Basics of metallurgy, Gibb's phase rule, Solid solution with its types, types of cooling curves, types of Phase diagrams

1. Mr. A.A. Shinde
Assistant Professor
Department of Mechanical Engineering
Introduction to Ferrous Alloys
A Presentation
on
by
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2. SYLLABUS CONTENT:
SECTION-I
UNIT-1 Introduction to ferrous alloys No. of lectures-06
Brief classification of Metals, Concept of alloying, Classification of
cooling curves, Types of equilibrium diagram, Lever rule, phase rule,
Solid solution & its types, Intermetallic compounds, allotropy.
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3. Course Prerequisites:
 Engineering Chemistry
 Work shop practices
 Manufacturing processes.
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4. Crystal Structure:
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6. Crystal structures….
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7. Crystal structures with examples
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8. Basic Terms:
Crystal Structure:
The ordered arrangement of atoms, ions or molecules
in a crystalline material.
Unit Cell:
The smallest group of atoms which has the overall
symmetry of a crystal and from which the entire
lattice can be built up by repetition in three
dimensions.
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9. Basic Terms….
Crystalline Solids:
Particles are arranged in a repeating pattern. They
have a regular and ordered arrangement resulting
in a definite shape.
Amorphous Solids:
Particles are arranged randomly. They do not have
an ordered arrangement resulting in irregular
shapes.
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10. Basic Terms….
Metal:
It is a solid material which conduct heat & electricity ,hard, shiny, malleable, fusible, and
ductile.
Nonmetal:
It is a substance that do not exhibit properties of metals such as hardness, luster, malleability
,ductility and the ability to conduct electricity.
Metalloid:
an element (e.g. arsenic, antimony, or tin) whose properties are intermediate between
those of metals and solid non-metals or semiconductors.
Alloy:
It is a combination of a metal with at least one other metal or nonmetal. The combination must
be part of a solid solution, a compound, or a mixture with another metal or nonmetal in order
for it to be considered an alloy.
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12. Solid Solutions:
 A solid solution is a solid-state
solution of one or more solutes in
a solvent, in which atoms of the
solutes are distributed in the
solvent without changing its
crystal structure.
 Depending on the distribution of
the solute atoms in the solvent
Solid solutions are classified in
Two types.
Solid Solutions
Substitutional
Solid Solution
Ordered/
Regular
Substitutional
Solid Solution
Dis-Ordered/
Random
Substitutional
Solid Solution
Interstitial Solid
Solution
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13. Substitutional Solid Solutions:
 A solid solution in which atoms of the
solutes are substituted at the atomic
sites of the solvent without changing
its crystal structure.
 The solute may incorporate into the
solvent crystal lattice Substitutionally
by replacing a solvent particle in the
lattice.
 Atomic size of the two components
should not differ by more than 15%.
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14. Interstitial Solid Solutions:
 It is a solid solution in which atoms of the
solute occupies interstitial gaps between
solvent atoms without changing its crystal
structure.
 If the size of the solute is less than 40% that
of solvent, interstitial solid solution may be
formed.
 The solute may incorporate into the solvent
crystal lattice Interstitially, by fitting into the
space between solvent particles.
 Carbon, Nitrogen, Hydrogen, Oxygen and
Boron are elements which commonly form
Interstitial solid solution. 14
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15. Types of Substitutional Solid solution:
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17. Types of Substitutional Solid solution:
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19. Classification of Metallic Materials
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21.  Hume-Rothery rules, named after William Hume-Rothery, are a set of basic rules
that describe the conditions under which an element could dissolve in a metal,
forming a solid solution.
 There are two sets of rules; one refers to substitutional solid solutions, and the
other refers to interstitial solid solutions.
 Factors affecting formation of Solid solution.
Atomic Size Factor
Crystal Structure Factor
Relative Valency Factor
Electro-negativity Factor
Hume-Rothery’s Rule of Solid Solubility:
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22. Substitutional solid solution rules:
For substitutional solid solutions, the Hume-Rothery rules are as follows:
1. The atomic radius of the solute and solvent atoms must differ by no more than 15%.
2. The crystal structures of solute and solvent must be similar.
3. Complete solubility occurs when the solvent and solute have the same valency.A metal with lower
valency is more likely to dissolve in a metal of higher valency.
4. The solute and solvent should have similar electronegativity. If the electronegativity difference is too
great, the metals tend to form intermetallic compounds instead of solid solutions.
Hume-Rothery’s Rule of Solid Solubility…
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23. For interstitial solid solutions, the Hume-Rothery Rules are:
1. Solute atoms should have radius no larger than 15% of the radius of
solvent atoms.
2. The solute and solvent should have similar electronegativity.
3. They should show a wide range of composition.
4. Valency factor: two elements should have the same valence. The
greater the difference in valence between solute and solvent atoms, the
lower the solubility.
Hume-Rothery’s Rule of Solid Solubility…
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24. Metallic
Materials
Ferrous Metal
and its Alloys
Steels
Plain Carbon
Steel
Low Carbon
Steel
Medium
Carbon Steel
High Carbon
Steel
Alloy Steels
Cast Irons
White Cast
Irons
Grey Cast
Irons
Mottled Cast
Irons
Ductile Cast
Irons
Chilled Cast
Irons
Malleable
Cast Irons
Alloy Cast
Irons
Non-Ferrous
Metals and its
Alloys
Copper and
its Alloys
Aluminium
and its Alloys
Magnesium
and its Alloys
Zinc and its
Alloys
Nickel and its
Alloys
Tin and its
Alloys
Lead and its
Alloys, etc.
Classification of Metallic Materials:
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25. Alloy Steels
Low Alloy Steel
Low Carbon
Low Alloys
Steels
Medium Carbon
Low Alloys
Steels
High Carbon
Low Alloys
Steels
Medium Alloy
Steel
High Alloy
Steel
Tools Steels
Cold Worked
Tool Steels
Water
Hardening Tool
Steels
Air Hardening
Tool Steels
Oil Hardening
Tool Steels
High Carbon
High Chromium
Steels
Hot Worked
Tool Steels
Chromium
Type
Tungsten Type
Molybdenum
Type
High Speed
Tool Steels
Tungsten Type
Molybdenum
Type
Special
Purpose Tool
Steels
S-Series
L-Series
F-Series
P-Series
Stainless
Steels
Ferritic
Stainless Steel
Austenitic
Stainless Steel
Martinsitic
Stainless Steel
Precipitation-
Hardenable
Stainless Steel
Classification of Metallic Materials….
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26. Cooling Curves:
 A cooling curve is a line graph that represents the change of phase of matter, typically
from a gas to a solid or a liquid to a solid.
 The independent variable is time and the dependent variable is temperature.
 A cooling curve is a graph of the variation of the temperature of a sample with time as it is
allowed to cool.
 There are four types of Cooling curves:
1. Cooling curve for Pure Metals
2. Cooling curve for Binary Solid Solution Alloy
3. Cooling curve for Binary Eutectic Alloy
4. Cooling curve for Binary Off-Eutectic Alloy
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27. Cooling Curve for Pure Metal:
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28. Cooling Curve for Binary Solid
Solution Alloy:
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29. Cooling Curve for Binary
Eutectic Alloy:
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30. Cooling Curve for Binary Off-Eutectic
Alloy:
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31.  Eutectic alloy (plural eutectic alloys):
1. A mixture of metals having a melting point lower than that of any of its components.
e.g. lead-tin solder, cast-iron (a eutectic mixture of iron and carbon), copper
silver eutectic (silver solder).
2. If an alloy is not of eutectic composition then it is either hypereutectic or hypoeutectic.
3. If the alloys' composition places it to the left of the eutectic point on a phase diagram, then
it is hypoeutectic.
4. If it is to the right of the eutectic point then it is called hypereutectic.
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32. Applications of Eutectic Alloys:
 Eutectic alloys melts at constant temperature, hence they are used for measurement
of temperature. Commercially they are available in the form of sticks known as
Tempil sticks for measurement of temperature from as low as 60°C to 1100°C.
 Since they fuse at constant temperature, they are used for manufacturing of
electrical and thermal fuses.
 They are suitable for giving coating on other metal surfaces by spraying technique.
Such coatings are known as Metallized coatings.
 They shows super-plastic character hence they can be shaped by using a technology
similar to that used for forming of plastics. This is called as super-plastic forming.
Components such as instrument covers, refrigerators & car doors, salt and paper
shaker and car body panels have been manufactured from these alloys by super-
plastic forming.
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33.  Equilibrium diagram or Phase diagrams are the diagrams which indicate the phases
existing in the system at any temperature and composition.
 The co-ordinate system of binary phase diagrams uses temperature as the ordinate
(Y-axis) and weight percent of second element i.e. solute on abscissa (X-axis).
 These diagrams are used to find out the amounts of phases existing in a given alloy
with their compositions at any temperature.
 These diagrams also help in understanding the phenomena that occur during rapid
heating and cooling of the alloys.
Equilibrium Diagram:
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34. Plotting of Equilibrium Diagram:
 Techniques to draw Equilibrium Diagrams:
1. Thermal analysis
2. Dilatometry
3. Optical and Electron Microscopy
4. X-ray and Electron Diffraction
5. Thermodynamic Data Analysis
6. Electrical Resistivity
7. Magnetic Measurements
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35. Plotting of Equilibrium Diagram…
% Cu 100 90 80 70 60 50 40 30 20 10 0
% Ni 0 10 20 30 40 50 60 70 80 90 100
Material
No.
1 2 3 4 5 6 7 8 9 10 11
Table : Number of Alloys of Varying Compositions
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36. Plotting of Equilibrium Diagram…
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37. Plotting of Equilibrium Diagram…
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38. Plotting of Equilibrium Diagram…
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40.  Depending on the solubility of one metal into the another in liquid and solid
states, phase diagrams are classified in following four types.
1. Isomorphous System
2. Layer Type System
3. Eutectic System
4. Partial Eutectic System
Types of Phase Diagrams:
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41. Isomorphous System:
 These diagrams are obtained for
two metals having complete
solubility in the liquid state as
well as solid state.
 These diagrams are loop type.
 e.g. Cu-Ni, Au-Ag, Au-Cu, W-V,
Mo-V, Mo-W, Mo-Ti, Au-Ni, Bi-
Sb, etc Fig: Schematic phase diagram of an Isomorphous system
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42. Layer Type System:
 These diagrams are obtained for
two metals which have complete
insolubility in the liquid state as
well as solid state.
 These diagrams shows different
layers of metals.
 e.g. Cu-Mo, Cu-W, Ag-W,
Ag-fe, etc
Fig: Schematic phase diagram of a Layer Type system
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43. Eutectic Systems:
 These diagrams are obtained for
two metals having complete
solubility in the liquid state and
complete insolubility in the solid
state.
 e.g. Pb-As, Bi-Cd, Th-Ti, Au-Si,
etc.
Fig: Schematic phase diagram of an Eutectic system
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44. Cooling of a Hypoeutectic alloy with Z % of B:
Fig: Schematic representation of changes in Microstructure during solidification of a
Hypoeutectic alloy.
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45. Cooling of an Eutectic alloy with ZE % of B:
Fig: Schematic representation of changes in Microstructure during solidification of
an Eutectic alloy.
A & B
Liquid
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46. Cooling of a Hypereutectic alloy with Z’ % of B:
Fig: Schematic representation of changes in Microstructure during solidification of a
Hypereutectic alloy.
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47. Partial Eutectic Systems:
 These diagrams are obtained
for two metals which have
complete solubility in the
liquid state and partial
solubility in the solid state.
 e.g. Ag-Cu, Pb-Sn, Sn-Bi, Pb-
Sb, Cd-Zn, Al-Si, etc.
Fig: Schematic phase diagram of a Partial Eutectic system
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48. Fig: Schematic phase diagram of a Partial Eutectic system for Ag-Cu Alloy.
Partial Eutectic Systems….
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49. Fig: Schematic representation of changes in Microstructure during solidification of a
Ag-6%Cu Alloy a) Rapid Cooling but supersaturated, b) Slow Cooling & c) Rapid Cooling
Partial Eutectic Systems….
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50. Fig: Schematic representation of changes in Microstructure during solidification OR
cooling of a Ag-20%Cu Alloy
Partial Eutectic Systems….
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51. Liquid
Fig: Schematic representation of changes in Microstructure during solidification OR
cooling of a Ag-28.1%Cu Alloy ( Eutectic Alloy).
Partial Eutectic Systems….
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52. A) Eutectoid Transformation:
1. It is a solid state transformation in which one solid decomposes into two different solids at a
constant temperature during cooling.
2. Eutectoid transformation can be expressed as,
Solid A Solid B +Solid C
e.g. Fe-C, Cu-Sn, Cu-Al, Zn-Al, Al-Mn, etc.
B) Peritectoid Transformation:
1. It is a solid state transformation in which two different solids reacts with each other to form a
third solid at a constant temperature during cooling.
2. Peritectoid transformation can be expressed as,
Solid A + Solid B Solid C
e.g. Ni-Zn, Ni-Mo, Cu-Sn, Fe-Nb, etc.
Other Transformations in Alloy systems:
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53. C) Eutectic Transformation:
1. In this transformation a liquid decomposes at a constant temperature to form a mixture of
two different solids during cooling.
2. Peritectic transformation can be expressed as,
Liquid A Solid B + Solid C
e.g. Fe-C, Th-Ti, Pb-As, Bi-Cd, etc.
D) Peritectic Transformation:
1. In this transformation a liquid reacts with a solid and forms a new solid at a constant
temperature during cooling.
2. Peritectic transformation can be expressed as,
Liquid A + Solid B Solid C
e.g. Fe-C, Cu-Zn, Al-Ti, Pt-Ag, etc.
Other Transformations in Alloy systems:
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54. E) Monotectic transformation:
1. In this transformation a liquid decomposes to produce a mixture of a solid and another
new liquid during cooling.
2. Monotectic transformation can be expressed as,
Liquid A Liquid B + Solid A
e.g. Cu-Pb, Al-Pb, Zn-Pb, Zn-Bi, etc.
Other Transformations in Alloy systems:
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