↪ An alloy is a homogenous mixture of two or more metals or a metal and a non-metal.
↪ It possesses in general the properties of metals as a class and in particular the general properties of the elements of which it is composed but these are not necessarily intermediate.
↪ Alloys may be completely homogenous mixtures or may contain small particles of one phase in the other phase.
↪ Alloys are usually harder than their components but very often less ductile and less malleable.
↪ Thus the hardness of gold and silver is increased by the addition of copper but malleability is considerably decreased.
↪ The melting point of an alloy is always lower than the melting point of the constituent metals.
↪ The chemical properties are altered to a very great extent and an alloy is generally more stable so far as corrosion and solubility in acids is concerned.
↪ Above five thousands alloys have so far been prepared from forty metals and out of these about a hundred are in common use and constant use.
↪ Alloys are broadly classified into two classes:
⇲ Ferrous alloys
⇲ Non-ferrous alloys
↪ Ferrous alloy contains iron as the one of the constituent.
↪ Steel, stainless steel, manganese steel, invar, tungsten steel etc. are some examples of ferrous alloys.
↪ Similarly, brass, bronze, bell metal, duralumin etc. are examples of non-ferrous alloys.
↪ Examples of some common alloys with their exact composition and uses are tabulated below:
|Brass||Cu: 60-80% Zn: 40-20%||For making household utensils|
|Bronze||Cu: 75-90% Sn: 25-10%||For making utensils, statues.|
|Stainless steel||Cr: 12% Ni: 2% and Fe: 86%||For making cycles.|
|Manganese steel||Mn: 12-15% Fe: 88-85%||In making railway tracks.|
|Invar||Ni: 36% Fe: 64%||For making pendulums.|
|Duralumin||Al: 95% Cu: 4% Mg: 0.5% Mn: 0.5%||Used to make bodies of aircraft|
|Type metal||Pb: 82% Sb: 15% Sn: 3%||For making type words.|
|Pewter||Sn: 80% Pb: 20%||For making fuse|
|Bell metal||Cu: 80% Sn: 20%||For making bells.|
|Rose metal||Bi: 50% Pb: 28% Sn: 22%||For making fire protection|