Heat Treatment of Aluminum Castings

Most aluminums require aging to maximize and stabilize their properties.  Not all require heat treatment to promote aging.  Many age at room temperature over a period of time.  Some do require heat treatment.  Below is a list of the heat treatments commonly used for aluminum and their designations.

• T4

  • Solution heat treated and naturally aged to substantially stable condition.   Mechanical properties and stability may change over a long period of time. 

• T5    

  • Naturally cooled from the mold then artificially aged to attain optimum mechanical properties and dimensional stability.

• T6    

  • Solution heat treated and over-aged for improved dimensional stability, but usually with some reduction from the optimum mechanical properties.

• F

  • The designation for as-cast, naturally cooled aluminum.

• 0

  • The designation for annealing.  Usually the weakest, softest, most ductile and most dimensionally stable.

The T5, T6, and T7 designations are sometimes followed by one or more numbers which indicate changes from the originally developed treatment.