Tungsten-Titanium Alloys

The alloy W-lOTi is used as a sputtering target in the manufacture of microelectronics devices, such as VLSI, ULSI (very large resp. ultralarge-scale integration), and DRAM (dynamic random access memory) chips. Thin W-Ti layers are sputtered onto silicon substrates and act as a diffusion barrier against aluminum (intercormect). 

W-lOTi alloy targets are produced by blending ultrapure tungsten (see also Section 5.7.6) and titanium powders (obtained by vacuum melting and subsequent pulverizing), followed by pressure sintering. The impurity level has to be very low, in particular, with respect to radioactive elements (U, Th) and mobile alkaline metals (Na, K). 

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Niobium is important as an alloy addition in steels (see Steel). This use consumes over 90% of the niobium produced. Niobium is also vital as an alloying element in superalloys for aircraft turbine engines. Other uses, mainly in aerospace appHcations, take advantage of its heat resistance when alloyed singly or with groups of elements such as titanium, tirconium, hafnium, or tungsten. Niobium alloyed with titanium or with tin is also important in the superconductor industry (see High temperature alloys Refractories). 

The basic corrosion behaviour of stainless steels is dependent upon the type and quantity of alloying. Chromium is the universally present element but nickel, molybdenum, copper, nitrogen, vanadium, tungsten, titanium and niobium are also used for a variety of reasons. However, all elements can affect metallurgy, and thus mechanical and physical properties, so sometimes desirable corrosion resisting aspects may involve acceptance of less than ideal mechanical properties and vice versa. 

Titanium and Titanium Alloys Tungsten and Tungsten Alloys Zinc Alloy Die Castings... 

A ZnS insulating layer 114 is deposited on a sensing layer 112 of HgCdTe. A refractory metal, such as tantalum, molybdenum, tungsten, titanium or refractory metal alloys such as titanium/tungsten, is sputter-deposited onto the insulating layer. The structure is connected to... 

Tungsten-base alloys have been used in the friction stirring of copper alloys, nickel-aluminum bronze, titanium alloys, and steels (Ref 4, 15, 26, 28, 33, 34, 38 8). The FSW of 1018 steel (Ref 4) and ultrahard 0.29C-Mn-Si-Mo-B 500 Brinell steel (Ref 40) caused tool wear on tungsten alloy FSW tools. Four tungsten-base materials have been specifically cited... 

Until recently, there were no tool materials that would stand up to the high stresses and temperatures necessary for FSW of materials with higher melting points, such as steels, stainless steels, and nickel-base alloys. In 1998, tungsten alloys and polycrystalline cubic boron nitride (PCBN) were developed to create FSW tools for use in steel, stainless steel, titanium alloys, and nickel-base alloys. Properties of the resultant welds have been shown to be outstanding. Although some issues remain (primarily limited tool life with tungsten-base tools), FSW has been demonstrated as a technically and eco-... 

One key factor was not investigated here. Several researchers have reported in presentations that there may be an interaction between the tungsten-rhenium tool and some titanium alloys during FSW that makes welding difficult. At present, no quantitative explanation has been offered for this interaction. Nonetheless, the choice of tool material in the current study may have had unintended consequences on the results. 

Alloy steel pipe composition has various elements, with total concentration between 1.0% and 50% by weight, which enhances the mechanical properties and corrosion resistance. These steels can be grouped under low-alloy steels. Along with economic growth, the demand of alloy steel pipes and tubes for industrial use has increased enormously. The most common alloying elements are nickel, chromium, silicon, vanadium, and molybdeniun. Special pipe steels also contain very small amounts of aluminum, cobalt, tungsten, titanium, and zirconium. Alloy steel has different properties on the basis of its composition. Alloy steel tubes cater to domestic and industrial requirements, such as gas drilling, offshore projects, refineries, and petrochemical plants. 

Rud] Rudy, E., Constitution of Ternary Titanium-Tungsten-Carbon Alloys , J. Less-Common Met., 33, 245-273 (1973) (Phase Diagram, Experimental) as quoted by [1991Nag]... 

Although not an ore, ferroniobium is produced by a smelting operation from columbite, in reasonably large quantities and at a cost which is sufficiently attractive for it to be used as a source material for the produc-ton of pure niobium. It consists essentially of an alloy of about 60 per cent niobium, 9 per cent tantalum and 24 per cent iron with smaller amounts of tungsten, titanium, manganese and aluminium, etc. Processes have been based upon dissolution of ferroniobium in acids (e.g. a mixture of sulphuric and hydrofluoric acids) or fusion with potassium carbonate, but the most satisfactory method is to dissolve the alloy in a concentrated potassium hydroxide solution. 

There are at least four compositions of cobalt-base alloys in use which are similarly designated by code numbers such as F75, F90, F562, and F563. Again, these differ in the relative composition of the following elements manganese, silicon, chromium, nickel, molybdenum, carbon, iron, phosphorus, sulfur, tungsten, titanium, and cobalt. These alloys are used because of their superior... 

Weldability. Lake other titanium alloys, Ti-5Al-2.5Fe can be welded, but preferably by the more sophisticated methods such as gas tungsten-arc and electron beam welding. Other precaution-aiy procedm-es such as preheating, postheating, control of interpass temperattu-e, and control of environmental conditions should be used. 

Figure 10.3 Photographs of the segregated state of binary granular mixtures of particles differing only in density after being shaken repeatedly until a steady segregation state is reached. The lighter particles are made of aluminum oxide (density p 1.31 g/cm ) and the heavier ones are made of (a) zirconium oxide (density p 2.87 g/cm ), (b) titanium alloy (density p 4.45 g/cm ), (c) cobalt-chromium-molybdenum alloy (density p 8.37 g/cm ), and (d) tungsten alloy (density p = 18.0 g/cm ), respectively. (Shi, Q. et al., Phys. Rev. E, 061302/1-4, 2007.)...

Besides the material based characteristics, the difference of density of the used particle/substrate combination is a very important criterion. The difference of density influences the contrast of the radiographic tests. Tungsten carbides were used as mechanically resistant particles and titanium based alloys as substrate. The substrate material is marked by an advantageous relation of strength to density. This material is often used in aeronautics, astronautics, and for modification of boundary layers. The density of tungsten carbide (15.7 g/cm ) is about 3.5 times higher than the density of titanium (4.45-4.6 g/cm ). 

Nitrogen and carbon are the most potent solutes to obtain high strength in refractory metals (55). Particulady effective ate carbides and carbonitrides of hafnium in tungsten, niobium, and tantalum alloys, and carbides of titanium and zirconium in molybdenum alloys. 

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