6061-T6511 Round Bar: Specs, Sizes, Weights, and What T6511 Actually Means
By Boromir
6061-T6511 round bar is extruded aluminum bar that has been solution heat treated, stress relieved by stretching, artificially aged, and then lightly straightened. The 511 suffix is the part most buyers do not decode: 51 means stress relieved by stretching, and the final 1 means minor straightening was permitted after the stretch. It is the temper you get when you buy extruded 6061 round bar from essentially any distributor in North America, it is supplied to ASTM B221, and its guaranteed minimums are 38,000 psi tensile and 35,000 psi yield. This post covers what that temper buys you, the size and weight tables, and what to specify when you order.
In Short
- →6061-T6511 is the standard temper for extruded aluminum round bar: solution heat treated, stress relieved by stretching, artificially aged, with minor straightening permitted afterwards.
- →The governing commercial specification is ASTM B221. Older prints call out AMS-QQ-A-200/8, which is the legacy designation for the same product.
- →Minimum mechanical properties for extruded 6061-T6 and T6511 are 38,000 psi ultimate tensile and 35,000 psi yield, with 17 percent elongation on a half-inch specimen.
- →That 38,000 psi is lower than cold-finished 6061-T6 and T651 bar, which carries a 42,000 psi minimum at the same 35,000 psi yield. Same alloy, different process, different minimum.
- →The stress relief is why T6511 machines predictably. Bar that has not been stretched moves when you take material off one side.
- →Standard mill stock length is 12 feet. Buying cut to length is almost always cheaper than buying a full stick you cannot use.
What the Temper Designation Means
Aluminum temper codes are readable once you know the parts. T6511 breaks into three pieces, and each one tells you something you can act on.
| Code | Meaning | Why it matters to you |
|---|---|---|
| T6 | Solution heat treated, then artificially aged | This is where the strength comes from |
| T651 | T6 plus stress relieved by stretching | Applies to rolled plate and cold-finished bar |
| T6510 | T6 plus stretched, no straightening afterwards | Extrusions, left as stretched |
| T6511 | T6 plus stretched, minor straightening permitted | Extrusions, straightened to hit tolerance |
Mechanical Properties: The Number Most Buyers Get Wrong
Here is the detail that catches people out. Extruded 6061-T6511 and cold-finished 6061-T651 are the same alloy in the same nominal condition, and they do not carry the same guaranteed tensile minimum.
- Yield is identical at 35,000 psi. If your design is yield-driven, which most structural aluminum design is, the two are equivalent.
- Ultimate differs by 4,000 psi. If your print or analysis calls out a 42,000 psi minimum ultimate, extruded T6511 does not meet it on paper even though typical values sit well above the minimum.
- Elongation is 17 percent in 2 inches on a half-inch diameter specimen for both.
- Typical hardness is Brinell 95 and typical shear strength is 30,000 psi for both.
- This is a specification distinction, not a quality one. Read the print before you assume extruded bar satisfies a cold-finished callout.
| Product | Alloy and temper | Min ultimate (psi) | Min yield (psi) | Elongation |
|---|---|---|---|---|
| Extruded | 6061-T6, -T6511 | 38,000 | 35,000 | 17 percent |
| Cold finished | 6061-T6, -T651 | 42,000 | 35,000 | 17 percent |
Standard Sizes and Weight Per Foot
Weight per foot is pi times the radius squared, times 12, times density. These figures use 0.0975 lb per cubic inch.
| Diameter (in) | lb per foot | 12 ft stick | Diameter (in) | lb per foot | 12 ft stick |
|---|---|---|---|---|---|
| 0.500 | 0.230 | 2.8 lbs | 2.000 | 3.676 | 44.1 lbs |
| 0.750 | 0.517 | 6.2 lbs | 2.500 | 5.743 | 68.9 lbs |
| 1.000 | 0.919 | 11.0 lbs | 3.000 | 8.270 | 99.2 lbs |
| 1.250 | 1.436 | 17.2 lbs | 4.000 | 14.703 | 176.4 lbs |
| 1.500 | 2.068 | 24.8 lbs | 5.000 | 22.973 | 275.7 lbs |
| 1.750 | 2.815 | 33.8 lbs | 6.000 | 33.081 | 397.0 lbs |
Why the Stress Relief Is the Whole Point
The strength comes from the T6 heat treatment. The stretching does something different and, for a machinist, more important.
- Quenching after solution heat treatment locks residual stress into the bar. That stress is balanced while the bar is whole.
- The moment you machine a flat, a slot, or a bore off centre, you unbalance it, and the part moves. On a long slender part it bows visibly.
- Stretching the bar past yield after the quench redistributes and relieves that stress before you ever see it.
- This is why T6511 exists as a distinct temper and why it is worth specifying rather than accepting plain T6 for machined work.
- It is the same reasoning behind T651 in plate and T7451 in thick 7050. Stress relief is a machinability feature, not a strength feature.
What to Specify When You Order
Six lines on a purchase order remove almost every ambiguity that causes a rejected receipt.
- Alloy and temper: 6061-T6511.
- Specification: ASTM B221. Add AMS-QQ-A-200/8 if your print calls the legacy designation.
- Diameter and the length you actually need, rather than the 12 foot stock length.
- Whether you need certification. We ship mill certs with heat number and lot traceability on every order, and DFARS-compliant and domestic-melt material is available.
- Straightness or twist requirement, if the part is long and slender. Commercial extruded tolerances are looser than most people assume.
- Cut tolerance on the length, if you are machining to a shoulder rather than facing both ends.
Round Bar or Plate?
A question worth asking before you order, because for some parts bar is the wrong buy.
- Buy round bar when the part is round: shafts, spacers, bushings, pins, standoffs, turned components.
- Buy plate and cut a rectangle when the part is prismatic. Machining a square part out of round bar wastes the corners and the metal you remove is bought at full price.
- For a large diameter, short part, a disc sawn from plate is often cheaper than a slug from bar. Run the buy-to-fly ratio both ways.
- We stock plate in 6061-T651 from 0.25 to 10 inches alongside bar, so we can price both against your part.
6061-T6511 round bar is the workhorse extruded bar product, and the temper code is telling you it was stretched and straightened so it will hold its shape when you cut into it. Order it to ASTM B221, remember the 38,000 psi extruded minimum is not the 42,000 psi cold-finished minimum, and buy the length you need rather than the stick the mill happened to make.
Frequently Asked Questions
What does 6061-T6511 mean?
It is 6061 aluminum that has been solution heat treated and artificially aged (the T6 part), stress relieved by stretching (the 51), and lightly straightened afterwards (the final 1). It is the standard temper for extruded round bar, flat bar, squares, hexagons and shapes.
What is the difference between T6510 and T6511?
Only the straightening step. Both are stretched for stress relief. T6510 is not straightened after stretching, T6511 permits minor straightening to meet dimensional tolerances. Mechanical minimums are identical, and most extruded bar in distribution is T6511.
What is the tensile strength of 6061-T6511?
The specified minimum for extruded 6061-T6 and T6511 is 38,000 psi ultimate tensile with 35,000 psi yield and 17 percent elongation. Cold-finished 6061-T6 and T651 bar carries a higher 42,000 psi ultimate minimum at the same yield, so check which product form your print requires.
What specification covers 6061-T6511 round bar?
ASTM B221, the standard for aluminum extruded bars, rods, wire, profiles and tubes. Older drawings often reference AMS-QQ-A-200/8, the legacy designation for the same extruded product.
Can I buy 6061-T6511 round bar cut to length?
Yes. Standard mill stock is 12 foot, and we cut to the length you need so you are not paying for a stick you cannot use. Mill certs with heat number and lot traceability ship with every order, and you get a committed ship date at quote time.
6061-T6511 round bar
Price round bar cut to your length.
Extruded 6061-T6511 to ASTM B221, cut to size, with mill certs on every order and a committed ship date before you commit.