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.
3.
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.
6.
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
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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.
33.
34. R
R = V/I or,
R = ρ(L/A)
V = Voltage, I = Current, ρ =
Resistivity
