Modeling of Strain Hardening in the Aluminum Alloy AA6061

In this paper, the evolution of work-hardening and dynamic recovery rates vs the flow stress increase (sigma - sigma (y) ) in Al-Mg-Si alloys is presented. The experimental data have been extracted from stress-strain curves. All curves show an initial very rapid decrease in slope of the sigma-epsilon curve, which is associated with the elastic-plastic transition. After the elastic-plastic transition, there are typically two distinctive behaviors. For underaged alloys, there is an approximately linear decrease of work-hardening rate as (sigma - sigma (y) ) increases. However, for overaged alloys after elastic-plastic transition, there is a plateau in the work-hardening rate followed by an almost linear decrease. The maximum work-hardening and dynamic recovery rates are found to be dependent on the aging state. In order to investigate these phenomena, a model has been employed to simulate the work-hardening behavior of Al-Mg-Si alloys. The model is based on a modified version of Kocks-Mecking-Estrin (KME) model, in which there are three main components: (1) hardening due to forest dislocations, grain boundaries, and sub-grains; (2) hardening due to the precipitates; and (3) dynamic recovery. The modeling results are discussed and compared with the experimental data.