Classification of Engineering Materials

Classification of Engineering Materials

Basically Engineering Materials Can be classified into two categories-

1.   Metals

2.   Non-Metals

Metals

Metals are polycrystalline bodies which are having 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. All metals are having high thermal and electrical conductivity.  All metals are having positive temperature coefficient of resistance. Means resistance of metals increase with increase of temperature.
Examples of metals – Silver, Copper, Gold, Aluminum, Iron, Zinc, Lead, Tin etc.
Metals can be further divided into two groups-

1.   Ferrous Metals – All ferrous metals are having iron as common element. All ferrous materials are having very high permeability which makes these materials suitable for construction of core of electrical machines. Examples: Cast Iron, Wrought Iron, Steel, Silicon Steel, High Speed Steel, Spring Steel etc.

 

2.   Non-Ferrous Metals- All non-ferrous metals are having very low permeability. Example: Silver, Copper, Gold, Aluminum etc.

Non-Metals

Non-Metal materials are non-crystalline in nature. These exists in amorphic or mesomorphic forms. These are in both solid & gases forms at normal temperature.
Normally all non-metals are bad conductor of heat and electricity. 
Examples: Plastics, Rubber, Leathers, Asbestos etc.
As these non-metals are having very high resistivity which makes them suitable for insulation purpose in electrical machines.

Difference between Metals and Non Metals

Sl. No.

Property

Metals

Non-Metals

1.

Structure

All metals are having crystalline structure

All Non-metals are havingamorphic & mesomorphic structure

2.

State

Generally metals are slid 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 with in 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)

Other classification of engineering materials:

Engineering materials can also be classified as below-

1.   Metals and Alloys

2.   Ceramic Materials

3.   Organic Materials

Metals and Alloys

Metals are polycrystalline bodies which are have 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 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, Brass, Bronze, Gunmetal, Invar. Super Alloys etc.

Ceramic Materials

Ceramic materials are non-metallic solids. These are made of inorganic compounds such as Oxides, Nitrides, Silicides and Carbides. Ceramic materials possess exceptional Structural, Electrical, Magnetic, Chemical & Thermal properties. These ceramic materials are now extensively used in different engineering fields. 
Examples: Silica, glass, cement, concrete, garnet, Mgo, Cds, Zno, SiC etc.

Organic Materials

All organic material 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.