Effect of precipitate morphology evolution on the strength-toughness relationship in Al-Mg-Si alloys

Experimental results show that the gradual evolution of precipitate morphology in Al-Mg-Si alloys, from spherical to rod-/needle-shaped, leads to an increase in ductility but a decrease in both yield strength and fracture toughness. The strength-ductility relationship reported here is similar to general observations but the strength-toughness relationship is distinctly different from the conventional one. These relationships are rationalized by considering a competition between dislocation-precipitate interaction and precipitate-matrix deformation discrepancy as the dominant strain localization mechanism, which is modulated by the evolution of precipitate morphology.