UNS C87610 (Alloy 12A) Silicon Bronze
C87610 bronze is a bronze formulated for casting. Cited properties are appropriate for the as-fabricated (no temper or treatment) condition. C87610 is the UNS number for this material. Older literature may refer to this material as ASTM Alloy 12A, but this is now discouraged.
It has a fairly low thermal conductivity among cast bronzes. In addition, it has a very low embodied energy and a very low electrical conductivity.
The graph bars on the material properties cards below compare C87610 bronze to: cast bronzes (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
110 GPa 17 x 106 psi
Elongation at Break
22 %
Poisson's Ratio
0.34
Shear Modulus
43 GPa 6.2 x 106 psi
Tensile Strength: Ultimate (UTS)
350 MPa 50 x 103 psi
Tensile Strength: Yield (Proof)
140 MPa 21 x 103 psi
Thermal Properties
Latent Heat of Fusion
270 J/g
Maximum Temperature: Mechanical
190 °C 380 °F
Melting Completion (Liquidus)
970 °C 1780 °F
Melting Onset (Solidus)
820 °C 1510 °F
Specific Heat Capacity
410 J/kg-K 0.1 BTU/lb-°F
Thermal Conductivity
28 W/m-K 16 BTU/h-ft-°F
Thermal Expansion
17 µm/m-K
Electrical Properties
Electrical Conductivity: Equal Volume
6.1 % IACS
Electrical Conductivity: Equal Weight (Specific)
6.4 % IACS
Otherwise Unclassified Properties
Base Metal Price
29 % relative
Density
8.5 g/cm3 530 lb/ft3
Embodied Carbon
2.6 kg CO2/kg material
Embodied Energy
43 MJ/kg 18 x 103 BTU/lb
Embodied Water
300 L/kg 36 gal/lb
Common Calculations
Resilience: Ultimate (Unit Rupture Work)
62 MJ/m3
Resilience: Unit (Modulus of Resilience)
88 kJ/m3
Stiffness to Weight: Axial
7.4 points
Stiffness to Weight: Bending
19 points
Strength to Weight: Axial
11 points
Strength to Weight: Bending
13 points
Thermal Diffusivity
8.1 mm2/s
Thermal Shock Resistance
13 points
Alloy Composition
Among cast copper alloys, the composition of C87610 bronze is notable for containing a comparatively high amount of silicon (Si) and including manganese (Mn). Silicon is used to improve casting fluidity and lower melting temperature. It also raises strength at the expense of ductility. Manganese is used to improve strength without a proportional reduction in ductility.
| Cu | 90 to 94 | |
| Si | 3.0 to 5.0 | |
| Zn | 3.0 to 5.0 | |
| Mn | 0 to 0.25 | |
| Fe | 0 to 0.2 | |
| Pb | 0 to 0.2 | |
| res. | 0 to 0.5 |
All values are % weight. Ranges represent what is permitted under applicable standards.
Followup Questions
Similar Alloys
Further Reading
ASTM B271: Standard Specification for Copper-Base Alloy Centrifugal Castings
ASM Specialty Handbook: Copper and Copper Alloys, J. R. Davis (editor), 2001