Computer simulation of local atomic displacements in alloys. Application to Guinier-Preston zones in Al-Cu

A new computer program has been developed for the simulation of local atomic displacements in alloys with face-centered-cubic and body-centered-cubic lattices. The combined use of this program with the Gehlen-Cohen program for the simulation of chemical short-range order completely describes atomic fluctuations in alloys. The method has been applied to the structural simulation of Guinier-Preston (GP) zones in an Al-Cu alloy, using the experimental data of Matsubara & Cohen [Acta Metall. (1985), 33, 1945-1955]. Characteristic displacements of atoms have been observed around the GP zones and new structural models including local displacements have been proposed for a single-layer zone and several multilayer zones.