Published by Australian Academy of Science
Glossary | Making light of metals

alloy. A substance made of two or more metals, or a metal and one or more non-metals, that has mostly metallic properties. Alloys are often created to improve the properties of metals such as strength, resistance to corrosion and hardness. For example, steel is an alloy of iron with up to two per cent carbon and often small amounts of other elements. The properties of steel such as strength, malleability and machinability can be changed by adjusting the amounts of its component elements.

alumina. (aluminium oxide). A compound that occurs naturally and can also be produced from the mineral ore bauxite. Aluminium is produced from alumina via electrolysis.

bauxite. A naturally occurring rock with one or more minerals containing aluminium, oxygen and hydrogen. Globally, most bauxite is used to produce alumina, which is used to produce aluminium. For more information see Aluminium (Geoscience Australia).

cast. To pour a metal (or other material) as a liquid into a mould and allow it to solidify into the shape of the mould. For example, cast iron is often used to make manhole covers.

desalination. The removal of salts from water or soil. Desalination can be used to produce fresh water from sea water. For more information see Desalination (Ask an Expert, Australian Broadcasting Corporation).

ductile. Describes the ability of a material (mostly metals) to be drawn out into a wire without cracking or breaking.

electron. A negatively charged particle that is a constituent of an atom.

electrolysis. Chemical reaction brought about by passing electricity through a solution. Electrolysis is often used in industry to separate out the elements in a substance. The following equation illustrates the process of the electrolysis of water (H₂O).

fly ash. Fine particles of ash produced from the burning of fuels, particularly from power stations.

ion. A positively or negatively charged atom or group of atoms.

Kroll process. The process used to produce titanium (or zirconium) from its ore. The ore is converted first to titanium tetrachloride, and then reduced to produce titanium, usually by reacting it with magnesium. For more information see Titanium (Chemguide, UK)

lustre. The way that light interacts with the surface of a material, its sheen or gloss. Lustre is used to describe minerals eg, metallic lustre, greasy lustre.

magnesite. A mineral ore containing magnesium carbonate and used as a source of magnesium. For more information see Magnesium (Geoscience Australia).

malleable. The ability of metals to be shaped or hammered when cold without breaking. For example, aluminium can be hammered or rolled into sheets (aluminium foil).

ore. A naturally occurring mineral, or group of minerals, that is mined to extract materials such as metals. For example, bauxite ore is mined for the production of aluminium.

powder technology. (powder metallurgy). The production of metal as a powder which is then used to form shaped products. The powdered metal is usually placed in a mould, compacted and heated (sintered) to make the powder particles bond together.

quenching. A technique used by blacksmiths and in the metal processing industry which involves rapid cooling of a metal by immersing it into water or oil to achieve certain hardness or mechanical properties.

rutile. A mineral from which titanium is extracted. Rutile is black, yellow or brownish-red in colour and contains titanium dioxide.

smelter. An industrial plant that uses a high-temperature process to separate a pure metal, usually in a molten form, from an ore.

tempering. A heat treatment used by blacksmiths and in the metal processing industry that is applied to iron and steel. Tempering increases the toughness of the metal to improve performance in applications such as horseshoes and impact tools, for example, hammers.

valence (valency). The number of electrons in the outermost electron shell of an atom. These are the electrons involved in chemical reactions.