Effect of SPD processing on the strength and conductivity of AA6061 alloy

The extruded and artificially aged at 177 °C high strength commercial alloy AA6061-T651 is subjected to severe plastic deformation (SPD) by cyclic extrusion up to 1000% of the true strain at 400 °C. Unexpectedly, the electrical conductivity of the deformed alloy increased by 10% International Annealed Copper Standard (IACS), while the hardness dropped by only 40 HV. Further, it is shown that low temperature aging at 130 °C after SPD results in the following phenomena: the hardness of the alloy is restored almost to the initial level, with a slight decrease in conductivity, which still remained higher than in the original state. All microstructural parameters of the alloy including aluminum matrix composition, grain size, grain boundaries fraction, and morphology of the precipitates are characterized and correlated with the observed effect of SPD on the strength and electrical conductivity of alloy AA6061.