Beryllides intermetallics

Nb-Aluminides, precious metal and exotic aluminides. Laves phases and in-situ composites, silicides, and beryllide intermetallics. Given previous excellent reviews of the oxidation of intermetallics (e.g. Aitken, 1967 Doychak, 1994 Meier, 1996 Welsch et al., 1996), these sections emphasize the findings of recent studies. Areas in need of additional research, and issues that have already been well explored or are unlikely to yield fruitful results, are noted. 

The beryllides, being intermetallic compounds, are hard, strong materials which exhibit litde ductility at room temperature. Strength properties increase gradually as a function of temperature up to about 870°C, above which a sharp increase in strength occurs, peaking in the region of 1260°C the modulus of rupture values exceed 280 MPa (40,000 psi) at this latter temperature. 

The present monograph was first written as a chapter for Volume 8 of the series Materials Sdence and Technology A Comprehensive Treatment , edited by Robert W. Cahn, Peter Haasen, and Edward J. Kramer (Volume Editor Dr. Karl Heinz Matucha). Its aim is to give an overview of intermetallics, which is both detailed and comprehensive and which includes the fundamentals as well as applications. The result is an extended, critical review of the whole field of intermetallics with an emphasis on those intermetallic phases which have already been applied as functional or structural materials or which are currently the subject of materials developments. A historical introduction and a discussion of the relationship between atomic bonding, crystal structure, phase stability and properties is followed by a discussion of the major classes of intermetallics. The titanium aluminides, nickel aluminides, iron aluminides, copper phases, A15 phases. Laves phases, beryllides, rare earth phases, and siliddes are reviewed. In particular, the crystal structures, phase diagrams, and physical properties as well as the mechanical and corrosion behavior are treated. The state of developments as well as prospects and problems are discussed in view of present and future applications. The publisher has decided to publish the review as a separate monograph in order to make it accessible to a wider audience. 

Beryllia. See beryllium oxide. Beryllides. A group of intermetallic compounds of potential interest as special ceramics. Cell dimensions and types of structure have been reported for the beryllides of Ti, V, Cr, Zr, Nb, Mo, Hf and Ta (A. Zalkin el ai, Acta Cryst., 14, 63,1961). 

Finally, three elements of the periodic system occupy an intermediate position with regard to the ability to form refractory metal-like and non-metallic compounds. These elements, beryllium, magnesium, and aluminum, are capable of forming fairly refractory semiconductor compounds with nonmetals (beryllium, magnesium, aluminum borides, aluminum nitride, magnesium silicides), and they may also enter into the composition of intermetallic compounds of the beryllide, aluminide, etc., type. 

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