The Role of Mandrel Rotation during CSET Processing Demonstrated on a 3003 Aluminium Alloy

Abstract

Recently, the complex shearing of extruded tube (CSET) technique was proposed representing a new way of processing tubes from a bulk billet as a combination of extrusion with two passes of equal channel angular processing and possible mandrel rotation. In the present paper, the influence of mandrel rotation on the final microstructure and mechanical properties of the tube fabricated of a 3003 aluminium alloy was investigated. Electron back scatter diffraction (EBSD) revealed differences in grain size and misorientation angles between tubes processed with stationary and rotating mandrel. Kernel average misorientation maps obtained from EBSD experiments and ASTAR analysis performed in transmission electron microscopy proved differences in the dislocation density and arrangement. The tube processed using a stationary mandrel showed a recovered microstructure with elongated grains separated by low-angle grain boundaries into subgrains. The microstructure of the tube processed with a rotating mandrel was dynamically recrystallized with the grain size in submicrometer range. Vickers microhardness measurements revealed only a 40% HV increase in the sample prepared using stationary mandrel as compared with the initial billet. The mandrel rotation resulted in a much higher HV increase up to 200% as a result of substantial grain refinement.