In:
Bulletin de la Société française de Minéralogie et de Cristallographie, PERSEE Program, Vol. 91, No. 6 ( 1968), p. 557-574
Kurzfassung:
Both experimental and theoretical aspects of the study of long period structures in alloys are briefly reviewed. In an assembly of free electrons as found in metals and alloys, there is always a tendency to create Brillouin zone boundaries at the Fermi surface to reduce their energy. Therefore, if the energy associated with the formation of special periodicities in the crystal which create the necessary Brillouin zone boundaries is small, a long period structure will be created. Many types of long period structures found in alloys can be systematically explained from this principle. The most clear-cut explanation based on the above concept can be given to the formation of the so-called long period superlattices in ordered noble metal alloys, as found for example in the Cu-Au alloys, where the period of the alloy is uniquely related to the electron-atom ratio (e/a). If the period of the long period superlattice becomes extremely short, as in the M = 1 or M = 2 structure, the period generally will no longer respond to a change in e/a. In such a case, alloys tend to respond to the change of e/a by some other means. A distortion of the crystals determined by e/a or a series of long period stacking order modulations in such alloys thus results. In the martensitic transformation of the β˗phase of noble metal alloys, a series of structures with long period stacking order is found. However, here, contrary to the above cases, a particular kind of stacking order modulation is proven to be due to external strains rather than to the response to e/a only.
Materialart:
Online-Ressource
ISSN:
0037-9328
DOI:
10.3406/bulmi.1968.6157
Sprache:
Französisch
Verlag:
PERSEE Program
Publikationsdatum:
1968
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