Tantalum and its alloys are midway between tungsten and molybdenum in density and melting points Tantalum has a melting point of 2996oC and a density of 16.654 gm/cc. Tantalum is one of the refractory metals that offer a valuable combination of properties. Tantalum can be worked easily at room temperature. Its thermal conductivity is one-fourth that of molybdenum and its coefficient of expansion is one-third greater. Its elevated temperature strength is low compared with Tungsten and Molybdenum.
Typical Properties
Atomic Number: 73
Atomic Weight: 180.95
Atomic Volume: 10.9
Crystal Structure: Body-centered cubic, a = 0.33026
Isotope (Natural): 181
Density at 20 oC, g/cc: 16.6, .600 lb/in3
Melting Point: 2,996 oC
Boiling Point: 5,430 oC
Linear Coefficient of Expansion: 6.5 x 10-6 per oC
Thermal Conductivity at 20 oC: 0.130 cal/cm 2/cm/oC/sec
Specific Heat at 20 oC: 0.036 cal/g/oC
Electrical Conductivity : 13% IACS
Electrical Resistivity at 20 oC: 135.0 nΩ ⋅ m
Temperature Coefficient of Electrical Resistivity(0-100 oC): 0.0038 per oC
Tensile Strength:
at Room Temperature: 35,000-70,000 psi
at 500 oC: 25,000-45,000 psi
at 1000 oC: 13,000-17,000 psi
Young’s Modulus of Elasticity:
Room Temperature: 27 x 106 lb/in2
500 oC: 25 x 106 lb/in2
1000 oC: 22 x 106 lb/in2
Poisson’s Ratio: 0.35
Thermionic Work Function: 0.657 aJ (4.10 eV)
Magnetic Susceptibility: 0.93 10-6 cgs
Spectral Emissivity: .46 (900 oC) (Wave Length Approx. 0.65 micron)
Total Emissivity:
at 1500 oC: .21
at 2000 oC: .26
Working Temperature: Room temperature
Recrystallization Temperature: 1200 oC – 1400 oC
Stress Relieving Temperature: 850 oC
Thermal Neutron Cross Section: 21.3 b
Polishing: Emery to 000 levigated alumina to finish.
Etchant: Hf-NH4F Solution. Etch and Polish repeatedly until grain boundaries appear.
Applications:
Tantalum is also used to produce a variety of alloys that have high melting points, are strong and have good ductility. Alloyed with other metals, it is also used in making carbide tools for metalworking equipment and in the production of superalloys for jet engine components, chemical process equipment, nuclear reactors, and missile parts. Because of its ductility, tantalum can be drawn into fine wires or filaments, which are used for evaporating metals such as aluminium. Since it resists attack by body fluids and is nonirritating, tantalum is widely used in making surgical instruments and implants. For example, porous tantalum coatings are used in the construction of orthopedic implants due to tantalum’s ability to form a direct bond to hard tissue