A novel severe plastic deformation (SPD) process, namely expansion equal channel angular extrusion (Exp-ECAE) is proposed in this paper. With this regard, a spherical cavity is provided at the junction of the ECAE channels. The numerical simulations of the Exp-ECAE process resulted in finding suitable tool geometry for this operation. Using this optimum shape, several practical Exp-ECAE experiments were conducted with AA6063 aluminum at different process conditions. Because of the expansion cavity, a pseudo back-pressure mechanism was provided for the tests. The experimental findings showed that after the 1st pass of the Exp-ECAE process, the yield stress and hardness of the material were increased about 300 and 50 %, respectively. These improvements were much more than those achieved via other SPD techniques such as ECAE and twist extrusion for the same alloy. The homogeneity of hardness distribution along the cross section of the Exp-ECAE product was also acceptable. Further passes of the process just resulted in better ductility for the component such that after the 3rd pass, almost 97 % of ductility of the annealed billet was recovered. However, a slight decrease in the strength of the product was observed after the 2nd and 3rd passes.