The influence of precipitation on the work-hardening behavior of the aluminum alloys AA6111 and AA7030

Tensile tests were conducted on the aluminum alloy, AA6111, after various artificial aging treatments in order to examine the influence of precipitation state on yield stress and work-hardening behavior. During artificial aging, significant changes in the work-hardening rate were observed as the precipitation reaction proceeded. A semiempirical model has been developed to interpret these changes in work-hardening rate. This model shows that the significant changes in work-hardening rate can be related to the manner in which flow stress contributions from different obstacles are summed and the transition from shearable to nonshearable precipitates. The present study presents a new approach to determining the shearable/nonshearable transition from a series of tensile tests. Results on the aluminum alloy AA7030 were also found to be consistent with the proposed theoretical framework. Finally, the proposed model allows the overall mechanical response for a variety of aging conditions to be rationalized.