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How to Read Aluminum Alloys and Tempers

Properties of aluminum materials can vary significantly based on alloy composition and how that alloy is tempered after its creation. Read this article to learn more about aluminum alloys within the standard naming system.

Greg Paulsen - Xometry Contributor
By Greg Paulsen
 3 min read
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Aluminum is a metal that combines robust mechanical properties with low weight. It is significantly lighter than other metal counterparts, such as steels. Many applications are weight-sensitive, so the use of aluminum in vehicular, aircraft, spaceflight, and equipment designs is very common. Aluminum materials are most often formed from casts or extrusions and are go-to materials for CNC machining and sheet metal parts.


Not all aluminum stock is the same. Properties of aluminum materials can vary significantly based on alloy composition and how that alloy is tempered after its creation. Aluminum alloy is defined using standard naming, this article helps better understand the aluminum alloy designation system.

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  • Annotation of Aluminum Alloy Nomenclature

The specification of aluminum alloy can be broken down by its series, temper, and conditions.

An additional suffix after tempers can signify the wrought product type for even more specific material specifications. The example table below shows the classifications for aluminum 7075-T7351.

Classifications for Aluminum 7075-T7351
Letter Indicator in 7075-T7351
Letter Indicator in 7075-T7351

7XXX-series

Letter Indicator in 7075-T7351

T7

Letter Indicator in 7075-T7351

351

A breakdown of what each character in aluminum 7075-T7351 means for that specific alloy.

Understanding Aluminum Series

Aluminum is typically alloyed with other elements to produce different strengths. These alloys are defined by strength in their series, with labels ranging from 1xxx- to 7xxx-series depending on the alloying agents used. The chart below shows different alloy series and what makes them unique.

Types of Aluminum Alloys
Alloy SeriesAlloying Agent(s)DescriptionExamples
Alloy Series

1xxx

Alloying Agent(s)

99%+ Pure Aluminum

Description

Is soft, ductile, and easily welds. Is not heat-treatable.

Examples

Aluminum 1100

Alloy Series

2xxx

Alloying Agent(s)

Copper

Description

Has high strength and durability and requires corrosion protection.

Examples

Aluminum 2024

Alloy Series

3xxx

Alloying Agent(s)

Manganese

Description

Is highly ductile, great for bending, and best suited for forming.

Examples

Aluminum 3003

Alloy Series

4xxx

Alloying Agent(s)

Silicon

Description

Has a lower melting point and is used as a welding wire.

Examples

Aluminum 4032

Alloy Series

5xxx

Alloying Agent(s)

Magnesium

Description

Has high strength and malleability, is great for bending, and is corrosion-resistant.

Examples

Aluminum 5052

Alloy Series

6xxx

Alloying Agent(s)

Magnesium + Silicon

Description

Has high strength and formability. Is weldable, heat-treatable, and corrosion resistant. Has wide range of use across industries.

Examples

Aluminum 6061, Aluminum 6063

Alloy Series

7xxx

Alloying Agent(s)

Zinc

Description

Has very high tensile strength and stiffness as well as high usage in aerospace designs. Is not suitable for bending.

Examples

Aluminum 7050,
Aluminum 7075

Wrought aluminum alloy lookup table. 2xxx, 5xxx, 6xxx, and 7xxx-series are the most typical alloys used in aerospace and defense.

The secondary numbers before the temper are specific alloy compositions per aluminum series. 6XXX-series aluminum, like 6061, is very popular because it does not work-harden quickly, allowing greater ease of raw material manufacturing through the extrusion of profiles. This reduces the costs of raw stock material fabrication. The material is also easily CNC milled for custom manufacturing. However, 6061 may be too brittle for rolling or forming. This is why 5XXX-series aluminum, like 5052, is most common in sheet metal fabrication or stamping applications.

An alternative to wrought billets is cast aluminum. This material provides a near-net-shape of the product. MIC-6 is a cast 5083 aluminum that is used for tooling plates and test fixtures.

Understanding Aluminum Tempers

To classify aluminum types beyond the net shape and strength of the alloy, temper is used in the naming series. Tempers add additional mechanical properties through rapid cooling (quenching), cold working, or precipitation heat treatment combinations.

Aluminum and alloys from 1XXX-, 3XXX-, 4XXX-, 5XXX-series can not be heat treated but can be strain hardened. This is signified with a suffix of -H##. Strain hardening strengthens a material through cold working. For example, Aluminum 5052-H32. 2XXX-, 6XXX-, and 7XXX-series aluminum can be precipitation hardened, or heat-treated, signified by a -T#, such as 6061-T6. The following reference chart depicts different aluminum tempers.

Reference Table for Different Aluminum Tempers
Extrusion TemperDescription
Extrusion Temper

F

Description

Extruded, air-cooled with no special controls

Extrusion Temper

O

Description

Fully annealed to the lowest strength temper

Extrusion Temper

H1

Description

Strain-hardened

Extrusion Temper

H2

Description

Strain-hardened and partially annealed

Extrusion Temper

H3

Description

Strain-hardened and stabilized

Extrusion Temper

H4

Description

Strain-hardened and lacquered or painted

Extrusion Temper

W

Description

Solution heat-treated

Extrusion Temper

T1

Description

Cooled from an elevated temperature and naturally aged

Extrusion Temper

T2

Description

Cooled from an elevated temperature, cold-worked, and naturally aged

Extrusion Temper

T3

Description

Solution heat-treated, cold-worked, and naturally aged

Extrusion Temper

T4

Description

Solution heat-treated and naturally aged

Extrusion Temper

T5

Description

Cooled from an elevated temperature and artificially aged

Extrusion Temper

T6

Description

Solution heat-treated and artificially aged

Extrusion Temper

T7

Description

Solution heat-treated and stabilized

Extrusion Temper

T8

Description

Solution heat-treated, cold-worked, and artificially aged

Extrusion Temper

T9

Description

Solution heat-treated, artificially aged, and cold-worked

Extrusion Temper

T10

Description

Cooled from elevated temperature, cold-worked, and artificially aged

Extrusion temper lookup chart. Tempers may have multiple digits after a letter to indicate sub-classifications in each temper, material age condition, and final state.

Looking Beyond Aluminum Alloys and Tempers

Beyond tempers, there may be additional suffix classifications that are specific to that series/temper combination. The Metallic Materials Properties Development and Standardization Handbook, MMPDS-14, is a powerful reference for more complete definitions and standards of metals used in manufacturing.

This excerpt was inspired by Xometry’s ebook: Custom Manufacturing for Aerospace and Defense. You can get an instant quote on custom CNC or sheet metal projects here.

Greg Paulsen - Xometry Contributor
Greg Paulsen
They call me the Director of Application Engineering at Xometry. This means I not only get to produce great design-for-manufacturing content, but also consult on a variety of custom manufacturing projects using CNC machining, additive manufacturing, sheet metal, urethane casting, and injection molding. If you have a question, I'm your guy.