Commensurately modulated stable states related to the gamma phase in Mg-Al alloys

Author: Donnadieu P.   Harmelin M. G.   Seifert H. J.   Aldinger F.  

Publisher: Taylor & Francis Ltd

ISSN: 0141-8610

Source: Philosophical Magazine. A. Physics of Condensed Matter. Defects and Mechanical Properties, Vol.78, Iss.4, 1998-10, pp. : 893-905

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Abstract

Recent investigations have shown that quenched Mg-Al alloys exhibit metastable quasiperiodic states for concentrations ranging from 47 to 61 at.% Al. We report here a structural study of the related high-temperature equilibrium states by means of electron diffraction. We derive that the stable states can be described as three-dimensional modulated states, the difference from the quenched states being that the modulation is commensurate with the mean lattice. The modulation wave-vector depends on composition and temperature. We observe that the wave-vector is proportional to a rational value p/q which follows a simple series (n/(3n + 1)) when the composition or temperature is modified.

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