A quantitative model of grain refinement and strain hardening during severe plastic deformation

The effect of severe plastic deformation (SPD) on grain refinement and strain hardening in polycrystalline metals is studied quantitatively. The decrease in size of dislocation cells and cell-blocks is expressed as a function of the effective plastic strain influenced by strain-rate reversals. The estimated growth of the high-angle boundary area fraction depends on the complexity of the three-dimensional deformation path. The strain hardening due to both dislocation and boundary strengthening is described in terms of microstructural parameters and incorporated in the continuum mechanics framework of finite strain plasticity. The proposed model provides a tool for quantitative comparison of different SPD processes. Examples of simulation of the behaviour of pure aluminium deformed by equal channel angular pressing (ECAP) and cyclic extrusion–compression are calculated.