Aluminum & Alloys Heat Treatment Services

Product Description

Aluminumheat treatment is a process by which the strength and hardness of a specificsubset of aluminum alloys, namely the wrought and cast alloys that areprecipitation hardenable, are increased. Precipitation hardenable aluminumalloys include the 2XXX, 6XXX, 7XXX and 8XXX series. In addition, annealing maybe required for parts that have experienced strain hardening during theirforming process. It is important to keep in mind that the heat treating ofaluminum is quite different from steel.

Aluminumalloys are subject to work hardening, also known as strain hardening. Strainhardening occurs when the aluminum alloy is being shaped by plasticdeformation. The plastic deformation causes the grain structures within thealuminum to slide against each other along areas referred to as slip planes. Asmore and more plastic deformation takes place, there are fewer and fewer slipplanes left that are easy to deform. As a result, more force is required toachieve further deformation. When a part has reached this state, it is said tobe work hardened. In order to continue plastically deforming the material, thestrain hardening has to be removed from the part.

Solution Heat Treatment

While the cooling rate is not a factor in annealing, itis a factor in another similar aluminum heat treatment process called solutionheat treatment. During the solution heat treatment process, the elements thatare responsible for age hardening (which makes the metal part difficult to workwith over time) are dissolved. Those dissolved elements then become spheroids,and the result is a homogenized structure. However, the part must be quenched,or rapidly cooled, to preserve that final distribution of dissolved elements inthe alloy that was achieved as a result of heat treatment. The part is thenmuch easier to work with. Over time, though, those trapped elements willprecipitate out again and cause age hardening.

Precipitation Hardening

For some aluminum alloys to be able to reach maximumhardness, they need to have the dissolved elements fully precipitated out. Notall aluminum alloys can reach sufficient hardness during natural aging at roomtemperature. Some can only harden to a certain point, but that can be resolvedthrough precipitation hardening, which is sometimes called artificial aging.

 It will then soakfor a period of between six to twenty-four hours, followed by cooling to roomtemperature. The result includes a significant increase in the yield strengthof the aluminum, slightly less of an increase in tensile strength, and adecrease in ductility.