T6x (T61, T651)
Aged near peak strength. Highest strength; lower stress-corrosion resistance.
Aerospace · High-toughness sheet & plate
7475 Aerospace Aluminium Sheet and Plate
7475 is a high-purity version of 7075 developed for fracture toughness: at similar strength it resists crack growth far better, which suits fuselage skins, wing skins and bulkheads designed to damage-tolerance rules. Metline supplies 7475 sheet and plate in T61, T761, T651, T7651 and T7351, bare or alclad, to SAE AMS specifications, to aerospace customers worldwide.
- Alloy
- 7475 (high-purity 7075)
- Tempers
- T61, T761, T651, T7651, T7351
- Plate
- 6.35 – 101.6 mm (AMS 4202)
- Specs
- AMS 4202 · 4089 · 4090 · 4100
What 7475 is and why toughness matters
Aircraft structure is designed on the assumption that cracks exist and must not grow to a critical size between inspections. The property that governs this is fracture toughness. 7475 was developed to give 7075-level strength with markedly higher toughness, so sheets and plates tolerate longer cracks before failure.
The gains come from purity and processing. Iron is held to 0.12 % and silicon to 0.10 %, far below 7075 limits, so there are fewer coarse intermetallic particles for cracks to link through. Controlled rolling and heat treatment give a fine, uniform structure. In the over-aged T7351 condition, 7475 plate typically shows plane-strain fracture toughness 30 – 50 % higher than 7075-T7351 plate of similar thickness.
7475 is used for fuselage skins and bulkheads, wing skins on fighters and business jets, wing spar webs and pressure-cabin structure. Its fine-grained sheet can also be superplastically formed into complex one-piece parts.
7475 chemical composition compared with 7075 (wt %)
| Element | 7475 | 7075 | Why it matters |
|---|---|---|---|
| Silicon (Si) | ≤ 0.10 | ≤ 0.40 | Low Si and Fe reduce coarse particles |
| Iron (Fe) | ≤ 0.12 | ≤ 0.50 | Main reason for higher toughness |
| Copper (Cu) | 1.2 – 1.9 | 1.2 – 2.0 | Strength |
| Manganese (Mn) | ≤ 0.06 | ≤ 0.30 | Kept low |
| Magnesium (Mg) | 1.9 – 2.6 | 2.1 – 2.9 | Slightly lower in 7475 |
| Chromium (Cr) | 0.18 – 0.25 | 0.18 – 0.28 | Grain control |
| Zinc (Zn) | 5.2 – 6.2 | 5.1 – 6.1 | Main strengthening element |
| Titanium (Ti) | ≤ 0.06 | ≤ 0.20 | Grain refiner |
| Others, each / total | 0.05 / 0.15 | 0.05 / 0.15 |
Registered Aluminum Association limits. The AMS titles give the nominal 7475 chemistry as 5.7 Zn - 2.2 Mg - 1.6 Cu - 0.22 Cr.
Mechanical properties by temper
Minimum properties are set in each AMS specification by thickness band and direction. The values below are approximate typical values for medium-thickness material, given to compare tempers. Use the specification minimums or MMPDS allowables for design.
| Temper and form (approx. typical) | Tensile strength | Yield strength | Elongation | Fracture toughness KIc (L-T) |
|---|---|---|---|---|
| T651 plate | About 560 MPa | About 495 MPa | About 11 % | About 35 – 40 MPa√m |
| T7651 plate | About 530 MPa | About 460 MPa | About 12 % | About 38 – 45 MPa√m |
| T7351 plate | About 500 MPa | About 430 MPa | About 13 % | About 42 – 50 MPa√m |
| T61 sheet | About 540 MPa | About 470 MPa | About 12 % | High (plane stress) |
| T761 sheet | About 510 MPa | About 440 MPa | About 12 % | High (plane stress) |
| 7075-T7351 plate (comparison) | About 505 MPa | About 435 MPa | About 13 % | About 30 – 33 MPa√m |
Physical properties
- Density
- 2.81 g/cm³ (0.101 lb/in³)
- Modulus of elasticity
- About 70 – 72 GPa
- Electrical conductivity
- About 33 % IACS (T6x); about 40 % IACS (T73x)
- Coefficient of thermal expansion
- About 23.2 µm/m·°C
- Melting range
- About 475 – 635 °C
7475 tempers and their AMS specifications
| Temper and form | Specification | Typical use |
|---|---|---|
| T7351 plate, 6.35 – 101.6 mm | AMS 4202 | Bulkheads, spar webs, fittings needing maximum SCC resistance |
| T7651 plate, 6.35 – 38.1 mm | AMS 4089 | Wing skins and panels needing exfoliation resistance with more strength |
| T651 plate | AMS 4090 | Parts with no special stress-corrosion requirement |
| T61 sheet | AMS 4084 | Fuselage and wing sheet, highest sheet strength |
| T761 sheet | AMS 4085 | Sheet needing exfoliation resistance |
| Alclad T761 sheet, 1.02 – 6.32 mm | AMS 4100 | External fuselage skins |
T76x (T761, T7651)
Moderately over-aged for good exfoliation resistance with a small strength loss.
T73x (T7351)
Fully over-aged for maximum SCC resistance; typically the highest toughness.
7475 sheet and plate sizes
Supply range
- Sheet
- About 1.0 – 6.3 mm, bare or alclad
- Plate
- 6.35 – 101.6 mm depending on temper and specification
- Widths and lengths
- Mill sizes, or saw-cut pieces to drawing
- Surface
- Mill finish, film or interleaf protected
| Thickness (mm) | kg per m² | 1250 × 2500 mm piece (kg) |
|---|---|---|
| 1.6 | 4.5 | 14.1 |
| 2 | 5.6 | 17.6 |
| 3.2 | 9.0 | 28.1 |
| 4 | 11.2 | 35.1 |
| 6.35 | 17.8 | 55.8 |
| 12.7 | 35.7 | 111.5 |
| 19.05 | 53.5 | 167.3 |
| 25.4 | 71.4 | 223.0 |
| 38.1 | 107.1 | 334.6 |
| 50.8 | 142.7 | 446.1 |
| 76.2 | 214.1 | 669.1 |
| 101.6 | 285.5 | 892.2 |
Testing and inspection
Typical requirements
- Tensile
- L and LT tests; ST tests on thicker plate
- Fracture toughness
- KIc to ASTM E399 on plate where the specification requires it
- Corrosion
- Exfoliation (ASTM G34) and SCC lot acceptance for over-aged tempers
- Conductivity
- Eddy-current conductivity on each lot
- Ultrasonic
- Plate to AMS-STD-2154 or ASTM B594 when ordered
- Certification
- EN 10204 3.1 certificate with chemistry, properties and lot traceability
Machining, forming and finishing
Machining
Machines like 7075. Stretched plate tempers (T651, T7651, T7351) stay flat during heavy pocketing.
Forming
Sheet can be formed in O or W condition and aged. Fine-grain 7475 sheet is used for superplastic forming at around 500 °C.
Joining
Riveted or bolted; not fusion-welded.
Protection
Alclad for external skins; anodise or conversion coat and prime bare material.
Where 7475 is used
- Fuselage: skins, pressure bulkheads and frames sized by damage tolerance
- Wing: skins of fighters and business jets, spar webs and ribs
- Fittings: machined from T7351 plate where SCC resistance is critical
- Superplastic parts: complex one-piece panels and doors formed from fine-grain sheet
- Space: launcher and satellite structure where crack tolerance matters
How to order 7475 sheet and plate
- SpecifyAlloy and temper, temper, bare or alclad, thickness and size, quantity and the governing specification with its revision letter (AMS 4202, 4089, 4090, 4084, 4085 or 4100). Add any customer or prime-contractor material specification that sits on top of the AMS.
- ConfirmWe confirm the specification can be met, the tolerance class, any extra tests (ultrasonic class, conductivity, fracture toughness, grain flow) and the delivery terms (EXW, FOB, CIF or DAP).
- InspectMaterial is checked for dimensions, surface condition and marking; tests named on the order are carried out or arranged with an independent laboratory.
- DocumentEach lot ships with a mill test certificate to EN 10204 3.1 giving chemistry, mechanical results and heat-treatment lot, traceable to the cast number.
- Pack and shipExport packing in sealed, moisture-protected wooden cases or on pallets, shipped by sea or air to your port or door.
References and standards
- SAE AMS 4202 – Plate, 5.7Zn - 2.2Mg - 1.6Cu - 0.22Cr (7475-T7351)
- SAE AMS 4089 – Plate, 7475-T7651
- SAE AMS 4100 – Alclad Sheet, 7475-T761
- ASTM E399 – Linear-Elastic Plane-Strain Fracture Toughness of Metallic Materials
- The Aluminum Association – International Alloy Designations and Chemical Composition Limits (Teal Sheets)
- MMPDS – Metallic Materials Properties Development and Standardization (successor to MIL-HDBK-5)
7475 aerospace aluminium (aluminum) plate: FAQ
What is the difference between 7475 and 7075?
They have similar zinc, magnesium and copper, but 7475 limits iron to 0.12 % and silicon to 0.10 %. Fewer coarse particles give much higher fracture toughness and better fatigue crack growth resistance at similar strength.
Which 7475 temper should I choose?
T7351 for maximum stress-corrosion resistance and toughness, T7651 for more strength with good exfoliation resistance, and T651 or T61 where strength matters most and SCC is not a concern.
Which specification covers 7475-T7351 plate?
SAE AMS 4202, for plate 0.250 to 4.000 in (6.35 to 101.6 mm) thick.
Is 7475 available alclad?
Yes. Alclad 7475-T761 sheet is covered by AMS 4100 for thicknesses 1.02 to 6.32 mm and is used for external fuselage skins.
Can 7475 be superplastically formed?
Yes. Fine-grain 7475 sheet is one of the established aluminium alloys for superplastic forming of complex aircraft parts.
Do you supply 7475 plate worldwide?
Yes. Metline ships 7475 sheet and plate worldwide with EN 10204 3.1 certificates and export packing.
Need 7475 sheet or plate?
Send the temper, thickness, size and specification. We will confirm availability and a delivered price.
