6061-T6511 Aluminum properties at a glance
Values labeled typical are orientation- and section-dependent references, not design allowables. Use the current governing specification and the supplied mill certificate for acceptance.
| Property | Reference value | How to use it |
|---|---|---|
| Density | 0.0975 lb/in³ (2.70 g/cm³) | Nominal; temper does not materially change density |
| Ultimate tensile strength | 38 ksi minimum | ASTM B221 extruded 6061-T6/T6511 reference minimum |
| Yield strength | 35 ksi minimum | ASTM B221 extruded 6061-T6/T6511 reference minimum |
| Elongation | 8% through 0.249 in; 10% at 0.250 in and above | Dimension-dependent Aluminum Association table; verify the applicable row |
| Elastic modulus | About 10,000 ksi | Typical reference value, not a lot acceptance test |
History of 6061
6061 traces to Alcoa alloy 61S, introduced in 1935 as a corrosion-resistant, weldable, heat-treatable structural aluminum. The modern 6061 designation arrived with the industry-wide four-digit system in the 1950s. Extrusion made the alloy especially useful because mills could create efficient bar and profile sections while preserving a practical balance of strength and fabrication behavior.
T6511 describes how that extruded product is finished, not a new alloy. Stretching was adopted to reduce residual stress after solution heat treatment, while the final “1” permits the mill to straighten the extrusion enough to meet dimensional requirements. SAE first issued AMS 4173 for 6061-T6511 extrusions in 1969, giving aerospace buyers a dedicated specification alongside the broader ASTM B221 commercial standard.
- 1935
Alcoa introduces 61S
The alloy later known as 6061 is launched for medium-strength, corrosion-resistant applications.
- 1969
AMS 4173 is issued
SAE publishes a dedicated specification for stretched and straightened 6061-T6511 extrusions.
- Today
A standard bar temper
T6511 is common for extruded round, rectangular, square, hex, and shaped 6061 products.
Decode T6511 correctly
T6 identifies solution heat treatment followed by artificial aging. The 51 adds stress relief by stretching. The last 1 permits minor straightening after that stretch. T6510 is the closely related extrusion temper in which no straightening is allowed after stretching. Neither suffix means “stronger than T6”; the useful change is residual-stress control and, for T6511, the ability to meet commercial straightness.
Product form matters when reading strength tables. Extruded 6061-T6511 carries different specified minimums from cold-finished 6061-T651 bar or rolled T651 plate. The alloy name alone cannot establish acceptance. Match the form, controlling specification, dimension range, and test direction before comparing values.
- T6511: stretched extrusion, minor straightening permitted.
- T6510: stretched extrusion, no straightening after stretching.
- T651: commonly plate or cold-finished bar, not a synonym for extruded T6511.
Machining and dimensional behavior
The stretched condition makes T6511 a good starting point for shafts, spacers, rails, and rectangular parts, but extruded bar is not precision-ground stock. Expect commercial diameter, thickness, width, twist, and straightness tolerances. Long, slender sections can arrive within the standard and still require generous cleanup stock for a precision finished part.
Use sharp tools, clear chips, and avoid clamping a bowed bar so forcefully that it springs after release. For asymmetric pockets or thin walls, rough both sides and allow the work to relax. If the finished part requires tightly controlled flatness on all faces, a blank cut from T651 plate may be more economical than forcing a commercial extrusion to behave like precision stock.
Specify the bar, not just the alloy
A complete order calls out 6061-T6511, extruded product form, ASTM B221 or the drawing specification, section size, cut length, quantity, and any required origin or certification. If a legacy drawing uses AMS-QQ-A-200/8, confirm how the supplier certifies the current replacement rather than silently deleting the requirement.
Check elongation against the correct dimension row. The often-repeated 17% figure is not the ASTM B221 extrusion minimum: Aluminum Association data gives 8% through 0.249 inch and 10% at 0.250 inch and above for the referenced 6061-T6/T6511 ranges. Use the current standard and the actual mill cert for acceptance.
Specifications and purchase callouts
The controlling drawing decides which specification applies. A similar alloy name or typical-property table does not demonstrate compliance.
- ASTM B221
- SAE AMS 4173
- AMS-QQ-A-200/8 (legacy federal callout)
- ANSI H35.2 dimensional tolerances
Frequently asked questions
What does 6061-T6511 mean?
It means 6061 was solution heat treated, stress relieved by stretching, and artificially aged, with minor straightening permitted after stretching. The designation is common for extruded bar, rod, and shapes where machining stability and commercial straightness both matter.
Is T6511 stronger than T651?
Not as a general rule. They describe processing and product form, and their guaranteed values come from different specification tables. Extruded T6511 commonly has a 38 ksi minimum ultimate and 35 ksi minimum yield, while plate or cold-finished T651 may carry other values.
What is the minimum elongation of extruded 6061-T6511?
It depends on dimension. Aluminum Association data for the referenced ASTM B221 extrusion ranges shows 8% through 0.249 inch and 10% at 0.250 inch and above. Always select the row for the actual shape and dimension in the current governing standard.
Can 6061-T6511 be welded?
Yes, 6061 is readily weldable, but welding locally removes the T6/T6511 strength condition. Design the heat-affected zone with the appropriate post-weld properties and do not assume the parent-bar strength continues through the joint.
Primary references
Technical standards change. These sources support the history and reference discussion; obtain the current specification revision for design or acceptance work.
Related guides and tools
From reference to real stock
Choose a size and get a real ship date.
Open the live material builder for current sizes and availability. Confirm the alloy, condition, specification, and mill certification against your drawing before release.
Shop 6061-T6511 bar