First-principles and genetic modelling of precipitation sequences in aluminium alloys

摘要

Aluminium alloys display complex phase transitions to achieve their desired properties. Many of these involve elaborated precipitation sequences where the main role is not played by ther-modynamically stable species, but by metastable precipitates instead. An interplay between phase stability, crystal symmetry, diffusion, volume and particle/matrix interfaces sets the pace for the kinetics. Thermodynamic modelling, which focuses on stable precipitates, is not an aid in describing such processes, as it is usually transitional phases that achieve the desired properties. The model presented here combines first-principles to obtain the transition precipitate energetics (both at the bulk and at the interface with the matrix) with thermochemical databases to describe the overall kinetics of stable precipitates. Precipitate size and number density are captured via the Kampmann-Wagner numerical approach, which is embedded in a genetic algorithm to obtain optimal compositional and heat treatment scenarios for the optimisation of the mechanical properties in aluminium alloys of the 7000 series.