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UNS C81400 (Alloy 70C) Beryllium Copper

C81400 copper is a lightly alloyed grade of copper, formulated for casting. Cited properties are appropriate for the heat treated (HT) condition. C81400 is the UNS number for this material. Older literature may refer to this material as ASTM Alloy 70C, but this is now discouraged.

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

The graph bars on the material properties cards below compare C81400 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 17 x 106 psi

Elongation at Break

11 %

Poisson's Ratio

0.34

Rockwell B Hardness

69

Shear Modulus

41 GPa 5.9 x 106 psi

Tensile Strength: Ultimate (UTS)

370 MPa 53 x 103 psi

Tensile Strength: Yield (Proof)

250 MPa 36 x 103 psi

Thermal Properties

Latent Heat of Fusion

210 J/g

Maximum Temperature: Mechanical

200 °C 400 °F

Melting Completion (Liquidus)

1090 °C 2000 °F

Melting Onset (Solidus)

1070 °C 1950 °F

Specific Heat Capacity

390 J/kg-K 0.092 BTU/lb-°F

Thermal Conductivity

260 W/m-K 150 BTU/h-ft-°F

Thermal Expansion

17 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

60 % IACS

Electrical Conductivity: Equal Weight (Specific)

61 % IACS

Otherwise Unclassified Properties

Base Metal Price

33 % relative

Density

8.9 g/cm3 560 lb/ft3

Embodied Carbon

2.8 kg CO2/kg material

Embodied Energy

45 MJ/kg 19 x 103 BTU/lb

Embodied Water

310 L/kg 37 gal/lb

Common Calculations

Resilience: Ultimate (Unit Rupture Work)

36 MJ/m3

Resilience: Unit (Modulus of Resilience)

260 kJ/m3

Stiffness to Weight: Axial

7.3 points

Stiffness to Weight: Bending

18 points

Strength to Weight: Axial

11 points

Strength to Weight: Bending

13 points

Thermal Diffusivity

75 mm2/s

Thermal Shock Resistance

13 points

Alloy Composition

Among cast copper alloys, the composition of C81400 copper is notable for including beryllium (Be) and chromium (Cr). Beryllium is used to permit precipitation hardening (which increases strength) without much effect on electrical conductivity, but at the cost of substantial toxicity. Chromium additions permits certain types of heat treatment to improve mechanical strength.

Copper (Cu) 98.4 to 99.38
Chromium (Cr) 0.6 to 1.0
Beryllium (Be) 0.020 to 0.1
Residuals 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