A cyclic forward-backward extrusion process as a novel severe plastic deformation for production of ultrafine grains materials

► A new SPD process based on a cyclic forward-backward extrusion is introduced. ► Ultrafine grains were produced in extrusion of AA1050 aluminum alloy. ► TEM exhibited a significant grain refinement from 47 μm to about 1 μm. ► A substantial increase in the hardness, from 25 Hv to 47-52 Hv, was recorded.