Vanadium alloys fabrication

The fabrication of most vanadium alloys is difficult because of increased strength and decreased ductihty, especially at low temperatures. Generally, higher temperatures are used for each step of fabrication. Also, processes, eg, extmsion in which the forces are largely compressive, are used for the initial ingot breakdown. 

Alloys of the P type respond to heat treatment, are characterized by higher density than pure titanium, and are more easily fabricated. The purpose of alloying to promote the P phase is either to form an aE-P-phase aEoy having commercially useful quaUties, to form aEoys that have duplex a- and P-stmcture to enhance he at-treatment response, ie, changing the a and P volume ratio, or to use P-eutectoid elements for intermetallic hardening. The most important commercial P-aEoying element is vanadium. 

Low-carbon, low-alloy steels are in widespread use for fabrication-welded and forged-pressure vessels. The carbon content of these steels is usually below 0.2%, and the alloying elements that do not exceed 12% are nickel, chromium, molybdenum, vanadium, boron and copper. The principal applications of these steels are given in Table 3.8. 

In the beginning of the twentieth century, surgical techniques were developed for the fixation of bone fractures with a plate and screw combination. Sherman-type bone plates were fabricated from the best available alloy at the time, vanadium steel. By the 1920s the use of vanadium steel became questionable because of poor tissue compatibility. At that time however, no other alloy was available with high strength and good corrosion resistant properties. 

Aircraft turbines in jet engines are usually fabricated from nickel-based alloys, and these are subject to combustion products containing compounds of sulphur, such as S02, and oxides of vanadium. Early studies of the corrosion of pure nickel by a 1 1 mixture of S02 and 02 showed that the rate of attack increased substantially between 922 K and 961 K. The nickel-sulphur phase diagram shows that a eutectic is formed at 910 K, and hence a liquid phase could play a significant role in the process. Microscopic observation of corroded samples showed islands of a separate phase in the nickel oxide formed by oxidation, which were concentrated near the nickel/oxide interface. The islands were shown by electron microprobe analysis to contain between 30 and 40 atom per cent of sulphur, hence suggesting the composition Ni3S2 when the composition of the corroding gas was varied between S02 02 equal to 12 1 to 1 9. The rate of corrosion decreased at temperatures above 922 K. 

Typical U.S. materials for solid-wall ammonia converter shells have been A516 Gr. 70, A212 Gr. B and A302 Gr. C (Mn-Mo-Ni) and nickel-vanadium steel for multilayer vessels. For similar conditions, most European fabricators have selected alloy material WSB 62, 24-CrMo 10 and Ducol W30, for example. 

The alloys recently investigated in the fabrication of Ni-MH batteries include the AB5 (LaNij) type and ABj (zirconium vanadium [ZrVj]) type. During the evaluation of these alloys, the material scientists failed to explore critical performance characteristics of the alloys other than the discharge capacity and progressive... 

The next alternatives, the refractory metals, have been used with measurable success to contain the various alloys of plutonium. Tungsten and tantalum have been somewhat better containers than molybdenum and niobium and much better than chromium, vanadium, and titanium. The requirement of fabricability eliminates several of the refractory metals, such... 

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