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.
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. Thus we see that alloys are very useful to us.