Microstructure gradient after hot torsion deformation of powder metallurgical 6061 Al alloy

Abstract

The microstructure and the texture of extruded 6061 Al alloy processed by powder metallurgy (PM), using three different initial powder particle sizes, have been studied after torsion deformation at 300°C at strain rate of 6s−1. The initial extruded microstructure of the three alloys consisted of elongated grains confining substructure with a typical 〈111〉+〈100〉 fiber texture. After torsion deformation, the torque (Γ) as a function of the equivalent strain (ɛeq) showed softening and the microstructure exhibited a gradient across the section so that the inner and outer zones contained sheared-elongated and small-equiaxed subgrains, respectively. It was observed that the equivalent strain to failure for the material processed using powder particles size of less than 45μm was of about ɛeq∼12, compared to ɛeq∼1 for material processed using powder particles size of less than 25μm. The microstructural changes during hot torsion deformation of PM 6061 Al alloy should involve continuous dynamic processes.