PPT: Phase Diagrams Mechanical Engineering Notes | EduRev

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Mechanical Engineering : PPT: Phase Diagrams Mechanical Engineering Notes | EduRev

 Page 1


ISSUES TO ADDRESS...
•  When we combine two elements...
what is the resulting equilibrium state?
•  In particular, if we specify...
-- the composition (e.g., wt% Cu - wt% Ni), and
-- the temperature (T)
then...
How many phases form?
What is the composition of each phase?
What is the amount of each phase?
Chapter 9:  Phase Diagrams
Phase B
Phase A
Nickel atom
Copper atom
Page 2


ISSUES TO ADDRESS...
•  When we combine two elements...
what is the resulting equilibrium state?
•  In particular, if we specify...
-- the composition (e.g., wt% Cu - wt% Ni), and
-- the temperature (T)
then...
How many phases form?
What is the composition of each phase?
What is the amount of each phase?
Chapter 9:  Phase Diagrams
Phase B
Phase A
Nickel atom
Copper atom
Phase Equilibria: Solubility Limit
Question: What is the
solubility limit for sugar in 
water at 20ºC?
Answer: 65 wt% sugar.
At 20ºC, if C < 65 wt% sugar: syrup
At 20ºC, if C > 65 wt% sugar:
syrup + sugar
65
•  Solubility Limit:
Maximum concentration for
which only a single phase 
solution exists.
Sugar/Water Phase Diagram
Sugar
Temperature (ºC)
0 20
40 60
80 100
C = Composition (wt% sugar)
L
(liquid solution 
i.e., syrup)
Solubility 
Limit
L
(liquid) 
+ 
S
(solid 
sugar) 20
40
60
80
100
Water
Adapted from Fig. 9.1, 
Callister & Rethwisch 8e.
•  Solution – solid, liquid, or gas solutions, single phase
•  Mixture – more than one phase
Page 3


ISSUES TO ADDRESS...
•  When we combine two elements...
what is the resulting equilibrium state?
•  In particular, if we specify...
-- the composition (e.g., wt% Cu - wt% Ni), and
-- the temperature (T)
then...
How many phases form?
What is the composition of each phase?
What is the amount of each phase?
Chapter 9:  Phase Diagrams
Phase B
Phase A
Nickel atom
Copper atom
Phase Equilibria: Solubility Limit
Question: What is the
solubility limit for sugar in 
water at 20ºC?
Answer: 65 wt% sugar.
At 20ºC, if C < 65 wt% sugar: syrup
At 20ºC, if C > 65 wt% sugar:
syrup + sugar
65
•  Solubility Limit:
Maximum concentration for
which only a single phase 
solution exists.
Sugar/Water Phase Diagram
Sugar
Temperature (ºC)
0 20
40 60
80 100
C = Composition (wt% sugar)
L
(liquid solution 
i.e., syrup)
Solubility 
Limit
L
(liquid) 
+ 
S
(solid 
sugar) 20
40
60
80
100
Water
Adapted from Fig. 9.1, 
Callister & Rethwisch 8e.
•  Solution – solid, liquid, or gas solutions, single phase
•  Mixture – more than one phase
•  Components:
The elements or compounds which are present in the alloy
(e.g., Al and Cu)
•  Phases:
The physically and chemically distinct material regions
that form (e.g., a and b).
Aluminum-
Copper
Alloy
Components and Phases
a (darker 
phase)
b (lighter 
phase)
Adapted from chapter-
opening photograph, 
Chapter 9, Callister, 
Materials Science & 
Engineering: An 
Introduction, 3e. 
Page 4


ISSUES TO ADDRESS...
•  When we combine two elements...
what is the resulting equilibrium state?
•  In particular, if we specify...
-- the composition (e.g., wt% Cu - wt% Ni), and
-- the temperature (T)
then...
How many phases form?
What is the composition of each phase?
What is the amount of each phase?
Chapter 9:  Phase Diagrams
Phase B
Phase A
Nickel atom
Copper atom
Phase Equilibria: Solubility Limit
Question: What is the
solubility limit for sugar in 
water at 20ºC?
Answer: 65 wt% sugar.
At 20ºC, if C < 65 wt% sugar: syrup
At 20ºC, if C > 65 wt% sugar:
syrup + sugar
65
•  Solubility Limit:
Maximum concentration for
which only a single phase 
solution exists.
Sugar/Water Phase Diagram
Sugar
Temperature (ºC)
0 20
40 60
80 100
C = Composition (wt% sugar)
L
(liquid solution 
i.e., syrup)
Solubility 
Limit
L
(liquid) 
+ 
S
(solid 
sugar) 20
40
60
80
100
Water
Adapted from Fig. 9.1, 
Callister & Rethwisch 8e.
•  Solution – solid, liquid, or gas solutions, single phase
•  Mixture – more than one phase
•  Components:
The elements or compounds which are present in the alloy
(e.g., Al and Cu)
•  Phases:
The physically and chemically distinct material regions
that form (e.g., a and b).
Aluminum-
Copper
Alloy
Components and Phases
a (darker 
phase)
b (lighter 
phase)
Adapted from chapter-
opening photograph, 
Chapter 9, Callister, 
Materials Science & 
Engineering: An 
Introduction, 3e. 
70 80 100 60 40 20 0
Temperature (ºC)
C = Composition (wt% sugar)
L
(liquid solution 
i.e., syrup)
20
100
40
60
80
0
L
(liquid) 
+ 
S
(solid 
sugar)
Effect of Temperature & Composition
•  Altering T can change # of phases: path A to B.
• Altering C can change # of phases: path B to D.
water-
sugar
system
Adapted from Fig. 9.1, 
Callister & Rethwisch 8e.
D (100ºC,C = 90)
2 phases 
B (100ºC,C = 70)
1 phase 
A (20ºC,C = 70)
2 phases
Page 5


ISSUES TO ADDRESS...
•  When we combine two elements...
what is the resulting equilibrium state?
•  In particular, if we specify...
-- the composition (e.g., wt% Cu - wt% Ni), and
-- the temperature (T)
then...
How many phases form?
What is the composition of each phase?
What is the amount of each phase?
Chapter 9:  Phase Diagrams
Phase B
Phase A
Nickel atom
Copper atom
Phase Equilibria: Solubility Limit
Question: What is the
solubility limit for sugar in 
water at 20ºC?
Answer: 65 wt% sugar.
At 20ºC, if C < 65 wt% sugar: syrup
At 20ºC, if C > 65 wt% sugar:
syrup + sugar
65
•  Solubility Limit:
Maximum concentration for
which only a single phase 
solution exists.
Sugar/Water Phase Diagram
Sugar
Temperature (ºC)
0 20
40 60
80 100
C = Composition (wt% sugar)
L
(liquid solution 
i.e., syrup)
Solubility 
Limit
L
(liquid) 
+ 
S
(solid 
sugar) 20
40
60
80
100
Water
Adapted from Fig. 9.1, 
Callister & Rethwisch 8e.
•  Solution – solid, liquid, or gas solutions, single phase
•  Mixture – more than one phase
•  Components:
The elements or compounds which are present in the alloy
(e.g., Al and Cu)
•  Phases:
The physically and chemically distinct material regions
that form (e.g., a and b).
Aluminum-
Copper
Alloy
Components and Phases
a (darker 
phase)
b (lighter 
phase)
Adapted from chapter-
opening photograph, 
Chapter 9, Callister, 
Materials Science & 
Engineering: An 
Introduction, 3e. 
70 80 100 60 40 20 0
Temperature (ºC)
C = Composition (wt% sugar)
L
(liquid solution 
i.e., syrup)
20
100
40
60
80
0
L
(liquid) 
+ 
S
(solid 
sugar)
Effect of Temperature & Composition
•  Altering T can change # of phases: path A to B.
• Altering C can change # of phases: path B to D.
water-
sugar
system
Adapted from Fig. 9.1, 
Callister & Rethwisch 8e.
D (100ºC,C = 90)
2 phases 
B (100ºC,C = 70)
1 phase 
A (20ºC,C = 70)
2 phases
Criteria for Solid Solubility 
Crystal
Structure
electroneg
r (nm)
Ni FCC 1.9 0.1246
Cu FCC 1.8 0.1278
• Both have the same crystal structure (FCC) and have 
similar electronegativities and atomic radii (W. Hume –
Rothery rules) suggesting high mutual solubility. 
Simple system (e.g., Ni-Cu solution)
• Ni and Cu are totally soluble in one another for all proportions.
Read More
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