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UNS C82500 (Alloy 20C) Beryllium Copper

C82500 copper is a lightly alloyed grade of copper, formulated for casting. C82500 is the UNS number for this material. Older literature may refer to this material as ASTM Alloy 20C or ASTM Alloy 20CT.

It has a very low melting temperature among cast coppers. In addition, it has a fairly low thermal conductivity and a fairly low electrical conductivity.

The properties of C82500 copper include two common variations. This page shows summary ranges across both of them. For more specific values, follow the links immediately below. The graph bars on the material properties cards further below compare C82500 copper to: cast coppers (top), all copper alloys (middle), and the entire database (bottom). A full bar means this is the highest value in the relevant set. A half-full bar means it's 50% of the highest, and so on.

Mechanical Properties

Elastic (Young's, Tensile) Modulus

120 GPa 18 x 106 psi

Elongation at Break

1.0 to 20 %

Poisson's Ratio


Shear Modulus

45 GPa 6.6 x 106 psi

Tensile Strength: Ultimate (UTS)

550 to 1100 MPa 80 to 160 x 103 psi

Tensile Strength: Yield (Proof)

310 to 980 MPa 45 to 140 x 103 psi

Thermal Properties

Latent Heat of Fusion

240 J/g

Maximum Temperature: Mechanical

280 °C 540 °F

Melting Completion (Liquidus)

980 °C 1800 °F

Melting Onset (Solidus)

860 °C 1570 °F

Specific Heat Capacity

390 J/kg-K 0.092 BTU/lb-°F

Thermal Conductivity

130 W/m-K 75 BTU/h-ft-°F

Thermal Expansion

17 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

20 % IACS

Electrical Conductivity: Equal Weight (Specific)

21 % IACS

Otherwise Unclassified Properties


8.8 g/cm3 550 lb/ft3

Embodied Carbon

10 kg CO2/kg material

Embodied Energy

160 MJ/kg 68 x 103 BTU/lb

Embodied Water

310 L/kg 37 gal/lb

Common Calculations

Resilience: Ultimate (Unit Rupture Work)

11 to 94 MJ/m3

Resilience: Unit (Modulus of Resilience)

400 to 4000 kJ/m3

Stiffness to Weight: Axial

7.7 points

Stiffness to Weight: Bending

19 points

Strength to Weight: Axial

18 to 35 points

Strength to Weight: Bending

17 to 27 points

Thermal Diffusivity

38 mm2/s

Thermal Shock Resistance

19 to 38 points

Alloy Composition

Among cast copper alloys, the composition of C82500 copper is notable for including cobalt (Co) and beryllium (Be). Cobalt is used to improve strength. Beryllium is used to permit precipitation hardening (which increases strength) without much effect on electrical conductivity, but at the cost of substantial toxicity.

Copper (Cu)Cu 95.3 to 97.8
Beryllium (Be)Be 1.9 to 2.3
Cobalt (Co)Co 0.15 to 0.7
Silicon (Si)Si 0.2 to 0.35
Iron (Fe)Fe 0 to 0.25
Nickel (Ni)Ni 0 to 0.2
Aluminum (Al)Al 0 to 0.15
Titanium (Ti)Ti 0 to 0.12
Chromium (Cr)Cr 0 to 0.1
Tin (Sn)Sn 0 to 0.1
Zinc (Zn)Zn 0 to 0.1
Lead (Pb)Pb 0 to 0.020
Residualsres. 0 to 0.5

All values are % weight. Ranges represent what is permitted under applicable standards.

Followup Questions

Similar Alloys

Further Reading

ASM Specialty Handbook: Copper and Copper Alloys, J. R. Davis (editor), 2001