- Definition of Engineering Materials: Engineering materials are substances used to construct machines and structures, classified into metals and non-metals.
- Classification of Engineering Materials: The classification includes metals, non-metals, ceramics, and organic materials.
- Characteristics of Metals: Metals conduct heat and electricity well and are usually solid at room temperature.
- Ferrous and Non-Ferrous Metals: Ferrous metals contain iron and have high permeability, while non-ferrous metals do not contain iron and have low permeability.
- Other Types of Engineering Materials: Ceramics and organic materials are also important, with ceramics being non-metallic and organic materials containing carbon.
Basic Classification of Engineering Materials
A basic chemical classification divides Engineering Materials into two broad categories:
- Metals
- Non-Metals
Metals
Metals usually have a crystalline atomic structure, although metallic glasses are amorphous. Most are solid at room temperature, while mercury is liquid. Metals generally conduct heat and have higher electrical conductivity than insulating materials. Many pure metals have resistance that rises with temperature. Examples include silver, copper, gold, aluminum, iron, zinc, lead and tin.
Metals are also grouped by whether iron is the main constituent:
- Ferrous Metals –
Ferrous metals are iron-based metals and alloys. Their magnetic permeability varies by composition and heat treatment, so only suitable soft-magnetic grades are used for machine cores. Examples include cast iron, wrought iron, carbon steel, silicon steel, high-speed steel and spring steel. - Non-Ferrous Metals –
Non-ferrous metals do not use iron as the main constituent. They cannot all be assigned one magnetic permeability. Examples include silver, copper, gold and aluminum.
Non-Metals
Non-Metal materials include elements and compounds with crystalline or amorphous structures. At room temperature they may be solid, liquid or gas.
Many are poor conductors, but graphite and other carbon forms show that this is not a universal rule.
Engineering examples include plastics, rubber, leather and ceramics. Asbestos appears in older products but is a regulated carcinogenic hazard and should not be treated as a current material recommendation.
Electrical insulation uses materials with sufficiently high resistivity, dielectric strength and suitable thermal properties for the application.
Difference between Metals and Non Metals
| Sl. 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) |
Other classification of engineering materials:
A more useful engineering classification groups materials by structure and properties:
- Metals and Alloys
- Ceramic Materials
- Organic Materials
Metals and Alloys
Metals are usually crystalline solids with grains of different orientations. Mercury is a familiar metal that remains liquid at room temperature, and metallic glasses are solid amorphous alloys.
Pure metals and alloys span a wide range of strength. Alloying is used to adjust strength, corrosion resistance, conductivity and other properties for a particular service.
Alloys contain a metal and one or more other elements. Their mechanical strength and temperature coefficient of resistance depend on composition and processing.
Examples include steels, brass, bronze, gunmetal, Invar and superalloys.
Ceramic Materials
Ceramic materials are inorganic, non-metallic solids such as oxides, nitrides, silicates and carbides. Their electrical, magnetic, chemical and thermal properties vary widely, so the selected grade must match the service conditions.
Examples include silica, glass, cement, concrete, garnet, MgO, CdS, ZnO and SiC.
Organic Materials
In this classification, organic materials are carbon-based materials such as polymers. Carbon is bonded with hydrogen, oxygen or other elements to form molecular chains and networks.
Examples include plastics, PVC and synthetic rubbers.
