Phase diagramMaterial science© Su-Jin Kim, GNU

Phase Diagrams(상태도)

1

Associate Professor Su-Jin Kim

School of Mechanical EngineeringGyeongsang National University

Phase diagramMaterial science© Su-Jin Kim, GNU

OCWSolids Liquids and Gases (kids)https://youtu.be/dCcTSfa82yU

17. Intro to Phase Diagramshttps://youtu.be/MJoYwtX_zFA

18. Phase Diagrams: The Lever Rulehttps://youtu.be/_UGVDKlquxo

(Texas A&M)

Phase diagramMaterial science© Su-Jin Kim, GNU

OCWFe-Fe3C Phase Diagram1https://www.youtube.com/watch?v=IUMcbctDNtM

Fe-Fe3C Phase Diagram2https://www.youtube.com/watch?v=WUy4qED9Fv4

Fe-Fe3C Phase Diagram3https://www.youtube.com/watch?v=wZgpTHZSuNY

Phase diagramMaterial science© Su-Jin Kim, GNU

KOCW11. 상태도http://www.kocw.net/home/cview.do?lid=18a806f68e3cbebchttp://www.kocw.net/home/cview.do?lid=44ea277862a107cahttp://www.kocw.net/home/cview.do?lid=6d6c6800c280f9cf

Phase diagramMaterial science© Su-Jin Kim, GNU

• Phases(상): physically and chemically distinct material regions (s l v)

Pressure-Temperature Diagram (Water)

0 100

Temperature (ºC)

Pre

ssur

e (a

tm)

1

0.006

218

Solid Liquid Vapor

Critical point

Triple point

Phase diagramMaterial science© Su-Jin Kim, GNU

Cu-Ni Phase Diagram

1000

1100

1200

1300

1400

1500

0 20 40 60 80 100

Composition (wt% Ni) (Ni)(Cu)

Tem

pera

ture

(ºC

)

Liquid, L

Solid, α

L+α

Time

Ni

Cu

Cu + Ni

Tem

p.

Phase diagramMaterial science© Su-Jin Kim, GNU

Lever rule

Composition (조성)L : 30 wt% Niα : 40 wt% Ni

Weight ratio (비율)L = b/c

= (40-32)/(40-30)= 80%

α = a/c= (32-30)/(40-30)= 20%

1100

1200

1300

30 40 (wt% Ni)

(ºC)

Liquid, L

Solid, α

L+α

32

1230a b

c

Phase diagramMaterial science© Su-Jin Kim, GNU

Non-Equilibrium Cooling

1100

1200

1300

20 40 (wt% Ni)

(ºC)

Liquid, L

Solid, α

L+α

40%

35%

Equilibrium(slow) cooling(평형냉각) Uniform 32% Ni

Non-Equilibrium cooling(비평형각) Cored structure inside 40%~outside 30% Ni

32

30%

Phase diagramMaterial science© Su-Jin Kim, GNU

Fe-Fe3C Phase Diagram• Austenite, Ferrite, Cementite phase vs. Perlite

microstructure• Hypoeutectoid

Phase diagramMaterial science© Su-Jin Kim, GNU

• Iron-Cementite Alloy : Steel (탄소강)

Fe-Fe3C Phase Diagram

Liquid, L

Austenite, γ

Ferrite, α

Cementite, Fe3C

α+γ

α+Fe3C

γ+Fe3C

γ+L

0 1 2 3 4 5 6 6.7400

Composition (wt% C)

Tem

pera

ture

(ºC

)

600

800

1000

1200

1400

1600

Phase diagramMaterial science© Su-Jin Kim, GNU

• Austenite, Ferrite, Cementite

Fe-Fe3C Phase Diagram

Liquid, L

Austenite, γ

Ferrite, α Cementite, Fe3C

α+γ

α+Fe3C

γ+Fe3C

γ+L

0 1 2 3 4 5 6 6.7400

Composition (wt% C)

Tem

pera

ture

(ºC

)

600

800

1000

1200

1400

1600

2.14

0.022

ductileFCC

ductileBCC

hard, brittlefixed compositionorthorhombic crystal

(Fe) (Fe3C)

Phase diagramMaterial science© Su-Jin Kim, GNU

• Eutectic(공정): liquid transforms to two solid phases• Eutectoid(공석): one solid phase transforms to two other

solid phases

Eutetoid

Liquid, L

Austenite, γ

Ferrite, α

Cementite, Fe3C

α+γ

α+Fe3C

γ+Fe3C

γ+L

0 1 2 3 4 5 6 6.7400

Composition (wt% C)

Tem

pera

ture

(ºC

)

600

800

1000

1200

1400

1600

2.14 4.3

0.022

Eutectic

Cast Iron Carbon Steel

0.76

Eutectoid

727 ºC

1147ºC

Pearlite: α Fe3C layers (lamellar structure)

Phase diagramMaterial science© Su-Jin Kim, GNU

• Hypoeutectoid(아공석): C0.76wt%, Pearlite+Cementite• Increase C Strength & Hardness ↑, Ductility ↓

Hypo. Hypereutectoid

Austenite, γ

Ferrite, α

α+γ

α+Fe3C

γ+L

0 1 2400

Composition (wt% C)

Tem

pera

ture

(ºC

)

600

800

1000

1200

1400

0.022

0.76

HypereutectoidHypoeutectoid

γ+Fe3C

Ferrite, αFe3C

pearlitepearlite

(Fe)

Phase diagramMaterial science© Su-Jin Kim, GNU

• Aluminum-Copper Alloy: Duralumin (4.4%Cu 1.5%Mg 0.6%Mn)

Al-AlCu2 Phase Diagram

CuAl2, θ

Liquid, L

α α+θ

α+L

0 10 20 30 40 50300

Composition (wt% Cu)

Tem

pera

ture

(ºC

)

400

500

600

700

θ+L

(Al) (CuAl2)

Phase diagramMaterial science© Su-Jin Kim, GNU

Cu-Zn Phase Diagram

• Copper-Zinc Alloys: Brasses(황동)

Red brass Cartridge brass Brazing solderCu