Aluminum Sheet can be heat-treated to achieve different tempers or states that impart specific mechanical properties and characteristics to the material. The heat treatment processes involve controlled heating and cooling of the alloy to modify its microstructure. The most common tempers for aluminum alloys are indicated by a combination of letters and numbers.
Here are some of the most common aluminum alloy tempers:
F: As Fabricated
This temper indicates that the material has not undergone any significant heat treatment after forming. It is often used for materials in their initial state after being shaped.
O: Annealed
Annealing involves heating the material to a specific temperature and then slowly cooling it. This temper is characterized by low strength and maximum ductility. It's commonly used for deep drawing and forming operations.
H: Strain Hardened
The "H" tempers involve a cold working process to increase strength. The higher the number after "H," the greater the level of strain hardening and strength. For example:
H12: Strain-hardened to a quarter-hard condition.
H22: Strain-hardened and partially annealed to quarter-hard condition.
H32: Strain-hardened and stabilized, with a three-quarter-hard condition.
H112: Strain-hardened and temper-softened for alloy 6XXX series (T4 tempered).
T: Thermally Treated / Heat Treated
The "T" tempers involve a heat treatment process that enhances strength and other properties. The number following "T" indicates the specific treatment process and its resulting properties. For example:
T4: Solution heat-treated and naturally aged to obtain a stable temper (for alloy 6XXX series).
T6: Solution heat-treated and artificially aged to achieve maximum strength and hardness (common for many aluminum alloys).
W: Solution Heat-Treated
This temper is used for casting alloys that are solution heat-treated to dissolve precipitates before undergoing additional heat treatment.
Hx: Cold Worked and Partially Annealed
These tempers involve cold working to increase strength, followed by partial annealing to reduce hardness and improve formability.
Tx51, Tx52, Tx53, etc.: Stress-Relieved Tempers
These tempers are produced by cold working and then thermally relieving residual stresses to improve dimensional stability. The specific number indicates the degree of cold work and stress relief.
Welded Tempers
These tempers are specific to aluminum alloys used in welded applications and are designed to minimize distortion and stress corrosion cracking after welding.
It's important to note that the temper designations can vary slightly depending on the alloy series. The above examples provide a general overview of common temper designations for aluminum alloys. When working with specific aluminum alloys, it's recommended to refer to the alloy's specifications and standards to ensure accurate selection of the desired temper for your application.
