Systematic study of stacking fault energies of random Al-based alloys

We have determined intrinsic stacking fault energies, formation energies and structural energies differences for Al–X alloys, where X=Cu, Ag or Mg, from self-consistent electronic structure calculations, using the Layer Korringa Kohn Rostoker method within the coherent potential approximation. We find that the intrinsic stacking fault energy is almost 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 modified rigid band model is used to understand the origin of the non-linear variation of the stacking fault energy in Al–Cu and Al–Ag with composition. 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 element that has a filled d-band.