This document discusses various engineering materials and their properties. It begins by classifying materials into metals, non-metals and composites. Metals are further divided into ferrous and non-ferrous categories. The document then discusses properties of materials including physical, mechanical, electrical, magnetic and chemical properties. It provides examples to illustrate different types of materials like metals, alloys, ceramics and polymers. The document also compares properties of metals and non-metals in a table and discusses composites as a combination of two materials to achieve specialized properties.

1. CHAPTER ONE
Introduction to Engineering Materials

2. 1. Classification of materials
The engineering materials are classified as follows:
1.1 Metals: Metals are the iron groups which includes all types of iron and steel. Metals are dense, shiny elements
that are good conductors of heat and electricity. Most metals are malleable and ductile and are, in general,
denser than the other elemental substances. Example of metals are iron, aluminum, copper, zinc, lead
etc.
Metals also devided into:
i) Ferrous metals: are metals contain iron and are magnetic. They are prone to rust and therefore require a
protective finish, which is sometimes used to improve the aesthetics of the product it is used for as well.
Example of ferrous metals are cast iron, wrought iron and steel and alloys of ferrous metal are silicon,
steel, high speed steel, spring steel etc.
ii) Non-ferrous metals: are metals that do not contain iron and are not magnetic. They do not rust. Examples
of non- ferrous metals are copper, aluminum, zinc, lead etc. and alloys of non- ferrous metals are Brass,
bronze, duralumin etc.
1.2 Non metals: Non-metals are those which lack all the metallic attributes. They are good insulators of heat and
electricity. They are mostly gases and sometimes liquid. Some are even solid at room temperatures
like Carbon, Sulphur and phosphorus. Examples of Non-metals are leather, rubber, plastics,
asbestos, carbon etc.

4. 1.2 Other classification of engineering materials:
Engineering materials can also be classified as below-
a) Metals and Alloys
b) Ceramic Materials
c) Organic Materials
a) Metals and Alloys
Metals are polycrystalline bodies which have a number of differentially oriented fine crystals. Normally
major metals are in solid states at normal temperature. However, some metals such as mercury are also in
liquid state at normal temperature.
Pure metals are having very a low mechanical strength, which sometimes does not match with the
mechanical strength required for certain applications. To overcome this draw back alloys are used.
Alloys are the composition of two or more metals or metal and non-metals together. Alloys are having good
mechanical strength, low temperature coefficient of resistance.
Example: Steels, Copper, Aluminium,Brass, Bronze, Gunmetal, Invar. Super Alloys etc.

5. b) Ceramic Materials
Ceramic materials are non-metallic solids. These are made of inorganic compounds such as Oxides,
Nitrides, Silicates and Carbides. Ceramic materials possess exceptional Structural, Electrical,
Magnetic, Chemical and Thermal properties. These ceramic materials are now extensively used in
different engineering fields.
Examples: Silica, glass, cement, concrete, garnet, Magnesium oxide (MgO), Cadmium sulfide(Cds),
Zinc oxide (Zno), Silicon Carbide (sic) etc.
c) Organic Materials (Polymers)
All organic materials are having carbon as a common element. In organic materials carbon is
chemically combined with oxygen, hydrogen and other non-metallic substances. Generally organic
materials are having complex chemical bonding.
Example: Plastics, PVC, Synthetic Rubbers etc.

7. 1.3 A composite material: is a combination of two materials with different physical and chemical
properties. When they are combined they create a material which is specialised to do a certain job, for
instance to become stronger, lighter or resistant to electricity.
They can also improve strength and stiffness. The reason for their use over traditional materials is because
they improve the properties of their base materials and are applicable in many situations.

8. No. Property Metals Non-Metals
1. Structure
All metals are having crystalline
structure
All Non-metals are having amorphic &
mesomorphic structure
2. State
Generally metals are solid at normal
temperature
State varies material to material. Some
are gas state and some are in solid
state at normal temperature.
3.
Valance electrons and
conductivity
Valance electrons are free to move
within metals which makes them
good conductor of heat & electricity
Valence electrons are tightly bound
with nucleus which are not free to
move. This makes them bad conductor
of heat & electricity
4. Density High density Low density
5. Strength High strength Low strength
6. Hardness Generally hard Hardness is generally varies
7. Malleability Malleable Non malleable
8. Ductility Ductile Non ductile
9. Brittleness Generally non brittle in nature Brittleness varies material to material
10. Lustre Metals possess metallic lustre
Generally do not possess metallic
lustre (Except graphite & iodine)
2. Difference between Metals and Non Metals

29. What are material properties?
Properties are factors that qualitatively or quantitatively influence the response of a given material to the
imposition of stimuli and constraints.
e.g., forces, temperature, etc. Similarly, properties make a material suitable or unsuitable for a particular
industrial use. In other words, when we refer to the properties of a material, we are talking about characteristics
that we can recognize, measure or test.
1. Physical properties of materials
2. Mechanical properties of materials
3. Electrical properties of materials
4. Magnetic properties of materials
5. Chemical properties of materials
3. Properties of materials

30. 1. Physical properties of materials
Physical properties are those that can be observed without changing the composition of the material. For
example, some of the most important physical properties of metals are:
•Density: The density of a substance is its mass per unit volume. The symbol most often used for density is ρ
although the Latin letter D can also be used.
•Boiling point:The boiling point of a liquid varies according to the applied pressure; the normal boiling point is the
temperature at which the vapour pressure is equal to the standard sea-level atmospheric pressure (760 mm of
mercury). At sea level, water boils at 100° C (212° F).
•Melting or Freezing point: Freezing point is the temperature at which a liquid becomes a solid at normal
atmospheric pressure. Alternatively, a melting point is the temperature at which a solid becomes a liquid at normal
atmospheric pressure.
•Linear coefficient of expansion: is a material property which characterizes the ability of a matrial to expand
under the effect of each degree rise in temperature. It tells you how much the developed part will remain
dimensionally stable under temperature variations.

31. •Thermal conductivity: Thermal conductivity refers to the inherent ability of a material to transfer or
conduct heat.
•Electrical resistivity: Eletrical resistivity, represented by the Greek letter ρ (rho), is a measure of the
resistance of a specific material of a given size, to the electrical current conduction that flows through it.
The SI unit of electrical resistivity is expressed in ohm-metres (Ωm).

32. 2. Mechanical properties of materials
The following are the mechanical properties of materials.
They are those that determine the
behavior of a material under the forces
applied to it and reflect the relationship
between its response to a load and the
deformation it undergoes.

34. R
R = V/I or,
R = ρ(L/A)
V = Voltage, I = Current, ρ =
Resistivity

40. 4.

44. CHAPTER TWO
Introduction to Conducting Materials

45. 2.1 Conducting materials:
A conductor, or electrical conductor, is a substance or material that allows electricity to flow through it. In a
conductor, electrical charge carriers, usually electrons or ions, move easily from atom to atom when voltage is
applied.
2.2 Resistivity and factors affecting resistivity
2.2.1 Resistance: Every conductor possesses some resistance. It may be very high (insulator) or maybe low
(conductor). Resistance is effectively helpful in controlling the flow of electric current. So before understanding
resistivity and what are the factors affecting resistivity, you have to understand resistance. What is it, and how
it works?
Resistance of a material can be measured by: R = ρ(L/A)
Where,
L = length of the conductor
A = area of the cross-section of the conductor
ρ = resistivity

46. 2.2.2 What is resistivity?
The electrical resistivity of a particular conductor material is a measure of how strongly the material
opposes the flow of electric current through it. This resistivity factor, sometimes called its “specific
electrical resistance”, enables the resistance of different types of conductors to be compared to one
another at a specified temperature according to their physical properties without regards to their
lengths or cross-sectional areas. Thus the higher the resistivity value of ρ the more resistance and vice
versa.
From the above equation, resistance (R) is directly proportional to the (L) length of the conductor and (ρ)
resistivity. And the resistance (R) is inversely proportional to (A) area of the cross-section of the conductor.
So, the resistance of a material is affected by its length, area of cross-section, material, and temperature.

47. 2.3 Factors effecting the resistivity of electrical materials are listed below:
I. Temperature
II. Alloying
III. Mechanical stressing
IV. Age Hardening
V. Cold Working
2.3.1 Temperature
The resistivity of materials changes with temperature. Resistivity of most of the metals increase with temperature.
The change in the resistivity of material with change in temperature is given by formula as:
Where,
ρt1 is the resistivity of material at temperature of t1
o C and
ρt2 is the resistivity of material at temperature of t2
oC
α1 is temperature coefficient of resistance of material at temperature of t1
o C.
If the value of α1 is positive, the resistivity of material is increase.

48. The resistivity of metals increase with increase of temperature. Means the metals are having positive
temperature coefficient of resistance. Several metals exhibit the zero resistivity at temperature near to
absolute zero. This phenomenon is “called the superconductivity”.
The resistivity of semiconductors and insulators decrease with increase in temperature. Means the
semiconductors and insulators are having negative temperature coefficient of resistance.
2.3.2 Alloying
Alloying is a solid solution of two or more metals. Alloying of metals is used to achieve some mechanical
and electrical properties. The atomic structure of a solid solution is irregular as compared to pure metals.
Due to which the electrical resistivity of the solid solution increases more rapidly with increase of alloy
content. A small content of impurity may increase the resistivity of metal considerably. Even the impurity
of low resistivity increases the resistivity of base metal considerably. For example the impurity of silver
(having lowest resistivity among all metals) in copper increase the resistivity of copper.

49. 2.3.3 Mechanical Stressing
Mechanical stressing of the crystal structure of material develops the localized strains in the material crystal
structure. These localized stains disturb the movement of free electrons through the material. Which results in
an increase in resistivity of the material. Subsequently, annealing, of metal reduces the resistivity of metal.
Annealing of metal, relieve the mechanical stressing of material due to which the localized stains got removed
from the crystal structure of the metal. Due to which the resistivity of metal decrease. For example, the
resistivity of hard drawn copper is more as compared to annealed copper.
2.3.4 Age Hardening
Age hardening is a heat treatment process used to increase the yield strength and to develop the ability in alloys
to resist the permanent deformation by external forces. Age hardening is also called “Precipitation Hardening”.
This process increases the strength of alloys by creating solid impurities or precipitate. These created solid
impurities or precipitate, disturb the crystal structure of metal which interrupts the flow of free electrons
through metal/Due to which the resistivity of metal increases.

50. 2.3.5 Cold Working
Cold working is a manufacturing process used to increase the strength of metals. Cold working is also known as “Work
hardening” or “Strain hardening”. Cold working is used to increase the mechanical strength of the metal. Cold working
disturbs the crystal structure of metals which interfere with the movement of electrons in metal, due to which the
resistivity of metal increases.
3. Conducting Materials:
Materials used for conducting electricity are known as Conducting materials. These materials play a vital role in
Electrical Engineering. It is interesting to know the applications of these materials in the field of Electrical
Engineering, like the type of materials used in Transmission lines, Electrical Machines, Starters, and Rheostats,
etc., along with different conducting materials, we will also go through their alloys.

51. A classification chart of conducting materials based on resistivity or conductivity
Electrical conducting materials are the basic requirement for electrical engineering products. They can be
classified as below based on Resistivity or Conductivity. .
4. Materials of low and high resistivity
4.1 Classification of conducting material based on Resistivity or Conductivity

52. 4.1.1 Low Resistivity or High Conductivity Conducting Material
Material having low resistivity or high conductivity are very useful in electrical engineering products. These materials are
used as conductors for all kind of windings required in electrical machines, apparatus and devices. These materials are
also used as conductor in transmission and distribution of electrical energy.
Some of low resistivity or high conductivity materials and their resistivity are given below:
•Silver with resistivity of 1.58 µΩ -cm
•Copper with resistivity of 1.68 µΩ -cm
•Gold with resistivity of 2.21 µΩ -cm
•Aluminum with resistivity of 2.65 µΩ -cm
4.1.2 High Resistivity or Low Conductivity Conducting Material
Materials having High resistivity or Low conductivity conducting are very useful for electrical engineering products.
These material are used to manufacture the filaments for incandescent lamp, heating elements for electric heaters,
space heaters and electric irons etc. Some of materials having High resistivity or Low conductivity are listed below:
•Tungsten
•Carbon
•Nichrome or Bright ray – B
•Nichrome – Vor Bright ray – C
•Manganin

53. Chart of conducting materials based on their applications
5. Conducting materials used for different applications
Classification of Electrical Conducting Materials based on their application.

54. Conducting materials based on area of application
1. Materials used as conductor for coils of electrical machines
2. Materials for heating elements
3. Materials for lamp filaments
4. Material used for transmission line
5. Bimetals
6. Electrical Contact Materials
7. Electrical Carbon Materials
8. Material for Brushes used in Electrical Machines
9. Materials used for fuses

55. 5.1 Materials Used as Conductor for Coils of Electrical Machines
Materials having low resistivity or high conductivity such as copper, silver and aluminum can be used for making
coils for electrical machines. However, looking to optimum conductivity, mechanical strength and cost, copper is
much suitable for making coils for electrical machines.
5.2 Materials for Heating Elements
Materials having high resistivity or low conductivity such as Nichrome, Kanthal, Cupronickel and Platinum etc.
are used for making heating elements. Materials used for heating elements must possess following properties-
•High melting point
•Free from oxidation in operating atmosphere
•High tensile strength
•Sufficient ductility to draw the metal or alloy in the form of wire

56. 5.3 Materials for Lamp Filaments
Materials having high resistivity or low conductivity such as Carbon, Tantalum and Tungsten etc. are used for making
incandescent lamp filament. Materials used for making incandescent lamp filament must possess following properties-
• High melting point
• Low vapour pressure
• Free from oxidation in inert gas (argon, nitrogen etc.)
medium at operating temperature
• High resistivity
• Low thermal coefficient of expansion
• Low temperature coefficient of resistance
• Should have high young modulus and tensile strength
• Sufficient ductility so that can be drawn in the form of very thin wire
• Ability to be converted in the shape of filament
• High fatigue resistance against thermally induced fluctuating stresses
• Cost should minimum

57. 5.4 Material Used for Transmission Line
Materials used for making conductor for transmission line must possess following properties
•High conductivity
•High tensile strength
•Light weight
•High resistance to corrosion
•High thermal stability
•Low coefficient of thermal expansion
•Low cost
Materials use for transmission lines are listed below:
•Copper
•Aluminum
•Cadmium-Copper alloys
•Phosphor bronze
•Galvanized steel
•Steel core copper
•Steel core aluminum
5.6 Bimetals
Many combinations of metals with different “Coefficient of linear thermal expansion” can be used to form the
bimetals. Some of the commonly used combinations for making bimetallic strips are listed below-
•Iron, nickel, constantan (high “Coefficient of linear thermal expansion”)
•Alloy of iron and nickel (low “Coefficient of linear thermal expansion”)

59. 5.7 Electrical Contact Materials
Electrical contact materials refer to a class of metals that are used in the electrical interfaces of electrical
connectors and electrical switches. While selecting a suitable material for electrical contact, we have to
consider basic factors. Some of most important factors of these are listed below :
•Contact resistance
•Contact force
•Voltage and current
5.8 Electrical Carbon Materials
Carbon in widely used in electrical engineering. Electrical carbon materials are manufactured from graphite and
other forms of carbon. Carbon is having following applications in electrical Engineering
•For making filament of incandescent lamp
•For making electrical contacts
•For making resistors
•For making brushes for electrical machines such as DC
machines, alternators.
•For making battery cell elements
•Carbon electrodes for electric furnaces
•Arc lighting and welding electrodes
•Component for vacuum valves and tubes
•For makings parts for telecommunication equipment’s

60. 5.9 Material for Brushes Used in Electrical Machines
Before selecting the material for brushes, we should keep in our mind the following requirements in a brush :
•Contact resistance
•Thermal stability
•Lubrication properties
•Mechanical strength
•Low brittleness
Material used for Brushes in electrical machines are listed as:
•Carbon
•Natural graphite
•Electro graphite
•Metal graphite
•Copper

61. 5.10 Materials Used for Fuse Elements
A fuse commonly consists of a current-conducting strip or wire of easily fusible metal that melts, and
thus interrupts the circuit of which it is a part, whenever that circuit is made to carry a current larger
than that for which it is intended.
Fuse element is primary requirement of a fuse unit. The fuse element should have following properties-
Low resistance – to avoid the undesirable voltage drop across the fuse element, so that it should effects the normal
functioning or performance of circuit or device or equipment.
Low melting point – the fuse element must have low melting point. So that it blow out due to heating by excess
current during over load or short circuit.
Different types of metals and alloys are used for fuse element. Some of these elements are listed below –
•Aluminum
•Lead and tin
•Copper
•Silver
•Rose’ Alloys
•Wood alloys

62. Many metals and metallic alloys are suitable to be used in thermocouples as thermoelectric effect
occurs when two materials are put in contact forming a thermal junction. However, thermocouple
materials are chosen according to some important characteristics: maximum sensibility over the
entire operating range, long-term stability including high temperatures, cost, and compatibility with
the available instrumentation. Most often thermocouple materials are metallic alloys with two or
more components to achieve the desired characteristics to a range of temperatures.
6.1 What is a Thermocouple?
A Thermocouple is a sensor used to measure temperature. A thermocouple consists of two dissimilar metals,
joined together at one end, which produce a small voltage when heated (or cooled). This voltage is measured and
used to determine the temperature of the heated metals. The voltage for any one temperature is unique to the
combination of metals used.
6. Thermocouple Material

63. 6.2 Types of Thermocouple?
Thermocouples are available in different combinations of metals, usually referred to by a letter, e.g. J, K
etc giving rise to the terms type J thermocouple, type K thermocouple etc. Each combination has a
different temperature range and is therefore more suited to certain applications than others.

65. 7. Superconductivity
Superconductivity is the ability of certain materials to conduct electric current with practically zero
resistance. This capacity produces interesting and potentially useful effects. For a material to behave as
a superconductor, low temperatures are required. Or
Superconductivity is the property of certain materials to conduct direct current (DC) electricity without
energy loss when they are cooled below a critical temperature (referred to as Tc). These materials also
expel magnetic fields as they transition to the superconducting state.
Superconductivity explained

66. If you think you can’t relate to the real-life applications of superconductors, well, here is your chance to think
again…!!!
•Superconducting magnets are used for accelerating the particles in the Large Hadron Collider.
•SQUIDs (superconducting quantum interference devices) are being used in the production of highly sensitive
magnetometers. They are generally used for the detection of land mines.
•Superconducting magnets are also used in Magnetic Resonance Imaging (MRI) machines.
•As we know due to the electrical resistance, there is a power loss while power transmission. So nowadays,
superconducting cables are used in place of ordinary cable lines to avoid power loss.
•Superconductors are also being used for the development of high-intensity Electro Magnetic Impulse (EMP). They
are used to paralyze all the electronic equipment within the range.
•Last but not least, Maglev trains work on the superconducting magnetic levitation phenomenon. Japenese Maglev
train is a real-life example of magnetic levitation.
8. Applications of Superconductors