Key facts
Where to buy| Property | Value | Source |
|---|---|---|
| Temper T4 | Solution heat-treated, naturally aged to a stable condition | AC 43.13-1B Table 4-4 |
| Temper T351 | Solution heat-treated, stretched 1 to 3 % permanent set | AC 43.13-1B Table 4-4 |
| Density | 0.100 lb/in³ (2.78 g/cm³) | MIL-HDBK-5J; Teal Sheets |
| Brinell hardness, 2024-T4 | 120 (500 kg load, 10 mm ball) | AC 43.13-1B Table 4-5 |
| Arc welding / spot welding | C (limited) / B (special techniques) | MIL-HDBK-5J Table 3.1.3.4(a) |
| Stress corrosion, 2024-T3, T4 plate | L: A · LT: B · ST: D (lowest) | MIL-HDBK-5J Table 3.1.2.3.1(a) |
The AC lists 2024 among aluminum alloys not to be welded (par. 4-89d). The handbook's C rating is a relative rating, not a permission.
Reading the alloy and temper code
Composition limits, weight percent
| Element | Limit |
|---|---|
| Si | 0.50 |
| Fe | 0.50 |
| Cu | 3.8–4.9 |
| Mn | 0.30–0.9 |
| Mg | 1.2–1.8 |
| Cr | 0.10 |
| Zn | 0.25 |
| Ti | 0.15 |
| Al | Remainder |
A single number is a maximum. Other elements: 0.05 each, 0.15 total, except where the Teal Sheets say otherwise. Source: Aluminum Association Teal Sheets (Aug 2018).
Quick check
You need thick stock to machine a fitting from 2024. Which temper is listed for plate?
- T351
Best fit. MIL-HDBK-5J lists T351 for plate from 0.250 in. The stretch relieves quench stress.
- T3
Not this one. In the handbook table, T3 is sheet up to 0.249 in.
- O
Not this one. O is annealed and has no strength allowables here.
On a real job, the SRM decides.
Design allowables, 2024-T4 coiled sheet and T351 plate
| Property, ksi | T4 A | T4 B | T351 A | T351 B |
|---|---|---|---|---|
| Ftu, L | 62 | 64 | 64 | 66 |
| Ftu, LT | 62 | 64 | 64 | 66 |
| Fty, L | 40 | 42 | 48 | 50 |
| Fty, LT | 40 | 42 | 42 | 44 |
| Fcy, L | 40 | 42 | 39 | 41 |
| Fcy, LT | 40 | 42 | 45 | 47 |
| Fsu | 37 | 38 | 38 | 39 |
| Fbru, e/D = 1.5 | 93 | 96 | 97 | 100 |
| Fbru, e/D = 2.0 | 118 | 122 | 119 | 122 |
| Fbry, e/D = 1.5 | 56 | 59 | 72 | 76 |
| Fbry, e/D = 2.0 | 64 | 67 | 86 | 90 |
T4: coiled sheet, 0.010–0.249 in, AMS-QQ-A-250/4, Table 3.2.3.0(b2), p. 3-72. T351: plate, 0.250–0.499 in, AMS 4037 and AMS-QQ-A-250/4, Table 3.2.3.0(b1), p. 3-71. S, A and B are the MIL-HDBK-5J statistical bases. L is the longitudinal grain direction, LT the long transverse. Bearing values are dry-pin values.
Minimum bend radius, inches (AMT Handbook Chart 204)
| Alloy and temper | 0.020" | 0.032" | 0.040" | 0.063" | 0.125" | 0.190" |
|---|---|---|---|---|---|---|
| 2024-T3, 2024-T4 | .09 | .12 | .16 | .22 | .50 | 1.00 |
| 2024-T6 | .09 | .12 | .16 | .25 | .62 | 1.00 |
Selected thicknesses from FAA-H-8083-31B Chart 204, p. 4-61. Chart 204 and AC Table 4-6 do not agree everywhere: where they differ, use the larger radius or the SRM.
Bend radii (AC 43.13-1B Table 4-6)
| Alloy and temper | 0.016" | 0.032" | 0.064" | 0.128" | 0.182" | 0.258" |
|---|---|---|---|---|---|---|
| 2024-O | 0 | 0 – 1t | 0 – 1t | 0 – 1t | 0 – 1t | 0 – 1t |
| 2024-T3 | 1½t – 3t | 2t – 4t | 3t – 5t | 4t – 6t | 4t – 6t | 5t – 7t |
Recommended radii for 90-degree bends, as multiples of sheet thickness t. Alclad sheet may go slightly tighter than bare (Table 4-6 note 1). The drawing or SRM governs.
T4, T351 or T3
T4 has lower yield than T3 for the same ultimate: 40 against 47 ksi on the A basis (L direction). AMT Handbook Chart 204 groups T3 and T4 for bending.
T351 is listed for plate from 0.250 in. Thicker plate falls in strength: at 3.001–4.000 in the A basis Ftu is 57 ksi (L).
T42 is what a user gets by heat-treating from O or F. The handbook gives it separately, S basis, with Fty 38 ksi in sheet, and warns that a user's properties may differ if the material was formed or cold worked first (Table 3.2.3.0(b2)).
Rivets. 2024-T4 rivets are too hard to drive as received: they are kept cold in the quenched condition or reheat-treated just before driving (AC par. 4-57). The AMT Handbook says most have been replaced by E-type rivets (p. 4-31).
Corrosion and heat treatment
2024-T3, T4 and T42 plate, rod, bar and extrusions carry a D stress-corrosion rating in the short transverse direction: failures have occurred in service or would be expected under any sustained stress (MIL-HDBK-5J 3.2.3.0).
Where short times at 150 to 500 °F may occur, the handbook recommends precipitation-hardened tempers of 2024 over naturally aged ones (3.1.2.3.1). Heat-treat to the manufacturer's instruction (AC par. 4-54).
Specifications and product forms
| Specification | Form |
|---|---|
| AMS 4037 | Bare sheet and plate |
| AMS 4035 | Bare sheet and plate |
| AMS-QQ-A-250/4 | Bare sheet and plate |
| AMS-QQ-A-250/5 | Clad sheet and plate |
| AMS 4120, AMS-QQ-A-225/6 | Bar, rod, wire |
| AMS 4152, AMS 4164, AMS 4165, AMS-QQ-A-200/3 | Extrusion |
| AMS 4086, AMS-WW-T-700/3 | Drawn tubing |
Specifications as listed by MIL-HDBK-5J. Federal QQ-A specifications passed to SAE as AMS-QQ-A. Check the current revision.
Questions people actually ask
What is the difference between 2024-T3 and 2024-T351?
T3 is cold-worked by flattening or straightening. T351 is stretched 1 to 3 percent to relieve stress (AC Table 4-4). In MIL-HDBK-5J, T3 is sheet and T351 is plate.
Are 2024-T4 and 2024-T42 the same?
The AMT Handbook's material substitution figure says they are equivalent (Figure 4-168), but MIL-HDBK-5J lists different allowables. Use the value for the temper on the certificate.
Limits — when NOT to use this
- Not a source of design allowables. Values are for reference. MMPDS and the SRM govern a repair.
- Not a substitution approval. A different alloy or temper needs approved data.
- Not for welding. AC par. 4-89d lists 2024 among alloys not to be welded.
Where to buy
Distributors coming soon.
Sources
- FAA AC 43.13-1B CHG 1, Chapters 4 and 7 — Tables 4-4, 4-5, 4-6; pars. 4-54, 4-57, 4-89.
- FAA-H-8083-31B, AMT Handbook — Airframe, Volume 1, Chapter 4 — Chart 204, p. 4-61; Figure 4-168, p. 4-87; rivets, p. 4-31.
- MIL-HDBK-5J (31 Jan 2003), Chapter 3 — Tables 3.1.2.3.1(a), 3.1.3.4(a), 3.2.3.0(a), (b1), (b2). Cancelled and superseded by MMPDS: check current MMPDS before design use.
- Aluminum Association, International Alloy Designations (Teal Sheets), rev. Aug 2018 — chemical composition limits and nominal densities.
- MMPDS (formerly MIL-HDBK-5) — the current home of design allowables. A repair substantiation cites MMPDS or the SRM, not a website.