The first materials used in old ages were wood and stone, but later metals became much greater importance. Copper and gold were the first metals discovered by man. Another breakthrough in developing materials was the discovery of iron ore and creating iron. Iron is extremely strong compared to wood and copper and it is still the most widely used metal today.

The main advantage of metals and especially their alloys is their toughness and strength. The properties of metals can be further improved by the use of heat. By heating and cooling the metal changes its qualities, e.g. it could become tougher and more brittle. Metals are good conductors of both electricity and heat. Unfortunatelly, some of them oxidize or corrode relatively easily. Examples of metals include iron, nickel, lead, zinc, zin, aluminium, copper, gold or silver. Iron metal has been used since ancient times, though lower-melting copper alloys were used first in history. Pure iron is soft (softer than aluminium), but is unobtainable by smelting. The material is significantly hardened and strengthened by impurities from the smelting process, such as carbon. A certain proportion of carbon (between 0.2% and 2.1%) produces steel, which may be up to 1000 times harder than pure iron.

Steel product – rail

An alloy is a mixture of two or more elements in solid solution in which the major component is a metal. Most pure metals are either too soft, brittle or chemically reactive for practical use. The aim of making alloys is generally to make them less brittle, harder, resistant to corrosion, or have a more desirable colour and luster.

Of all the metallic alloys in use today, the alloys of iron (steel, stainless steel, cast iron, tool steel, alloy steel) make up the largest proportion both by quantity and commercial value. Iron alloyed with various proportions of carbon gives low, mid and high carbon steels, with increasing carbon levels reducing ductility and toughness. The addition of silicon will produce cast irons, while the addition of chromium, nickel and molybdenum to carbon steels (more than 10%) results in stainless steels. Other significant metallic alloys are those of aluminium, titanium, copper and magnesium. Copper alloys have been known since prehistory - bronze gave the Bronze Age its name — and have many applications today, most importantly in electrical wiring as they have high resistance against corrosion. Bronze contains as principal component copper and tin is a significant addition, in brass zink is used instead. The alloys of aluminium, titanium and magnesium are valued for their high strength-to-weight ratios; magnesium can also provide electromagnetic shielding. These materials are ideal for situations where the high strength-to-weight ratio is more important than material costs, such as in aerospace and some automotive applications. Alloys specially designed for highly demanding applications, such as jet engines, may contain more than ten elements.