2218 aluminium alloy

(ρ)2.77Mechanical propertiesYoung's modulus (E)73 GPa (10,600 ksi)Tensile strength (σ_t)330 MPa (48 ksi)Elongation (ε) at break11%Poisson's ratio (ν)0.33Hardness—Rockwell56 HRBThermal propertiesMelting temperature (T_m)510 °C (950 °F)Thermal conductivity (k)140 W/m*KLinear thermal expansion coefficient (α)2.2*10⁻⁵ K⁻¹Specific heat capacity (c)870 J/kg*KElectrical propertiesVolume resistivity (ρ)41.3 nOhm*m

2218 aluminium alloy is an alloy in the wrought aluminium-copper family (2000 or 2xxx series). It is one of the most complex grades in the 2000 series, with at least 88.4% aluminium by weight. Unlike most other aluminium-copper alloys, 2218 is a high work-ability alloy, with relatively low for 2xxx series alloy yield strength of 255 MPa. Despite being highly alloyed, it have a good corrosion and oxidation resistance due sacrificial anode formed by magnesium inclusions, similar to marine-grade 5xxx series alloys. Although 2218 is wrought alloy, owing to granular structure it can be used in casting and been precisely machined after casting. It is easy to weld, coat, or glue.

Good workability, thermal conductivity and dimensional stability make 2218 alloy a material of choice whenever high-precision parts subject to thermal shocks (especially piston engine cylinders and cylinder heads) are needed.^[1]

2218 alloy can be heat treated to increase tensile strength in expense of workability, with most common grades been F, T61, T71 and T72.

Alternative names for 2218 alloy are A2218 and A92218.

Chemical Composition

The chemical composition of 2218 alloy is poorly standardized, with several variants in production. All variants include both copper (4%) and magnesium (1.5%) as major alloying elements. Common alloy variants also include 2% of nickel. The alloy composition of 2218 aluminium is:^[2][3][4]

• Aluminium: 91.35 to 92.95%
• Copper: 3.5 to 4.5%
• Magnesium: 1.2 to 1.8%
• Nickel: 1.7 to 2.3%
• Iron: 1% max
• Silicon: 0.9% max
• Zinc: 0.25% max
• Manganese: 0.5% max
• Tin: 0.25% max
• Chromium: 0.1% max

See also

• Y alloy (precursor of A2218 with same major alloying elements)

References

Aluminium alloy table