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.
| Cu | 98.4 to 99.38 | |
| Cr | 0.6 to 1.0 | |
| Be | 0.020 to 0.1 | |
| res. | 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