Alloys are metallic materials consisting of two or more elements combined in such a way that they cannot be readily separated by physical means. More than 90% of metals used are in the form of alloys. They represent an enormous family of engineering materials that provide useful properties to a wide range of products.

The physical and chemical properties of an alloy can be modified by heat treatment and mechanical working. In most cases, the alloy is chemically more stable than the component elements, so that alloys are designed for specific resistance to actions such as corrosion, wear, fatigue and temperature. Other alloys are made to impart magnetic or electrical properties, strength, formability, etc.