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UNS R05255 Tantalum-Tungsten Alloy

R05255 alloy is a tantalum alloy. Cited properties are appropriate for the annealed condition. It has a fairly high density among alloys in the same category. In addition, it has a fairly low heat capacity and a moderately high tensile strength.

The graph bars on the material properties cards below compare R05255 alloy to: tantalum 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

190 GPa 27 x 106 psi

Elongation at Break

20 %

Poisson's Ratio


Shear Modulus

70 GPa 10 x 106 psi

Tensile Strength: Ultimate (UTS)

540 MPa 79 x 103 psi

Tensile Strength: Yield (Proof)

450 MPa 65 x 103 psi

Thermal Properties

Latent Heat of Fusion

140 J/g

Specific Heat Capacity

140 J/kg-K 0.034 BTU/lb-°F

Thermal Conductivity

59 W/m-K 34 BTU/h-ft-°F

Thermal Expansion

6.6 µm/m-K

Otherwise Unclassified Properties


17 g/cm3 1040 lb/ft3

Embodied Water

630 L/kg 76 gal/lb

Common Calculations

Resilience: Ultimate (Unit Rupture Work)

100 MJ/m3

Resilience: Unit (Modulus of Resilience)

530 kJ/m3

Stiffness to Weight: Axial

6.3 points

Stiffness to Weight: Bending

11 points

Strength to Weight: Axial

9.1 points

Strength to Weight: Bending

8.9 points

Thermal Diffusivity

25 mm2/s

Thermal Shock Resistance

31 points

Alloy Composition

Tantalum (Ta)Ta 95.9 to 98
Tungsten (W)W 2.0 to 3.5
Niobium (Nb)Nb 0 to 0.5
Molybdenum (Mo)Mo 0 to 0.020
Oxygen (O)O 0 to 0.015
Carbon (C)C 0 to 0.010
Nickel (Ni)Ni 0 to 0.010
Iron (Fe)Fe 0 to 0.010
Nitrogen (N)N 0 to 0.010
Titanium (Ti)Ti 0 to 0.010
Silicon (Si)Si 0 to 0.0050
Hydrogen (H)H 0 to 0.0015

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

Followup Questions

Similar Alloys

Further Reading

ASTM B365: Standard Specification for Tantalum and Tantalum Alloy Rod and Wire

ASTM B521: Standard Specification for Tantalum and Tantalum Alloy Seamless and Welded Tubes

ASTM B708: Standard Specification for Tantalum and Tantalum Alloy Plate, Sheet, and Strip

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

Sintering of Advanced Materials: Fundamentals and Processes, Zhigang Zak Fang (editor), 2010