A theoretical investigation of the dynamic interaction between dislocations and precipitates in an age hardenable Al-Zn-Mg-Cu alloyWednesday (06.11.2019) 15:15 - 15:35 Part of:
The Kampmann-Wagner numerical (KWN) framework has been extended to include the contribution from deformation induced excess vacancies and forest dislocations and capture the complex interplay between plasticity and precipitation. Simulations were performed at various strain rates ranging from 10-4 sec-1 to 1 sec-1 to demonstrate the effect of strain rate on excess vacancy concentration, forest dislocation density, diffusivity and precipitate nucleation and growth rate. It is shown that strain rate has a positive impact on excess vacancy concentration and diffusivity which in turn gets manifested as a rapid increase in precipitate number density, radius and volume fraction compared with the deformation free case. Comparison of the effect of strain rate for a fixed strain reveals the competition between deformation and time (which is lower for higher strain rates). Although higher strain rates accelerate kinetics, this is predicted to be not sufficient to compensate for the reduced time (to reach a fixed strain level). Furthermore, to delineate the role of strain rate on precipitate nucleation rate and growth rate, simulations were performed for various pre-aged conditions ranging from the fully supersaturated solute condition to the peak-aged condition. The initial condition controls the dominant effect of deformation; in the fully supersaturated state, deformation most strongly affects nucleation, in the peak-aged state it affects coarsening. Finally, a comparison is presented between vacancy assisted nucleation and dislocation assisted nucleation at various strain rates to illustrate the possibility of a composite model considering both mechanisms, the significance of each with depends upon the strain rate.