inJolled CopperI+ TransAIME+ 1''+ 1KE0+ p.222.#

1%EC 11KC 11%C 10=C 22C @%C

1 10 10= 10@


9/30

Chapter 10 -9

Eute!toi% Transformation Rate

Course pearlite formed at higher T- softer

!ine pearlite formed at low T - harder

,iffusie flow

of C needed

Lrowth of pearlite from austenite

dapted from!ig. K.1E+Callister 7e.

pearlitegrowth

direction

ustenite "#grainboundar*

cementite "!e%C#!errite "#

Jecr*stalli>ation rate increases

with T. dapted from!ig. 10.1=+Callister 7e

.

MNE3C"Tsmaller#

0

E0

y"Opearlite#

M003C"T larger#

ME03C

100


10/30

Chapter 10 -10

Jeaction rate is a result of nucleation and growth

of cr*stals.

$4amples

dapted from

!ig. 10.10+ Callister 7e.

u!"eation an% (ro)th

O earlite

0

E0

100

(ucleationregime

Lrowthregime

log"time#t0.E

(ucleation rate increases with T

Lrowth rate increases with T

TPust below TE(ucleation rate low

Lrowth rate high

pearlitecolon*

Tmoderatel* below TE

(ucleation rate med .

Lrowth rate med.

(ucleation rate high

Twa* below TE

Lrowth rate low


11/30

Chapter 10 -11

Transformations # Un%er!oo"ing

Can make it occur at...N=N7C "cool it slowl*# ...below N=N7C "5undercool6 it#

$utectoidtransf. "!e-C *stem# & !e%C

0.NM wtO C0.0== wtO CM.N wtO C

!e%C"c

ementite#

1M00

1@00

1=00

1000

200

M00

@000 1 = % @ E M M.N

L

"austenite#

&L

&!e%C

&!e%C

L&!e%C

"!e# Co, wtOC

11@23C

T"3C#

ferrite N=N3C

$utectoid

$quil. Cooling Ttransf.9 N=NCT

Qndercooling b* Ttransf.: N=NC

0.NM

0.0==

dapted from !ig.K.=@+Callister 7e. "!ig. K.=@

adapted from inary Alloy!"ase #ia$rams+ =nd ed.+ol. 1+ T.'. Rassalski "$d.-in-Chief#+ R Gnternational+Raterials ark+ SH+ 1KK0.#


12/30

Chapter 10 -12

dapted from !ig. 10.1%+Callister 7e."!ig. 10.1% adapted from H. 'o*er "$d.#Atlas o% Isot"ermal Trans%ormation an&

Coolin$ Trans%ormation #ia$rams+merican ociet* for Retals+ 1KNN+ p.%MK.#

Isotherma" Transformation Diagrams

!e-C s*stem+ Co9 0.NM wtO C Transformation at T9 MNE3C.

100

E0

01 10= 10@

T 9 MNE3Cy+

Otransformed

time "s#

400

500

600

700

1 10 10= 10% 10@ 10E

0Op

earlite

100O

E0O

ustenite "stable#TE"N=NC#ustenite

"unstable#

earlite

T"3C#

time "s#

isothermal transformation at MNE3C


13/30

Chapter 10 -13

$utectoid composition+ Co9 0.NM wtO C

'egin at T< N=N3C Japidl* cool to M=E3C and hold isothermall*.

dapted from !ig.10.1@+Callister 7e."!ig. 10.1@ adapted fromH. 'o*er "$d.#Atlas o%Isot"ermal Trans%ormation

an& Coolin$

Trans%ormation #ia$rams+

merican ociet* forRetals+ 1KKN+ p. =2.#

Effe!t of Coo"ing Histor$ in *e+C S$stem

@00

E00

M00

N00

0O

pearlite

100O

E0O

ustenite "stable#TE"N=NC#

ustenite

"unstable#

earlite

T"3C#

1 10 10= 10% 10@ 10E

time "s#


14/30

Chapter 10 -14

Transformations )ith

Proeute!toi% ,ateria"s

H*pereutectoid composition ) proeutectoid cementite

CO9 1.1% wtO C

TE"N=N3C#

T"3C#

time -s

&

C

1 10 10= 10% 10@

E00

N00

K00

M00

200

&

dapted from !ig. 10.1M+Callister 7e.

dapted from !ig. K.=@+Callister 7e.

!e%C"cemen

tite#

1M00

1@00

1=00

1000

200

M00

@000 1 = % @ E M M.N

L

"austenite#&L

&!e%C

&!e%C

L&!e%C

"!e# Co, wtOC

T"3C#

N=N3CT

0.NM

0.0==

1.

1/


15/30

Chapter 10 -15

on+Eui"irium Transformation

Pro%u!ts: *e+C 'ainite

--lathes "strips# with long rods of !e%C --diffusion controlled. Gsothermal Transf. ,iagram

dapted from !ig. 10.12+ Callister 7e.

"!ig. 10.12 adapted from H. 'o*er "$d.#Atlas o% Isot"ermal Trans%ormation an& Coolin$Trans%ormation #ia$rams+ merican ociet* for Retals+ 1KKN+ p. =2.#

"dapted from !ig. 10.1N+ Callister, 7e. "!ig.10.1N from Metals Han&'ook+ 2th ed.+ol. 2+ Metallo$ra("y, Str)t)res, an& !"ase#ia$rams+ merican ociet* for Retals+

Raterials ark+ SH+ 1KN%.#

*e/C

-!ementite

E m

-ferrite

10 10% 10E

time "s#10-1

@00

M00

200

T"3C#ustenite "stable#

=00

'

TE

0O

100O

E0O

pearliteFbainite boundar*

100O bainite

100O pearlite


16/30

Chapter 10 -16

pheroidite --grains with spherical !e%C --diffusion dependent. --heat bainite or pearlite for long times --reduces interfacial area "driing force#

Spheroi%ite: *e+C S$stem

"dapted from !ig. 10.1K+ Callister, 7e."!ig. 10.1K cop*right Qnited tates

teel Corporation+ 1KN1.#

M0 m

"ferrite#

"cementite#

!e%C


17/30

Chapter 10 -17

Rartensite

--"!CC# to Rartensite "'CT#

dapted from

!ig. 10.==+Callister 7e.

"dapted from !ig. 10.=1+ Callister, 7e."!ig. 10.=1 courtes* Qnited tatesteel Corporation.#

Gsothermal Transf. ,iagram

to R transformation.. -- is rapid -- O transf. depends on T onl*.

"dapted from !ig.10.=0+ Callister, 7e.

,artensite: *e+C S$stem

Rartensite needlesustenite

M0m

10 10% 10E time "s#10-1

@00

M00

200

T"3C#ustenite "stable#

=00

'

TE

0%

100OE0O

R & R &

R &

0OE0OK0O

xx x

x

x

xpotentialC atom sites

!e atomsites

"inoles single atom Pumps#


18/30

Chapter 10 -18

"!CC# "'CC#& !e%C

,artensite *ormation

slow cooling

tempering

quench

R "'CT#

R 9 martensiteis bod* centered tetragonal "'CT#

,iffusionless transformation 'CT if C< 0.1E wtO'CT few slip planes hard+ brittle


19/30

Chapter 10 -19

Phase Transformations of A""o$s

$ffect of adding other elements

Change transition temp.

Cr+ (i+ Ro+ i+ Rn

retard & !e%Ctransformation

dapted from !ig. 10.=%+ Callister 7e.


20/30

Chapter 10 -20

dapted from!ig. 10.=E+Callister 7e.

Coo"ing Cur2e

p"ot temp 2s. time


21/30

Chapter 10 -21

D$nami! Phase Transformations

Sn the isothermal transformation diagram for0.@E wtO C !e-C allo*+ sketch and label thetime-temperature paths to produce thefollowing microstructures

a# @=O proeutectoid ferrite and E2O coarsepearlite

b# E0O fine pearlite and E0O bainite

c# 100O martensited# E0O martensite and E0O austenite


22/30

Chapter 10 -22

A 3 4

A 3 P

A 3A

4P

A&05

0

600

700

800

'00

0.1 10 10/ 10&time -s

M-start

M-&05

M-905

Eamp"e Pro"em for Co; 0.7& )t5

a# @=O proeutectoid ferrite and E2O coarse pearlite

first make ferrite

then pearlite

course pearlite

higher T

dapted from!ig. 10.=K+Callister +e.

T-


23/30

Chapter 10 -23

b# E0O fine pearlite and E0O bainite

first make pearlite

then bainite

fine pearlite

lower T

T-


24/30

Chapter 10 -24

A 3 4

A 3 P

A 3A

4

P

A&05

0

600

700

800

'00

0.1 10 10/ 10&time -s

M-start

M-&05

M-905

Eamp"e Pro"em for Co; 0.7& )t5

c# 100 O martensite ) quench 9 rapid coold# E0 O martensite

and E0 Oaustenite

d#

c#dapted from!ig. 10.=K+Callister +e.

T-


25/30

Chapter 10 -25

,e!hani!a" Prop: *e+C S$stem -1

dapted from !ig.10.=K+ Callister 7e."!ig. 10.=K based ondata from MetalsHan&'ook Heat

Treatin$+ ol. @+ Kthed.+ . Rasseria"Ranaging $d.#+

merican ociet* forRetals+ 1K21+ p. K.#

dapted from !ig. K.%0+Callister7e. "!ig. K.%0 courtes* Jepublicteel Corporation.#

dapted from !ig. K.%%+Callister 7e."!ig. K.%% cop*right 1KN1 b* Qnitedtates teel Corporation.#

Rore wtO C TSand Sincrease+ OELdecreases.

$ffect of wtO C

Co: 0.NM wtO C

H*poeutectoid

earlite "med#ferrite "soft#Co0.NM wtO C

H*pereutectoid

earlite "med#

Cementite"hard#

%00

E00

N00

K00

1100S"Ra#

TS"Ra#

wtO C0 0.E 1

hardness

0.NM

H*po H*per

wtO C0 0.E 1

0

E0

100

OEL

Gmpac

tenerg*"G>od+ft-lb

#

0

@0

20

0.NM

H*po H*per


26/30

Chapter 10 -26

,e!hani!a" Prop: *e+C S$stem -6

dapted from !ig. 10.%0+ Callister 7e."!ig. 10.%0 based on data from MetalsHan&'ook Heat Treatin$+ ol. @+ Kthed.+ . Rasseria "Ranaging $d.#+merican ociet* for Retals+ 1K21+ pp.K and 1N.#

!ine s coarse pearlite s spheroidite

Hardness OJ

fine < coarse < spheroiditefine : coarse : spheroidite

20

1M0

=@0

%=0

wtOC0 0.E 1

'rinellha

rdness

finepearlite

coarsepearlite

spheroidite

H*po H*per

0

%0

M0

K0

wtOC

,uctil

it*"OJ#

finepearlite

coarse pearlite

spheroidite

H*po H*per

0 0.E 1


27/30

Chapter 10 -27

,e!hani!a" Prop: *e+C S$stem -/

!ine earlite s Rartensite

Hardness fine pearlite :: martensite.

dapted from !ig. 10.%=+

Callister 7e. "!ig. 10.%= adaptedfrom $dgar C. 'ain+ /)ntions o%t"e Alloyin$ Elements in Steel+merican ociet* for Retals+1K%K+ p. %M; and J.. Lrange+C.J. Hribal+ and /.!. orter+Metall. Trans. A+ ol. 2+ p.1NNM.#

0

=00

wtO C0 0.E 1

@00

M00

'rinellha

rdness

martensite

fine pearlite

H*po H*per


28/30

Chapter 10 -28

Tempering ,artensite

reduces brittleness of martensite+

reduces internal stress caused b* quenching.

dapted from!ig. 10.%%+Callister 7e."!ig. 10.%%cop*right b*Qnited tatesteelCorporation+1KN1.#

decreases TS+ Sbut increases ORA produces e4tremel* small !e%C particles surrounded b* .

dapted from!ig. 10.%@+Callister 7e."!ig. 10.%@adapted from!ig. furnishedcourtes* ofJepublic teelCorporation.#

Km

S"Ra#TS"Ra#

200

1000

1=00

1@00

1M00

1200

%0

@0

E0

M0

=00 @00 M00Tempering T"3C#

ORA

TS

S

ORA


29/30

Chapter 10 -29

Summar$: Pro!essing Optionsdapted from!ig. 10.%M+

Callister 7e.

ustenite "#

'ainite"& !e%C platesFneedles#

earlite"& !e%C la*ers & aproeutectoid phase#

Rartensite"'CT phasediffusionless

transformation#

TemperedRartensite"& er* fine

!e%C particles#

slowcool

moderate cool

rapidquench

reheat

trengt

h

,uctilit*

RartensiteT Rartensite

bainitefine pearlite

coarse pearlitespheroidite

Leneral Trends


30/30

Chapter 10 -30

Core roblems

elf-help roblems

AOUCE,ETS

Jeading

lec2 - ch10 ppts callister7ebbb

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