Arch Appl Mech DOI 10.1007/s00419-014-0850-1 SPECIAL ISSUE K. C. Le · P. Junker A thermodynamically consistent model of static and dynamic recrystallization Received: 6 February 2013 / Accepted: 22 August 2013 © Springer-Verlag Berlin Heidelberg 2014 Abstract We propose a thermodynamically consistent model of static and dynamic recrystallization for metals during and after severe plastic deformations that is capable of predicting the evolution of dislocation density as well as mean grain size. Keywords Severe plastic deformation · Recrystallization · Dislocation density · Grain size · Yield stress 1 Introduction The creation of metals having high yield strength requires comprehensive information about the microstructure as well as its evolution during the material processing and afterward. Depending on the specific material design purposes, various aspects of microstructure have to be taken into account such as different crystallographic phases, elastic and plastic anisotropy, concentrations of vacancies and impurities, orientations and textures, grain size, and dislocation density . Herein, grain size and dislocation density play a dominant role for the respective yield strength a material exposes [1–3]. During material processing, these two observable and measurable quantities are influenced directly and, in some sense, are also the easiest to be captured. If recast processes producing severe plastic deformations like equal channel angular extrusion (ECAE) [4–7] or torsion under high pressure [8] (see also the recent book [9] and the references therein) are applied to metals, the number of dislocations in the crystal lattice increases immediately. There exists, however, a large, but still specific saturated density of dislocations which can be accommodated by the crystal during severe plastic deformations. If the external load conditions are maintained even when this saturated dislocation density has been reached, the material has to adapt itself to this new situation in a smart way: Dislocations that are excessively generated should join together in certain areas to form new (sub)grain boundaries. Thus, the mean size of the grains may be reduced dramatically by this effect. The end product of this recast process with increasing plastic deformations, called for short dynamic recrystallization process, could be a metal having ultra fine grains with high yield limit (see [4–9]). If metals are not applied to loads for a long time period at increased temperature, the slow process of static recrystallization will take place. The number of dislocations will shrink again to reduce internal stresses. At the same time, the total area of grain boundaries will be diminished gradually: Larger grains absorb smaller ones, so that various grain boundaries disappear and at the end the material becomes a single crystal. It should be emphasized that during the metal forming both processes of dislocation accumulation and static recrystallization may occur simultaneously. Static and dynamic recrystallization have a strong influence on the material’s engineering properties. Hence, a deeper insight into the kinetics of microstructural changes during these processes is of essential importance. K. C. Le (B ) · P. Junker Lehrstuhl für Mechanik - Materialtheorie, Ruhr-Universität Bochum, 44780 Bochum, Germany E-mail: chau.le@rub.de