Aluminium is available in both wrought and cast forms. The wrought forms comprise hot and cold rolled sheet, plate, rod, wire and foil. The ductility and workability of aluminium mean that extrusion is a simple method of producing complex shapes, particularly for long, structural members such as I and H beams, angles, channels, T-sections, pipes and tubes. Forging, both hot and cold, is used extensively as a fast, economical method of producing simple shapes. Precision forging is particularly suitable for aluminium alloys, giving advantages of good surface finish, close tolerances, optimum grain flow and the elimination of machining.
The four most commonly used methods of casting are sand casting, lost wax casting, permanent steel mould casting and die-casting. The requirement for high fluidity in a casting alloy means that many are based on aluminium-silicon alloys although heat-treatable (age-hardening) alloys are often used for sand, lost wax and permanent mould castings. Lost wax and die-casting give products with smooth surfaces to close tolerances and are processes used extensively for aerospace products. A number of alloys, their product forms and applications are listed in Table 1.1.