Common Nonferrous Metals

Abstract

Aluminum (aluminium in the UK) [7429-90-51 with the chemical symbol Al, the atomic number 13, and the relative atomic mass 26.981538(5) is the second element of the group IIIA(13) of Mendeleev’s periodic chart. Pure aluminum is a light (2698 kg.m−3), silvery white metal with a low melting point (660.3°C) and a boiling point approximately 2519°C. From a mechanical point of view, pure aluminum metal is ductile, malleable, and exhibits good formability, but the mechanical strength of the metal can be largely improved by either (i) cold working, or (ii) adding alloying elements such as manganese, silicon, copper, magnesium, or zinc. At low temperatures, aluminum is stronger than at room temperature and is no less ductile. Actually, the mechanical strength of aluminum increases under very cold temperatures, making it especially useful for cryogenic applications and in the extreme cold of outer space, as well as for aircraft and for construction in high latitudes. Hence, aluminum is an attractive structural material for applications requiring high strength-to-weight ratios such as aerospace, high-rise construction, and automotive design. Due to the high thermal conductivity (237 W.m.−1.K−1) of aluminum, this element and its alloys provide better heat transfer capabilities than other common metals. This makes aluminum ideal for applications requiring heat exchangers, especially because extrusion, as a metal-forming process, is well-suited to produce shapes that make optimal use of thermal conduction properties. In addition, aluminum is nonsparking, and hence it is appropriate for applications involving explosive materials or taking place in highly flammable environments. On the other hand, aluminum exhibits a low electrical resistivity (2.6548 μΩ.cm), i.e. 60% IACS, and is paramagnetic. Hence aluminum does not acquire a magnetic charge, and it is useful for high-voltage applications, as well as for electronics, especially where magnetic field interference occurs. The high reflective index of polished aluminum can be used to shield products or areas from light, radio waves, or infrared radiation. Aluminum is a mononuclidic element with the nuclide 27A1. From a chemical point of view, aluminum, due to its excellent valve action property, when put in contact with oxidizing environments, develops spontaneously onto the exposed surface area a thin passivating film of impervious aluminum oxide (alumina). Moreover, the thickness of this passivating film can be further enhanced artificially by anodizing or other finishing techniques. Therefore, aluminum by contrast with iron and steels is corrosion resistant to normal atmospheric conditions (i.e., air, water), and it does not rust. However, aluminum is readily attacked by both diluted strong mineral acids and alkaline solutions evolving hydrogen, and reacts vigorously with chlorinated organic solvents. Cost (1998) — pure aluminum (99.99wt%) is priced at 1.44 $US.kg−1 (0.655 $US.1b−1).