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
0.33
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
Density
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.
| Cu | 95.3 to 97.8 | |
| Be | 1.9 to 2.3 | |
| Co | 0.15 to 0.7 | |
| Si | 0.2 to 0.35 | |
| Fe | 0 to 0.25 | |
| Ni | 0 to 0.2 | |
| Al | 0 to 0.15 | |
| Ti | 0 to 0.12 | |
| Cr | 0 to 0.1 | |
| Sn | 0 to 0.1 | |
| Zn | 0 to 0.1 | |
| Pb | 0 to 0.020 | |
| 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