Predicting grain refinement by cold severe plastic deformation in alloys using volume averaged dislocation generation

Grain refinement during severe plastic deformation (SPD) is predicted using volume averaged number of dislocations generated. The model incorporates a new expansion of a model for hardening in the parabolic hardening regime, in which the work hardening depends on the effective dislocation-free path related to the presence of non-shearable particles and solute-solute nearest-neighbour interactions. These two mechanisms give rise to dislocation multiplication in the form of generation of geometrically necessary dislocations and dislocations induced by local bond energies. The model predicts the volume averaged number of dislocations generated and considers that they distribute to create cell walls and move to existing cell walls/grain boundaries, where they increase the grain boundary misorientation. The model predicts grain sizes of Al alloys subjected to SPD over two orders of magnitude. The model correctly predicts the considerable influence of Mg content and content of non-shearable particles on the grain refinement during SPD. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.