MSEASUSlides: Muddiest Point- Phase Diagrams II: Eutectic Microstructures Slide Sets

Muddiest Points Phase Diagrams II: Eutec6c Microstructures

Muddiest Points: •  “How do I determine what microstructure looks like?”

• “How does size of area in the microstructure diagram relate to its phase frac6on?”

•  “When is the microstructure alterna6ng platelets of alpha and beta vs. blobs of alpha or beta?

• “Why is maximum strength at the eutec6c composi6on?

Pb-Sn Phase Diagram: Effect of Composition on Strength

0

100

200

300

20%Sn 80%Sn60%Sn40%Sn0%Sn 100%Sn

Composition, wt%

T, Co

327

18319.2 61.9 97.5

232

o

o

o

0%Pb100%PbStrength (M

pa) 40

30

20

10

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Eutectic Phase Diagram Terminology

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Single-‐Phase Region Microstructures

L L

α β β

1. T= 325°, Co = 10% Sn

2. T= 182°, Co = 10% Sn

3. T= 325°, Co = 99% Sn

4. T=182°, Co = 99% Sn

Phases: Chem. Comp: Phase wt. Fract.:




α

Co Co

X

X

X

X

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Eutec6c Microstructure 61.9 wt. % Sn

L

EutecAc α+ β

αβαβα

L

1. T= 184 °C, Co=61.9% Sn


2. T= 182°C, Co= 61.9% Sn Phases: Chem. Comp: Phase wt. Fract.:

R S

S R+S

Wα= Wβ= 1- Wα

X X

α β

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Hypoeutec6c Microstructure: 40 wt. % Sn

L

1. T= 300 °C, Co= 40 % Sn

2. T= 225°C, Co= 40 % Sn

3. T= 184°C, Co= 40 %

4. T= 182°C, Co= 40 %


α

α

α

α

α



Phases: Chem. Comp:

Phase wt. Fract.:

α

T U

U T+U

Wα= WL= 1- Wα

C D

WL= 1- Wα

F E

α

α

α F E+F

Wα= Wβ= 1 - Wα

Co

L

L

D C+D

Wα=

X

X X X

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Hypereutec6c Microstructure: 85 wt. % Sn 1. T= 300 °C, Co= 85 % Sn Phases: Chem. Comp: Phase wt. Fract.:

L

2. T= 210°C, Co= 85 % Sn Phases: Chem. Comp: Phase wt. Fract.:

3. T= 184°C, Co= 85 % Sn

4. T= 182°C, Co= 85 % Sn



β β

β

β

β

β β

β

Co

β β β

L

L

G H

G G+H

Wβ=

J K

J J+K

Wβ=

WL= 1- Wβ X X+Y Wβ=

X Y

β + L

X

X

XX

WL= 1- Wβ

Wα= 1 - Wβ

80 98

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Summary of Eutec6c Microstructures

α

α

α β

β β

T= 182°C, Co = 40% Sn T= 182°C, Ceu = 61.9 % Sn T= 182°C, Co = 85% Sn

α

T= 182°C, Co = 10% Sn

X β β

T= 182°C, Co = 99% Sn

X X X X

Pb-Sn Phase Diagram: Effect of Composition on Strength

0

100

200

300

20%Sn 80%Sn60%Sn40%Sn0%Sn 100%Sn

Composition, wt%

T, Co

327

18319.2 61.9 97.5

232

o

o

o

0%Pb100%Pb

Strength (M

pa) 40

30

20

10

α

α

α β

β β

Co = 40% Sn Ceu = 61.9 % Sn Co = 85% Sn

Homework 12. Problem 5. Focused reading: Ch. 9, sec 9.12, pp. 305 – 309Quiz the Wiz- Eutectic Microstructures

Muddiest Points Phase Diagrams II: Eutec6c Microstructures

Muddiest Points: •  “How do I determine what microstructure looks like?”

• “How does size of area in the microstructure diagram relate to its phase frac6on?”

•  “When is the microstructure alterna6ng platelets of alpha and beta vs. blobs of alpha or beta?

• “Why is maximum strength at the eutec6c composi6on?

MSEASUSlides: Muddiest Point- Phase Diagrams II: Eutectic Microstructures Slide Sets

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