Phase diagram type 1 (1) (1).pdf

material phase diagram

1. Phase diagram my new
lecture

2. Lecture 4 phase diagram

4. ISSUES TO ADDRESS...
• When we combine two elements...
what equilibrium state do we get?
• 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 Diagrams
Phase B
Phase A
Nickel atom Copper atom

5. •
Components
:
The elements or compounds which are present in the mixture
(e.g., Al and Cu)
•
Phases
:
The combination of two or more elements in specific form to
consist a certain region of material with distinct physical and
chemical properties.
(e.g., αand β).
Aluminum-
Copper
Alloy
Components and Phases
α (darker
phase)
β(lighter
phase)
Adapted from
chapter-opening
photograph,
Chapter 9,
Callister 3e.

6. Phase Equilibria: Solubility Limit
– Solutions
–solid solutions, single phase
– Mixtures
–more than one phase
•
Solubility Limit
:
Max concentration for
which only a single phase
solution occurs.
Question:
What is the
solubility limit at 20°C?
Answer:
65 wt% sugar
.
If C
o
< 65 wt% sugar:
syrup
If C
o
> 65 wt% sugar:
syrup + sugar.
65
Sucrose/Water Phase Diagram
Pure
Sugar
Temperature (°C)
02040 6080 100
C
o
=Composition (wt% sugar)
L
(liquid solution
i.e., syrup)
Solubility
Limit
L
(liquid)
+
S
(solid
sugar)
20
40
60
80
100
Pure
Water
Adapted from Fig. 9.1,
Callister 7e.

7. Effect of T& Composition (C
o
)
• Changing Tcan change # of phases:
Adapted from
Fig. 9.1,
Callister 7e.
D
(100°C,90)
2 phases
B
(100°C,70)
1 phase
path
A
to
B
.
• Changing C
o
can change # of phases:path
B
to
D
.
A
(20°C,70)
2 phases
70 80 100 60 40 20 0
Temperature (°C)
C
o
=Composition (wt% sugar)
L
(
liquid solution
i.e., syrup)
20
100
40
60
80
0
L
(liquid)
+
S
(solid
sugar)
water-
sugar
system

8. Definition and types of phase
diagrams
•Phase diagrams;
indicate phases as function of Temp (T) ,
Composition (C0), and Pressure (P).
-
just 2 components in phases diagrams wil be studied in this course.
- independent variables are: Tand Co only while (P= 1 atm is
constant, almost always used).
• Types of phase diagrams • 1-Solid solution type
• 2-Simple eutectic type
• 3-Binary or combination eutectic type

9. Methods of construction phase
diagrams
• 1-From cooling curve
• 2-By high temperature X-ray diffraction
measurement
• 3-From thermal expansion curves
(Dilatometer).
• 4-By high temperature microscopy.
• 5-From electrical resistivity
measurements

10. 1-solid solution type of Phase diagram
0.1278 1.8 FCC Cu
0.1246 1.9 FCC Ni
r(nm)
electronega
tivity
Crystal
Structure
• Both have the same crystal structure (FCC) and hav e
similar electronegativities and atomic radii (
W. Hume –
Rothery rules
) suggesting high mutual solubility.
Solid solution system: the two elements dissolve in each
other with any percentages
(e.g., Ni-Cu solution)
• Ni and Cu are totally miscible in all proportions.

11. 1
-
solid solution type of Phase diagram
cont.
•
Phase
Diagram
for Cu-Ni
system
Adapted from Fig. 9.3(a), Callister 7e.
(Fig. 9.3(a) is adapted from Phase
Diagrams of Binary Nickel Alloys, P. Nash
(Ed.), ASM International, Materials Park,
OH (1991).
Present phases:
L
(liquid)
α
(FCC solid solution)
L+α
wt% Ni
20 40 60 80 100 0
1000
1100
1200
1300
1400
1500
1600
T(°C)
L(liquid)
α
(FCC solid
solution)
L
+
α
liquidus
solidus
Cu

12. Cooling curve of pure metal

14. Construction of phase diagram from series
of cooling curves

15. wt% Ni
20 40 60 80 100 0
1000
1100
1200
1300
1400
1500
1600
T(°C)
L(liquid)
α
(FCC solid
solution)
L
+
α
liquidus
solidus
Cu-Ni
phase
diagram
1-solid solution type of Phase diagramcont.
Numberand types of phases •
Rule 1
:
If we know Tand Co, then we know:
--the
nomber
and types of phases present.
• Examples:
A(1100°C, 60):
1 phase: α
B(1250°C, 35):
2 phases: L+ α
Adapted from Fig. 9.3(a), Callister 7e.
(Fig. 9.3(a) is adapted from Phase
Diagrams of Binary Nickel Alloys, P. Nash
(Ed.), ASM International, Materials Park,
OH, 1991).
B(1250°C,35)
A(1100°C,60)

16. wt% Ni
20
1200
1300
T(°C)
L(liquid)
α
(solid)
L
+
α
liquidus solidus
30 40 50
L
+
α
Cu-Ni
system
1
-
solid solution type of Phase diagram
cont.
composition of phases
•
Rule 2:
If we know Tand Co, then we know:
--the composition of each phase.
• Examples:
TA
A
35
Co32
CL
At TA= 1320°C:
Only Liquid (L)
CL= Co
( = 35 wt% Ni)
At TB= 1250°C:
Both αand L
CL= Cliquidus
( = 32 wt% Ni here)
Cα= Csolidus
( = 43 wt% Ni here)
At TD= 1190°C:
Only Solid (α)
Cα= Co
( = 35 wt% Ni
)
Co= 35 wt% Ni
Adapted from Fig. 9.3(b), Callister 7e.
(Fig. 9.3(b) is adapted from Phase Diagrams
of Binary Nickel Alloys, P. Nash (Ed.), ASM
International, Materials Park, OH, 1991.)
B
TB
D
TD
tie line
4
Cα
3

17. •
Rule 3:
If we know Tand Co, then we know:
--the amount of each phase (given in wt%).
• Examples:
At TA: Only Liquid (L)
WL= 100 wt%, Wα= 0
At TD: Only Solid (α)
WL= 0, Wα= 100 wt%
Co= 35 wt% Ni
Adapted from Fig. 9.3(b), Callister 7e.
(Fig. 9.3(b) is adapted from Phase Diagrams of
Binary Nickel Alloys, P. Nash (Ed.), ASM
International, Materials Park, OH, 1991.)
1
-
solid solution type of Phase diagram
cont.
weight fractions of phases
wt% Ni
20
1200
1300
T(°C)
L(liquid)
α
(solid)
L
+
α
liquidus solidus
30 40 50
L
+
α
Cu-Ni
system
TA
A
35
Co32
CL
B
TB
D
TD
tie line
4
Cα
3
R
S
At TB: Both αand L
% 73
32 43
35 43
wt =
−
−
= = 27 wt%
W
L
=
S
R
+
S
W
α
=
R
R
+
S

18. •Tie line –connects the phases in equilibrium
with each other -essentially an isotherm
The Lever Rule
How much of each phase?
Think of it as a lever (teeter-totter)
M
L
M
α
R
S
R M S M
L
⋅
=
⋅
α
wt% Ni
20
1200
1300
T(°C)
L(liquid)
α
(solid)
L
+
α
liquidus solidus
30 40 50
L
+
α
B
TB
tie line
C
o
C
L
C
αααα
S
R

19. Prove of Lever Rule

20. Example
• Find the types, composition and weight
fraction of phases present at the points’
A,B,C,D,E shown in the figure, during
cooling in a Cu-Ni Binary

21. wt% Ni
20
1200
1300
30 40 50
1100L(liquid)
α
(solid)
L
+
α
L
+
α
T(°C)
A
35
Co
L: 35wt%Ni
Cu-Ni
system
•Phase diagram:
Cu-Ni system.
•System is:
--
binary i.e., 2 components:
Cu and Ni.
--
isomorphous i.e., complete
solubility of one
component in
another; αphase
field extends from
0 to 100 wt% Ni.
Adapted from Fig. 9.4,
Callister 7e.
•Consider
Co= 35 wt%Ni
.
Solution
46
35
43
32
α: 43 wt% Ni L: 32 wt% Ni L: 24 wt% Ni α: 36 wt% Ni
B
α: 46 wt% Ni L: 35 wt% Ni
C D E
24
36

22. •C
α
changes as we solidify.
• Cu-Ni case:
•Fast rate of cooling:
Cored structure
•Slow rate of cooling:
Equilibrium structure
First αto solidify has C
α
= 46 wt% Ni.
Last αto solidify has C
α
= 35 wt% Ni.
Cored vsEquilibrium Phases
First αto solidify:
46 wt% Ni
Uniform Cα:
35 wt% Ni
Lastα to solidify:
< 35 wt% Ni

23. Mechanical Properties:
Cu
-
Ni
System
• Effect of solid solution strengthening on:
--Tensile strength (TS) --Ductility (%EL,%AR) --Peak as a function of C
o
--Min. as a function of C
o
Adapted from Fig. 9.6(a), Callister 7e.Adapted from Fig. 9.6(b), Callister 7e. Tensile Strength (MPa)
Composition, wt% Ni
CuNi
0 20 40 60 80 100
200
300
400
TSfor
pure Ni
TSfor pure Cu
Elongation (%EL)
Composition, wt% Ni
CuNi
0 20 40 60 80 100
20
30
40
50
60
%ELfor
pure Ni
%ELfor pure Cu