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.