Wednesday , 23 October 2019
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Alloys

Kedar Kulkarni

“Hello students we learnt about metals and their properties last year. We also saw how pure metals are obtained from the ores from mines by using separation techniques. We also have studied the different states that are rich in different types of ores. Each of the metal has its own characteristics. We have also seen that metals like iron, copper and aluminum are more widely used in our day-to-day life. We have also seen that metals like gold and silver are very costly. Do you remember when we studied the various properties of metals like ductility, malleability, conductivity or resistance, strength, hardness, melting points, etc?” said the teacher.

“Yes teacher, copper is ductile and very conductive. Hence they are used in making electrical cables,” said Meers.

“Aluminum is also malleable and light in weight and is used in making the body of airplanes,” added Raju.

“Teacher, iron is used in making machines, automobiles, construction, etc,” said Rahul.

“Tin is used in coating,” said Anthony.

“And lead is used in making soldering wires,” said Mohan.

“All of you are right but remember that except for copper and aluminum which are highly conductive, it’s their ductility that allows them to be used in making cables. Many metals cannot be used in applications in their pure forms as they do not have the desirable properties in their pure form: iron in its purest form is reactive and will rust very easily, aluminum is light and soft, copper cannot be used in making cooking vessels although people use it to store drinking water for health benefits,” she said.

She continued, “A small amount of other metals or elements are added to produce different properties so as to make them more suitable for certain applications. Such combinations are known as alloys. The proportions in which the alloying elements are added depend on the properties desired in the final alloy. We know the different types of steel such as stainless steel, high speed steel, and more. When carbon is added to iron it converts into steel. It reduces ductility but improves tensile (relating to tension) strength and wear resistance. The addition of chromium improves corrosion resistance and it finds application in machinery in the food industry, surgical instruments and implants, catering items, piping in corrosive environments and the automobile industry. By adding cobalt and tungsten, the hardness of steel is improved and finds application in industrial cutting tools. Other alloying elements added to iron are sulphur, silicon, titanium, molybdenum, etc. Whereas tin is added to copper to get bronze which has low friction with other metals and finds application in bearings, in musical instrument strings, electrical contacts, etc. Zinc added to copper makes brass which can be cast easily and has high resistance to corrosion and finds use in water taps, valves in pipelines and also making locks. With modern metallurgical techniques there are a large number of alloys made for specific applications.”s

(Writer is a mechanical engineer and runs a hands-on science activity centre

at Margao)

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