Aluminum and aluminum alloys-heat treatment of aluminum and aluminum alloys(1)

annealing

Annealing is applicable to two grades to promote softening. Fully and partially annealed heat treatments are the only alloys that cannot be heat treated. 5000 series alloys are sometimes stabilized at a low temperature and are carried out by the manufacturer.

Depending on the alloy, annealing is performed in the range of 300-410°C. Depending on the load and the type of alloy, the heating time varies from 0.5 to 3 hours. Generally, the time need not be longer than the time required to stabilize the load at temperature. The cooling rate after annealing is not important.

If the parts have been solution heat treated, the maximum cooling rate of 20°C per hour must be maintained until the temperature drops to 290°C. Below this temperature, the cooling rate is not important.

Heat treatment

This applies to heat-treatable alloys and involves a heat-treatment process whereby the alloy components are dissolved into the solution and retained by rapid quenching. Subsequent heat treatment at the tower temperature, that is, aging at room temperature or natural aging, can control the precipitation of components, thereby obtaining increased hardness and strength.

The temperature time of solution treatment depends on the type of alloy and the load of the furnace. If you want to get the best performance, you must allow enough time to bring the alloy into the solution.

Solution processing temperature is critical to the success of the procedure. Ideally, the solution heat treatment is as close to the liquidus temperature as possible to obtain maximum dissolution of the components. For most alloys, accurate furnace temperature and special temperature changes must be controlled within ±5°C. Overheating must be avoided, that is, the initial eutectic melting temperature is exceeded. The early stage of overheating is often not obvious, but it will lead to the deterioration of mechanical properties.

Proper solution heat treatment of aluminum alloys requires expertise in the treatment of alloys and correct heat treatment equipment.