7475 Aluminium Sheet & Plate

What is 7475 aluminium?

7475 is an Al-Zn-Mg-Cu alloy with the same strengthening elements as 7075, but with iron capped at 0.12 % and silicon at 0.10 %, against 0.50 % and 0.40 % in 7075. Removing those impurities removes most of the coarse iron- and silicon-rich particles that act as starting points for cracks, which is where the gain in toughness comes from.

The alloy was developed for airframe structures designed on damage-tolerance principles, where the question is not only "how strong is the part?" but "how long will a crack take to grow, and how big can it get before the part fails?" In those designs, plane-strain fracture toughness (K_Ic) and fatigue crack growth rate govern skin thickness as much as tensile strength does. Published comparisons put 7475 well ahead of 7075 in the same temper, which is why it is used for wing skins, fuselage panels, bulkheads and spars on military and commercial aircraft.

Processing matters as much as chemistry. 7475 is rolled and solution heat-treated under tighter control than general-purpose 7xxx plate, and it is usually sold to aerospace material specifications rather than to general commercial standards. That makes it a specialist product: more expensive than 7075, available in a narrower range of sizes, and normally ordered with full traceability.

7475 chemical composition (wt %)

Limits are the registered Aluminum Association values for 7475, which AMS and EN 573-3 (EN AW-7475) follow. Compare the iron and silicon maxima with 7075 to see where the toughness advantage comes from.

Alclad 7475 sheet carries a cladding layer, typically 7072 or a similar zinc-bearing pure aluminium, metallurgically bonded to each face. The cladding is anodic to the core and corrodes sacrificially to protect it.

Mechanical properties of 7475 by temper

The values below are typical figures for room temperature, rounded from published data. They show how the tempers rank against each other. For design, use the minimum values in the governing AMS specification or MMPDS for your thickness band, and check the mill certificate for each lot.

Two patterns are worth noting. First, each step of over-ageing from T6 to T76 to T73 gives up roughly 30 – 50 MPa of strength in exchange for better corrosion behaviour. Second, Alclad sheet always reads lower than bare sheet of the same temper, because the soft cladding layer carries part of the cross-section; the reduction is larger in thinner gauges, where the cladding is a greater share of the thickness.

Choosing a 7475 temper

7475 is sold in more tempers than most alloys because the airframer chooses a different balance of strength and corrosion resistance for each part. The table below summarises the options and the specifications they are usually bought to.

7475 specifications and international designations

Most 7475 is bought to SAE AMS specifications or to an airframer's own material specification (for example Boeing BMS or Airbus AIMS documents). Commercial orders can also reference ASTM B209 or EN 485. Tell us which document governs your drawing and we will quote material certified to it.

If your purchase order quotes an airframer specification, the material must come from a mill qualified to that specification. Tell us at the enquiry stage so we can confirm the approved source before quoting.

7475 sheet and plate sizes

At a density of 2.81 g/cm³, 7475 weighs 2.81 kg per square metre for each millimetre of thickness, about 4 % heavier than 6061. The table gives reference weights for common gauges; use the plate weight calculator for other sizes.

Tolerances, flatness and inspection

Aerospace sheet and plate is rejected for defects that would pass in general engineering. The checks below are the ones buyers most often specify; list any additional requirement in your enquiry so it is part of the quotation.

Machining, forming, joining and finishing

Where 7475 sheet and plate are used

• Wing structure: upper and lower wing skins, spar webs and stiffened panels designed for damage tolerance
• Fuselage: skins, bulkheads, frames and pressure-deck panels, often in Alclad sheet or T7351 plate
• Military aircraft: structural panels where fatigue life under high load spectra governs design
• Space and launch vehicles: machined panels and fittings that need toughness at low temperature
• Defence equipment: high-strength structural parts and protective panels
• Superplastic forming: fine-grain 7475 sheet has been used for complex superplastically formed aircraft parts
• Precision industrial parts: highly loaded components where crack tolerance matters more than lowest cost

7475 compared with 7075, 7050 and 2024

Choose 7475 when a thin-to-medium section must combine 7xxx strength with damage tolerance. For very thick plate machined into large frames, 7050 is usually preferred because it is less quench-sensitive. Where cost matters more than fracture behaviour, 7075 remains the workhorse, and where fatigue in tension-dominated skins is the issue, 2024 is still common.

Related aerospace grades and guides

How to order 7475 sheet and plate

1. SpecifyAlloy and temper (e.g. 7475-T7351), bare or Alclad, thickness, width, length or drawing, quantity, and the governing specification (AMS, airframer or ASTM).
2. Confirm requirementsState ultrasonic class, conductivity, short-transverse testing, source approvals and any third-party inspection.
3. QuoteWe confirm the certified source, size availability, documents and delivery terms (EXW, FOB, CIF or DAP).
4. Process and packCut to size if required, interleaved or film-protected, and packed flat in seaworthy wooden cases.
5. Ship and documentShipped by sea or air with the EN 10204 3.1 mill certificate and full lot traceability.

7475 aluminium (aluminum) sheet and plate: FAQs