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Heat-treatable alloys
From GAWDAwiki
Heat-treatable alloys are alloys that can be strengthened or hardened by the application of heat.[1]
The initial strength of these these heat-treated alloys is produced by the addition of alloying elements to pure aluminum. These elements include copper, magnesium and silicon, which is able to form the compound magnesium silicide (6xxx series), and zinc. When present in a given alloy, singly or in various combinations, these elements exhibit increasing solid solubility in aluminum as the temperature increases. Because of this reaction, it is possible to produce significant additional strengthening to the heat-treatable alloys by subjecting them to an elevated thermal treatment, quenching, and, when applicable, precipitation heat-treatment known also as artificial aging.
Note: Because of additions of magnesium and or copper, there are also a number of silicon alloys that are heat-treatable.
In solution heat treatment, the material is typically heated to temperatures of 900 to 1050 deg F, depending upon the alloy. This causes the alloying elements within the material to go into solid solution. Rapid quenching, usually in water, which freezes or traps the alloying elements in solution, follows this process.
Precipitation heat-treatment or artificial aging is used after solution heat treatment. This involves heating the material for a controlled time at a lower temperature (around 250 to 400 deg F). This process, used after solution heat-treatment, both increases strength and stabilizes the material.[2]
