Effect of Aging on Impact Toughness and Fracture Behavior of Three Wrought Aluminum Alloys

Herein, the effect of the aging state on the impact toughness of three typical wrought Al alloys (7075, 2024, and 6A01) is investigated. At room temperature, the fracture mode of the three aluminum alloys at different aging states is a ductile transgranular fracture. At low temperatures, high-strength aluminum alloys exhibit a mixture fracture of transgranular and intergranular, while medium-strength aluminum alloys are still dominated by transgranular fractures. The effect of the aging state on the impact toughness of aluminum alloys was analyzed based on the deformation mechanism and morphology near grain boundaries. The underaged state with planar slip dislocations exhibits good plasticity and work-hardening ability, which reduces the strain localization caused by dislocation plugging and thus improves the impact toughness of the alloy. Furthermore, the fine grain boundary precipitates and the narrow precipitation-free zone of the underaged increase the uniform deformation capacity near the grain boundaries and inhibit the initiation and propagation of cracks. Compared with high-strength aluminum alloys, medium-strength aluminum alloys exhibit higher impact toughness due to the formation of a larger plastic zone and shear lip area during impact.