Solution Heat Treatment
This involves heating of Aluminum alloy to a particular temperature for sufficient time so that the alloying elements go into solid solution and forma single phase. The factors which affect the final properties of the alloy are soaking temperature, soaking time and cooling rate.
The Soaking temperature depends on various phases which are present in alloys. Each phase will dissolve in solid solution at different rates. The soaking time is based on the rate of dissolution of alloying elements into solid solution. It also depends on the conditions under which the alloy is cast. Sand cast parts have coarser structure than permanent mould casting. Hence Aluminium Sand Castings take time for dissolution of phases necessitating longer soaking time.
Commonly used T6 Heat Treatment Process:
- Solutionising : Keep in furnace at 525 Deg Celsius for 8 Hrs.
- Quenching : Sudden Quenching in Water at 30 Deg Celsius.
- Natural Ageing : Upto 5 Hrs
- Precipitation : Keep in furnace at 165 Deg Celsius for 8 Hrs.
- Hardness to be achieved between 80-100 BHN