Alloy + Temper

Alloy and temper answer different questions.

In a designation such as 5052-H32 or 6061-T6, the four-digit number identifies the alloy family and chemistry. The suffix after the dash identifies the controlled condition created by fabrication, strain hardening, heat treatment, aging, or stress relief.

The first digit points to the alloy family.

For wrought aluminum, the first of four digits identifies the principal alloying family. That family is a useful first clue, but the complete four-digit designation defines the registered composition.

The second digit and final two digits have series-specific meanings. For 2xxx through 8xxx wrought alloys, the second digit generally indicates modification of the original alloy, while the last two identify the alloy registration. In 1xxx, the digits relate to purity and impurity control. Do not try to reconstruct exact chemistry from the number alone; use the registered composition and governing specification.

Start with the first letter.

The basic temper letter describes the broad processing condition. Additional digits refine the treatment, degree of strain hardening, aging route, or stress-relief method.

H codes use process + degree.

H tempers normally use at least two digits. The first digit after H describes how strain hardening and supplementary treatment were combined. The second describes the degree of strain hardening.

The second digit: degree of strain hardening

Even-numbered degrees are commonly described as quarter-hard, half-hard, three-quarter-hard, and full-hard. These are standardized property positions relative to the annealed and full-hard conditions—not a statement that a specific percentage of forming capacity remains.

Odd second digits identify intermediate limits. A third H digit indicates a variation of the two-digit temper. Examples such as H111, H116, or H321 have definitions tied to alloy, product form, and registered requirements; they should be ordered by the complete designation rather than approximated from a nearby two-digit temper.

The first T digit records the route.

T tempers describe stable conditions achieved by controlled cooling, solution heat treatment, aging, and sometimes cold work. The order matters.

Extra digits carry real requirements.

Additional digits can identify a registered variation of the basic temper or a stress-relief method. They often correlate with product form, so removing them can change both processing history and minimum properties.

The suffix can change the manufacturing plan.

Temper affects more than a tensile-property table. It can determine whether a bend cracks, a machined pocket moves, a welded region must be derated, or a finished part meets the drawing.

Welding deserves special attention. Heat can locally anneal strain-hardened 5xxx material and reduce the precipitation-hardened strength of 6xxx or 7xxx material. The designation on incoming stock does not describe the final heat-affected-zone properties after welding.

Likewise, a stress-relieved temper helps control machining movement but does not guarantee a finished part will remain flat after aggressive, one-sided material removal. Toolpath strategy, workholding, thermal control, and roughing/rest cycles still matter.

Specify the complete material identity.

A complete callout names the alloy, temper, product form, governing specification, stock size, finish, and certification requirements. The temper should never be guessed from the part description.

Temper questions worth asking early.

This guide is educational. It does not replace the current ANSI standard, governing material or product specification, mill certification, approved design allowables, heat-treatment procedure, welding qualification, inspection plan, or engineering approval for the actual part.