The heat treatment of aluminium alloy castings is to select a heat treatment specification, control the heating speed to a certain temperature and keep it cool for a certain time at a certain speed to change the structure of the alloy. Its main purpose is to improve the mechanical properties of the alloy, enhance the corrosion resistance, improve the processing performance and obtain dimensional stability.

T6 heat treatment of aluminium alloy castings is generally divided into two stages: solution treatment (quenching) and aging treatment.

Solid solution treatment: It refers to the heat treatment process of heating aluminium alloy castings to a certain temperature for a period of time, so that the excess phase can be fully dissolved into the solid solution and quickly cooled, so as to obtain supersaturated solid solution, improve mechanical properties and enhance corrosion resistance.

Aging treatment: Aging is the heat treatment of T6 process for aluminium alloy castings after solution treatment. Aging treatment uses higher aging temperature and longer holding time to obtain maximum hardness and tensile strength, and to achieve dimensional stability.
The strength and hardness of the quenched alloy will increase significantly after being placed for a period of time (e.g. 4-6 days and nights), while the plasticity will decrease significantly. The phenomenon that the strength and hardness of quenched aluminium alloy increase significantly with time is called aging.

Aging can occur at room temperature, which is called natural aging. It can also occur in a temperature range higher than room temperature (e.g. 100-200 C). It is called artificial aging. Aluminum alloy is treated by solid solution (quenching) and artificial aging, which is commonly called T6 heat treatment process.