Die forgings
Metal is forged in closed dies so the grain flow follows the part shape. This gives the best fatigue and stress-corrosion performance for complex fittings, but needs dedicated tooling, so it suits repeat production.
Aerospace materials guide
Aluminium Alloys for Aerospace Components
Aerospace components such as frames, spars, landing-gear fittings, window frames, intake panels and propeller hubs are machined from aluminium forgings, thick plate and extrusions in a small family of alloys: 7050, 7075, 2024, 2014, 2618, 2219 and 6061. Each is chosen for a particular balance of strength, fracture toughness, stress-corrosion resistance and temperature capability, and bought to SAE AMS specifications. This guide maps components to alloys, tempers, product forms and standards for engineers and buyers.
- Key alloys
- 7050, 7075, 2024, 2014, 2618, 2219
- Forms
- Forgings, plate, extrusions, bar
- Specs
- SAE AMS · ASTM B247
- Inspection
- Ultrasonic to AMS-STD-2154
Why aluminium still dominates many aircraft parts
Composites now make up much of the skin of the newest wide-body airliners, but aluminium remains the main material for most of the world's fleet and for a large share of internal structure, fittings and systems on every aircraft. It is light, well understood, easy to machine and inspect, repairable and comparatively inexpensive.
Aerospace components fall into a few groups. Primary structure (frames, spars, ribs, bulkheads, wing and fuselage fittings) carries flight loads and must resist fatigue and crack growth. Landing-gear and engine-mount fittings see high static loads and need stress-corrosion resistance. Engine-adjacent parts such as propeller hubs, intake components and compressor housings need strength at elevated temperature. Secondary structure, ducts and ground equipment need weldability or formability more than peak strength.
Higher-temperature engine parts, such as compressor discs and turbine components, are made from titanium and nickel alloys rather than aluminium. Landing-gear cylinders are typically high-strength steel. This guide focuses on the aluminium parts, which Metline supplies as certified raw material: forgings, plate, bar and extrusions for machining by component makers.
Aerospace aluminium alloys at a glance
| Alloy and temper | Typical tensile / yield (MPa) | Character | Typical components |
|---|---|---|---|
| 7050-T7451 plate / T74, T7452 forgings | ≈ 524 / 469 (T7451 plate) | High strength with good toughness and stress-corrosion resistance in thick sections | Frames, bulkheads, spars, wing and fuselage fittings, window frames |
| 7075-T6 / T651 | ≈ 572 / 503 | Very high strength; lower stress-corrosion resistance in T6 | Fittings, gears, seat tracks, highly loaded thin parts |
| 7075-T73 / T7351 | Lower than T6 | Overaged for much better stress-corrosion resistance | Forged fittings and thick parts loaded in short-transverse direction |
| 2024-T3 / T351 | ≈ 483 / 345 (T3 sheet) | Excellent fatigue and damage tolerance | Fuselage skins, lower wing skins, tension structure |
| 2014-T6 / T652 | ≈ 483 / 414 | High strength, good forgeability | Forged fittings, wheels, hydraulic components |
| 2618-T61 | ≈ 440 / 370 | Keeps strength at about 150 – 250 °C | Propeller hubs, compressor and engine parts, pistons |
| 2219-T87 / T851 | ≈ 476 / 393 (T87) | Weldable, good at cryogenic and elevated temperatures | Cryogenic tanks, space structures, welded assemblies |
| 6061-T6 / T651 | ≈ 310 / 276 | Weldable, corrosion-resistant, moderate strength | Secondary structure, ducting, ground support equipment |
Values are typical room-temperature figures from published Aluminum Association / ASM data for the form indicated. Design and acceptance use the specified minimums in the AMS specification for the exact product, thickness and direction.
Which material for which component
| Component | Usual aluminium choice | Usual product form | Why |
|---|---|---|---|
| Fuselage frames and bulkheads | 7050-T7451 or T7452 | Thick plate or hand forging, then machined | Strength and toughness with good stress-corrosion resistance |
| Wing spars and ribs | 7050-T7451, 7075-T7351, 2024 for lower wing | Plate, extrusion, forging | Combination of compression strength and damage tolerance |
| Landing-gear fittings and side braces | 7050-T74, 7075-T73 | Die forging | High strength with stress-corrosion resistance in the forging grain flow |
| Cockpit window frames | 7050-T7452 | Hand or die forging | Large, complex parts machined from thick sections |
| Engine intake panels and ducts | 7050-T7452, 5xxx for formed panels | Forging, sheet | Strength, or formability for curved duct skins |
| Propeller hubs and blades | 2618-T61 hubs; 2xxx alloys for blades | Die forging | Strength retained at elevated temperature; fatigue resistance |
| Seat tracks and floor beams | 7075-T6, 7050, 7150 | Extrusion | High strength in long, constant sections |
| Space tanks and structures | 2219, 2195 (Al-Li) | Plate, forging, rolled ring | Weldability and cryogenic toughness |
Forgings, plate and extrusions compared
Hand (open-die) forgings
Forged between flat or simple dies into blocks, bars and rough shapes, then machined. T7452 and T7352 hand forgings are compression stress-relieved to keep machined parts stable.
Rolled rings
Seamless rings for engine casings, adapters and tank joints, forged and rolled to diameter.
Thick plate
Stretched T7451 or T651 plate up to about 150 – 200 mm is machined into frames and ribs; "buy-to-fly" ratios can exceed 10:1.
Extrusions
Seat tracks, stringers, floor beams and spar caps are extruded to near-final shape in T6511, T73511 or T76511 tempers.
Sheet and clad sheet
Alclad 2024-T3 and 7075-T6 sheet for skins, with a thin pure-aluminium layer for corrosion protection.
Specifications that govern aerospace aluminium
| Specification | Scope |
|---|---|
| AMS 4107 | 7050-T74 die forgings and forging stock |
| AMS 4108 | 7050-T7452 hand forgings, compression stress-relieved and overaged |
| AMS 4050 | 7050-T7451 plate |
| AMS 4045 / AMS 4078 | 7075-T6/T651 sheet and plate; 7075-T7351 plate |
| AMS 4132 | 2618-T61 die and hand forgings, rolled rings and forging stock |
| ASTM B247 | Aluminium alloy die forgings, hand forgings and rolled ring forgings (general) |
| AMS 2770 / AMS 2772 | Heat treatment of aluminium parts and raw materials |
| AMS 2750 | Pyrometry for heat-treatment furnaces |
| AMS-STD-2154 | Ultrasonic inspection of wrought metals, classes AAA to B |
| AS9100 | Quality management standard used across the aerospace supply chain |
Customer and programme specifications often add their own requirements on top of AMS, such as additional ultrasonic classes, grain-flow checks, conductivity checks to confirm temper, or first-article inspection. Buyers should send these with the enquiry so the material is certified correctly from the start.
Inspection and certification of aerospace aluminium
- Chemistry: melt analysis per heat, checked against the AMS or Aluminum Association limits
- Mechanical tests: tensile tests in longitudinal, long-transverse and, for thick sections, short-transverse directions
- Temper verification: electrical conductivity and hardness checks, especially for overaged 7xxx tempers
- Stress-corrosion and exfoliation testing where the specification requires it
- Ultrasonic inspection to the class stated on the order, typically class A or AA for thick plate and forgings
- Dimensional and surface inspection, and grain-flow or macro-etch checks on forgings
- Certification: EN 10204 3.1 or AMS-compliant certificates traceable to heat and lot
Traceability is as important as the test results. Every plate, bar or forging should be marked so it can be traced back to its heat, lot and certificate throughout machining.
Practical selection advice and common mistakes
| Mistake | Better practice |
|---|---|
| Specifying 7075-T6 for a thick fitting loaded through its thickness | Use 7050-T74/T7452 or 7075-T73, which resist stress-corrosion cracking in the short-transverse direction |
| Machining thick plate in unstretched tempers | Use T7451 or T651 stretched plate, or T7452 compression-stressed forgings, to limit distortion |
| Ordering by alloy only | State alloy, temper, AMS specification, dimensions, ultrasonic class and any customer specifications |
| Ignoring grain direction | Place the highest loads along the longitudinal grain; ask for test results in the critical direction |
| Choosing 7xxx for parts above about 120 °C | Use 2618-T61 or 2219 where sustained elevated temperature is expected |
- Define the partLoad case, operating temperature, environment, size and shape.
- Choose alloy and temperBalance strength, toughness and stress-corrosion needs using the table above.
- Choose the formDie forging for repeat complex parts, hand forging or plate for prototypes and large machined parts, extrusion for long constant sections.
- Specify certificationAMS specification, ultrasonic class, test directions and documentation.
- Quote and shipDelivery on EXW, FOB, CIF or DAP terms, with export packing that protects machined or sensitive surfaces.
References and standards
- SAE AMS 4107 – Aluminum Alloy Die Forgings (7050-T74), Solution Heat Treated and Overaged
- SAE AMS 4108 – Aluminum Alloy Hand Forgings (7050-T7452)
- SAE AMS 4132 – Aluminum Alloy Die and Hand Forgings, Rolled Rings (2618-T61)
- ASTM B247 – Standard Specification for Aluminum and Aluminum-Alloy Die Forgings, Hand Forgings, and Rolled Ring Forgings
- AMS-STD-2154 – Inspection, Ultrasonic, Wrought Metals, Process for
- ASM International – Properties of Wrought Aluminum and Aluminum Alloys
Aluminium (aluminum) for aerospace components: frequently asked questions
What is the most common aluminium alloy in aircraft structure?
7050 and 7075 dominate high-strength structure and fittings, while 2024 remains the standard for fatigue-critical skins and tension structure. 6061 is used for secondary structure and ground equipment.
Why is 7050 preferred over 7075 for thick forgings?
7050 keeps high strength and toughness through thick sections and, in T74/T7451/T7452 tempers, resists stress-corrosion cracking much better than 7075-T6. That makes it the usual choice for frames, bulkheads and large fittings.
Which aluminium alloy is used for propeller hubs?
2618-T61 is commonly used because it keeps its strength at elevated temperatures better than 7xxx alloys. It is supplied as die or hand forgings to AMS 4132.
What is the difference between a die forging and a hand forging?
A die forging is shaped in closed dies to near the final geometry, with grain flow following the part. A hand forging is formed between open dies into a simple shape and then machined. Die forgings suit repeat production; hand forgings suit prototypes, large parts and low volumes.
What ultrasonic class do aerospace forgings need?
It depends on the part and the customer specification. Class A or AA to AMS-STD-2154 is common for thick plate and critical forgings; the class must be stated on the order.
Does Metline supply finished aircraft parts?
Metline supplies certified aluminium raw material, including forgings, plate, bar and extrusions to AMS and ASTM specifications, for component makers to machine and qualify. Cutting to size is available on request.
Sourcing aerospace aluminium?
Send the alloy, temper, specification and dimensions. Our team will reply with a certified offer and delivery terms.
