High melting temperature alloys

Rotating electrode atomization may be applied to almost all metals and alloys since it does not require a crucible for melting and/ or pouring. In particular, high melting-temperature metals and alloys, such as Ti and Zr, are well suited for the process. However, the production cost is still a drawback associated with the process, since electrode production is generally more expensive than a metal melt. In addition, production rates are relatively low compared to other atomization processes such as gas atomization and water atomization. 

While convenient, it should be noted that most of these approximations require the same precision of measurement as do curve fitting techniques and obviously lead to less accurate results. They have been particularly used to derive values for high melting temperature metals and alloys, yielding values that have an author to author reproducibility of typically 10%, as demonstrated by examination of collected data for Cu and Fe, (lida and Guthrie 1988). It is, however, often difficult when making such comparisons to decide whether the differences reflect varying precisions of measurement, differences in experimental procedure or qualities of materials. 

The fuels for fast breeder reactors include alloys such as U-Pu-Zr and the ceramic materials UO2-PUO2, UC-PuC, and UN-PuN, but the mixed oxides, UO2-PUO2, are the choice for prototype fast breeder fuel elements because of their high melting temperature, compatibility with cladding and coolants, and relatively good irradiation stability and fission product retention. The disadvantages are the relatively low metal density, the... 

Aluminium Non-magnetic. Various alloys of aluminium not easily distinguished. Highly energy-intensive, basic material. High melt temperature, removes virtually all impurities, but possible pollutant source. Recovery value 600-700 per... 

Titanium s physical properties (high melting temperature, resistance to corrosion, strength, light weight) make it an ideal additive to alloys used by the aerospace industry in rockets and jet aircraft, for ship components that are exposed to seawater, and for biomedical implants such as artificial joints or pacemakers. Titanium dioxide is utilized as a white pigment in paint, paper, plastics, and cosmetics. It is also used in some stmscreens because of its abihty to absorb ultraviolet (UV) light. 

S. Packer, T. Nelson, C. Sorensen, R. Steel, and M. Matsunaga, Tool and Equipment Requirements for Friction Stir Welding Ferrous and Other High Melting Temperature Alloys, Proceedings of the Fourth International Conference on Friction Stir Welding, May 14—16,2003 (Park City, UT), TWl, paper on CD... 

Stiff Machines. Cyclic process loads in FSW tend to be higher in many high-melting-temperature alloys than in aluminum. Deflections under load can lead to problems with fatigue failure, particularly with PCBN tools. To minimize these problems, the stiffness for the machine is specified. A deflection of 0.75 mm (0.030 in.) under a load of 45 kN (10 kip) is suggested by Ref 7. 

Mehl, M.J., Osburn, J.E., Papaconstan-topoulas, D.A. and Hein, B.M. (1990) Structural properties of ordered high-melting-temperature interm etallic alloys from first-principles total-energy calculations. Phys. Rev. B, 41,10311-10323. 

The oxides of metals or alloys with good resistance to high temperature corrosion generally have a high melting temperature. They therefore remain in the solid state under typical working conditions. However, there are several exceptions to this rule. 

A considerable difference in composition between the evaporated and deposited materials. Therefore, many compounds and alloy compositions, due to stoichiometry problem, can only be deposited with difficulty. The same problems take place for materials that have high melting temperature and low saturated vapor pressure Line-of-sight trajectories and hmited-area sources result in poor film-thickness uniformity and in poor surface coverage on complex surfaces Possible contamination from the evaporator The need to periodically load the evaporator... 

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