Aerospace forgings · elevated-temperature alloy

2018 T61 Aluminium Forgings for Aerospace

2018 is an aluminium-copper-nickel-magnesium forging alloy designed to keep its strength at elevated temperature. Forged and heat-treated to T61, it has been used for aircraft piston-engine cylinder heads, pistons and other parts that run warm. Metline supplies 2018 die forgings and forging stock to AMS and ASTM specifications, with full mill certification, to customers worldwide.

By Metline Technical Team · Updated 17 October 2026

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Racing aircraft with a polished bare-aluminium fuselage

Alloy: 2018 (Al-Cu-Ni-Mg)
Temper: T61
Forms: Die forgings, forging stock
Standards: AMS 4140 · ASTM B247

Overview

What is 2018 aluminium?

2018 belongs to the small family of nickel-bearing 2xxx alloys, alongside 2218 and 2618. About 2 % nickel forms stable aluminium-copper-nickel and aluminium-iron-nickel particles that resist coarsening when the metal is hot, so 2018 holds its strength better than 2014 or 2024 at temperatures around 150 – 250 °C.

The alloy is used almost entirely as forgings. Its classic application is the air-cooled aircraft piston engine, where cylinder heads and pistons must combine strength, thermal conductivity and resistance to softening. ASM describes 2018 as an age-hardenable forging alloy with relatively high strength, fair ductility and good elevated-temperature properties.

For new designs, 2618A is the more widely used nickel-bearing alloy, especially for jet-engine compressor parts and high-performance pistons, and 4032 is common for pistons where low expansion matters. 2018 remains relevant where existing drawings and engine type certificates call it up, and for warm-running fittings in which its properties are already qualified.

Chemical composition

2018 chemical composition (wt %)

Element	Limit	Role
Copper (Cu)	3.5 – 4.5	Precipitation strengthening
Nickel (Ni)	1.7 – 2.3	Heat-resistant intermetallic particles
Magnesium (Mg)	0.45 – 0.9	Ageing response
Silicon (Si)	0.9 max
Iron (Fe)	1.0 max	Combines with Ni in stable particles
Manganese (Mn)	0.20 max
Chromium (Cr)	0.10 max
Zinc (Zn)	0.25 max
Others, each / total	0.05 / 0.15
Aluminium (Al)	Remainder

Properties

Mechanical and physical properties (T61)

Property	Typical value, 2018-T61
Tensile strength	about 420 MPa / 61 ksi
Yield strength (0.2 %)	about 315 MPa / 46 ksi
Elongation	about 12 %
Brinell hardness	about 120 HB
Density	about 2.80 g/cm³
Thermal conductivity	about 155 W/m·K
Electrical conductivity	about 40 % IACS

Typical values from published alloy data. Specified minimums depend on forging type, thickness and test direction and are given in the order specification and on the certificate. Older product listings rate 2018 as having excellent weldability and good corrosion resistance; in practice it is not fusion-welded in structure and needs protection like other copper-rich alloys.

Temper

The T61 temper

T61 means the forging is solution heat-treated, quenched (often in boiling or hot water to limit distortion and residual stress in complex shapes) and artificially aged. The hot-water quench is why 2018 and 2618 forgings are listed in T61 rather than T6: strength is slightly lower than a cold-water quench would give, but the parts are more stable dimensionally, which matters for pistons and heads that are machined to fine clearances.

Standards

Specifications

2018 forging specifications

AMS 4140: 2018-T61 die forgings and forging stock (check current revision status with SAE; the document has been stabilised)
ASTM B247: Die forgings, hand forgings and rolled ring forgings
AMS-QQ-A-367: General aluminium alloy forgings
UNS: A92018

Applications

Cylinder heads for air-cooled aircraft piston engines
Forged pistons for aero and high-performance engines
Warm-running fittings and housings near engines and exhausts
Replacement parts for legacy engines that are certified on 2018

Comparison

2018 compared with 2618A and 4032

Property	2018-T61	2618A-T61	4032-T6
Main additions	Cu, Ni, Mg	Cu, Mg, Ni, Fe	Si (~12 %), Cu, Mg, Ni
Typical tensile strength	~420 MPa	~440 MPa	~380 MPa
Elevated-temperature strength	Good	Very good	Good
Thermal expansion	Normal (~22 – 23 µm/m·°C)	Normal	Low (~19 µm/m·°C)
Typical use	Heads, legacy pistons	Compressor parts, pistons	Pistons

Working with 2018

Machining and finishing

Machines well in T61 with carbide tools; finish-machine after heat treatment.
Not fusion-welded for structural parts.
Protect with anodising or conversion coatings; pistons are often given wear coatings on skirts and ring grooves.
Inspect forgings ultrasonically and with penetrant where the drawing requires.

Ordering

How to order

SpecifyAlloy and temper (2018-T61), forging drawing, quantity and first-article needs.
Name the standardAMS 4140, ASTM B247 or the engine maker's specification.
QuoteWe confirm availability, tolerance, test scope, certification and delivery terms (EXW, FOB, CIF or DAP) for your port or site.
Process and inspectForgings are heat-treated, tested and inspected for dimensions and surface.
Document and shipEach lot ships with an EN 10204 3.1 mill test certificate traceable to the heat and lot, plus a packing list. Material is packed in seaworthy wooden cases with moisture protection; third-party inspection can be arranged on request.