Key facts
| Property | Value | Source |
|---|---|---|
| Brinell hardness, 6061-T6 | 95 (500 kg load, 10 mm ball) | AC 43.13-1B CHG 1, Table 4-5 |
| Brinell hardness, 6061-T4 / 6061-O | 65 / 30 | AC 43.13-1B CHG 1, Table 4-5 |
| Weldability | Generally weldable by all commercial procedures | FAA-H-8083-31, p. 4-31 |
Hardness is a check on temper, not a strength value. Bend radii are in the table below.
Bend radii, 6061 (AC 43.13-1B Table 4-6)
| Alloy and temper | 0.016" | 0.032" | 0.064" | 0.128" | 0.182" | 0.258" |
|---|---|---|---|---|---|---|
| 6061-O | 0 | 0 – 1t | 0 – 1t | 0 – 1t | 0 – 1t | 0 – 1t |
| 6061-T4 | 0 – 1t | 0 – 1t | ½t – 1½t | 1t – 2t | 1½t – 3t | 2½t – 4t |
| 6061-T6 | 0 – 1t | ½t – 1½t | 1t – 2t | 1½t – 3t | 2t – 4t | 3t – 4t |
Recommended radii for 90-degree bends, sheet thickness t. “0” means no radius required. Alclad sheet may be bent over slightly smaller radii than the uncoated alloy (Table 4-6 footnote 1).
Design allowables — 6061-T6/T62 sheet
0.010–0.249 in thick. MIL-HDBK-5J Table 3.6.2.0(b1). A and B bases in ksi unless a unit is shown.
| Property | A basis | B basis | Unit |
|---|---|---|---|
| Ftu, L | 42 | 43 | ksi |
| Ftu, LT | 42 | 43 | ksi |
| Fty, L | 36 | 38 | ksi |
| Fty, LT | 35 | 37 | ksi |
| Fcy, L | 35 | 37 | ksi |
| Fcy, LT | 36 | 38 | ksi |
| Fsu | 27 | 28 | ksi |
| Fbru, e/D = 1.5 | 67 | 69 | ksi |
| Fbru, e/D = 2.0 | 88 | 90 | ksi |
| Property | A basis | B basis | Unit |
|---|---|---|---|
| Fbry, e/D = 1.5 | 50 | 53 | ksi |
| Fbry, e/D = 2.0 | 58 | 61 | ksi |
| Elongation, LT, 0.010–0.020 in (minimum) | 8 | — | % |
| Elongation, LT, 0.021–0.249 in (minimum) | 10 | — | % |
| E | 9.9 | 9.9 | 10³ ksi |
| Ec | 10.1 | 10.1 | 10³ ksi |
| G | 3.8 | 3.8 | 10³ ksi |
| Density | 0.098 | 0.098 | lb/in³ |
Form: sheet; temper: T6 and T62; specification: AMS 4025, AMS 4027 and AMS-QQ-A-250/11; thickness 0.010–0.249 in. The handbook gives elongation in its Table 3.6.2.0(b3), p. 3-266, as a minimum by thickness (the values here), not by basis. E, Ec, G and density are printed once across all columns. T651 plate is in Table 3.6.2.0(b2), p. 3-265, and is not shown here. Source: MIL-HDBK-5J (31 Jan 2003), Table 3.6.2.0(b1), p. 3-264. MIL-HDBK-5J (2003) is superseded by MMPDS; check current MMPDS before design use. Density 0.098 lb/in³ is about 2.71 g/cm³ (converted); the sheet weight calculator uses the same figure.
Where it is used
The AMT Handbook says 6061 is easily extruded and commonly used for hydraulic and pneumatic tubing, and that it keeps acceptable toughness in many cryogenic applications (p. 4-31).
The sources give no application list beyond this; the drawing decides. Where a drawing calls for 2024-T3 it generally has a reason. See the comparison.
Temper and heat treatment
T4 is solution heat-treated. T6 is solution heat-treated and artificially aged (AC 43.13-1B Table 4-4). The gap shows in Table 4-5 (hardness 65 against 95) and in Table 4-6: T4 bends tighter than T6 at every thickness from 0.032" up.
Heat-treat to the manufacturer's instruction; heat-treat riveted parts before riveting (AC par. 4-54).
Forming
At 0.064" the AC allows 1t to 2t in T6, where 2024-T3 needs 3t to 5t. That is the main reason to pick it for a bracket.
Bending across the grain still matters. If a 6061-T6 bracket cracks at a radius Table 4-6 permits, check the grain direction and the thickness before blaming the alloy. Setback and flat pattern: bend allowance.
Questions people actually ask
Which bends tighter, 6061-T4 or 6061-T6?
T4. At 0.064" Table 4-6 gives ½t to 1½t for T4 and 1t to 2t for T6.
Is 6061 in the AC's rivet splice tables?
No. Tables 4-9 and 4-10 list 2014, 2017, 1017 Alclad, 2024 and 7075 products. 6061 data comes from the structural repair manual or MMPDS.
Limits — when NOT to use this
- Not a source of design allowables. Strength values come from MMPDS with their basis and thickness range; the structural repair manual governs a repair.
- Not a substitute for 2024-T3 or 7075-T6 unless the drawing permits it. It is weaker and less fatigue-tolerant. Material substitution in a structural repair is approved-data territory.
- Weld repair of primary structure is not covered here. Follow the SRM.
- Corrosion protection is not rated on this page. Neither source gives a table for it; follow the finish in the SRM.
Sources
- FAA AC 43.13-1B CHG 1, Chapter 4 — Tables 4-4, 4-5, 4-6, 4-9, 4-10; par. 4-54 — temper definitions, hardness, bend radii, heat treatment, and the alloys the splice tables cover.
- FAA-H-8083-31, AMT Handbook — Airframe, Volume 1, Chapter 4, p. 4-31 — weldability, extrusion and tubing use, cryogenic toughness.
- MIL-HDBK-5J, Metallic Materials and Elements for Aerospace Vehicle Structures — density (Table 3.6.2.0(b1)), and the home of the design allowables (Chapter 3, aluminum). Cancelled; replaced by MMPDS.
- MIL-HDBK-5J (31 Jan 2003), Table 3.6.2.0(b1), p. 3-264 — 6061-T6/T62 sheet, 0.010–0.249 in: Ftu, Fty, Fcy, Fsu, Fbru, Fbry, E, Ec, G and density.
- MIL-HDBK-5J (31 Jan 2003), Table 3.6.2.0(b3), p. 3-266 — minimum elongation values for 6061 T6 or T62 sheet.
- MMPDS (formerly MIL-HDBK-5) — the current home of design allowables with A, B and S basis. Cancelled MIL-HDBK-5J was superseded by it. A repair substantiation cites MMPDS or the SRM, not a website.