Classification of the role of microalloying elements in phase decomposition of Al based alloys

The fundamental role of microalloying elements in several aluminium alloys such as AI-Cu, Al-Li-Cu and Al-Cu-Mg has been investigated using a Monte Carlo computer simulation. All the utilized simulation parameters, e.g. pair interactions between same atoms species, between different atom species and between an atom and a vacancy, were derived from known thermodynamic or kinetic quantities. A small addition of Mg to AI-Cu alloys exhibits a strong tendency to form Mg/Cu/Vacancy complexes in the atom configurations, which is more remarkably revealed in Al-Li-Cu alloys. The combined addition of Ag or Si with Mg significantly increases the number of Mg/Cu/Vacancy complexes in Al-Cu-Mg alloys. From the comparison with experimentally reported results, these complexes are reasonably regarded as an effective heterogeneous nucleation site for GP zones, GPB zones and/or the Omega phase. The utilized simulation model, furthermore, permits the role of microalloying elements to be well classified in terms of the characteristic features of each element. (C) 2000 Acta Metallurgica Inc. Published by Elsevier Science Lid All rights reserved.