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Annealed 85-Platinum 15-Iridium Alloy

Annealed 85-platinum 15-iridium is 85-platinum 15-iridium in the annealed condition. The graph bars on the material properties cards below compare annealed 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

34 %

Poisson's Ratio


Shear Modulus

81 GPa 12 x 106 psi

Shear Strength

370 MPa 54 x 103 psi

Tensile Strength: Ultimate (UTS)

560 MPa 80 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 points

Strength to Weight: Bending

6.9 points

Thermal Shock Resistance

21 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

Further Reading

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