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February 25, 2008

The Aluminum Sources

The aluminum industry, founded in 1854, is the newest of the nonferrous metal industries.

Bauxite, the source of Aluminum.

Most aluminum produced today is made from bauxite. First discovered in 1821 near Les Baux, France (from which its name is derived), bauxite is an ore rich in hydrated aluminum oxides, formed by the weathering of such siliceous aluminum rocks as fieldspars, nepheline, and clays.

Most of the large bauxite deposits are found in tropical and subtropical climates, where heavy rainfall, warm temperature, and good drainage combine to encourage the weathering process. Because bauxite is always found at or near the surface, it is mixed by open pit method.

Alloys: Aluminum to Aluminum Products

Aluminum alloys are generally divided into two basic types, casting alloys and wrought alloys. Aluminum casting alloys most frequently contain silicon, magnesium, copper, zinc, or nickel, alone or in various combinations. Silicon improve the fluidity and cast ability of molten aluminum; copper and zinc harden the alloy and increase its strength; magnesium improve corrosion resistance, strength and machine ability, and nickel improves dimensional stability and high-temperature strength.

Wrought alloys are alloys that have mechanically worked after casting. Working operations include forging, rolling, drawing, and extruding. Alloying elements (magnesium, silicon, copper, and others) usually make pure aluminum stronger and harder but also render. It less ductile and more difficult to fabricate. Working and heat treatment change these alloy's structure, which in turn determines their corrosion resistance and mechanical properties.