# 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 10 ^{6} psi*

Elongation at Break

11 *%*

Poisson's Ratio

0.34

Rockwell B Hardness

69

Shear Modulus

41 *GPa* 5.9 *x 10 ^{6} psi*

Tensile Strength: Ultimate (UTS)

370 *MPa* 53 *x 10 ^{3} psi*

Tensile Strength: Yield (Proof)

250 *MPa* 36 *x 10 ^{3} 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/cm ^{3}* 560

*lb/ft*

^{3}Embodied Carbon

2.8 *kg CO _{2}/kg material*

Embodied Energy

45 *MJ/kg* 19 *x 10 ^{3} BTU/lb*

Embodied Water

310 *L/kg* 37 *gal/lb*

## Common Calculations

Resilience: Ultimate (Unit Rupture Work)

36 *MJ/m ^{3}*

Resilience: Unit (Modulus of Resilience)

260 *kJ/m ^{3}*

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 *mm ^{2}/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