Effect of cryorolling and warm rolling on precipitation evolution in Al 6061 alloy

In the present investigation, the effect of deformation on precipitation sequence and microstructural evolution in Al 6061 alloy was studied using low temperature differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). The precipitation sequence was greatly influenced by deformation in cryorolled and warm rolled samples. At low temperatures (<150 °C), two distinct cluster peaks have been observed upon cryorolling (CR). At high temperatures (>150 °C), the peak corresponding to β′ formation has disappeared in the deformed alloy as compared to undeformed coarse grained material. TEM investigation of the deformed alloy revealed bimodal distribution of precipitate sizes with both very fine and coarse structures. Pre-deformation of the alloy led to the simultaneous formation of β″ and β′ precipitates. Activation energies of clusters and major strengthening phase formation were calculated for the cryorolled and warm rolled materials and compared with the undeformed coarse grained material. The reduction of free energy for the formation of strengthening phase has occurred in the deformed material as compared to undeformed bulk material.