Tantalum-tungsten alloys

Tantalum-tungsten alloys are in the refractory metals group, keeping the chemical and physical properties the same in high temperatures. The tantalum-tungsten alloys are characterized also because of the high melting point and the tension resistance. The properties of the final alloy are a combination of properties from the two elements, tungsten is the element with the highest melting point in the periodic table, and tantalum has high corrosion resistance.^[1]

The tantalum tungsten alloys are divided in the percentage of tungsten, they are:

(Ta – 2.5% W) → also called tantaloy 63 metal, the percentage of tungsten is about 2 to 3% and 0.5% of niobium, the material have good resistance to corrosion that works in high temperatures too, can be used in piping in chemical industries.^[1]
(Ta - 7.5% W) → also called 61 metal, it uses from 7 to 8% of tungsten the difference from this alloy to the others is that this alloy represents a high resilience modulus, and still have the refractory properties.^[1]
(Ta - 10% W) → also called tantaloy 60 metal it uses 9 to 11% of tungsten, this alloy is less ductile than the other alloys, with less plasticity the material can be used in different situations like in aerospace materials and furnaces. This alloy can also be used in some different applications like piping in nuclear plants.^[1]

Mechanical properties

The alloys of tantalum-tungsten have high corrosion resistance, and refractory properties. The crystalline structure of the material is body-centered cubic with a substitutional solid solution with atoms of tungsten. The alloy also has a high melting point and can reach high elastic modulus and high tensile strength.^[2]

Alloys	Hardness (HV)	Density (g/cm³)	Melting Point (^oc)	Tensile Strength (MPa)	Yield Strength (MPa)	Elastic Modulus (GPa)
Ta - 2.5% W	130	16.7	3005	345	230	195
Ta - 7.5% W	245	16.8	3030	550	460	205
Ta - 10% W	325 - 400	16.8	3025	1035 - 1165	875 - 1005	200

^[1]

Phase diagram

The equilibrium phase diagram of the alloy formed between the two components Tantalum and tungsten is a binary diagram, where the two components are totally soluble on each other. In this diagram the melting temperature of the two elements are shown. It can be seen that there are two lines, representing the solidus and liquidus.^[2]

Binary Phase Diagram (Ta-W)

References

1 2 3 4 5 ASM Handbook. Properties and Selection Nonferrous Alloys and Special-Purpose Materials. V.2. USA: ASM International, 1990, p. 1746-1747
1 2 Handbook. Alloy Phase Diagrams. V.3. USA: ASM International, 1990, p. 1453.

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