A model of grain refinement and strengthening of Al alloys due to cold severe plastic deformation

Abstract

This paper presents a model which quantitatively predicts grain refinement and strength/hardness of Al alloys after very high levels of cold deformation through processes including cold rolling, equal channel angular pressing (ECAP), multiple forging (MF), accumulative roll bonding (ARB) and embossing. The model deals with materials in which plastic deformation is exclusively due to dislocation movement within grains, which is in good approximation the case for many metallic alloys at low temperature, for instance aluminium alloys. In the early stages of deformation, the generated dislocations are stored in grains and contribute to overall strength. With increase in strain, excess dislocations form and/or move to new cell walls/grain boundaries and grains are refined. We examine this model using both our own data as well as the data in the literature. It is shown that grain size and strength/hardness are predicted to a good accuracy.

Keywords:

• Al alloys
• severe plastic deformation
• grain refinement
• strengthening
• modelling

Acknowledgements

This work was funded by the Engineering and Physical Sciences Research Council (EPSRC) PhD plus under Grant No. EP/P503841/1. Prof. Hans Roven (Norwegian University of Science & Technology) is gratefully acknowledged for providing selected alloys.