The Metals Behind Modern Aircraft and Aerospace Alloys Explained

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Aerospace alloys must carry large loads, survive millions of stress cycles and resist heat and corrosion, all at the lowest possible weight. Aluminium suits most of the airframe, titanium 6Al-4V gives strength at low density, steels such as 15-5PH serve landing gear and fittings, and nickel alloys such as Inconel 718, Waspaloy and A286 handle engine heat.Titanium alloys can provide a high strength-to-weight ratio for structural components. 15-5PH is an example of a high-strength stainless steel which is utilized for structural parts that require strength and fatigue resistance, while nickel-based superalloys, such as Inconel 718 and Waspaloy, ensure good mechanical properties under elevated temperatures. A286 is a material for parts that need to have heat resistance and strength.

Why Aircraft Need Special Alloys

A metal that is fine for a bridge or a pressure vessel can fail in an aircraft, because aircraft ask for several hard things at once:

• Strength-to-weight: weight saved in structure is payload or range gained, so the useful measure is strength per unit of density, not strength alone.
• Fatigue life: wings, landing gear and engine discs see millions of stress cycles, so resistance to crack growth matters as much as static strength.
• Temperature: skin is cold at altitude, while turbine sections run red hot. Strength must hold across that whole range.
• Corrosion and environment: moisture, de-icing fluids, fuel and combustion gases attack metal from outside and inside.
• Traceability: every critical part must be traceable to the melt it came from, which is why aerospace metal grades are bought to specifications and certificates rather than by name alone.

Aircraft Alloy Materials by Zone

The table below shows which alloys usually appear in each part of an aircraft, and why. Individual aircraft differ, but the pattern holds: the hotter and more heavily loaded the zone, the further the choice moves from aluminium toward titanium, steel and nickel.

Zone	Typical Alloys	Why
Fuselage and wing skins	Aluminium 2024, 7075	Light, easy to form, good fatigue life
Wing box, frames, engine pylons	Titanium 6Al-4V; aluminium 7xxx	High strength-to-weight, corrosion resistant, compatible with composites
Landing gear, actuators, shafts	AISI 4340, 300M, 15-5PH, 17-4PH	Very high strength and toughness
Engine cold section (fan, compressor)	Titanium 6Al-4V; 15-5PH; A286	Strength and low density at moderate temperature
Engine hot section (discs, turbine cases)	Inconel 718, Waspaloy	Strength and creep resistance at high temperature
Fasteners and fittings	A286, Inconel 718, Ti-6Al-4V, Waspaloy	Strength, corrosion and temperature resistance

The Four Families of Aerospace Alloys

Family	Example Grades	Strength / Limit	Main Use
Aluminium alloys	2024, 7075, 6061	Lightest; lower temperature limit	Airframe skin and structure
Titanium alloys	Ti-6Al-4V (Grade 5)	High strength at low density; about 315–400 °C	Airframe, engine cold section, fasteners
Alloy and PH stainless steels	4340, 300M, 15-5PH, 17-4PH, A286	Highest room-temperature strength	Landing gear, shafts, fittings, fasteners
Nickel and iron-nickel superalloys	Inconel 718, Waspaloy, A286	Strength to 650 °C and above	Engine hot section, exhaust, fasteners

Aluminium deserves its own guide, because it makes up a large share of airframe structure on many aircraft. We cover it separately, and you can browse our aluminium bars, rods and wires and aluminium plates, sheets and coils. The rest of this guide focuses on titanium, steel and nickel alloys.

Aerospace Alloys and Their Applications

Inconel 718 in Aerospace

Inconel 718 is a nickel-based superalloy used in aircraft engines and other high-temperature aerospace equipment. It offers high strength, excellent corrosion resistance and good weldability. Typical applications include engine discs, casings, shafts and high-strength fasteners. It contains about 5% niobium, which combines with other alloying elements to form strengthening precipitates during ageing heat treatment. AMS 5662 generally covers solution-treated material, while AMS 5663 covers material supplied in a precipitation-hardened condition. Mechanical properties should always be evaluated against the applicable specification and heat-treatment condition.

Titanium 6Al-4V in Aerospace

Grade 5 titanium (Ti-6Al-4V) is the most widely used aerospace titanium alloy because of its excellent strength-to-weight ratio, corrosion resistance and suitability for demanding structural applications. It is also compatible with carbon-fibre structures when appropriate design measures address galvanic corrosion. Typical applications include aircraft frames, wing structures, engine pylons and other structural components. The alloy is supplied to specifications such as AMS 4928 for bar and ASTM B348 Grade 5 for bars and billets. Although titanium offers substantial weight savings, its machining costs are relatively high, and its use in engine components depends on local temperature and operating conditions.

A286 Aerospace Alloy

A286 is an iron-nickel-chromium precipitation-hardening alloy that provides high strength, good oxidation resistance and useful mechanical properties at elevated temperatures. It also maintains toughness at lower temperatures. Aerospace applications include fasteners, bolts, fittings, engine casings and exhaust-system components. Where the temperature and strength requirements are less demanding than those typically addressed by Inconel 718, A286 can be a more economical choice. It retains useful strength at temperatures approaching 700°C, although its suitability depends on the applied stress, exposure duration and operating environment.

15-5PH Stainless Steel in Aerospace

15-5PH is a precipitation-hardening stainless steel that offers high strength, corrosion resistance and good toughness. Its mechanical properties can be adjusted through heat treatment to meet specific component requirements. Aerospace applications include landing gear components, structural fittings, actuators and precision-engineered parts. AMS 5659 is a commonly specified material standard for aerospace applications. The required heat-treatment condition should be selected according to the component's strength, toughness and other applicable design requirements.

Alloy, UNS and AMS Specifications

Alloy	UNS	Common AMS Specification	Product Forms
Inconel (Alloy) 718	N07718	AMS 5662 (solution treated), AMS 5663 (aged)	Bar, forgings
Waspaloy	N07001	AMS 5706	Bar, forgings
A286	S66286	AMS 5731 / 5732	Bar, forgings
15-5PH	S15500	AMS 5659	Bar, forgings
Titanium 6Al-4V	R56400	AMS 4928 (bar), AMS 4911 (sheet)	Bar, sheet, forgings
4340	G43400	AMS 6414 / 6415	Bar, forgings

Composition and Strength Compared

Alloy	Base	Main Alloying Elements (% by mass)
Inconel 718	Nickel (50–55)	Cr 17–21; Fe balance; Nb + Ta 4.75–5.50; Mo 2.80–3.30; Ti 0.65–1.15; Al 0.20–0.80; Co 1.0 max
Waspaloy	Nickel (balance)	Cr 18–21; Co 12–15; Mo 3.5–5.0; Ti 2.75–3.25; Al 1.2–1.6; C 0.02–0.10; Zr 0.02–0.12; B 0.003–0.010
A286	Iron (balance, ~55)	Ni 24–27; Cr 13.5–16; Mo 1.0–1.5; Ti 1.9–2.35; V 0.10–0.50; B 0.001–0.010; Al 0.35 max
15-5PH	Iron (balance)	Cr 14.0–15.5; Ni 3.5–5.5; Cu 2.5–4.5; Nb + Ta 0.15–0.45; C 0.07 max; Mn 1.0 max; Si 1.0 max
Titanium 6Al-4V (Grade 5)	Titanium (balance)	Al 5.50–6.75; V 3.50–4.50; Fe 0.40 max; O 0.20 max; C 0.08 max

Alloy and Condition	Tensile Strength	Yield Strength	Elongation	Practical Temperature Limit
Inconel 718, aged bar (AMS 5663)	185 ksi (1275 MPa) min	150 ksi (1035 MPa) min	12% min	~650–700 °C for strength
Waspaloy, aged (AMS 5706)	185 ksi (1275 MPa) min	130 ksi (895 MPa) min	15% min	650 °C critical rotating; 760–870 °C non-rotating
A286, aged (AMS 5731)	140 ksi (965 MPa) min	95 ksi (655 MPa) min	12% min	~700 °C
15-5PH H900	190 ksi (1310 MPa) min	170 ksi (1170 MPa) min	10% min	~300 °C
15-5PH H1025	155 ksi (1070 MPa) min	145 ksi (1000 MPa) min	12% min	~300 °C
Titanium 6Al-4V, annealed	130 ksi (895 MPa) min	120 ksi (828 MPa) min	10% min	~315–400 °C

How to Choose an Aerospace Alloy

Need	Choose	Check First
Lightest airframe structure	Aluminium 7075 / 2024	Corrosion protection, fatigue
High strength, low weight, corrosion resistant	Titanium 6Al-4V	Cost, machinability, galling
Highest strength landing gear part	4340 / 300M, or 15-5PH where corrosion matters	Toughness, coating, hydrogen embrittlement
Corrosion resistant, high-strength fitting	15-5PH (H1025 or H1150 for toughness)	Condition and transverse properties
Fastener to about 700 °C	A286 or Inconel 718	AMS spec, non-magnetic need
Hot-section disc or shaft	Waspaloy or Inconel 718	Temperature, creep, forging source

Have a part in mind but unsure which grade, form or condition to specify? Request a quote with your drawing or specification, and we will help you match the alloy to the requirement.