The general types of heat treatments applied to aluminum and its alloys are:
Preheating or homogenizing, to reduce chemical segregation of cast structures and to improve their workability
Annealing, to soften strain-hardened (work-hardened) and heat treated alloy structures, to relieve stresses, and to stabilize properties and dimensions
Solution heat treatments, to effect solid solution of alloying constituents and improve mechanical properties
Precipitation heat treatments, to provide hardening by precipitation of constituents from solid solution....
Heat treating processes for aluminum are precision processes. They must be carried out in furnaces properly designed and built to provide the thermal conditions required, and adequately equipped with control instruments to insure the desired continuity and uniformity of temperature-time cycles. To insure the final desired characteristics, process details must be established and controlled carefully for each type of product.