Alloy titanium-aluminum—niobium

Titanium-aluminum-niobium alloys have been developed for biocompatible, high-strength surgical implants (Semlitsch et al. 1985), while metal-resin composites containing niobium as filler have potential use as restorative materials in dentistry (Misra and Bowen 1977). The metal possesses superior superconductive properties in strong magnetic fields, which may be... 

The activation of aluminum with ultrasound or dispersion of liquid aluminum. The suspension of powder aluminum in petrol or n-geptane without oxygen is subjected to ultrasound the tough oxide film on the surface of aluminum is removed and aluminum becomes reactive. The second activation technique is the dispersion of liquid aluminum with argon or purified nitrogen flow into a finely dispersed state. It should be noted, however, that the most reactive aluminum powder for direct synthesis is the powder alloyed with transition metals (titanium, zirconium, niobium, tantalum) with the size of particles from 10 to 125 pm. 

Alnico /al-ma-koh/ (Trademark) Any of a group of very hard brittle alloys used to make powerful permanent magnets. They contain nickel, aluminum, cobalt, and copper in various proportions. Iron, titanium, and niobium can also be present. They have a high remanence and coercive force. 

Metallic materials with the exception of noble metals are also thermodynamically not stable in the acidic environment under the PEFC operating conditions and therefore subject to corrosion. Nevertheless, many different metals such as stainless steels, aluminum, aluminum composites, copper, nickel and nickel alloys, titanium alloys and even highly corrosion resistant materials used in chemical industry such as tantalum, hafnium, niobium or zirconium have been investigated with respect to applicability in PEFC with respect to corrosion resistance [68—71]. 

Special Alloys. Steels containing small alloying additions of aluminum, titanium, or niobium plus tantalum [19], which react preferentially with carbon and nitrogen, exhibit improved resistance to S.C.C., but are not immune. Alloyed additions of <2% Ni increase susceptibihty of low-carbon steels in nitrates >1% Cr or Mo decrease susceptibility. Furnace-cooled (pearlitic) steels of >0.2% C are resistant [20]. 

Jep70] Jepson, K.S., Brown, A.R.G., and Gray, J.A., The Effect of Cooling Rate on the Beta Transformation in Titanium-Niobium and Titanium-Aluminum Alloys, in [Jaf70], p. 677-690... 

Alloy Inconel X750 contains additions of aluminum, niobium and titanium which form an intermetallic compound, NislAl, Ti) to make it age hardenable and provide high strength. It is extremely resistant to SCC in chloride environment. It is used in gas turbines, vacuum envelopes, extrusion dies and springs. 

Low Expansion Alloys. Binary Fe—Ni alloys as well as several alloys of the type Fe—Ni—X, where X = Cr or Co, are utilized for their low thermal expansion coefficients over a limited temperature range. Other elements also may be added to provide altered mechanical or physical properties. Common trade names include Invar (64%Fe—36%Ni), F.linvar (52%Fe—36%Ni—12%Cr) and super Invar (63%Fe—32%Ni—5%Co). These alloys, which have many commercial appHcations, are typically used at low (25—500°C) temperatures. Exceptions are automotive pistons and components of gas turbines. These alloys are useful to about 650°C while retaining low coefficients of thermal expansion. Alloys 903, 907, and 909, based on 42%Fe—38%Ni—13%Co and having varying amounts of niobium, titanium, and aluminum, are examples of such alloys (2). 

The lattice of vanadium expands approximately linearly with the addition of aluminum [64]. The aluminum intermetallic compound, V3AI (V-25 atom% Al), expands the lattice by about 1% from 0.3025 nm in unalloyed vanadium to 0.3054 nm [64]. Molybdenum, cobalt and titanium also expand the lattice of vanadium, whereas elements such as chromium and iron cause the lattice to contract [83]. Addition of these elements can increase the mechanical strength of alloys relative to unalloyed vanadium [85]. For niobium and tantalum, mechanical properties can also be improved by alloying [86]. Buxbaum has patented a number of alloys of niobium, tantalum and vanadium for membrane use, including Ta-W, V-Co, V-Pd, V-Au, V-Cu, V-Al, Nb-Ag, Nb-Pt, Nb-Pd, V-Ni-Co, V-Ni-Pd, V-Nb-Pt, and V-Pd-Au [45]. 

Design of cathodic protection for marine structures in both fresh and salt water require special techniques. Galvanic systems usually employ zinc or aluminum alloy anodes. Impressed current systems frequently use high silicon, chromium bearing iron, platinized niobium, or mixed-metal oxide/titanium anodes. The structure being protected affects the design. Stationary facihties such as bulkheads and support piles require different techniques from ship hulls [55]. 

Nickel-based alloys, which form the bulk of alloys produced, are basically nickel-chrome alloys with a face-centered cubic solid-solution matrix containing carbides and the coherent intermetallic precipitate y-NijlAfTi). This latter precipitate provides most of the alloy strengthening and results in useful operating temperatures up to 90% of the start of melting. Further additions of aluminum, titanium, niobium, and tantalum are made to combine with nickel in the y phase, and additions of molybdenum, tungsten, and chromium strengthen the solid solution matrix. 

F 1295, Specification for Wrought Titanium-6 Aluminum-7 Niobium Alloy for Surgical Implant Applications (UNS R56700)... 

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