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Infiltrated ASTM B631 Class B Silver-Tungsten Alloy

Infiltrated ASTM B631 class B is a type of ASTM B631 class B. Cited properties are appropriate for the as-fabricated (no temper or treatment) condition. The graph bars on the material properties cards below compare infiltrated ASTM B631 class B 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

210 GPa 30 x 106 psi

Flexural Strength

790 MPa 110 x 103 psi

Poisson's Ratio


Rockwell B Hardness


Shear Modulus

78 GPa 11 x 106 psi

Tensile Strength: Ultimate (UTS)

380 MPa 55 x 103 psi

Thermal Properties

Latent Heat of Fusion

150 J/g

Specific Heat Capacity

170 J/kg-K 0.040 BTU/lb-°F

Thermal Conductivity

450 W/m-K 260 BTU/h-ft-°F

Thermal Expansion

12 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

53 % IACS

Electrical Conductivity: Equal Weight (Specific)

34 % IACS

Otherwise Unclassified Properties


14 g/cm3 880 lb/ft3

Embodied Carbon

49 kg CO2/kg material

Embodied Energy

760 MJ/kg 330 x 103 BTU/lb

Common Calculations

Stiffness to Weight: Axial

8.1 points

Stiffness to Weight: Bending

14 points

Strength to Weight: Axial

7.5 points

Strength to Weight: Bending

8.3 points

Thermal Diffusivity

190 mm2/s

Thermal Shock Resistance

11 points

Alloy Composition

Tungsten (W)W 60.6 to 67
Silver (Ag)Ag 33 to 37
Cobalt (Co)Co 0 to 1.0
Carbon (C)C 0 to 0.2
Copper (Cu)Cu 0 to 0.2
Residualsres. 0 to 1.0

All values are % weight. Ranges represent what is permitted under applicable standards.

Followup Questions

Similar Alloys

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