Insight to the evolution of nano precipitates by cryo rolling plus warm rolling and their effect on mechanical properties in Al 6061 alloy

Abstract

Evolution of nano-precipitates after Cryorolling (CR) followed by warm rolling (WR) at rolling temperatures of 100 °C, 145 °C and 175 °C on the microstructure and strengthening of Al-6061 alloy has been investigated. The enhanced yield (401 MPa) and tensile strength (415 MPa) with 6% ductility was achieved after CR plus 80% WR. The evolution of various precipitates such as G.P. zones, Cluster/co-cluster, β’ and β” after CR plus WR was investigated, by studying the thermal behavior using Differential scanning calorimetry studies (DSC). Time of the optimized artificial ageing temperature (125 °C for 45 Hrs) was obtained using hardness testing and DSC study. Significant improvement in ductility (9%) of CR plus 80% WR Al 6061 alloy after peak ageing showing 450 MPa tensile strength was obtained, due to the evolution of highly dense coherent nano-precipitates (β”) responsible for uniform flow localization. A graphical model is proposed explaining the effect of solution treatment, deformation temperature, dislocations and peak ageing on evolution of precipitates.