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Metals and Non-Metals - Part XVI |
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9.
Compounds of metals and alloys Mixture of two or more metals is called an alloy. These mixtures are homogenous and are prepared by heating and bonding the metals together. The resultant alloy has completely different properties from the starting metals. Sometimes to make an alloy, a non-metal is also added. For example for obtaining various grades of steel, carbon is added in varying proportions. Thus an alloy is a uniform mixture of metals and/or metals and non-metals. Some common alloys are steel, brass, and duraluminium. Alloys
of aluminium : Al is a bright metal and conducts heat and electricity well.
But it is not a strong metal. An alloy of Al that retains its good
properties and makes it strong would be ideal for many applications.
Duraluminium, magnalium and Alnico are alloys of Al that are light but
strong. Duraluminium : Duraluminium is also called duralium or duralumin. It is an alloy of Al and Cu. Some traces of other metals such as Mg and Mn are added to enhance the strength of the alloy. The proportion of the metals in duralium Al – 95 %, Cu – 4 %, Mg – 0.5 % and Mg – 0.5 %. You can see that duralium has mostly Al. But duralium is found to be very strong, corrosion resistant. Duralium finds applications in aircraft engines, car engines, pressure cooker, and industrial cauldrons, under sea vessels and ships. Magnalium : This alloy of Al contains Al and Mg. The percentages are Al – 95 % and Mg – 5 %. Magnalium is a very hard alloy and is also light in weight. Magnalium can be machined easily. It finds applications in many instruments and structures. Alnico
: Alnico is an alloy containing
Al, Ni, Co and Fe. It has magnetic properties. It is used to make artificial
magnets useful in many industries. Alloys
of iron : To make use iron’s
good properties and eliminate its rusting, iron has to be alloyed with other
metals. Most important alloy of Fe is steel. Steel
: Steel contains 99.5 % Fe and 0.5 % Carbon. Sometimes carbon content can be
as high as 1.5 %. The different carbon contents gives steel a grade. Steel
is a much harder substance than Fe. Steel is used for making nails, screws,
railway lines, bridges, buildings, etc. The applications of steel is
limitless. Stainless
steel : Steel itself is not very bright to look at. To make it shining and
attractive to look, Ni, Cr is added to steel. Varying proportions of Ni and
Cr give different grades of steel. Stainless steel is shiny, strong and
corrosion resistant. It finds wide applications in making utensils,
equipments, tools, etc. It used extensively in many industries as
containers, etc. Alloys
of copper : Cu is a relatively soft metal and is prone to be oxidized in
air. An oxidized copper surface is dull and unattractive. To overcome these
drawbacks of Cu, it can be alloyed with Sn, Zn and Ni to give brass, bronze
and German silver. Brass : Brass is an alloy of Cu and Zn which generally has 80 % Cu and 20 % Zn. By varying these proportions we can obtain various grades of brass. Brass is stronger and more malleable than Cu. It is golden in colour. Brass is used to make nuts and bolts, tubes, decorative items such as vases, jewellery, lamps, etc. Bronze
: Bronze contains 90 % Cu and 1 % Sn (tin). Bronze is strong and is used to
make coins, medals, statues, decorative items, etc. German
silver : German silver has 60 % Cu, 20 % Zn and 20 % Ni. It has silvery shiny
look, hence the name German silver. It is used for electroplating so that
items look decorative. This also prevents atmospheric corrosion. Besides
the above alloys of Al, Fe and Cu, other common alloys that we encounter in
our day to day life are solder and amalgam. Solder is used for connecting
electronic circuits. It is an alloy that
contains 50 % tin and 50 % lead. Amalgam is an alloy of mercury,
silver, zinc and tin. Amalgam is a very hard substance. It is tasteless and
does not deteriorate with time. It is widely used by dentists filling gaps
in teeth or carries.
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