Modelling continuous dynamic recrystallization of aluminum alloys based on the polycrystal plasticity approach

A new physically based fully coupled crystal plasticity-continuous dynamic recrystallization (CDRX) frame work at elevated temperature is proposed. The CDRX model reformulates the subgrain formation and rotation, as well as the associated CDRX grain generation that is followed by constrained growth, in the context of crystal plasticity. The coupled CDRX-VPSC (visco-plastic self-consistent) model employs dislocation density based constitutive laws that represent accumulation and recovery of dislocations in the matrix and recrystallized grains. The validation of the proposed model is conducted by simulating the hot compression of extruded aluminum alloy 7075, in which the DRX mechanism is controlled by the subgrain related dynamic recovery (DRV) and CDRX. The simulated flow stresses and microstructural evolutions including DRX fraction, sub- and DRX grain sizes agree well with reported experimental observations of extruded aluminum alloy 7075. Various case studies can be performed using the proposed modeling approach. For example, the study on the effect of the characteristics of initial subgrain boundary is presented by employing both extruded and cast aluminum alloy 7075, which clarifies that a large amount of subgrain boundaries with high misorientation angles can efficiently promote CDRX. Furthermore, enhanced CDRX can be predicted in the extruded aluminum alloy 7075 when its initial grain size is small, which is also in good consistence with the experimental data.