What are alloys?

          An alloy is an intimate mixture of two or more substances, at least one of which is a metal. The mixture is usually more useful than each ingredient on its own. Almost all alloys are made by mixing constituent elements in the required proportions in the molten state. Man has known a few alloys like brass and bronze since ancient times. Brass is an alloy of copper and zinc while bronze is an alloy of copper and tin.

          Most metals in their pure form are often too soft to be used for practical purposes. Their strength, ductility, hardness, melting point and colour can be improved by mixing one or more metals. For example, pure aluminium is light and weak but when copper and magnesium are added to it, its alloy becomes stronger. Copper and tin are soft and weak but when mixed together they become harder. Brass, a mixture of copper and zinc, is another strong and useful alloy. Mixture of lead and tin is used for soldering purposes. Alloys have more corrosion resistance and better casting properties than metals. 

          Today, the most important alloys are the alloys of steel. They are used for making different machine parts. Copper-nickel, bronze and aluminium alloys are used in minting coins, shipping and airplane industries. Lead alloys are used in the making of electrodes of storage batteries. Zinc alloys are used in the making of automobiles. Nickel-silver, an alloy of copper, nickel and zinc, is best known for its use in domestic cutlery. Expensive alloys of platinum, gold and silver are used in jewelry. Stainless steel, aluminium alloys, Nimonic alloys are 20th century alloys. Super alloys of tungsten and molybdenum are the development of recent years which have proved very useful in rocketry. Thus we see that alloys are very useful to us.