4. 4
Solid Metals Classified as
Amorphous:- Material have no regular
arrangement of their molecules.
Crystalline:- The atoms are arranged in
a three dimension array called a lattice
Ferrous:- These material contain iron as
their main contain
Non-Ferrous:-These material contain
other than ferrous material
Classification of Engineering
Material
6. 6
A crystal is defined as an orderly array of atom in
space.
Crystalline form of solid has periodically reputed
arrangement of atoms
Polymorphism:-It is ability of solid material to
exist in more than one form or crystal structure.
Types :- (a) BCC; (b) FCC (c) HCP
Crystal Structure
7. 7
Body Centered Cubic (BCC)
A Unit Cell Contains
8 atoms at corner X 1/8 =01
1 Center atom =01
Total atoms = 02
Examples: chromium, tungsten
Alpha iron, delta iron, vanadium
8. 8
Face Centered Cubic (FCC)
A Unit Cell Contains
8 atoms at corner X 1/8 = 01
6 atoms at face X 1/2 =03
Total atoms = 04
Examples: aluminum, nickel,
Copper, gold, silver, lead,
platinum
9. 9
Hexagonal-Close Packed (HCP)
A Unit Cell Contains
12 atoms at corner X 1/8 =1.5
2 atoms at face X 1/2 =01
3 Center atom =03
Total atoms = 5.5
Examples: Magnesium, Beryllium,
Zinc, cadmium
10. 10
Lattice :- Unit Cell is the smallest part
of the lattice which when repeated in
three directions produces the lattice.
Unit Cell :-Unit Cell is the smallest
part of the lattice which represents
the lattice.
Lattice and Unit Cell
11. Atomic Packing Efficiency
Atomic Packing Efficiency is the
fraction of volume occupied by atoms
in a unit cell.
APE = vol. of atomic spheres in unit cell
total unit cell vol.
12. Atomic Packing Efficiency for BCC
Geometry:
2 atoms/unit cell
68.0
8
34
3
3
4
2
3
3
a
a
V
V
APE
cell
atoms
4R a 3
12
APE = vol. of atomic spheres in unit cell
total unit cell vol.
13. 13
Density:- It is defined as the mass per
unit volume of the material
Melting Point:- It is the fixed and
constant temperature at which pure
metal or non-metal changes from solid
to liquid form
Specific Heat:- The amount of heat
required to raise the temperature of
material by 1◦C
Physical Properties
14. 14
Thermal expansion:-When thermal
energy is added to a material, the
change in its dimension is known as
thermal expansion
Thermal Conductivity:- It is the mode
of transmission from one substance to
other in direction of fall of temperature
Physical Properties
15.
16. Stress and Strain
Stress:
When an external load is applied to a
material the material resist the deformation
force upon cross section area
Strain
When deformation is caused per unit length
or volume
Change in dimension to the original
dimension
17. “Ability of a material to resist deformation.” or
“The strength of material is its ability to
withstand external forces applied on it”
Tensile strength: Measure of level of tensile
stress required to make material fail.
Compressive strength: Maximum
compressive stress that a material can resist
without being crushed.
19. Ductility & Brittleness
Ability of a
material by
which it can be
drawn into
wires.
Opposite to
ductility.
Tendency of a
body to break
without being
distorted.
20. Malleability
Ability of a body to be plastically extended in all
directions without breaking under compressive forces
only.
Property by which metals drawn into sheets.
21. Resistance to the plastic deformation.
Hardness of a material indicates the strength of
material to resist penetration ,abrasion and wear
22. o Measure of amount of energy that a material
can absorb before fracturing.
o Work done to propagate a crack.
23. Stiffness
“Ability of a material to resist bending.”
“It is defined as resistance of material to
elastic deformation”
24. • Progressive deformation of
a material under constant
load with time.
• Important for some type of
engineering design
particularly those operating
on high temperature.
• Tertiary creep > Primary
creep > Secondary creep.
25. It occurs due to repeated loading and unloading.
It is defined as behavior of a material when
exposed to fluctuating or periodic loads
26. Elasticity and Plasticity
Elasticity:
ability of a material to return to its original
shape after applied load is removed
Plasticity:
Property of a material to its permanent
deformation of material after applied load
is removed
27. Metals
Ferrous metals Non-ferrous metals
Steels Cast Irons
Plain carbon steels
Low alloy steels
High alloy steels
Stainless & Tool steels
Grey Iron
White Iron
Malleable Irons
Low carbon steels
Medium carbon steels
High carbon steels
Ferrous-Carbon alloy
classification
Ductile Irons
28. 28
Pure Metal :- A pure metal is defined as
an element only one single element
Alloy :- It is the mixture of two or more
elements
Equilibrium Diagrams
29. Metal A+ Metal B Metal C
Equilibrium Diagrams for Isomorphous
system
Heating
Metal A Metal B
Solid
Liquid
Liquids
Liquid + solid
Solidus
T2
T1
Temp.
30. Solid A+ Solid B Liquid
Equilibrium Diagrams for Eutectic
system
Heating
Cooling
Metal A Metal B
Solid
Liquid
M-A+Liquid
Solid Metal A+B
T2
T1
Temp.
E Liquid + Metal B
31. Solid α+ Solid β Solid γ
Equilibrium Diagrams for Eutectoid
system
Heating
Cooling
Metal A Metal B
Solid
Solid Solution γ
Solid Metal α + β
T2
T1
Temp.
E
α + γ β + γ
35. a–ferrite (BCC) Fe-c Solid
Solution
Known as a –iron
a–ferrite is solid solution of carbon in iron.
It is BCC structure
Maximum solubility of Carbon in Iron is 0.02%
at 723◦C
Pure iron at room temperature
Soft & ductile and imparts these properties to
the steel.
36. g-austenite (FCC) Fe-C solid
solution
g–austenite is solid solution of carbon in iron.
It is FCC structure
Maximum solubility of Carbon in Iron is 2.08%
at 1148◦C
Known as g –iron
Much softer than ferrite
Not present at room temperatures.
More easily hot worked
37. d-ferrite (BCC) Fe-C solid
solution
d-ferrite is solid solution of carbon in iron.
It is BCC structure
Maximum solubility of Carbon in Iron is 0.09%
at 1195◦C
38. Fe3C (Iron Carbide) or
cementite
Maximum solubility of Carbon in Iron is 6.67%
at 1147◦C and Iron 93.3%
It is hard , brittle and crystal structure is
orthorhombic
Hard, brittle, white
melts at 1837°C , density of 7.4 g/cc
Its presence in steels causes an increase in
hardness and a reduction in ductility and
toughness
39. Pearlite
Pearlite is not a phase.
It is a microconstituent and is a mixture of
two phases a- Ferrite and Fe3C.
Pearlite is eutectoid steel
A laminated structure formed of alternate
layers of ferrite and cementite with average
composition 0.83% carbon
It combines the hardness and strength of
cementite with the ductility of ferrite and is the
key to the wide range of the properties of
steels.
This gives it toughness
40. Three invariant reactions
Peritectic reaction at 1495˚C and 0.18%C,
d-ferrite + L↔ g-iron (austenite)
Eutectic reaction at 1147˚C and 4.3 %C,
L ↔ g-iron + Fe3C (cementite)
Eutectoid reaction at 727˚C and 0.77%C,
g-iron ↔ a–ferrite+Fe3C (cementite) [pearlite]
41. Fe-C alloy classification
Fe-C alloys are classified according to wt.% C
present in the alloys
Commercial pure irons % C < 0.008
Low-carbon steels 0.008 - %C - 0.3
Medium carbon steels 0.3 - %C - 0.8
High-carbon steels 0.8- %C - 2.14
Cast irons 2.14 < %C
42. Cast irons
Cast irons that were slowly cooled to room
temperature consists of cementite, look whitish
– white cast iron.
If it contains graphite, look grayish – gray cast
iron.
It is heat treated to have graphite in form of
nodules – malleable cast iron.
If inoculants are used in liquid state to have
graphite nodules – spheroidal graphite (SG)
cast iron.
49. Heat Treatment of Steels
Heat Treatment process is a series of operations
involving the heating and cooling of metals in
the solid state.
Its purpose is to change a mechanical property or
combination of mechanical properties so that the
metal will be more useful, serviceable, and safe for
definite purpose.
By heat treating, a metal can be made harder,
stronger, and more resistant to impact,
51. Heat Treatment Purpose
and Application
Purpose
Harden and strengthen metals
Reliving internal stresses
Improve machinability
change in grain size
Improve ductility and
toughness
Improve electrical and
magnetic property
Applications
Hate treatment of forgings of
shaft and axels, drills, cutting
tools, taps, dies
Measuring instruments etc.
52. 1.Annealing Process
Purpose
Refining structure
Reliving internal stresses
Improve machinability
Reducing hardness
Producing desirable
microstructure
Improving mechanical,
physical and electrical
property
Applications
Steel used in sheet and wire
drawing
Casting of carbon and alloy steels
High carbon tool steels
Ball bearing steels
Types
a) Stress relieving
b) Process annealing
c) Spheroidise annealing
d) Full annealing
Process
Process of heating a metal which is in a metastable or
distortion state.
Temperature which remove the distortion and cooling in
furnace for slow cooling process.
53. A. Process Annealing
It is also called as subcritical annealing
The steel is heated below lower critical temperature 500◦ to
700 ◦ C
Holding time periods 2 to 4 hours
Process annealing is the continuous or batch type in furnace
cooling method
As slow cooling process
It is applied for low carbon steel used to draw the wires and
deep drawing operation
54. B.Spheroidise Annealing
Heat treatment used to produce spheroidal form of
cementite from of plates of cementite in steel is called
spheroidise annealing
It is applied for High carbon steels
The steel is heated below lower critical temperature 650◦ to
700 ◦ C
Holding prolonged time period.
This resulting steel has improved machinability, ductility
and toughness
55. C.Full Annealing
It is also called as conventional annealing
The steel is heated 30 ◦ C to 50 ◦ C above the upper critical
temperature.
Holding time periods 2 to 4 hours
Rate of cooling 30 ◦ C to 200 ◦ C / Hrs
The process is used mainly to remove the internal stresses.
It is applied for casting carbon and alloy steel
56. D. Stress relieving
Annealing
Stress relieving Annealing Relieves or eliminates stresses
induced by casting, machining, cold working
It is special type of annealing applied for the purpose of
stress reliving
The cold working steel is heated about temperature 500◦
Below its recrystallisation temperature
Holding time periods 1 to 2 hours
As slow cooling process
57. 2. Normalizing
Process
Process of heating a steel to about 40◦ C to 50◦ C above the upper
critical temperature
Cooling in air type because of faster cooling compared to annealing
Desirable temperature of steel shall maintained for a time period more
than 2 min/ mm of section thickness
Temperature shall not be exceed more than 50◦ C above the upper
critical temperature
The structure produced by this process is pearlite or pearlite in ferrite
matrix
Because the steel is cooled in air to produced the fine peralite with
improved mechanical properties
58. 2. Normalizing
Purpose
Uniform structure
Refines the grain size of steel
Improve machinability
Reducing internal stresses
Produces harder and stroner steel
Improve structure in welds
Improves engineering property of
steel
Applications
Normalizing is usually
performed on rolled and cast
steel to refine grain structure
Improve microstructure
Applied for low and mediuum
carbon steel
It is applied on welded
structure to improve
homogeneity
Advantages
Refines the grain size of steel structure
To encourage reduced grain segregation in casting and forgings
Provide moderate hardening
59. 3. Hardening
Process
Hardening is that heat treatment of steel which increases its hardness
Tools of machine and machine parts having heavy duty are required
often hardness
