Pure titanium wrought products, with minimum titanium contents ranging from approximately 98.635% to 99.5% by weight, are primarily utilized for their corrosion resistance. These titanium products also offer good fabrication characteristics, though they exhibit relatively lower strength in service applications.
Good overall strength properties
Superior resistance to erosion and erosion-corrosion
Very thin, conductive oxide surface film
Hard, smooth surface that minimizes adhesion of foreign materials
Surface characteristics that promote dropwise condensation
Commercially pure titanium with minor alloy additions includes various titanium-palladium grades and alloy Ti-0.3Mo-0.8Ni (ASTM grade 12 or UNS R533400). These alloy additions enable improvements in corrosion resistance and/or strength characteristics. Titanium-palladium alloys, containing nominal palladium contents of approximately 0.2% Pd, are utilized in applications requiring excellent corrosion resistance in chemical processing or storage where environments may be mildly reducing or fluctuate between oxidizing and reducing conditions.
Alloy Ti-0.3Mo-0.8Ni (UNS R533400, or ASTM grade 12) serves applications similar to those for unalloyed titanium but provides enhanced strength and corrosion resistance. However, its corrosion resistance does not equal that of titanium-palladium alloys. The ASTM grade 12 alloy demonstrates particular resistance to crevice corrosion in hot brine environments.
Common Titanium Alloys and Their Applications
The allotropic behavior of titanium enables diverse microstructural changes through variations in thermomechanical processing, allowing a broad range of properties and applications to be served with a minimal number of grades. This versatility is especially evident in alloys with a two-phase, α+β, crystal structure.
Ti-6Al-4V alpha-beta alloy stands as the most widely used titanium alloy. This well-understood alloy demonstrates excellent tolerance to variations in fabrication operations, despite its relatively poor room-temperature shaping and forming characteristics compared to steel and aluminum. With limited section size hardenability, Ti-6Al-4V is most commonly employed in the annealed condition.
Other titanium alloys are specifically designed for particular application areas:
Alloys Ti-5Al-2Sn-2Zr-4Mo-4Cr (commonly called Ti-17) and Ti-6Al-2Sn-4Zr-6Mo provide high strength in heavy sections at elevated temperatures
Alloys Ti-6242S, IMI 829, and Ti-6242 (Ti-6Al-2Sn-4Zr-2Mo) offer superior creep resistance
Alloys Ti-6Al-2Nb-1Ta-1Mo and Ti-6Al-4V-ELI are engineered to resist stress corrosion in aqueous salt solutions while maintaining high fracture toughness
Alloy Ti-5Al-2.5Sn is designed for excellent weldability, with its ELI grade extensively used in cryogenic applications
Alloys Ti-6Al-6V-2Sn, Ti-6Al-4V, and Ti-10V-2Fe-3Al deliver high strength at low-to-moderate temperatures
