A constitutive model for the mechanical behaviors of bcc and fcc nanocrystalline metals over a wide strain rate range

A new constitutive model based on the deformation mechanisms was developed for both bcc and fcc nanocrystalline metals over a wide strain rate range. Nanocrystalline metals were treated as composites consisting of grain interior and grain boundary phases, and the deformation mechanisms and physically based constitutive relations of grain interior and grain boundary phases over a wide strain rate range were analyzed and determined for both fcc and bcc nanocrystalline metals. Based on our recently established phase mixture method, a new mechanical model was built to calculate the stress-strain relations of nanocrystalline metals over a wide strain rate range; and the grain size and porosity effect was considered in the developed model, the predictions keep in good agreements with various experimental data in small plastic strain range, where uniform deformation can be assumed. Further discussion was presented for calculation results and relative experimental observations.