Plastic deformation of nanocrystalline aluminum at high temperatures and strain rate

The deformation of nanocrystalline, aluminum was studied using molecular dynamics simulation at homologous temperatures up to 0.97. The microstructures and stress-strain response were examined in a polycrystalline and bicrystal configuration. The activation energies for dislocation-based deformation as well as grain boundary sliding and migration were quantified by fitting simulation data to temperature using an Arrhenius relation. The activation energy for the flow stress response suggests that deformation is largely accommodated by sliding and migration of grain boundaries. This is in agreement with simulated micro structures, indicating a negligible degree of dislocation interaction within each grain, and microstructural observations from high strain rate processes are also consistent with this result. A steady-state grain size is maintained in the recrystallized structure following yielding due to boundary migration and grain rotation mechanisms, rather than by diffusion-based dislocation climb. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.