Abstract:Equal channel angular expansion extrusion with spherical cavity (ECAEE-SC) was introduced as a novel severe plastic deformation (SPD) technique, which is capable of imposing large plastic strain and intrinsic back-pressure on the processed billet. The plastic deformation behaviors of commercially pure aluminum during ECAEE-SC process were investigated using finite element analysis DEFORM-3D simulation software. The material flow, the load history, the distribution of effective strain and mean stress in the billet were analyzed in comparison with conventional equal channel angular extrusion (ECAE) process. In addition, single-pass ECAEE-SC was experimentally conducted on commercially pure aluminum at room temperature for validation, and the evolution of microstructure and microhardness of as-processed material was discussed. It was shown that during the process, the material is in the ideal hydrostatic stress state and the load requirement for ECAEE-SC is much more than that for ECAE. After a single-pass ECAEE-SC, an average strain of 3.51 was accumulated in the billet with homogeneous distribution. Moreover, the microstructure was significantly refined and composed of equiaxed ultrafine grains with sub-micron size. Considerable improvement in the average microhardness of aluminum was also found, which was homogenized and increased from HV 36.61 to HV 70.20, denoting 91.75% improvement compared with that of the as-cast billet.

Key words: severe plastic deformation; equal channel angular expansion extrusion with spherical cavity (ECAEE-SC); numerical simulation; strain accumulation; grain refinement