Aluminum 6061 - 3.3214 - EN AW-6061 - EN AW-AlMg1SiCu

What is 6061 aluminum alloy?

Widely used in aerospace (tooling, brackets, frames, machined parts, secondary structures depending on the specification), 6061 aluminum is valued for its balance of mechanical strength, low weight, machinability, and corrosion resistance.

Historically designated as 61S in the 1930s, this aluminum alloy is now identified under several designations depending on standards and markets. In Europe, it is commonly found as EN AW-6061, EN AW-AlMg1SiCu, and the material number 3.3211. In North American systems, it is referenced as 6061 (Aluminum Association) and UNS A96061.

Metallurgical family

6061 is a wrought alloy from the 6000 series (aluminum–magnesium–silicon). This family includes grades known for their versatility in rolled and extruded products. 6061 is often selected as an “all-purpose” grade when a solid compromise is needed between manufacturability, machinability, and mechanical performance.

Role of alloying elements and precipitation hardening

• The magnesium (Mg) and silicon (Si) in its composition (see table below) form Mg₂Si precipitates, which are leveraged by age hardening to increase strength.
• Copper (Cu) helps increase strength in alloys. However, at excessive levels it can reduce corrosion resistance.
• Chromium (Cr) helps limit recrystallization and stabilize the structure. Titanium (Ti) is often associated with grain refinement.

What mechanical properties does 6061 offer depending on temper and product form?

Comparison table — Rolled sheet and plate (EN 485-2 minimum requirements)

This table shows the minimum standard requirements at 20 °C (except hardness). A clear increase in Rp0.2 and Rm is observed from O → T4 → T6, along with a decrease in elongation at fracture (A).

Comparison table — Extruded bars (EN 755-2 minimum requirements)

The same trend applies: Rp0.2 and Rm increase from temper O to T6, while elongation (A) decreases.

How does 6061 perform in corrosion?

In the presence of chlorides (marine atmospheres, salt spray, industrial environments), pitting can occur and may initiate fatigue cracks. There is also a potential risk of intergranular corrosion, especially in areas near weld beads and depending on certain microstructures (for example, in precipitate-depleted zones).

Sensitivity to stress corrosion cracking (SCC) is, however, very low, as is general corrosion.

Is 6061 easy to weld?

For 6061 in the T6 temper, published study data indicate that a welded joint can lose a significant portion of the base material’s strength. The main reason is localized softening in the heat-affected zone (HAZ), which degrades the precipitation state responsible for hardening.

A comparison highlights the influence of the process, with the joint’s ultimate tensile strength (Rm) and joint efficiency calculated against a 310 MPa reference:

Post-weld improvement strategies

An approach combining a CMT-type welding process with a post-weld heat treatment can improve hardness (+25.6 %), tensile strength (+3.8 %), and even elongation (+21.5 %) compared with a “welded only” condition.

Is 6061 easy to form?

For demanding forming operations, deep drawing is generally recommended in 6061-O. The goal is to take advantage of a more ductile temper, with higher elongation than hardened tempers (see tables above).

For “moderate” bending or roll forming, 6061-T4/T451 is typically preferred. Conversely, tight bends should be avoided in 6061-T6/T651, as this temper is less tolerant of localized deformation.

The most effective sequence to balance formability and strength level is straightforward: form in O or T4, then apply the required heat treatment to reach a T6 condition.

After annealing (380–420 °C), a complete new heat-treatment cycle is required to recover a T6-type condition.