Yttrium alloys

Yttrium alloys have many applications. The metal doped with rare earths such as europium is used as phosphor for color television receivers. When added to iron, chromium, vanadium, niobium, and other metals it enhances resistance of these metals and their alloys to high temperature oxidation and recrystallization. It is a deoxidizer for vanadium and other nonferrous metals. Yttrium-aluminum garnets are used in lasers and in jewelery gemstones. Yttrium-iron garnets are used as transmitters and as transducers of acoustic energy. 

Implantations of yttrium and cerium in 15 % Cr/4% A1 steel and aluminized coatings on nickel-based alloys did not improve the high-temperature oxidation resistance even though conventional yttrium alloy addition had an effect. The differences for the various substrates are attributed to different mechanisms of oxidation of the materials. The austenitic steel forms a protective oxide film and the oxidation proceeds by cation diffusion. Thus, the yttrium is able to remain in a position at the oxide/metal interface. The other materials exhibit oxides based on aluminum. In their growth anion diffusion is involved which means an oxide formation directly at the oxide/metal interface. The implanted metals may, therefore, be incorporated into the oxide and lost by oxide spalling. 

Yttrium alloys have some special uses as well. These alloys tend to be hard, resistant to wear, and resistant to corrosion (rusting). They are used in cutting tools, seals, bearings, and jet engine coatings. 

D. Fort, J. P. G. Farr and I. R. Harris, A comparison of palladium-silver and palladium-yttrium alloys as hydrogen separation membranes, J. Les-Common Met., 1975, 39, 293-308. 

Carlson, O.N., D.W. Bare, E.D. Gibson, and F.A. Schmidt, 1959, Survey of the Mechanical Properties of Yttrium and Yttrium Alloys, in Symposium on Newer Metals, A.S.T.M. Special Technical Publication No. 272 (American Society for Testing Materials, Philadelphia), pp. 144-159. Yttrium prepared by reduction of YF3 with calcium in the presence of magnesium (intermediate alloy process) in a titanium reaction vessel. 

Effect of pressure on phase relationships Jayaraman et al. (1966) in a study of the effects of high pressure and temperature on binary cerium-rare earth alloys, tested three cerium-yttrium alloys that, under normal conditions, had the hep the Sm-type and the dhcp structures. Pressure-induced phase transformations in the sequence hep - Sm type dhcp fee were observed in several other intra rare earth alloy systems tested but in the Ce-Y... 

Fig. 75. Activity of samarium and yttrium in solid samarium-yttrium alloys at 900°C.

No experimental data for the europium-yttrium phase diagram were found. However, Miedema (1976), using Gschneidner s (1969) value for the energy difference between divalent and trivalent europium (96kJ/g-at), found his method would account for the known information on the valence state of europium in intermetallic compounds. The appUcation of his thermodynamic calculations to the europium-yttrium alloy system predicted that no stable compounds exist in this system. 

An investigation of the europium-yttrium alloy system would be complicated by the fact that the melting point of yttrium (1522°C, see table 1) is only 5°C below the boiling point of europium (1527°C, see table 4). 

Spedding et al. (1962) examined the gadolinium-yttrium alloy system using metals that were 99.9 -I- wt% pure with respect to other rare earth metals. The yttrium metal... 

Naigovzin et al. (1979) made a mass-spectrometric study of the vaporization of terbium-yttrium alloys. The activity coefficients of yttrium were calculated graphically and those of terbium were calculated using the Gibb-Duhem equation. The activities of yttrium and terbium, shown for 1577°C (1850 K) in fig. 102, deviate from ideal solution behavior, according to the authors, because of the differences in the polarizabilities and the electronegativities of terbium and yttrium. 

Thermal evaporation uses the atomic cloud formed by the evaporation of the coating metal in a vacuum environment to coat all the surfaces in the line of sight between the substrate and the target (source). It is often used in producing thin 0.5 pm coatings or a very thick 1-mm layer of heat-resistant materials, such as MCrAlY—a metal, chromium, aluminum, and yttrium alloy. 

Miller PL, Shaw BA, Wendt RG, Moshier WC, Assessing the corrosion resistance of nonequilibrium magnesium-yttrium alloys . Corrosion, 1995 51 922-931. 

Small amounts of yttrium (0.1 to 0.2%) can be used to reduce the grain size in chromium, molybdenum, zirconium, and titanium, and to increase strength of aluminum and magnesium alloys. 

Alloys with other useful properties can be obtained by using yttrium as an additive. The metal can be used as a deoxidizer for vanadium and other nonferrous metals. The metal has a low cross section for nuclear capture. 90Y, one of the isotopes of yttrium, exists in equilibrium with its parent 90Sr, a product of nuclear explosions. Yttrium has been considered for use as a nodulizer for producing nodular cast iron, in which the graphite forms compact nodules instead of the usual flakes. Such iron has increased ductility. 

No fewer than 14 pure metals have densities se4.5 Mg (see Table 10.1). Of these, titanium, aluminium and magnesium are in common use as structural materials. Beryllium is difficult to work and is toxic, but it is used in moderate quantities for heat shields and structural members in rockets. Lithium is used as an alloying element in aluminium to lower its density and save weight on airframes. Yttrium has an excellent set of properties and, although scarce, may eventually find applications in the nuclear-powered aircraft project. But the majority are unsuitable for structural use because they are chemically reactive or have low melting points." ... 

Fig. 4.35. GIAB depth profiling of yttrium ion-implanted NiCr that had been oxidized in air for 8 min at 700 °C. A = alloy substrate, C = Cr203,...

Other detrimental factors which should to be taken into account in the materials selection process include temperature cycling and the presence of halide gases. Specialist alloys containing rare earth element additions such as cerium, lanthanum and yttrium have been developed for use in certain environments up to 130°C. 

Fig. 2.—-Calculated values of p for the elements yttrium to rhodium and for binary alloys between adjacent elements. 0.2 / ...

A circular TLC spectrophotometric method for the determination of lanthanum and yttrium at concentration level of 0.01 to 1.0% in molybdenum-based alloys has also been developed. It involves the separation of lanthanum and yttrium on cellulose layers impregnated with 0.2-Mtrioctylamine using aqueous HCl as developer, extraction from sorbent layer, and determination by spectrophotometry [69]. 

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