Some extruded products require aging to achieve optimum strength, hence the name aging hardening. Natural aging is performed at room temperature. Artificial aging is carried out in the aging furnace. Technically it is called precipitation enhanced phase heat treatment.
The profiles are semisolid when extruded from the extruder. But it soon becomes solid when it is cooled or quenched (whether air or water cooled). Non-heat-treated strengthened aluminum alloys (such as those containing magnesium or manganese) gain strength through natural aging and cold working. Heat treatable strengthened aluminum alloys (such as those with copper, zinc, magnesium and silicon) can obtain better strength and hardness by heat treatment that affects the metallographic structure of the alloy.
In addition, the aging is to make the reinforced phase particles precipitate evenly to obtain the maximum yield strength, hardness and elasticity of the special alloy.