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UNS C17500 (CW104C) Cobalt-Beryllium Copper

C17500 copper is a lightly alloyed grade of copper, formulated for primary forming into wrought products. CW104C is the EN numeric designation for this material. C17500 is the UNS number. Additionally, the EN chemical designation is CuCo2Be. And the British Standard (BS) designation is C112. Older literature may refer to this material as ASMT Alloy 10, but this is now discouraged.

It has the highest base cost among wrought coppers. In addition, it has a moderately high embodied energy and a moderately low thermal conductivity.

The properties of C17500 copper include four common variations. This page shows summary ranges across all of them. For more specific values, follow the links immediately below. The graph bars on the material properties cards further below compare C17500 copper to: wrought 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 17 x 106 psi

Elongation at Break

6.0 to 30 %

Fatigue Strength

170 to 310 MPa 25 to 45 x 103 psi

Poisson's Ratio


Rockwell B Hardness

38 to 99

Shear Modulus

45 GPa 6.5 x 106 psi

Shear Strength

200 to 520 MPa 29 to 75 x 103 psi

Tensile Strength: Ultimate (UTS)

310 to 860 MPa 45 to 120 x 103 psi

Tensile Strength: Yield (Proof)

170 to 760 MPa 25 to 110 x 103 psi

Thermal Properties

Latent Heat of Fusion

220 J/g

Maximum Temperature: Mechanical

220 °C 430 °F

Melting Completion (Liquidus)

1060 °C 1940 °F

Melting Onset (Solidus)

1020 °C 1870 °F

Specific Heat Capacity

390 J/kg-K 0.092 BTU/lb-°F

Thermal Conductivity

200 W/m-K 120 BTU/h-ft-°F

Thermal Expansion

18 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

24 to 53 % IACS

Electrical Conductivity: Equal Weight (Specific)

24 to 54 % IACS

Otherwise Unclassified Properties

Base Metal Price

60 % relative


8.9 g/cm3 550 lb/ft3

Embodied Carbon

4.7 kg CO2/kg material

Embodied Energy

73 MJ/kg 31 x 103 BTU/lb

Embodied Water

320 L/kg 38 gal/lb

Common Calculations

Resilience: Ultimate (Unit Rupture Work)

30 to 120 MJ/m3

Resilience: Unit (Modulus of Resilience)

120 to 2390 kJ/m3

Stiffness to Weight: Axial

7.5 points

Stiffness to Weight: Bending

18 points

Strength to Weight: Axial

9.7 to 27 points

Strength to Weight: Bending

11 to 23 points

Thermal Diffusivity

59 mm2/s

Thermal Shock Resistance

11 to 29 points

Alloy Composition

Among wrought copper alloys, the composition of C17500 copper is notable for including beryllium (Be) and cobalt (Co). Beryllium is used to permit precipitation hardening (which increases strength) without much effect on electrical conductivity, but at the cost of substantial toxicity. Cobalt is used to improve strength.

Copper (Cu)Cu 95.6 to 97.2
Cobalt (Co)Co 2.4 to 2.7
Beryllium (Be)Be 0.4 to 0.7
Silicon (Si)Si 0 to 0.2
Aluminum (Al)Al 0 to 0.2
Iron (Fe)Fe 0 to 0.1
Residualsres. 0 to 0.5

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

Followup Questions

Similar Alloys

Further Reading

ASTM B441: Standard Specification for Copper-Cobalt-Beryllium, Copper-Nickel-Beryllium, and Copper-Nickel-Lead-Beryllium Rod and Bar (UNS Nos. C17500, C17510, and C17465)

Copper: Its Trade, Manufacture, Use, and Environmental Status, Gunter Joseph, 2001

Properties and Selection: Nonferrous Alloys and Special-Purpose Materials, ASM Handbook vol. 2, ASM International, 1993