SCOPE OF MATERIAL TECHNOLOGY

1.0 SCOPE OF MATERIAL TECHNOLOGY

“Material science” or “Science of Materials” as is sometimes called needs a clear idea of what it means to one who is just beginning to learn to know the subject. The term material science is a combination of two popular words used in engineering- Material and Science. The meaning of these words when integrated together therefore gives an insight to the subject.

1. Historical Perspective: Role of Engineering Material: -

The material science refers to that branch of applied science concerned with investigating the relationship between the structure of materials and their properties, and it concerns with the interdisciplinary study of materials for entirely practical purposes.

A wide range of materials is available today and proper selection has to be made to suit the requirements. The selection of a material for a particular application involves consideration of factors like service requirements (strength, the manner in which load is applied- steady, fluctuating, sudden, wear, corrosion resistance, electrical properties, etc), manufacturing requirements (ease of machining, finish desired, fabrication techniques to be adopted, casting, molding etc), method of forming- hot or cold, method of joining various assemblies, need of heat treatment to achieve or restore properties, cost of raw material. Usually two or three possible solutions in selection of a material will arise, and the final decision should be based on the preference and experience of the engineer and the user. Flow diagram is given below.

CLASSES OF ENGINEERING MATERIALS

After defining the limits of materials that come within the scope of material science, may be classified in the three broad groups according to their mode of occurrence.

1. Metals and alloys
2. Ceramics and
3. Organic Polymers

A metal is an elemental substance whilst an alloy is formed when two or more relatively pure metals are melted together to form a new metal, having properties quite different from those of the two metals used in its manufacture.

Ceramics are materials consisting of phases. A phase is a physically separable and chemically homogeneous constituent of a material. These are themselves compounds of metallic and non-metallic elements.  All metallic compounds, rocks, minerals, glass, glass-fiber, abrasive and all fired clay are ceramics.

Organic materials are those materials derived directly from carbon. They usually consists of carbon chemically combined with hydrogen, oxygen or other non-metallic substances, and their structures are, in many instances fairly complex. Termed polymers because they are formed by polymerization reaction in which relatively simple molecules are chemically combined in to massive long chain molecules or three-dimensional structures.

Some important grouping of materials Group of materials	Common examples of engineering Use
1. Metals and alloys	Steels, aluminium, copper, brass, bronze, super alloys, etc.
2. Ceramics	MgO, Cds, ZnO, SiC, silica, concrete, etc.
3. Organic Polymers	Plastics, Fibers, Natural and synthetic rubbers, leather etc.

Engineering requirements of Materials

Some of the most important properties of materials are:

Mechanical: Strength, stiffness, ductility, elasticity, plasticity, toughness, brittleness, hardness, and malleability.

Electrical: Conductivity, receptivity and dielectric strength.
Magnetic: Permeability, coercive force etc.
Thermal: Specific heat, thermal expansion, conductivity etc.
Chemical: Corrosion resistance, acidity, alkalinity, composition etc
Physical: Density, porosity, structures

2. Classification of Engineering Material

Different types of ferrous metals

The Latin word of iron is ferrum. So metals, which contain iron, are all classified as ferrous metals. The ferrous metals used in Engineering are classified under the following groups.

1. Pig Iron
2. Cast Iron
3. Wrought Iron
4. Carbon steel
5. Alloy steel

3. Materials applicable to Metal Working:

Different metals used in metalworking.

Ferrous metals: -

Ferrous metals and alloys are widely used because of the developments of a technology that has produced thousands of different alloys and grades that provide a wide range of properties not found in any other family of materials.

Ferrous metals can be classified as

1. Pig Iron
2. Wrought iron
3. Cast Iron

a. Grey Cast Iron

b. White Cast Iron

c. Malleable Cast Iron

d. Chilled Cast Iron

e. Alloy Cast Iron

f. Mechanite Cast Iron

4. Steels

a. Plain carbon steel - [Low carbon steel, Medium carbon steel, High carbon steel ]

b. Alloy steel - [ Low alloy steel, High alloy steel ]

Pig Iron: - It is raw material for all iron and steel products. Pig iron is of great importance in the foundry and in steel making process. All iron and steel products are derived originally from pig iron. This is the raw material obtained from the chemical reduction of iron ore in a Blast furnace.

Wrought Iron: - It is the mechanical mixture of very pure iron and a silicate slag. It is used in building construction, industrial purposes, etc. It is highly refined iron with a small amount of slag, forged out into fibers. The slag characteristic of wrought iron is useful in black smithing operations and gives the material its peculiar fibrous fracture. Also the presence of slag produces a structure, which diminishes the effect of fatigue caused by shock and vibration.

Cast Iron

Cast Iron is pig iron remelted and refined in a cupola or other form of remelting furnace and poured into suitable moulds of required shape. The varieties of cast iron in common use is

1. Grey Cast Iron

2. White Cast Iron

3. Malleable Cast Iron

4. Ductile Cast Iron

5. Chilled Cast Iron

6. Alloy Cast Iron

7. Mechanite Cast Iron

Grey Cast Iron: - It is an alloy of carbon silicon with iron. It is used for machine tool structures, manhole covers, ingot moulds, etc.

White cast iron: - White cast iron has almost all its carbon chemically combined with iron as iron carbide (Fe3C). It is used for producing malleable iron.

Malleable cast iron: - It is obtained from white cast iron through controlled heat conversion process. This is used for making gear case, automobile crankshaft etc.

Ductile Cast Iron: - it is also called as spheroidal graphite cast iron. It consists of graphite in the form of round particles.

Steel :- Steel is fundamentally an alloy of Iron and carbon, with the carbon content varying up to 1.5%. The carbon is distributed throughout the mass of the metal not as elemental or free carbon but as compound (chemical combination) with iron.

Plain Carbon Steels: - This is an alloy of iron and carbon and it is malleable in nature.

Alloy steels: - This steel contains one or more alloying elements other than carbon.

Non-ferrous metals: - These are all metals that are not iron based. The common non-ferrous metals are copper, aluminium, lead, magnesium, nickel, tin, and zinc and their alloys.

Copper and its alloys: - Copper has excellent resistance to corrosion, non-magnetic properties etc. Their alloys can be used for casting intricate shapes.

Aluminium and its alloys: - This has lightweight and its alloys are used for producing drums, pipes, heat exchangers etc.

Magnesium and its alloys: - Magnesium is not sufficiently strong, so it is not use in its purest form. Its alloys are used for producing material handling equipments, foundry equipment etc.

Tin: - It is soft and it is used in cold work such as extrusion, rolling etc.

Zinc: - It has resistance to corrosion and high thermal conductivity. It is used for shells for dry batteries etc.

Nickel: - It is used in incandescent lamp industry, and in chemical industries for producing evaporator’s etc.