Classification of microstructural evolution during large strain high Z deformation of a 0.15 carbon steel

Ultrafine grained structures formed by a single step large strain compression of 0.15 carbon steel at warm working temperatures have been investigated. The strain rate and temperature are summarized into the Zener-Hollomon parameter and its variation with plastic strain is studied on the basis of the evolved microstructures and grain boundary character with a view to understanding the critical conditions for the formation of ultrafine grains and to classifying these structures.