Non-Ferrous Metals

The heat treatment of cast / wrought aluminium and extruded alloys is carried out to change the mechanical properties of the castings or extrusions. The heat treatment consists of one or more thermal cycles being applied to the aluminium alloy components. The thermal treatments are designed by suffixes and main ones are as follows:

M – As cast or as manufactured
TB or T4 – Solution treated and naturally aged
TE or T5 – Artificially aged
TB7 – Solution treated and stabilized
TF or T6 – Solution heat treated and fully artificially aged
TF7 – Solution treated and artificially aged and stabilized
TS – Stress relieved and annealed
Freezing/Setting

Solution Treatment (TB Condition)

Castings or extrusion are heated to a temperature just below the alloy melting point (this varies depending on the chemical compositions), for a time (this varies with alloy and section of the component) to allow the alloying constituents to enter into a solid solution. This solid solution is maintained by rapid cooling either by polymer quenching, hot water quenching or cold water quenching in order to reduce distortion and reduce internal stresses.

Precipitation Treatment (TE Condition)

This treatment is carried out in order to increase the strength and hardness of solution treated / as cast / as manufactured extrusions. The times and temperature vary depending upon the alloy and are usually in the temperature range 150/200˚c. Times vary between 2/24 hours. Lower temperatures and longer times give better precipitation and thus better mechanical properties.

Solution Treated and Stabilized Treatment (TB7 Condition)

After solution treatment the casting can be brought into a stable state by heating to a temperature between 200/250˚c. Times and temperature vary with different alloys and mass of the components.

Solution and Precipitation Treatment (TF Condition)

The highest mechanical properties are obtained by solution treatment followed by a precipitation treatment as described in the section on precipitation.