Alloys phases

K. Ishida and T. Nishizawa, Bull Alloy Phase Diag. 11, 357 (1990). 

J. Mansfield. Convergent Beam Electron Dijfraction of Alloy Phases, (by the Bristol Group, under the direction of J. Steeds, and compiled by J. Mansfield) Hilger, Bristol, 1984. This book is an atlas of CBED patterns that may be used to identify phases by comparing published patterns with experimental patterns. 

P. Braun. Surf. Sci. 126,714,1983. VEELS study of bulk and surface plasmon energies across Al—Mg alloy phase diagram. 

Stocks, G.M. and Gonis, A. (eds.) (1989) Alloy Phase Stability (Kluwer Academic Publishers, Dordrecht). 

The fee lattice of the coinage metals has 1 valency electron per atom (d °s ). Admixture with metals further to the right of the periodic table (e.g. Zn) increases the electron concentration in the primary alloy ( -phase) which can be described as an fee solid solution... 

AUGMENTED SPACE RECURSION APPROACH FOR ALLOY PHASE STABILITY... 

One of the major ingredient for the understanding of alloy phase stability is the configurational energy. Models have been proposed to represent the configurational energies in terms of effective multisite interactions, in particular effective pair interactions (EPls). 

Binary Alloy Phase Diagrams, 2nd edition, editor-in-chief T. B. Massalski, ASM International, Materials Park, Ohio, (1990). 

Experimentally it is found that the Fe-Co and Fe-Ni alloys undergo a structural transformation from the bee structure to the hep or fee structures, respectively, with increasing number of valence electrons, while the Fe-Cu alloy is unstable at most concentrations. In addition to this some of the alloy phases show a partial ordering of the constituting atoms. One may wonder if this structural behaviour can be simply understood from a filling of essentially common bands or if the alloying implies a modification of the electronic structure and as a consequence also the structural stability. In this paper we try to answer this question and reproduce the observed structural behaviour by means of accurate alloy theory and total energy calcul ions. 

Here W(a,(i) is the p a transition probability for which we accept the conventional thermally activated atomic exchange model . Below we briefly review several recent works on the general formulation of this approach and on its applications to studies of alloy phase transformatious. 

Staunton, B. Ginatonpo, P.E.A. Turchi and M. Sluiter, in Statics and Dynamics of Alloy Phase Transformations , PE.A. Turchi and A. Gonis eds., NATO-ASI series B, vol. 319.Plenum. New York, USA (1994) and references therein. 

ASM Handbook, Vol. 3, Alloy Phase Diagram (ASM International, Materials Park Ohia 1992). 

Multiphase gold or palladium-based alloys never show dissolution of Au or Pd but often exhibit progressive surface ennoblement due to selective dissolution of copper or silver from the outer 2-3 atomic layers Heat treatment often decomposes multicomponent alloys into a Pd-Cu rich compound and an Ag-rich matrix with corrosion of the latter phase in deaerated artificial saliva and S -containing media . Au-Cu-rich lamellae have similarly been observed, again with preferential attack on Ag-rich phases or matrix. These effects presumably arise from the ability of the noble alloy phases to catalyse the cathodic reduction of oxygen . 

Averbach, B. L., in Theory of Alloy Phases, American Society for Metals Monograph, Cleveland, 1956. 

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