Metals Conservation Summer Institute Conservation Summer Institute ... Science and Design of Engineering Materials James P. Schaffer, ... which only a solution occurs

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Metals Conservation Summer Institute

Yancy W. Riddle, PhDUCT CoatingsStuart, Florida USA

Adapted from: Prof. Diran Apelian, WPI

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REFERENCES

Science and Design of Engineering MaterialsJames P. Schaffer, Ashok Saxena, Thomas H. Sanders, Stephen D. Antolovich,Steven B. Warner

Materials Science and Engineering : An Introduction by William D. Jr. Callister

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Phases in Metallic Alloys and Use of Phase Diagrams

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Processing

MicrostructureProperties

Performance

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OUTLINE• What is a phase?• Basis of phase diagrams• What do phase diagrams tell us?

- how do you use them?- equilibrium versus non-equilibrium

• Complete Solid Solubility Systems• Systems with no complete solid solubility• Invariant transformations

- eutectic; peritectic; eutectoid• Examples - uses of phase diagrams

- Pb-Sn system- Fe-C system

•Modern navigation tools

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Pb-Sn system

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When we combine two elements...

• In particular, if we specify...--a composition (e.g., wt%Cu - wt%Ni), and--a temperature (T)

then...How many phases do we get?What is the composition of each phase?How much of each phase do we get?

Phase BPhase A

Nickel atomCopper atom

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• Solubility Limit:Max concentration forwhich only a solutionoccurs.

• Ex: Phase Diagram:Water-Sugar System

Question: What is thesolubility limit at 20C?

Answer: 65wt% sugar.If Co < 65wt% sugar: sugarIf Co > 65wt% sugar: syrup + sugar.

• Solubility limit increases with T:e.g., if T = 100C, solubility limit = 80wt% sugar.

Pu

re

Su

ga

r

Te

mp

era

ture

(°C

)

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

L (liquid solution

i.e., syrup)

Solubility Limit L

(liquid)

+ S

(solid sugar)

65

20

40

60

80

100

Pu

re

Wa

ter

THE SOLUBILITY LIMIT

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• Components:The elements or compounds which are mixed initially

(e.g., Al and Cu)• Phases:

The physically and chemically distinct material regionsthat result (e.g., α and β).

Aluminum-CopperAlloy

α (darker phase)

β (lighter phase)

Adapted from Fig. 9.0, Callister 3e.

COMPONENTS AND PHASES

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

• water-sugarsystem

70 80 1006040200

Te

mp

era

ture

(°C

)

Co=Composition (wt% sugar)

L (liquid solution

i.e., syrup)

A(70,20) 2 phases

B(100,70) 1 phase

20

100

D(100,90) 2 phases

40

60

80

0

L (liquid)

+ S

(solid sugar)

EFFECT OF T & COMPOSITION (Co)

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• Tell us about phases as function of T, Co, P. • For practical considerations, P=1atm

--binary systems: just 2 components.--independent variables: T and Co (P = 1atm is always used).

• PhaseDiagramfor Cu-Nisystem

• 2 phases: L (liquid) α (FCC solid solution)

• 3 phase fields: L L + αα

wt% Ni20 40 60 80 10001000

1100

1200

1300

1400

1500

1600T(°C)

L (liquid)

α (FCC solid solution)

L + αliquidus

solidus

PHASE DIAGRAMS

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• Rule 1: If we know T and Co, then we know:--the # and types of phases present.

• Examples:

wt% Ni20 40 60 80 10001000

1100

1200

1300

1400

1500

1600T(°C)

L (liquid)

α (FCC solid solution)

L + α

liquidus

solidus

A(1100,60)B

(12

50

,35

) Cu-Niphase

diagram

A(1100, 60): 1 phase: α

B(1250, 35): 2 phases: L + α

PHASE DIAGRAMS: # and types of phases

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• Rule 2: If we know T and Co, then we know:--the composition of each phase.

• Examples:

wt% Ni20

1200

1300

T(°C)

L (liquid)

α(solid)L + α

liquidus

solidus

30 40 50

TAA

DTD

TBB

tie line

L + α

433532CoCL Cα

Cu-Ni system

At TA:

Only Liquid (L) CL = Co ( = 35wt% Ni)

At TB:

Both α and L CL = Cliquidus ( = 32wt% Ni here)

Cα = Csolidus ( = 43wt% Ni here)

At TD:

Only Solid (α) Cα = Co ( = 35wt% Ni)

Co = 35wt%Ni

PHASE DIAGRAMS: composition of phases

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• Rule 3: If we know T and Co, then we know:--the amount of each phase (given in wt%).

Cu-Nisystem• Examples:

At TB: Both α and L

At TA: Only Liquid (L)

WL = 100wt%, Wα = 0At TD: Only Solid (α)

WL = 0, Wα = 100wt%

Co = 35wt%Ni

WL = SR + S

Wα = RR + S

=

43 − 3543 − 32

= 73wt %

= 27wt%wt% Ni

20

1200

1300

T(°C)

L (liquid)

α (solid)

L + α

liquidus

solidus

30 40 50

TAA

DTD

TBB

tie line

L + α

433532CoCL Cα

R S

PHASE DIAGRAMS: weight fractions of phases

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• Phase diagram:Cu-Ni system.

• System is:--binary

i.e., 2 components:Cu and Ni.

--isomorphousi.e., completesolubility of onecomponent inanother; α phasefield extends from0 to 100wt% Ni.

wt% Ni20

1200

1300

30 40 501100

L (liquid)

α (solid)

L + α

L + α

T(°C)

A

D

B

35Co

L: 35wt%Ni

α: 46wt%Ni

C

E

L: 35wt%Ni

464332

24

35

36α: 43wt%Ni

L: 32wt%Ni

L: 24wt%Ni

α: 36wt%Ni

• ConsiderCo = 35wt%Ni.

Cu-Nisystem

EX: COOLING IN A Cu-Ni BINARY

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• Cα changes as we solidify.• Cu-Ni case:

• Fast rate of cooling:Cored structure

• Slow rate of cooling:Equilibrium structure

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

First α to solidfy: 46wt%Ni

Uniform Cα:

35wt%Ni

Last α to solidfy: < 35wt%Ni

CORED VS EQUILIBRIUM PHASES

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Partitioning &Conservation of Mass

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Mushy (Multi-Phase) Region

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SOLID LIQUID

region of interest

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23

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• Effect of solid solution strengthening on:

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

--Peak as a function of Co --Min. as a function of Co

MECHANICAL PROPERTIES: Cu-Ni System

Elo

ng

ati

on

(%

EL

)Composition, wt%Ni

Cu Ni0 20 40 60 80 10020

30

40

50

60

%EL for pure Ni

%EL for pure Cu

Te

nsi

le S

tre

ng

th (

MP

a)

Composition, wt%NiCu Ni0 20 40 60 80 100

200

300

400

TS for pure Ni

TS for pure Cu

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• Complete Solid Solubility Systems• Systems without complete solid solubility• Invariant transformations




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2 componentshas a special compositionwith a min. melting T.

• 3 single phase regions (L, α, β) • Limited solubility: α: mostly Cu β: mostly Ni • TE: No liquid below TE

• CE: Min. melting T

composition

Ex.: Cu-Ag system

L (liquid)

α L + α L+β β

α + β

Co, wt% Ag 20 40 60 80 100 0

200

1200 T(°C)

400

600

800

1000

CE

TE 8.0 71.9 91.2 779°C

Cu-Agsystem

BINARY-EUTECTIC SYSTEMS

Ag

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• For a 40wt%Sn-60wt%Pb alloy at 150C, find...--the phases present:

α + β--the compositions of

the phases:

Pb-Snsystem

EX: Pb-Sn EUTECTIC SYSTEM (1)

L + α L+β

α + β

200

T(°C)

18.3

Co, wt% Sn 20 40 60 80 100 0

Co

300

100

β

L (liquid)

α 183°C 61.9 97.8

150

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• For a 40wt%Sn-60wt%Pb alloy at 150C, find...--the phases present: α + β--the compositions of

the phases:Cα = 11wt%SnCβ = 99wt%Sn

--the relative amountsof each phase:

W α = 59 88

= 67 wt %

W β = 29 88

= 33 wt %

Pb-Snsystem

EX: Pb-Sn EUTECTIC SYSTEM (2)

L + α L+β

α + β

200

T(°C)

18.3

Co, wt% Sn 20 40 60 80 100 0

Co

300

100

L (liquid)

α 183°C 61.9 97.8

150

11 99

R S

β

29

L + α200

T(°C)

Co, wt% Sn10

2

200Co

300

100

L

α

30

L: Cowt%Sn

αL

α: Cowt%Sn

α + β

400

(room T solubility limit)

TE(Pb-Sn System)

• Co < 2wt%Sn• Result:

--polycrystal of α grains.

MICROSTRUCTURESIN EUTECTIC SYSTEMS-I

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• 2wt%Sn < Co < 18.3wt%Sn• Result:

--α polycrystal with fineβ crystals.

α: Cowt%SnL + α

200

T(°C)

Co, wt% Sn10

18.3

200Co

300

100

L

α

30

L: Cowt%Sn

α + β

400

(sol. limit at TE)

TE

2(sol. limit at Troom)

Lα

αβ

Pb-Snsystem

MICROSTRUCTURESIN EUTECTIC SYSTEMS-II

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L + α200

T(°C)

Co, wt% Sn

20 400

300

100

L

α

60

L: Cowt%Sn

α + β

TE

α: 18.3wt%Sn

β

080 100

L + β

CE18.3 97.861.9

183°C

β: 97.8wt%Sn160µm

Micrograph of Pb-Sn eutectic microstructure

• Co = CE• Result: Eutectic microstructure

--alternating layers of α and β crystals.

Pb-Snsystem

MICROSTRUCTURESIN EUTECTIC SYSTEMS-III

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L + α200

T(°C)

Co, wt% Sn

20 400

300

100

L

α

60

L: Cowt%Sn

α + β

TEβ

080 100

L + β

Co18.3 61.9

Lα

Lα

primary α

97.8

S

S

RR

eutectic αeutectic β

Pb-Snsystem

• 18.3wt%Sn < Co < 61.9wt%Sn• Result: α crystals and a eutectic microstructure

• Just above TE:

WL = (1-Wα) =50wt%

Cα = 18.3wt%Sn

CL = 61.9wt%SnS

R + SWα = =50wt%

• Just below TE:Cα = 18.3wt%Sn

Cβ = 97.8wt%SnS

R + SWα = =73wt%

Wβ = 27wt%

MICROSTRUCTURESIN EUTECTIC SYSTEMS-IV

3320

T(°C)

(Pb-Sn System)

L + α200

Co, wt% Sn20 400

300

100

L

α

60

α + β

TE β

080 100

L + β

18.361.9

97.8

Cohypoeutectic

Cohypereutectic

eutectic

hypereutectic: (illustration only)

160µm

eutectic: Co=61.9wt%Sn

175µm

β

ββ

ββ

β

α

α

α

αα

α

hypoeutectic: Co=50wt%Sn

eutectic micro-constituent

Adapted from Fig. 9.7, Callister 6e. (Fig. 9.7 adapted from Binary Phase Diagrams, 2nd ed., Vol. 3, T.B. Massalski (Editor-in-Chief), ASM International, Materials Park, OH, 1990.)

HYPOEUTECTIC & HYPEREUTECTIC

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Result: Pearlite = alternating layers of α and Fe3C phases.

120µm

• 2 important points

-Eutectic (A):

-Eutectoid (B): L ⇒ γ + Fe3C

γ ⇒ α +Fe3C

Fe

3C

(c

em

en

tite

)

1600

1400

1200

1000

800

600

4000 1 2 3 4 5 6 6.7

L

γ (austenite)

γ+L

γ+Fe3C

α+Fe3C

α+γ

L+Fe3C

δ

(Fe) Co, wt% C0.77 4.30

727°C = Teutectoid

1148°C

T(°C)

A

B

SR

R S

γ γγγ

Fe3C (cementite-hard)α (ferrite-soft)

αC

eu

tec

toid

IRON-CARBON (Fe-C) PHASE DIAGRAM

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HYPOEUTECTOID STEEL

(Fe-C System)

Co

Fe

3C

(c

em

en

tite

)

1600

1400

1200

1000

800

600

4000 1 2 3 4 5 6 6.7

L

γ (austenite)

γ+L

γ+Fe3C

α+Fe3C

L+Fe3C

δ

Co, wt% C0.7

7

727°C

1148°C

T(°C)

R S

γ γγγ

α

γγγ γ

γγ γ

γ r s

wα =s/(r+s)wγ =(1-wα)

wα =S/(R+S)wFe3C =(1-wα)

wpearlite = wγ

α

αα

αα

α pearlite

100µm Hypoeutectoid steel

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(Fe-C System)

Co

Fe

3C

(c

em

en

tite

)

1600

1400

1200

1000

800

600

4000 1 2 3 4 5 6 6.7

L

γ (austenite)

γ+L

γ+Fe3C

α+Fe3C

L+Fe3C

δ

Co, wt% C0.7

71148°C

T(°C)

R S

γ γγγ

αs

wFe3C =r/(r+s)wγ =(1-wFe3C)

wα =S/(R+S)wFe3C =(1-wα)

wpearlite = wγpearlite

60µm Hypereutectoid steel

rγγ

γ γ

γγγ γ

Fe3C

HYPEREUTECTOID STEEL

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40

TE

ute

cto

id (

°C)

wt. % of alloying elements

Ti

Ni600

800

1000

1200

0 4 8 12

Mo SiW

Cr

Mn

wt. % of alloying elementsC

eu

tec

toid

(w

t%C

)

Ni

Ti

0 4 8 120

0.2

0.4

0.6

0.8

Cr

SiMnW

Mo

• Teutectoid changes: • Ceutectoid changes:

ALLOYING STEEL WITH MORE ELEMENTS

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42

43

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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.

• Alloying to produce a solid solution usually--increases the tensile strength (TS)--decreases the ductility.

• Binary eutectics and binary eutectoids allow fora range of microstructures.

SUMMARY

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Features1) Point (0-D) Calculation Calculate the stable phase equilibrium at a given point. 2) Line (1-D) Calculation Calculate the stable phase equilibrium at several points

along a line. For example, as the temperature changes or as the composition changes.

3) Section (2-D) Phase Diagram Calculation Calculate stable two-dimensional phase diagrams in multi-component alloy systems. Mouse-click on phase regions to automatically label phase regions.

4) Solidification Simulation Simulate the solidification of a multi-component alloy using either the lever rule or Scheil model.

5) Liquidus Projection Project the liquidus surface of a multi-component alloy. Label the primary phase regions for a ternary liquidus projection.

6) Output of Results Calculated results are displayed in graphical form and exported to a text file.

7) Database A thermodynamic database of parameters is required to perform calculations.

8) Pandat Batch File Pandat can run a series of calculations predefined in a batch file.

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Phase Diagrams

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Phase Diagrams

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Phase Diagrams

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Point Calculations

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Point Calculations

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Solidification Simulation

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Solidification Simulation

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Ternary Diagrams

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Complex SystemsPD: Al-4.5Mg-0.22Fe and Al-4.5Mg-0.22Fe-20Si

T[C

]

W[SI]

540.0

542.5

545.0

547.5

550.0

552.5

555.0

557.5

560.0

562.5

565.0

567.5

570.0

572.5

575.0

0.12 0.13 0.14 0.15 0.16 0.17 0.18

L + Si

L + Si + pi

L + Si + pi + Al

L + pi

LIQUID

Si + Al + pi + Mg2Si

L + Al + pi

L + Al

0.12 0.13 0.14 0.15 0.16 0.17 0.18540

542.5545

547.5550

552.5555

557.5560

562.5565

567.5570

572.5575

W[SI]

T[C

]

L + Si

L + Si + pi

L + Si + pi + Al

L + pi

LIQUID


L + Al + pi

L + Al

L + Si

L + Si + pi

L + Si + pi + Al

L + pi

LIQUID


L + Al + pi

L + Al

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Calculations Options

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Metals Conservation Summer Institute Conservation Summer Institute ... Science and Design of Engineering Materials James P. Schaffer, ... which only a solution occurs