The influences of artificial aging on the microstructures and mechanical properties of an AI-1.01Mg-0.68Si-1.78Cu alloy were investigated.The detailed fracture surfaces,precipitates,and dislocation structures were also examined through scanning electron microscopy (SEM) and transmission electron microscopy (TEM).The results show that the tensile strengths exhibit two peak values and reach saturated values with increasing aging time,while the elongation decreases sharply to the minimum value and changes slightly later.The deformation and fracture behaviors arc also closely related to the aging conditions.