Intermetallic phases, alloying elements

Physical Properties. An overview of the metallurgy (qv) and solid-state physics of the rare earths is available (6). The rare earths form alloys with most metals. They can be present interstitially, in solid solutions, or as intermetallic compounds in a second phase. Alloying with other elements can make the rare earths either pyrophoric or corrosion resistant. It is extremely important, when determining physical constants, that the materials are very pure and well characterized. All impurity levels in the sample should be known. Some properties of the lanthanides are listed in Table 3. 

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 all-P-phase alloy having commercially useful qualities, to form alloys that have duplex a- and P-stmcture to enhance he at-treatment response, ie, changing the CC and P volume ratio, or to use P-eutectoid elements for intermetallic hardening. The most important commercial P-alloying element is vanadium. 

The A2 metals and the elements of the earlier B subgroups (Bj metals) form the electron compounds already discussed. With the metals of the later B subgroups the A2 metals, like the Aj, tend to form intermetallic phases more akin to simple homopolar compounds, with structures quite different from those of the pure metals. The nickel arsenide structure has, like typical alloys, the property of taking up in solid solution a considerable excess of the transition metal. From Table 29.12... 

W.B. Pearson, A Handbook of Lattice Spacings and Structures of Metals and Alloys, Vol. 2, Pergamon Press, Oxford, 1967, pp. 1,2. For tabulated lattice parameters and data on elemental metals and semi-metals, see pp. 79-91. See also, P. Villars and L.D. Calvert, Pearson s Handbook of Crystallographic Data for Intermetallic Phases, Vols. 1-3, American Society for Metals, Metals Park, Ohio, USA, 1985. 

The solubility of alkaline earth metals in molten alkali metals is limited. The elements of the third group of the periodic table of elements are still less soluble in alkali metals, only the aluminium-lithium system is an exception. This system contains two intermetallic phases, LiAl and the peritectic phase Li9Al4, and solid alloys of both metals are of technical importance. The metals of the fourth group have a better solubility in alkali metals. They tend to form intermetallics. Some of the liquid alloys have found technical interest. 

From the perspective of a materials scientist, tellurium is certainly the most attractive element, and it has found applications mainly in the electronics industry because of its p-type semiconducting properties. It can also be used for the synthesis of so-called II-VI semiconductors (such as MgTe) or may be alloyed to yield superior intermetallic phases. In addition, some Te alloys are under investigation in the realm of phase-change media for rapid data storage [273]. 

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