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Alloy and Amalgam


↪ 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:

AlloyComposition                                Uses
BrassCu: 60-80% Zn: 40-20%For making household utensils
BronzeCu: 75-90% Sn: 25-10%For making utensils, statues.
Stainless steelCr: 12% Ni: 2% and Fe: 86%For making cycles.
Manganese steelMn: 12-15% Fe: 88-85%In making railway tracks.
InvarNi: 36% Fe: 64%For making pendulums.
DuraluminAl: 95% Cu: 4% Mg: 0.5% Mn: 0.5%Used to make bodies of aircraft
Type metalPb: 82% Sb: 15% Sn: 3%
For making type words.
PewterSn: 80% Pb: 20%For making fuse
Bell metalCu: 80% Sn: 20%For making bells.
Rose metalBi: 50% Pb: 28% Sn: 22%For making fire protection


↪ An alloy of mercury with one or more other metals is known as alloy.
↪ Amalgams may be liquid or solid.
↪ For example, Sodium amalgam, Zinc amalgam, etc.