SYSTEMATIC STUDY OF STACKING-FAULT ENERGIES OF RANDOM AL-BASED ALLOYS

We have determined intrinsic stacking fault energies, formation energi es and structural energies differences for Al-X alloys, where X = Cu, Ag or Mg, from self-consistent electronic structure calculations, usin g the Layer Korringa Kohn Rostoker method within the coherent potentia l approximation. We find that the intrinsic stacking fault energy is a lmost equal to twice the energy difference between the h.c.p. and f.c. c. structures, which indicates that the inter-atomic interactions that are relevant for the structural properties are of short-range. A modi fied rigid band model is used to understand the origin of the non-line ar variation of the stacking fault energy in Al-Cu and Al-Ag with comp osition. For the Al-Zn system we show that conclusions drawn from the rigid band model hold for any system in which Al is alloyed with an el ement that has a filled d-band. (C) 1998 Acta Metallurgica Inc.