04-06-2013, 02:59 PM
Metallurgy and its Importance
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Significance
It is almost impossible to imagine any object used in everyday life that does not require metal for its fabrication. Tools and machines, from domestic usage to jet engines, from small watches to big space crafts, all objects are made chiefly of metals. Metallurgy tells us how to extract metals? How to refine it and how to make useful products from it?
In production engineering, metallurgy is concerned with the production of metallic components for use in consumer or engineering products. This involves the production of alloys, the shaping, the heat treatment and the surface treatment of the product. The task of the metallurgist is to achieve balance between material properties such as cost, weight, strength, toughness, hardness, corrosion and fatigue resistance, and performance in temperature extremes. To achieve this goal, the operating environment must be carefully considered because:
• In a saltwater environment, ferrous metals and some aluminium alloys corrode quickly;
• Metals exposed to cold or cryogenic conditions may endure a ductile to brittle transition and lose their toughness, becoming more brittle and prone to cracking.
• Metals under continual cyclic loading can suffer from metal fatigue.
• Metals under constant stress at elevated temperatures can creep.
Metallurgists also study the microscopic and macroscopic properties using metallography. In metallography, an alloy of interest is ground flat and polished to a mirror finish. The sample can then be etched to reveal the microstructure and macrostructure of the metal. The sample is then examined in an optical or electron microscope, and the image contrast provides details on the composition, mechanical properties, and processing history.
Crystallography, often using diffraction of x-rays or electrons, is another valuable tool available to the modern metallurgist. Crystallography allows identification of unknown materials and reveals the crystal structure of the sample.
Role of Materials /Metallurgical Engineers in an Industry
The principal goals of a materials scientists and metallurgical engineers are to:
(1) Make existing materials better and
(2) Invent or discover new phenomena, materials, devices, and applications.
Breakthroughs in the materials science and engineering field are applied to many other fields of study such as biomedical engineering, physics, chemistry, environmental engineering, and information technology.
Tetrahedron showed here which depicts the heart and soul of the material / metallurgical engineers.
Factor Affecting the Behavior of the Materials
Materials are affected due to:
Alloy contents such as addition of W, Cr, etc improve hardness and strength of materials.
Fine grain size materials exibit higher strengths and viceversa
Crystal’s imperfections such as dislocations reduce the strength of the materials.
Excessive cold working produces strain-hardening and the material may crack.
Manufacturing defects such as cracks, blowholes, etc, reduce the strentgth of the materials.
Polymers:-
• A polymer has a repeating structure, usually based on a carbon backbone (organic compounds). The repeating structure results in large chainlike molecules.
• Polymers are useful because they are lightweight, are corrosion resistant, are easy to process at low temperatures, and are generally inexpensive.
• One of the distinct properties of polymers is that they are poor conductors of electricity and heat, which makes them good insulators.
• PVC (polyvinyl chloride), PET (polyethylenetetraphathlate) and PE (polyethylene) are examples of this class of materials.
Composites:-
• Composite materials are mixtures of two or more materials. A selected filler or reinforcing material and a compatible resin binder (matrix)
• By combining different materials in certain proportion and ways, it is possible to obtain new materials, having properties, which are not possessed by any of the individual constituent materials.
• Many tennis rackets and racing bicycles, are now fabricated from a carbon fiber-epoxy composite that is strong, light, and moderately expensive
• A composite material of ceramic and metal is known as cermet.
• Examples of composites are glass, fiber reinforced plastics, carbon fiber-reinforced rubber, steel-reinforced concrete, etc.
Semiconductors:-
• Semiconductors or electronic materials are not a major type of material by volume but are an extremely important type of material for advanced engineering technology. The most important material is pure silicon.
• Other useful materials are germanium as well as a series of covalently bonded compounds including GaAs, CdTe, and InP.
• Semiconductors are widely used in devices like transistors, rectifiers, photoelectric cells etc. &
• “Microelectronic devices” have made possible such new products as communication satellites, advanced computers, calculators, digital watches, etc.