Development of new routes of severe plastic deformation through cyclic expansion-extrusion process

This paper introduces two new processing routes for a recently introduced severe plastic deformation technique, cyclic expansion-extrusion (CEE). Two processing Routes (I and II) were experimentally performed on aluminum alloy 1050; the processed samples were investigated and compared in terms of their microstructural and mechanical characteristics. A significant improvement in mechanical properties was observed after one CEE pass via both processing routes. However, different grain structures were achieved after Routes I and II showing a more homogeneous microstructure and hardness distribution in Route II compared to Route I. In addition, compression tests of the processed samples demonstrated that Route II results in a homogeneous compressive strength. Finally, microstructure evolution during subsequent passes of this process was investigated by electron back scattered diffraction. Micro-shear bands were found as potential sites for accelerating the formation of new grains which resulted in fragmentation of the initial grains and leading to an ultrafine-grained (UFG) microstructure.