Menu (ESC)

ASTM B631 Class A Silver-Tungsten Electrical Contact Alloy

ASTM B631 class A is a precious metal alloy formulated for use in electrical contacts. It has the lowest embodied energy among the precious metal electrical contact alloys in the database.

The properties of ASTM B631 class A include three common variations. This page shows summary ranges across all of them. For more specific values, follow the links immediately below. The graph bars on the material properties cards further below compare ASTM B631 class A to: precious metal electrical contact alloys (top), all alloys in the same category (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

220 GPa 32 x 106 psi

Poisson's Ratio


Rockwell B Hardness

63 to 98

Shear Modulus

85 to 86 GPa 12 x 106 psi

Thermal Properties

Latent Heat of Fusion

160 J/g

Melting Completion (Liquidus)

2680 to 2690 °C 4850 to 4880 °F

Specific Heat Capacity

160 J/kg-K 0.038 to 0.039 BTU/lb-°F

Thermal Conductivity

420 W/m-K 240 BTU/h-ft-°F

Thermal Expansion

11 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

40 to 47 % IACS

Electrical Conductivity: Equal Weight (Specific)

25 to 29 % IACS

Otherwise Unclassified Properties


15 g/cm3 910 lb/ft3

Embodied Carbon

43 kg CO2/kg material

Embodied Energy

670 MJ/kg 290 x 103 BTU/lb

Common Calculations

Stiffness to Weight: Axial

8.5 points

Stiffness to Weight: Bending

14 points

Thermal Diffusivity

180 mm2/s

Followup Questions

Further Reading

ASTM B631: Standard Specification for Silver-Tungsten Electrical Contact Materials

Tungsten: Properties, Chemistry, Technology of the Element, Alloys, and Chemical Compounds, Erik Lassner and Wolf-Dieter Schubert, 1999