There is process through which two or more metals are combines in a way that a new metal forms is called alloy development. This new metal is called alloy. About 3500 BC, this process of alloy development was discovered by combining copper and tin. Through this process a superior metal could be made. Bronze is an alloy that represents a major technological shit that began the bronze-age. Metals including aluminum, chromium, copper, iron, nickel, magnesium, titanium and zinc are most often used as alloys.
Steel and cast iron are the alloys that show the iron-carbon system. These days much effort has been placed to understand this iron-carbon system. Plain carbon steels that contain essentially only carbon as an alloying element are used in high strength and low cost applications where weight and corrosion are not a problem. Cast iron and ductile iron are also a part of iron-carbon system.
Alloy of stainless steel or it can be called galvanized steel are used where resistance to corrosion is very important. Where strength and lightness is required alloys of aluminium and magnesium are used. For the sake of non-magnetic and highly corrosive environments copper-nickle alloys can be used.
Unlike pure metals, most of the alloys do not have a single melting point but its range is in the phase where material is a mixture of solid and liquid. The temperature of the alloy at which it is to be melt is called solidus and the temperature at which melting is just complete is called liquidus. However, for most of the alloys here is specific proportion of constituents which gives the alloy a characteristic of unique melting point.
There are two mechanisms through which an alloy is formed one is atom exchange and the other is interstitial mechanism. During the mixing the relative size of each element plays a primary role in determining which mechanism will occur. Usually the mechanism of atom exchange method occurs when the atoms are of relatively similar size. It is also called the substitutional alloy because atoms composing the metallic crystals are substituted with the atoms of the other constituent for example, alloys of bronze and brass. When the size of the elements differs from each other usually interstitial mechanism occurs in the formation of the alloy. The atom with the smaller size is trapped in the spaces between the atoms in the crystal matrix which are called interstices.