Work hardening and microstructure of AlMg5 after severe plastic deformation by cyclic extrusion and compression

Deformation by cyclic extrusion/compression in AlMg5 leads to the same stages of work hardening as unidirectional deformation. The analogy is confirmed by studies of the microstructure, by analysis of long range internal stresses and by evaluation of dislocation densities. The strains leading to the various stages of work hardening are much higher than those in conventional deformation modes while the dislocation densities in the stages are about the same. The strain shift in cyclic extrusion/compression is attributed to the reversal of strain path. The resulting subgrain size is smaller than that resulting from conventional deformation modes which seems to be a consequence of the higher hydrostatic pressure of cyclic extrusion/compression.