Phase transformation metals

Phase Transform., Inst. Metal. Conf. Ser. 3,2, 98 (1979) P. R. Williams, M. K. Miller G. D. W. Smith, Proc. Int. Conf. Solid-Solid Phase Transform. Metal Soc., AIME, Warrendale, PA (1981). 

Gross et al. (2002) NaAlHj Phase transformation, metal transport + + n.a. Liberation of hydrogen, reversible storage... 

Pure barium is a silvery-white metal, although contamination with nitrogen produces a yellowish color. The metal is relatively soft and ductile and may be worked readily. It is fairly volatile (though less so than magnesium), and this property is used to advantage in commercial production. Barium has a bcc crystal stmcture at atmospheric pressure, but undergoes soHd-state phase transformations at high pressures (2,3). Because of such transformations, barium exhibits pressure-induced superconductivity at sufftciendy low temperatures (4,5). 

D. A. Porter and K.E. Easterling. Phase Transformations in Metals and Alloys. Van Nostiand (UK) (1982) TN 690P597 (2nd edition Chapman Hall (1992). 

While most of the earlier research was done on metals and alloys, more recently a good deal of emphasis has been placed on ceramics and other inorganic compounds, especially functional materials used for their electrical, magnetic or optical properties. A very recent collection of papers on oxides (Boulesteix 1998) illustrates this shift neatly. In the world of polymers, the concepts of phase transformations or phase equilibria do not play such a major role 1 return to this in Chapter 8. 

Repeatedly in this book, the important functions of dopants , intentional additives made in small amounts to materials, have been highlighted the use of minor additives to the tungsten used to make lamp filaments is one major example. The role of impurities, both intentional and unintentional, in matters such as phase transformations, mechanical properties and diffusion, was critically reviewed in one of the early seminar volumes published by the American Society for Metals (Marzke 1955). But extreme purity was not considered that came a little later. 

In this chapter studies of physical effects within the elastic deformation range were extended into stress regions where there are substantial contributions to physical processes from both elastic and inelastic deformation. Those studies include the piezoelectric responses of the piezoelectric crystals, quartz and lithium niobate, similar work on the piezoelectric polymer PVDF, ferroelectric solids, and ferromagnetic alloys which exhibit second- and first-order phase transformations. The resistance of metals has been investigated along with the distinctive shock phenomenon, shock-induced polarization. 

F. Soisson, C. Pareige, M. Athenes, G. Martin, D. Blavette. Kinetics of phase transformations in metallic alloys Monte-Carlo simulations versus experiments. Ann Phys 22 3, 1997. 

Many metals and metallic alloys show martensitic transformations at temperatures below the melting point. Martensitic transformations are structural phase changes of first order which belong to the broader class of diffusion js solid-state phase transformations. These are structural transformations of the crystal lattice, which do not involve long-range atomic movements. A recent review of the properties and the classification of diffusionless transformations has been given by Delayed... 

KINETICS AT EARLY STAGES OF PHASE TRANSFORMATIONS IN METALLIC ALLOYS... 

J.W.D. Coimolly and A.R. W hiams, Density-functional theory applied to phase transformations in transition metals, Phys. Rev. B 27 5169 (1983). 

This conclusion was additionally confirmed by Palczewska and Janko (67) in separate experiments, where under the same conditions nickel-copper alloy films rich in nickel (and nickel films as well) were transformed into their respective hydride phases, which were proved by X-ray diffraction. The additional argument in favor of the transformation of the metal film into hydride in the side-arm of the Smith-Linnett apparatus consists of the observed increase of the roughness factor ( 70%) of the film and the decrease of its crystallite size ( 30%) after coming back from low to high temperatures for desorbing hydrogen. The effect is quite similar to that observed by Scholten and Konvalinka (9) for their palladium catalyst samples undergoing the (a — j8) -phase transformation. 

A.K. Ardell, Mechanisms of Phase Transformations in Crystalline Solids, Inst. Metals, Monograph and Report Series, No. 33, 1969, p. 111. 

Ca3(BN2)2 is readily formed when (distilled) calcium metal is melted in the presence of (layer-type) boron nitride. This reaction provides some insight on how alkaline-earth metals like calcium may act as a catalyst in the phase transformation of layered a-BN into its cubic modification. Instead of metals, nowadays alkaline-earth (Ca, Sr, Ba) nitridoborates can be used as a flux catalyst in high-pressure and high-temperature transformation reactions to produce cubic boron nitride [15]. 

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