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Term Paper on Material Science
Term Paper Contents:
- Term Paper on the Meaning of Material Science
- Term Paper on the Classification of Materials
- Term Paper on the Bases of Properties of Materials
- Term Paper on the Testing of Materials
- Term Paper on the Selection of Materials
- Term Paper on the Manufacturing Processes of Materials
Term Paper # 1. Meaning of Material Science:
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The term ‘Material science’ consists of two words- Materials and science. ‘Materials’ means engineering materials and those are limited to only solid materials. In general the word ‘Science’ defines the knowledge arranged under general truth and principles and it naturally covers today a wide range of subjects but in material science, ‘science’ refers to the physical sciences relating to physics and chemistry.
In material science since we confine out attention to solid materials only so the subject is related to solid-state physics and solid-state chemistry. In general the ‘material science’ refers to that branch of applied science which is concerned with investigating the relationship existing between the structures of materials and their properties and their inter-disciplinary study of materials for practical purposes.
Term Paper # 2. Classification of Materials
:
The engineering materials may be classified as follows:
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1. Metals (e.g., iron, aluminium, copper, zinc, lead etc.).
2. Non-metals (e.g., leather, rubber, plastics, asbestos, carbon etc.).
Metals may be further subdivided as:
(i) Ferrous metals (e.g., cast iron, wrought iron and steel) and alloys (e.g., silicon steel, high speed steel, spring steel etc.)
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(ii) Non-ferrous metals (e.g., copper, aluminium, zinc, lead etc.) and alloys (brass, bronze, duralumin etc.)
The iron group which includes all types of iron and steel are called ferrous metals (ferrous iron), whilst others are specified as non-ferrous.
2. Non-Metals:
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The commonly adopted non-metallic materials are leather, rubber, asbestos and plastics.
Leather – It is used for belt drives and as packing or as washers. It is very flexible and will stand considerable wear under suitable conditions. The modulus of elasticity varies according to load.
Rubber – It is used as packing, belt drive and as an electric insulator. It has a high bulk modulus and must have lateral freedom if used as a packing ring.
Asbestos – It is used for lagging round steam pipes and steam boilers.
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Plastics, is a term applied to a large class or mouldable organic compounds which are sold under different trade names and are being discovered constantly. They are used for bushing, steering wheels, tubes for oil and water, automobile tyres etc. Plastics are divided roughly in two classes, called thermoplastic and thermosetting plastics.
Materials in the former group becomes soft and pliable when heated to moderate temperatures and then hardened when cooled. They will soften every time when heat is applied and reworked as often as desired. Thermosetting plastics soften the first time they are heated, hardened when cooled and cannot be softened by reheating. Plastics can be moulded, cast folded into sheets and extended.
Engineering materials may also be classified as follows:
1. Metals and alloys
2. Ceramics
3. Organic polymers.
1. Metals and Alloys:
Metals are polycrystalline bodies consisting of a great number of fine crystals (10-1 to 10-4 cm size) differently oriented with respect to one another. Depending upon the mode of crystallization, these crystals may be of various irregular shapes, and, in contrast to crystals of regular shape, are called crystallites or grains of the metal.
Metals in the solid state and, to some extent, in the liquid state possess high thermal and electrical conductivity, and a positive temperature coefficient of electrical resistivity. The general resistance of pure metals increases with the temperature.
Many metals display superconductivity; at temperatures near absolute zero, their electrical resistance drops abruptly to extremely low values. Besides, all metals are capable of thermionic emission, i.e., the emission of electrons upon being heated; they are good reflectors of light and lend themselves well to plastic deformation.
Pure metals are of low strength and in many cases, do not possess the required physiochemical and technological properties for some definite purpose. Consequently they are seldom used in engineering. The overwhelming majority of metals used are alloys.
Alloys are produced by melting or sintering two or metals, or metals and a non-metal, together. Alloys possess typical properties inherent in the metallic state, the substance that make up the alloy are called its components. An alloy can consist of two or more components.
Examples of Metals and Alloys:
Steels, copper, aluminium, brasses, bronze, invar, superalloys etc.
These materials are non-metallic solids made of inorganic compounds such as oxides, nitrides, borides, silicides and carbides. They are fabricated by first shaping the powder with or without the application of pressure into a compact which is subsequently subjected to a high temperature treatment, called sintering.
Traditional ceramics were made from crude naturally occurring mixtures of materials having inconsistent purity. These have been used essentially in the manufacture of pottery, porcelain, cement and silicate glasses. New ceramics possess exceptional electrical, magnetic, chemical, structural and thermal properties. Such ceramics are now extensively used in the electronic control devices, computers, nuclear engineering and aerospace fields.
Examples of Ceramics:
MgO, CdS, ZnO, SiC, BaTiQ2, silica, sodalime, glass, concrete, cement, ferrites, garnets, etc.
These materials are derived directly from carbon. They usually consist of carbon chemically combined with hydrogen, oxygen or other non-metallic substances. In many instances their structures are fairly complex.
Common organic materials are- Plastics and Synthetic rubbers. These are termed “polymers” because they are formed by polymerization reaction in which relatively simple molecules are chemically combined into massive long-chain molecules or “three dimensional” structures.
Examples of Organic Materials:
Plastics- PVC, PTFE, polythene; Fibers- terylene, nylon, cotton; Natural and synthetic rubbers, leather, etc.
Examples of Composites:
1. Metals and Alloys and Ceramics:
(i) Steel reinforced concrete
(ii) Dispersion hardened alloys.
2. Metals and Alloys and Organic Polymers:
(i) Vinyl-coated steel
(ii) Whisker-reinforced plastics.
3. Ceramics and Organic Polymers:
(i) Fibre-reinforced plastics
(ii) Carbon-reinforced rubber
Classification of Electrical Engineering Materials:
The electrical engineering materials may be classified into the following four types:
1. Conductors
2. Semiconductors
3. Insulators (or dielectrics)
4. Magnetic materials.
I. Conductors may be defined, as the materials which have free valence electrons in plenty far electric conduction. The commonly used conductors are copper, aluminium, tungsten, iron and steel, lead, nickel, tin etc. In this case the valence and conduction bands overlap. Since there is no physical distinction between the two bands, therefore, a large number of free electrons (conduction) are available.
II. The conductors are used in electric devices, instruments and all kinds of electrical machine windings. They are also employed in manufacturing of cables and wires, for the distribution of electrical energy over long distances and telephone and telegraph circuits.
Semiconductors are solid materials, either non-metallic elements or compounds which allow electrons to pass through them so that they conduct electricity in much the same way as the metals. They occupy an intermediate position between conductors and insulators. In this case, the valence band is almost filled but conduction band is almost empty; they are separated by a small energy gap.
The valence band is completely filled at 0°K and no electron is available for conduction. But as the temperature is increased the width of energy gap decreases and some of the electrons are liberated into the conduction band. In other words the conductivity of semiconductors increases with temperature. Semiconductors usually have high resistivity, negative temperature coefficient of resistance and axe generally hard and brittle.
The main difference between a conductor and semiconductor relates to the dependence of their conductivity on the degree of purity of metals. The conductivity of a good conductor increases with purification whereas that of semiconductor generally decreases with purification.
Examples of elements which are semiconductors are – Boron (B), Carbon (C), Silicon (Si), Germanium (Ge), Phosphorus (P), Arsenic (As), Antinomy (Sb), Sulphur (S), Selenium (Se), Iodine (1). A number of semiconducting compounds in the form of oxides, alloys, sulphides, halides and solenoids are also available.
Semiconductors are used in different fields of electrical engineering, e.g., telecommunication and radio communication, electronics and power engineering. They also render their services as amplifiers, rectifiers, photocells, special sources of electric current etc.
Insulators are those materials in which valence electrons are very tightly bound to their parent atoms thus requiring very large electric field to remove them from attraction of nuclei. They are not governed by electrodynamic phenomena involving the direction flow of number of electric charges by the electrostatic phenomena associated with the presence of an electric field.
They have:
(i) A full valence band,
(ii) An empty conduction band, and
(iii) A large energy gap between them; for conduction to take place, electrons must be given sufficient energy to jump from valence band to conduction band.
At ordinary temperature the probability of electrons from full valence band gaining sufficient energy so as to surmount energy gap and becoming available for conduction in conduction band is slight. But increase in temperature enables electrons to go to conduction band.
In electric circuits and devices the insulators insulate one current-carrying part from another.
The insulating materials may be of three types:
1. Solid:
Mica, micanite, porcelain, asbestos, slate, marble, bakelite, rubber, PVC, polythene, paper, glass, cotton, silk, wood, valcanised fibre, ceramic, aluminium oxide.
2. Liquid:
Natural resin varnishes, bituminous varnishes, phenolic varnishes, shellac varnishes, etc.
3. Gaseous:
Air, nitrogen freon.
4. Magnetic Materials:
A. Magnetic materials are those materials in which a state of magnetisation can be induced.
In accordance with the value of relative permeability the materials may be classified in the following three ways:
I. Ferromagnetic Materials:
The relative permeability of these materials is much greater than unity and is dependent on the field strength. The principal ferromagnetic elements are Iron, cobalt and nickel. Gadolinium however, also comes under this classification. They have high susceptibility,
II. Paramagnetic Materials:
They have relative permeability slightly greater than unity and are magnetised slightly. Aluminium, platinum and oxygen belong to this category.
III. Diamagnetic Materials:
The relative permeability of these materials is slightly less than unity. The examples are bismuth, silver, copper and hydrogen.
B. The magnetic properties of materials arise from the spin of electrons and orbital motion of electrons around the atomic nuclei. In several atoms the opposite spin neutralises one another, but when there is an excess of electrons spinning in one direction, a magnetic field is produced. All substances, except ferromagnetic materials which can form permanent magnets, exhibit magnetic effects only when subjected to an external electromagnetic field.
C. Since magnetic materials strengthen the magnetic field in which they are placed and possess high magnetic permeability, they claim wide field of applications in the form of magnetic waves, magnetic screens and permanent magnets.
I. Biomaterials are employed in components implanted into the human body for replacement of diseased or damaged body parts.
II. These materials must not produce toxic substances and must be compatible with body tissues (i.e., must not cause adverse biological reactions.
III. All of the above materials-metals, ceramics, polymers, composites and semiconductors may be used as biomaterials.
I. Materials that are utilised in high-technology (or high-tech) applications are sometimes “Advanced materials”. By high technology we mean a device or product that operates or functions using relatively intricate and sophisticated principles: Examples include electronic equipment (VCRs, CD players etc.) computers, fibrotic systems, spacecraft, aircraft, and military rocketry.
II. These advanced materials are typically either traditional materials whose properties have been enhanced or newly developed, high-performance materials. Furthermore, they may be of all materials types {e.g., metals, ceramics, polymers) and are normally relatively expensive.
Materials of Future—”Smart Materials”:
I. Smart (or intelligent) materials are a group of new and state-of-the-art materials now being developed that will have a significant influence on many of our technologies. The adjective “smart” implies that these materials are able to sense changes in their environments and then respond to these changes in predetermined manners- traits that are also found in living organisms. In addition, this “smart” concept is being extended to rather sophisticated systems that consist of both smart and traditional materials.
II. Components of a smart material (or system) include some types of sensor (that detects an input signal), and an actuator (that performs a responsive and adaptive function). Actuators may be called upon to change shape, position, frequency, or mechanical characteristics in response to changes in temperature, electric fields, and / or magnetic fields.
Following four types of materials are commonly used for actuators:
(i) Shape Memory Alloys:
These are metals that, after having been deformed, revert back to their original shapes when temperature is changed.
(ii) Piezoelectric Ceramics:
These expand and contract in response to an applied electric field (or voltage); conversely they also generate an electric field when their dimensions are altered.
(iii) Magnetostrictive Materials:
The behaviour of these materials is analogous to that of piezoelectrics, except that they are responsive to magnetic fields.
(iv) Electrorheological / Magnetorheological Fluids:
These are liquids that experience dramatic changes in viscosity upon the application of electric and magnetic fields, respectively.
Materials / devices employed as sensors include the following:
(i) Optical fibers.
(ii) Piezoelectric materials (including some polymers).
(iii) Microelectromechanical devices.
Example:
One type of smart system is used in helicopters to reduce aerodynamic cockpit noise that is created by the rotating rotor blades. Piezoelectric sensors inserted into the blades, monitor blade stresses and deformations; feedback signals from these sensors are fed into a computer-controlled adaptive device, which generates noise-cancelling antinoise.
Nanotechnology and Nanomaterials:
Nanotechnology:
I. The general procedure utilised by scientists to understand the chemistry and physics of materials, until recent times, has been to begin by studying large and complex structures, and then to investigate the fundamental building blocks of these structures that are smaller and simpler. This approach is sometimes termed “top-down” science.
II. However, with the advent of scanning probe microscopes, which permit observation of individual atoms and molecules, it has become possible to manipulate and move atoms and molecules to form new structures, and, thus design new materials that are built from atomic level constituents, (i.e., “materials by design”).
This ability to carefully arrange atoms provides opportunities to develop mechanical, electrical, magnetic and other properties that are not otherwise possible. This is termed as “bottom-up” approach and the study of the properties of these materials is termed “nanotechnology”; the “nano” prefix denotes that the dimensions of these structural entities are on the order of a nanometer (10-9 m) as a rule, less than 100 nanometres (equivalent to approximately 500 atom diameters).
One example of a material of this type is the carbon nanotube.
Nanomaterials:
I. “Nanomaterials” (nanocrystalline materials) are the materials which have grain sizes of the order of a billionth of metre.
II. They entail extremely fascinding and useful properties, which can be used for a variety of structural and non-structural applications.
III. These materials consist of grains, which in turn comprise many atoms. Normally these grains are visible to the naked eye, depending upon their size.
IV. The grains of conventional materials vary in size from 100’s of microns (μm) to millimeters (mm) whereas a nanocrystalline materials has grains on the order of 1-100 nm (1 nm = 10-9 m). A nanometer comprises 10 Å, and hence in one nm, there may be 3 to 5 atoms, depending on the atomic radii.
Characteristics of Nanomaterials:
Following are the characteristics/properties of nanomaterials:
1. Chemically very active.
2. Exceptionally strong, hard and ductile at high temperatures.
3. Wear-resistant.
4. Erosion-resistant.
5. Corrosion-resistant.
6. Much more formable than their conventional, commercially available counterparts.
Methods of Producing Nanomaterials:
Following are be widely known methods of producing nanomaterials:
1. Inert gas condensation.
2. Sol-gel synthesis.
3. Plasma synthesis.
4. Electrodeposition.
5. Mechanical alloying or high-energy ball milling.
Nanocomposites:
A nanocomposite is formed when phase mixing occurs on a nanometer length scale.
I. One successful method to achieve such nanocomposite is the in-situ polymerisation of metal oxides in organic matrices via the sol-gel process. Inorganic components, specially silica have been formed by the hydrolysis and condensation of nanonuclear precursor such as tetraethoxysilane (TEDS) in many polymer systems.
The drawback of this method is that due to the loss of volatile byproducts formed in the hydrolysis/ condensation reaction, it is difficult to control sample shrinkage after moulding.
Another method of synthesis of nanocomposites is direct dispersion of nanoparticles in polymer matrix.
II. Now-a-days technologies are available for synthesis of a wide variety of nanomaterials like silicon whiskers, carbon nanotubes etc.
However, the following factors limit the application of such nano-composites:
(i) High cost involved;
(ii) The difficulty associated with dispersion of such materials, in a polymer matrix;
(iii) Health hazards.
III. A new class of nanocomposite include “Polymer / clay nanocomposites”. These materials are cheap and well known filler for polymer materials. Another nanocomposite included in this category is a nyon-6/ clay nanocomposite, which results in dramatic improvement of properties compared to pristine polymer.
The following are the advantages of nanocomposites:
1. Lower residual stress.
2. Flame retardancy.
3. Decreased thermal expansion coefficients.
4. Increased solvent resistance.
5. Improved mechanical properties.
6. Reduced gas premeabiltiy.
Applications of Nanomaterials:
Nanomaterials can be used for a wide variety of applications; these applications include:
1. Low-cost float-panel displays.
2. High power magnets.
3. Tougher and harder cutting tools.
4. Next-generation computer chips.
5. Longer-lasting satellites.
6. Aerospace components with enhanced performance characteristics.
7. Better and future weapon platforms.
8. Longer-lasting medical implants.
9. Kinetric energy penetrators with enhanced lethality.
10. Phosphors for high-definition TV.
11. Automobiles with great fuel efficiency.
12. Ductile, machinable ceramics.
13. Large electrochromic display devices.
14. Better insulation materials.
Applications of Nanocomposite:
Nanocomposites find applications in the following industries:
1. Electronics
2. Packaging
3. Automotive
4. Aerospace
Term Paper # 3. Bases of Properties of Materials
:
The properties of all materials arise from their structure, i.e., from the manner in which their atoms aggregate into hierarchies of molecular or crystalline order or into disordered amorphous structures.
I. The properties of bulk matter of all kinds depend strongly on the nature and distribution of imperfections, either chemical or architectural, in the main array.
II. Most of the properties observed and exploited in materials are co-operative properties of the aggregate rather than of the constituent atoms.
III. The arrangements of outer electrons of the atoms are of primary importance, and these are strongly modified by the configurations of neighbouring ones.
Table 1.4 shows that the properties of materials are directly related to the structures found within the materials and to the conditions under which the materials are used. It gives the structure-property relationship in metals ceramics and polymers.
Term Paper # 4. Testing of Materials
:
Material are tested for one or more of the following purposes:
(i) To assess numerically the fundamental mechanical properties of ductility, malleability, toughness etc.
(ii) To check chemical composition.
(iii) To determine suitability of a material for a particular application.
(iv) To determine data i.e., force deformation (or stress) values to draw up sets of specifications upon which the engineer can base his design.
(v) To determine the surface or surface defects in raw materials or processed parts.
Tests on materials may be classified as:
1. Non-destructive tests.
2. Destructive tests.
In non-destructive testing a component does not break and so even after being tested it can be used for the purpose for which it was made.
Examples:
Radiography, ultrasonic inspection etc.
In destructive testing the component or specimen either breaks or remains no longer useful for further use.
Examples:
Tensile test, impact test, torsion test etc.
Non-Destructive Tests:
“Non – destructive tests” may be defined as those which in a specific context would not damage the material being examined to an extent such that it is rendered useless for future for which it was originally meant.
Although non-destructive tests do not provide direct measurement of mechanical properties, yet they are extremely useful in revealing defects in components that could impair their performance when put in service. These tests make components more reliable, safe and economical.
The various methods used for non-destructive testing are as follows:
1. X-ray radiography.
2. Gamma radiography.
3. Magnetic particle inspection.
4. Ultrasonic testing.
5. Electrical method.
6. Damping test.
Destructive Tests (Mechanical Tests):
The component or specimen, after being destructively tested, either breaks or remains no longer useful for further use. Examples of destructive or mechanical tests are- tensile test, impact test, torsion test, bend test, fatigue test etc.
Importance of mechanical tests:
A. Structures, machines and products of various kinds are usually subjected to load and deformation. Therefore, the properties of materials under the action of load and deformation so produced under various environments become an important engineering consideration.
The microscopic properties of materials under applied forces or loads are broadly classed as mechanical properties. They are a measure of the strength and lasting characteristic of a material in service and are of great importance particular to the design engineer.
Unfortunately these properties cannot be desired from the structural or bonding considerations alone since most of them are structure-sensitive, are much more affected by crystal imperfections and other factors such as composition, grain size, heat treatment etc.
Therefore, mechanical properties do not depend on them in all situations. A great number of mechanical properties, are, therefore, best evaluated by mechanical testing of the materials like metals and alloys.
B. The following important mechanical tests give valuable information about metals and alloys as given below:
Term Paper # 5. Selection of Materials
:
General considerations for selection of materials are enumerated and described as follows:
1. Mechanical Strength
2. Ductility
3. Design
4. Stability
5. Availability
6. Fabricability
7. Corrosion resistance 8. Cost.
1. Mechanical Strength:
While the primary selection criterion is often strength it may also be toughness, corrosion resistance, electrical conductivity, magnetic characteristics, thermal conductivity, specific gravity, strength-weight ratio or other properties.
Examples:
In household usage with relativity low water pressure, weaker and more expensive copper tubing may actually be a better choice than stronger steel pipe. One major difference lies in installation, since steel pipe comes in sections and is joined by threaded connections with elbows at corner, whereas soft copper can be obtained in coils and can be threaded around corners.
The lower installation cost of copper could overcome its higher material cost. Also since copper has adequate strength, the greater strength of steel is not necessary. Furthermore, in the event of freezing, copper tends to yield instead of burst.
2. Ductility:
Ductility is related to strength. Considerable ductility is generally obtained at a sacrifice of strength. For example – during cold working there is gain in strength and loss in ductility. It may be seen that some ductility is always required, and the more ductility obtainable without great loss in strength, the better. This is often true, but, at the same time, many metals and alloys have ductility and may not need much.
In some cases, brittleness may be an asset, for example, the use of readily replaceable fragile members that are intended to fail first and protect the rest of the system. At the same time appreciable ductility or plasticity is required for fabrication by rolling, drawing, extrusion, and other mechanical working processes.
3. Design:
In selection of materials design is closely related to strength and ductility. It is also quite widely recognised that a large portion or service failures are due to fatigue. Study of fatigue of materials is the joint duty of metallurgical engineering and production departments. There is no definite line between mechanical and metallurgical factors that contribute to fatigue.
There are several cases in which the search for a substitute material led to feasible design modifications which were much more advantageous than a change in alloy composition.
4. Stability:
Stability of material in service is related to:
(i) Temperature,
(ii) Fluctuations in temperature, and
(iii) Length of time at temperature.
In some application exposure to radiation may also be important condition.
Temperature not only directly affects strength and creep, but it can also produce changes in the micro structure of the material.
I. Obviously time is important in determining the extent to which these phenomena occur and, consequently, in the stringency of stability requirements. For example – a rocket motor may be required to operate only briefly, whereas a steam turbine is expected to operate for many years.
II. In several components it is desirable to have characteristics which produce shutting down for repairs. In other components, especially those subject to mechanical wear, replacement at regular intervals is anticipated, and the part is made to be readily detachable.
For example, in a nuclear reactor the problem of stability is far less drastic in a reactor that is to be operated for some months to test design feasibility than it is in a central power station reactor that is operated for a long period (several years).
III. Other aspect of stability is the question of seriousness of failure. For example, a leak in tea kettle may have only nuisance value but a leak in a vessel containing an inflammable or radioactive fluid is entirely different matter.
It may be noted that any design for long time operation may be an extrapolated or educated guess, since the best available data are often for times much shorter than anticipated in long term operation.
5. Availability:
If a material is not available, irrespective of the merits of a material, it is not reasonable to base a design on it. This question involves availability of material at an appropriate cost and availability in the desired form. Obviously a material obtainable only in castings cannot be used in applications requiring tubing wirecloth etc.
6. Fabricability:
There is a closer relation between fabricability and availability. A material may not be commercially available in the desired state of fabrication, but it may be possible, with relatively small-scale development type operations, to produce in it the desired from.
This, of course, entails considerable expense, but circumstances may justify the cost. The development of production and fabrication procedures of beryllium and zirconium for nuclear reactor use provides two specific examples.
7. Corrosion Resistance:
A material may or may not be regarded as corrosion resistant depending on the particular service requirement.
The criteria for corrosion resistance can be considered in three degrees:
(i) Avoiding contamination (e.g., food products).
(ii) Preventing leaks of closed containers or conduits.
(iii) Maintaining strength and other properties during corrosion attack.
The possibility of corrosion should always be considered in any design. We may obtain acceptable resistance to corrosive attack under a particular set of conditions only to discover that some change in condition gives a new or modified problem.
8. Cost:
The initial cost of a price of equipment involves raw material, fabrication and installation costs, in the form of replacements due to failure, shut down expenses while undergoing repair or replacement, and the economic damage of production losses.
No industry is immune to savings through more effective application of materials.
At least three major approaches may be taken to reduce cost through better use:
(i) Reconsider the material selected.
(ii) Reconsider the form of material.
(iii) Redesign to take full advantage of properties.
In several situations definite savings can be realized by the simple expedient of changing from one material to another without substantial change in form or processing procedure.
Ample savings can often be realized by changing fabrication procedure or the form in which material is used.
Term Paper # 6. Manufacturing Processes
of Materials:
The materials which are covered under the scope of material science are available either from nature or industry. However, these materials cannot be used in raw form (whatever the source may be) for useful purposes. They have to be shaped and formed into articles through different manufacturing processes.
Besides there are some processes which improves material properties. In some processes materials are changed into their primary forms for some selected parts. In some cases the materials are suitably finished for commercial uses. In other cases, neither surface finish nor the dimensions are satisfactory for the final product, and further work is necessary. However, the selection of the best process for a given product requires knowledge of all possible production methods.
Some important manufacturing processes are listed below:
(i) Drawing
(ii) Squeezing
(iii) Bending
(iv) Shearing
(v) Hobbing
(vi) Shot peening
(vii) Cold extruding.
(i) Rolling
(ii) Forging
(iii) Pipe welding
(iv) Hot piercing
(v) Hot drawing
(vi) Hot spinning
(vii) Hot extruding
(i) Hand forging
(ii) Machine forging.
(i) Sand casting
(ii) Shell moulding
(iii) Permanent mould casting
(iv) Die casting
(v) Centrifugal casting
(vi) Investment casting
(vii) Plaster casting