Titanium-zirconium-base alloys

Phase Transformations in Titanium- and Zirconium-Based Alloys... 

Non-equilibrium Processing of Materials edited by C. Suryanarayana Phase Transformations in Titanium- and Zirconium-based Alloys... 

Nobium also is added to nickel- and cobalt-based superaUoys and is a component of zirconium, titanium and tungsten alloys. 

More recently magnesium-base, iron-base, and zirconium-titanium-base alloys have been developed that do not require such rapid cooling. In 1992, W. L. Johnson and co-workers developed the first commercial alloy available in bulk form Vitreloy 1, which contains 41.2 a/o Zr, 13.8 a/o Ti, 12.5 a/o Cu, 10 a/o Ni, and 22.5 a/o Be. The critical cooling rate for this alloy is about 1 K/s so glassy parts can be made with dimensions of several centimeters. Its properties are given in Table 15.3. 

Rebak, R.B., Corrosion of Non-Ferrous Alloys, Part I Nickel-, Cobalt-, Copper-, Zirconium-and Titanium-Base Alloys, Corrosion and Environmental Degradation, Vol. II, Wiley-VCH, Weinheim, p. 69, 2000. 

The titanium alloys are not heat resisting materials being inferior to stainless steel in this respect. Recently titanium-based alloys alloyed with silicon, aluminium, zirconium (elements which considerably enhance heat resistance of technical metals Fe, Co, Ni) were elaborated in IPMS of NASU... 

Examples of metals that are passive under Definition 1, on the other hand, include chromium, nickel, molybdenum, titanium, zirconium, the stainless steels, 70%Ni-30% Cu alloys (Monel), and several other metals and alloys. Also included are metals that become passive in passivator solutions, such as iron in dissolved chromates. Metals and alloys in this category show a marked tendency to polarize anodicaUy. Pronounced anodic polarization reduces observed reaction rates, so that metals passive under Definition 1 usually conform as well to Definition 2 based on low corrosion rates. The corrosion potentials of metals passive by Definition 1 approach the open-circuit cathode potentials (e.g., the oxygen electrode) hence, as components of galvanic cells, they exhibit potentials near those of the noble metals. 

Inconel-625, Incoloy 800) perform better than stainless steel, but still significant corrosion occurs in the presence of HCl, H2SO4 and HNO3, or HF, HBr or HI. Oxidants such as O2 and H2O2 enhance the corrosion of many alloys (stainless steel, Ni-base alloys ). Some improvement is possible by adding Ti, Zr or Al/Nb/Ti to steels. Also, iron-free but very expensive metals like pure titanium or zirconium,or alloys like Monel (Ni- -Cu) and Ti60 have been tested. 

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