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

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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.