1. Thermal Equilibrium Diagrams

2. Thermal Equilibrium Diagrams
Thermal Equilibrium Diagrams show the temperatures at which phase changes take place in alloys of different percentage composition.

3. Phase
A Phase is a portion of a system that has uniform physical and chemical characteristics.

4. Thermal Equilibrium Diagrams are made for information gained form Cooling Curves.

5. Cooling Curve
When the temperature of a cooling molten metal alloy is plotted against time, a cooling curve is formed.

6. The Cooling Curve of 100% Copper
Remember this only happens for pure metals.
LIQUID
When cooling a solid pure metal, change from a solid to a liquid at constant temperature.
This is called the Melting Point Temperature.
The heat that is released in the transition from a solid to a liquid is called hidden or Latent Heat.
Solidification Starts
Solidification Ends
SOLID

7. The energy that goes in breaks the bond of the atoms.
Latent Heat
Latent heat is the quantity of heat energy absorbed or released when a substance changes its physical phase at constant temperature.
To Explaine Latent Heat
The energy that goes in breaks the bond of the atoms.

8. Pure Metal change directly from Liquid to Solid at
The Cooling Curve of Pure Metal
LIQUID
Pure Metal change directly from Liquid to Solid at
1 temperature.
SOLID

9. Undercooling
If a metal is 100% pure and contains no traces of other elements then some under cooling may occur before solidification begins. Under cooling is when the temperature drops below the liquid to solid temperature for a short period.
1500
1000
1100
Temperature 0C
Time
Undercooling
Fall in temperature stops temporarily at the freezing point because of Latent heat

10. The Cooling Curve of an Alloy
Alloys change from Liquid to Solid through a pasty state over a temperature range.
LIQUID
Solidification Starts
“PASTY” STATE
Solidification Ends
SOLID

11. Pure Metal
Alloy
Over a Temperature Range
1Temperature

12. Solid Solition Alloys

13. Solid Solution:
A Solid Solution is when two metals are completely soluble in each other in both the liquid and solid states.
When viewed under a microscope, a solid solution appears like a pure metal.
Iron Carbon
100% Lead

14. TASK
The given table shows the solidification temperatures for various alloys of Copper and Nickel. The melting point of Copper is 1083°C and Nickel is 1453°C.
Using the graph paper supplied:
(i) Draw the equilibrium diagram according to the given data.
(ii) Label the diagram and describe the main features.
(iii) For the alloy with 50% Nickel determine, from the diagram, the ratio of the phases at 1250°C.

15. Axis of Diagram TEMPERATURE (°C) PRECENTAGE COMPOSITION 200 400 600
800
1200
1400
1000
1600
NICKEL
COPPER
40%
60%
20%
80% 0%
100%
PRECENTAGE COMPOSITION

17. Copper/Nickel Equilibrium Diagram
TEMPERATURE (°C)
NICKEL
COPPER
PRECENTAGE COMPOSITION

18. How Equilibrium Diagrams Are Made
Equilibrium diagrams are made from taking information for cooling of different percentage of an alloy and putting it on one graph.

19. The Cooling Curve of Copper/ Nickel and alloys
This is know as a TERMAL ANALYSIS

20. How A Thermal Equilibrium Diagram Is Made
100% Copper

21. How A Thermal Equilibrium Diagram Is Made
100% NICKLE

22. How A Thermal Equilibrium Diagram Is Made
60% Copper
40% Nickel

23. How A Thermal Equilibrium Diagram Is Made
40% Copper
60% Nickel

24. How A Thermal Equilibrium Diagram Is Made

25. Copper/Nickel Equilibrium Diagram
Liquidus Line
TEMPERATURE (°C)
200
400
600
800
1200
1400
1000
1600
Liquid Phase
Liquid Phase and Solid Phase
Solidus Line
Solid Phase
Phases are defined as regions that differ from one another on an equilibrium diagram.
Phases defined by composition (not by state – solid, liquid, gas)
NICKEL
COPPER
40%
60%
20%
80% 0%
100%
PRECENTAGE COMPOSITION

26. Main Features of Equilibrium Diagram
Liquid: the two metals are soluble in each other in the liquid state.
Liquidus Line: the change from fully liquid to pasty state. Above the liquidus line, the alloy is liquid. This is the beginning of solidification.
Liquid and Solid: the alloy is in a pasty form, there are two phases one Liquid and one Solid.
Solidus Line: the change from pasty to solid. Below the solidus line, the alloy is cooling and solid. This is the end of solidification.
Solid: alloy is in solid form.

27. Introduction To Equilibrium Diagrams
Equilibrium may be defined as a state of balance or stability.
Diagrams indicates the phases the alloy is at different temperatures.
Phases are defined as regions that differ from one another on an equilibrium diagram. Phases defined by composition.

28. The Meaning of the Term Equilibrium
Equilibrium refers to Balance existing in a system
In Metallurgy, Equilibrium means, that the cooling of a metal or an alloy is so slow that all the changes that might take place get the chance to do so.
To achieve equilibrium to take place enough time for complete diffusion is required.
Metallurgy is the study of metals and their properties

29. Atoms move in a solid metal in this manner.
Diffusion
Diffusion is the processes by which a substance spread out through another substance.
Atoms move in a solid metal in this manner.
HIGH CONSTANTRATION
LOW CONSTANTRATION

30. Diffusion in a vacuum

31. Atom move form high concentration to low concentration
Diffusion in a Solid
Atom move form high concentration to low concentration

32. PHOTOS Water And Sugar How Many Phases Are There? A SINGLE PHASE
TWO-PHASES
Explain Phase

33. Phase
A Phase is a portion of a system that has uniform physical and chemical characteristics.

34. Phases defined by composition. NOT BY STATE (solid, liquid , gas)
Phases are defined as regions that differ from one another on an equilibrium diagram.
Phases defined by composition.
NOT BY STATE (solid, liquid , gas)

35. Substitution Solid Solution Alloys
Nickel
Copper

36. Copper/Nickel Equilibrium Diagram

37. Ratio of Phases Tie Line
iii)For the alloy with 50% Nickel determine, from the diagram, the ratio of the phases at 1250°C.
Tie Line
1250°C
TEMPERATURE (°C)
26%
NICKEL
66%
COPPER
PRECENTAGE COMPOSITION

38. Ratio of Phases A B C Ratio of phases at 1250℃ for 50% Nickel
26%
66%
Ratio of phases at 1250℃ for 50% Nickel
The ratio of Solid to Liquid is:

39. Ratio of Phases TEMPERATURE (°C) PRECENTAGE COMPOSITION
NICKEL
26%
66%
COPPER
35%
PRECENTAGE COMPOSITION
Ratio of phases at 1250°C for 35% Nickel

40. Ratio of Phases TEMPERATURE (°C) PRECENTAGE COMPOSITION
NICKEL
26%
66%
COPPER
PRECENTAGE COMPOSITION
Ratio of phases at 1250ºC for 60% Nickel

41. Eutectic Alloys

42. Eutectic Alloys
In a eutectic alloy the two metals are completely soluble in the liquid phase but are insoluble in the solid phase.

43. TASK
The given table shows the solidification temperatures for various alloys of Cadmium and Nickel.
Using the graph paper supplied:
Draw the equilibrium diagram according to the given data.
Label the diagram and describe the main features.

44. Axis of Diagram TEMPERATURE (°C) PRECENTAGE COMPOSITION 200 400 600
800
1200
1400
1000
1600
BISMUTH
CABMIUM
40%
60%
20%
80% 0%
100%
PRECENTAGE COMPOSITION

45. TEMPERATURE (°C)
PRECENTAGE COMPOSITION

46. Cadmium / Bismuth Equilibrium Diagram
TEMPERATURE (°C)
BISMUTH
CADMIUM
PRECENTAGE COMPOSITION

47. Cadmium / Bismuth Equilibrium Diagram50
100
150
200
300
350
250
400
Liquidus Line
TEMPERATURE (°C)
Liquid Phase
Eutectic
Point
Liquid Phase
and Solid Phase
Liquid Phase
and Solid Phase
Solidus Line
Solid Phases
BISMUTH
CADMIMUM
40%
60%
20%
80% 0%
100%
PRECENTAGE COMPOSITION

48. Cadmium / Bismuth Equilibrium Diagram
TEMPERATURE (°C)
40%
60%
20%
80% 0%
100% 50
100
150
200
300
350
250
400
Liquid Phase
Eutectic
Point
Liquid and Solid Bismuth
Liquid and Solid Cadmium
Solid Bismuth and Eutectic
Solid Cadmium
and Eutectic
BISMUTH
CADMIUM
PRECENTAGE COMPOSITION
Green Line
Eutectic Alloy
Solid Cadmium
Solid Bismuth
Eutectic

49. Cadmium / Bismuth
∘ Cadmium Atoms
∙ Bismuth Atoms
X 1 000 X

50. Eutectic Point
The point where the liquid alloy changes to solid without going through a liquid/solid state is called the eutectic point.

51. Partial Solubility Alloy

52. Partial Solubility Alloy
Some metals in an alloy only partially dissolve in each other. Lead/Tin Alloy (Solder) is an example of this.
The equilibrium diagram for this type of alloy is called a Partial Solubility thermal equilibrium diagram. It is a combination of the solid solution and eutectic diagrams and is a little more complex.

53. Make up of Partial Solubility Alloy Equilibrium Diagram
Eutectic Alloys
Solid Solution Alloys
Solid Solution Alloys
Partial Solubility Alloy

54. Lead / Tin Equilibrium Diagram BASIC
100
200
300
400
Liquidus Line
Liquid
and Solid
TEMPERATURE (°C)
Liquid Phase
Eutectic
Point
Liquid
and Solid
Solidus Line
Solid Phases
40%
60%
20%
80% 0%
100%
TIN
LEAD
PRECENTAGE COMPOSITION

55. Lead / Tin Equilibrium Diagram LINES
40%
60%
20%
80% 0%
100%
100
200
300
400
Liquidus Line
Liquid
and Solid
TEMPERATURE (°C)
Liquid Phases
Liquid
and Solid
Solid Solution
Solid Solution
Solidus Line
SOLVUS LINES
Solid
TIN
LEAD
PRECENTAGE COMPOSITION

56. Lead / Tin Equilibrium Diagram COMPLETE
40%
60%
20%
80% 0%
100%
100
200
300
400
α Solid and Liquid
TEMPERATURE (°C)
Liquid Phases
β Solid
and Liquid
α Solid Solution
β Solid Solution
α and β
Solid Solution
TIN
LEAD
PRECENTAGE COMPOSITION

57. Interstitial Solid Solution Alloys
Tin
Lead

58. Task 3 (Q6 2006)
Copy the given lead-tin diagram into your answer book and answer all of the following:
(i) Identify the lines labelled A, B and C;
(ii) Explain what each line represents;
(iii) For the alloy with 30% tin determine, from the diagram, the
composition of the phases at 250°C;
(iv) Indicate clearly on your diagram the eutectic point.

59. (i) Labelled lines A, B and C
Liquidus line
Solidus line
Solvus line

60. (ii) Explain what each line represents?
A – Liquidus line. For the alloy system this line represents the boundary between the fully liquid state and the beginning of solidification. B – Solvus line. The transition line from one solid form to another solid form of an alloy is called the solvus line. This line indicates the maximum amount of tin which can be dissolved in the lead. C – Solidus line. The boundary line that determines the end of solidification. Below this line the alloy is completely solid.

61. To determine composition of the phases
For the alloy with 30% tin determine, from the diagram, the composition of the phases at 250°C?
To determine composition of the phases A B
A – Solid composition consisting of 8% tin and 92% lead.
B – Liquid composition consisting of 43% tin and 57% lead.

62. (iv) Indicate the eutectic point

63. Recap

64. Copper/Nickel Equilibrium Diagram
200
400
600
800
1200
1400
1000
1600
Liquid Phase
Liquidus Line
TEMPERATURE (°C)
Liquid Phase and Solid Phase
Solidus Line
Solid Phase
Phases are defined as regions that differ from one another on an equilibrium diagram.
Phases defined by composition (not by state – solid, liquid, gas)
NICKEL
COPPER
40%
60%
20%
80% 0%
100%
PRECENTAGE COMPOSITION

65. Cadmium / Bismuth Equilibrium Diagram50
100
150
200
300
350
250
400
Liquidus Line
TEMPERATURE (°C)
Liquid Phase
Eutectic
Point
Liquid Phase
and Solid Phase
Liquid Phase
and Solid Phase
Solidus Line
Solid Phases
BISMUTH
CADMIMUM
40%
60%
20%
80% 0%
100%
PRECENTAGE COMPOSITION

66. Lead / Tin Equilibrium Diagram COMPLETE
40%
60%
20%
80% 0%
100%
100
200
300
400
α Solid and Liquid
TEMPERATURE (°C)
Liquid Phases
β Solid
and Liquid
α Solid Solution
β Solid Solution
α and β
Solid Solution
TIN
LEAD
PRECENTAGE COMPOSITION

67. What is a Equilibrium Diagrams
You should know that a pure metal has one clearly defined melting point.
Mixtures tend to solidify over a temperature range, that is they start to solidify at one temperature and do not complete the process until they reach a lower point.
A mix of 80% A with 20% B will solidify over a different range than a mix of 20% A with 80% B.
A phase diagram allows us to present all this information in a single (sometime simple) diagram.

68. Introduction To Equilibrium Diagrams
Equilibrium may be defined as a state of balance or stability.
Diagrams indicates the phases the alloy is at different temperatures.
Phases are defined as regions that differ from one another on an equilibrium diagram. Phases defined by composition.