Aging-dependent coupling effect of multiple precipitates on the ductile fracture of heat-treatable aluminum alloys

Heat-treatable aluminum alloys usually contain two or more kinds of precipitates but how the macro-properties depend on the multiple precipitates, especially in a quantitative manner, has not been well known. In this paper, systematic experiments and modeling are performed to study the coupling effect of multiple precipitates on the strength and ductility of aged Al-Mg-Si alloys that contain three kinds of precipitates. A density-dependent superposition effect of the multiple precipitates on the ductility, essentially similar to that on the yield strength, is clearly revealed and quantitatively modeled. It is surprisingly found that an appropriate combination of the multiple precipitates could increase the ductility significantly with sacrificing strength less. Calculations are in good agreement with experiments.