Multimodal ultrafine grain size distributions from severe plastic deformation at high strain rates

Severe plastic deformation at high strain rates in machining is explored as a vehicle for engineering grain size distributions in copper. Typical strengthening in unimodal, ultrafine grained chips is found to accompany poor ductility when generated at large strains but low strain rates. However, at higher rates, in situ heating in the deformation zone engenders dynamic recovery that results in material with a multimodal grain size distribution that is comparable in strength to the unimodal chips, but additionally possesses improved ductility. (C) 2009 Elsevier B.V. All rights reserved.