Because of their age-hardenability, 6061 commercial aluminum alloys sheets are used as outer panels for automobiles. Several researches have examined the effect of cold-rolling-induced strain on the aging behavior of these alloys. The present study investigates the effect of uniaxial tensile prestrain on the change of tensile properties during isothermal aging at 448K. The strength increased rapidly when increasing the aging time ranging from 10 to 32 min, corresponding to the time of serration disappearance. In contrast, the uniform elongation and n-value decreased rapidly with increasing aging time for the unstretched specimens; though, they showed an initial increase for the stretched specimens. The relationship between the uniform elongation #epsilon#_u and n-value was examined. The value of #epsilon#_u/n was slightly higher than 1 for the stretched specimens. The value is lower than 1 a the beginning of the aging, and becomes nearly 1 at the final stage of the aging for the unstretched specimens. The methods for deriving uniform elongation and n-value were discussed in detail. And then new approach for obtaining newly defined n value was proposed to obtain good correlation between the uniform elongation #epsilon#_u and n value for the unstretched and stretched specimens isothermally aged.
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