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85-Platinum 15-Iridium Electrical Contact Alloy

85-platinum 15-iridium is a precious metal alloy formulated for use in electrical contacts. It has a moderately high density among precious metal electrical contact alloys. In addition, it has the highest melting temperature and a moderately low electrical conductivity.

The properties of 85-platinum 15-iridium 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 85-platinum 15-iridium 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

Elongation at Break

5.5 to 34 %

Poisson's Ratio


Shear Modulus

81 GPa 12 x 106 psi

Shear Strength

370 to 420 MPa 54 to 61 x 103 psi

Tensile Strength: Ultimate (UTS)

560 to 730 MPa 80 to 110 x 103 psi

Thermal Properties

Latent Heat of Fusion

110 J/g

Melting Completion (Liquidus)

1820 °C 3310 °F

Melting Onset (Solidus)

1790 °C 3250 °F

Specific Heat Capacity

130 J/kg-K 0.032 BTU/lb-°F

Thermal Expansion

8.4 µm/m-K

Other Material Properties


22 g/cm3 1350 lb/ft3

Electrical Conductivity: Equal Volume

6.2 % IACS

Electrical Conductivity: Equal Weight (Specific)

2.6 % IACS

Common Calculations

Stiffness to Weight: Axial

5.7 points

Stiffness to Weight: Bending

9.3 points

Strength to Weight: Axial

7.1 to 9.3 points

Strength to Weight: Bending

6.9 to 8.3 points

Thermal Shock Resistance

21 to 28 points

Alloy Composition

Platinum (Pt)Pt 84.3 to 85.5
Iridium (Ir)Ir 14.5 to 15.5
Residualsres. 0 to 0.2

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

Followup Questions

Similar Alloys

Further Reading

ASTM B684: Standard Specification for Platinum-Iridium Electrical Contact Materials