Alloys
An alloy is a mixture of metals, or a mixture of a metal and another substance. Bronze is an alloy of copper and tin. Steel is an alloy of iron and carbon. Stainless Steel is an alloy of steel, nickel and chromium. One familiar alloy is silver combined with the liquid metal mercury, which forms the amalgam of tooth fillings. Titanium-Steel alloys are used for their lightness and strength in planes and spacecrafts. Nickel-cobalt ''super alloys'' are used in jet-engine turbine blades to withstand temperatures of over 1,000องศา. At the other end of the scale, alloys of metals such as lead. Bismuth and cadmium melt at temperatures as low as 50อาศา and used in fire alarms.
Aluminium.
This extremely light metal is also very abundant-it makes up one-twelfth of the Earth's crust. Its ores are mainly bauxitee in which aluminium is combined with oxygen, sand, titanium and other substances. The bauxite is first refined into aluminium, a purer form of aluminium oxide, by the Bayer process. The alumina is then separted into aluminium and oxygen by electrolysis. This is done at almost 1,000 องศา in a bath of molten.