6061 aluminum
Temper, product-form, thickness, processing, and service boundaries for selecting and specifying heat-treatable wrought 6061 aluminum.
Tags: materials, aluminum, heat-treatable, aluminum-magnesium-silicon
On this page
Choose the condition for the manufacturing route
Start with the product form and what happens to it: forming, machining, welding and finishing can make different conditions relevant. Keep the supplied stock condition separate from the required properties of the finished part.
| Choice to investigate | Why it matters | Detailed reference |
|---|---|---|
| O or T4 for a forming route | Softer or naturally aged conditions differ from artificially aged stock; final properties may require subsequent treatment | Temper and forming discussion below |
| T6 | Solution heat-treated and artificially aged; the basic label does not specify stretching for stress relief | T6 properties and product forms |
| T651 plate | Adds controlled stretching for stress relief; finished-part flatness still depends on the machining route | T651 plate and machining |
| T6511 extrusion | Retains extrusion-specific stress-relief and straightening information | T6 and stress-relieved variant comparison |
This is a selection map, not substitution authorization. Hydro's temper guidance explains the T6511 processing distinction. For complete specification inputs, use grade, temper and product form.
Example: a plate supplier's typical T6/T651 strength table should not replace an extrusion producer's specified minimums. Product form, thickness, test conditions and value basis must match. The tables below show why those numbers can differ without either source being wrong.
For a welded part, read the heat-affected-zone discussion below before using incoming-stock strength in a finished-assembly assessment. Link the chosen route to inspection-document selection and the complete cost estimate.
Identify the material completely
6061 is a wrought aluminum-magnesium-silicon alloy designation. The Aluminum Association's December 2025 Teal Sheets register 0.8–1.2% magnesium, 0.40–0.8% silicon, 0.15–0.40% copper, and 0.04–0.35% chromium by mass, with aluminum as the remainder and limits on other elements. This identifies chemistry, not a particular strength, product form, or delivered condition. Aluminum Association 6061 registration
A useful description retains the complete temper, sheet/plate/bar/extrusion/tube form, section dimensions, governing specification and edition, and required certification. “6061” or “aircraft aluminum” alone cannot establish an acceptable substitution for a drawing callout.
Temper and processing route
Hydro's sheet, Revision 2019/01 (2/2019), distinguishes O annealed, T4 solution heat-treated/naturally aged, and T6 solution heat-treated/artificially aged material. T6511 additionally involves stress relief by stretching. Preserve the complete suffix when purchasing plate or extrusions. Hydro 6061 temper definitions and notes
Heat treatment is part of the material's processing history. A part formed in a softer condition and subsequently heat treated needs requirements for its final condition and dimensions. Heating an already finished part does not establish a new temper without the applicable process controls and verification. Likewise, a stress-relieved stock designation does not guarantee that every thin-wall machining operation will be distortion free.
Typical properties versus guaranteed limits
Kaiser's Sheet Coil & Plate Alloy 6061, marked Rev. 05/06, labels the following values typical mechanical properties. Its tensile heading identifies a 0.500-inch-diameter specimen and elongation over 4D. These data illustrate differences between conditions; they are not universal sheet or plate acceptance minima. Kaiser 6061 typical mechanical properties
| Listed temper | Typical ultimate tensile strength | Typical yield strength | Typical elongation/4D |
|---|---|---|---|
| T451 | 241 MPa | 145 MPa | 25% |
| T6, T651 | 310 MPa | 276 MPa | 17% |
By contrast, Hydro's extruded-product limits list T6/T6511 minimum tensile/yield strengths of 260/240 MPa, with 8% elongation through 6.30 mm wall thickness and 10% above 6.30 mm. Its notes make the test-section thickness controlling and qualify elongation testing when a standard specimen cannot be taken or the shape is thinner than 0.062 inch. Do not replace those limits with Kaiser's typical 310/276 MPa values. Hydro extrusion limits and footnotes
For an engineering property record, keep source edition, form, temper, dimensional range, test orientation, specimen basis, and statistic with each number. A value described as minimum, maximum, typical, or design allowable has a different purpose. Matching one tensile result does not establish conformity with an unreviewed standard or finished-part load case.
Product-specific example: extruded wide bar
Hydro's ACC-U-PLATE brochure, Rev. 10/25, identifies the product as extruded wide bar, contrasting it with rolled 6061-T651 plate. Its longitudinal mechanical table lists 42 ksi minimum ultimate, 35 ksi minimum yield, and 10% minimum elongation for 6061 ACC-U-PLATE T6/T6511, but the footnote reduces minimum ultimate strength to 38 ksi below 0.375-inch thickness. Product geometry and footnotes matter even when both stock items look like plate. Hydro ACC-U-PLATE comparative properties
Illustrative conversion: 0.375 inch × 25.4 = 9.525 mm. This converts the cited boundary; it does not authorize rounding an ordered acceptance boundary to 10 mm. The brochure's inch-based condition and exact product callout remain the basis for that example.
The brochure also distinguishes flatness from mechanical properties and specifies how flatness is measured, including support by the piece's own weight on a flat surface. A material strength comparison cannot establish flatness, machining allowance, or interchangeability with another plate product. Hydro flatness tables and measurement notes
Forming, machining, and finish
Yieh's undated 6061 coil/sheet TDS offers O, T4, and T6 conditions in a stated 0.5–6.0 mm thickness range and describes cold forming in the annealed condition. This is a supplier's product envelope, not evidence for every thickness or an arbitrary T6 bend. Yieh 6061 coil/sheet scope and forming guidance
Choose the forming condition, bend radius, material direction, tooling, and sequence together. Qualify representative stock for cracks, springback, thinning, and surface marks as applicable. If the route includes later solution treatment, quenching, or aging, verify final dimensions and properties rather than treating the initial forming result as final-part qualification.
For machining, preserve stock orientation, clamping strategy, removal sequence, and final inspection conditions. Supplier-specific machinability or tolerance improvements belong with the named product, not all 6061. For appearance-critical work, approve a representative finished sample; an alloy or temper label alone cannot establish uniform anodized color across different stock forms and welds.
Welding and final strength
ESAB's September 19, 2024 HAZ guidance explains that welding heat can alter a heat-treatable alloy's strengthened condition through partial annealing and overaging. Heat input and thermal history affect the result. Assess weld metal, HAZ, and unaffected base separately; a T6 parent-stock certificate does not make the entire as-welded assembly T6-strength material. Post-weld treatment, where required, needs its own qualified route and final verification. ESAB heat-treatable aluminum HAZ behavior
ESAB's 6061-T6 filler-selection examples further distinguish anodized appearance, elevated-temperature service, and assemblies intended for post-weld heat treatment. A filler suitable for one requirement can be unsuitable for another. Specify mating alloys, joint design, service, strength/ductility, finish, and any subsequent heat treatment before selecting the consumable and procedure; do not reduce selection to one universal filler number. ESAB 6061-T6 filler-selection examples
Corrosion and service qualification
Hydro describes favorable atmospheric/seawater corrosion behavior while warning about galvanic contact. Check the actual fluids, temperature, crevices, fasteners, and protective system rather than treating that description as universal compatibility. Hydro corrosion guidance
Room-temperature tensile properties also do not establish fatigue life, elevated-temperature allowable stress, pressure suitability, or weld-joint performance. Retain the governing design basis, service conditions, material certificate, manufacturing route, and final inspection results. Resolve changes in alloy, temper, form, thickness, or thermal processing as explicit substitutions before release.