Heat treatment-modulated coupling effect of multi-scale second-phase particles on the ductile fracture of aged aluminum alloys

Experiments and multi-scale modeling were carried out in order to study the heat treatment-modulated coupling effect of multi-scale second-phase particles on the ductile fracture of two typical kinds of heat-treatable aluminum alloys, i.e. an Al–Cu–Mg alloy and an Al–Mg–Si alloy. It was revealed experimentally and theoretically that an appropriate combination of the multi-scale second-phase particles, which could be achieved by appropriate cooperation of the heat treatment steps, i.e. the solution, quenching and aging treatments, is necessary and sufficient for obtaining an excellent fracture toughness for the heat-treatable aluminum alloys. The experimental phenomenon, that the alloys containing more detrimental constituents but aged at a somewhat higher temperature exhibit ductility and fracture toughness superior to those of the alloys containing less detrimental constituents but aged at lower temperatures, could be reasonably explained by the cooperative effect of the heat treatment steps. Contours of the fracture toughness with respect to the technological parameters of the heat treatment, e.g. the aging temperature and quench factor, were developed to show the cooperative effect of the heat treatment steps on the fracture toughness of the aged aluminum alloys quantitatively. The good agreement between the calculations and the experimental results indicated that the present modeling is applicable for describing the heat treatment-modulated coupling effect of the multi-scale second-phase particles in aged aluminum alloys.