Dislocation storage-release-recovery model for metals under strain rates from 10−3 to 107 s−1, and application to tantalum

Abstract

Extending the storage-recovery model, we propose a new strengthening model, premised on detailed evolution laws for both mobile and immobile dislocations, for metals under moderate to intense loading. These dislocation density evolution laws include the multiplication, storage under the effect of dislocation junctions, release of pinned dislocations, and annihilation by cross-slip. The storage-release description is derived from a simplified depiction of the probability distribution function of the dislocation length in dislocation networks. Although the model requires only few parameters to characterize the evolution of dislocation densities, remarkable agreement is found with available experimental data. From a theoretical study of the long-time behavior of the model, analytical expressions are provided to easily extract most of these parameters from experimental stress–strain curves in the quasi-static regime, whereas the parameter that governs the strength of the release process is adjusted from dynamic tensile tests. Their values so determined for polycrystalline tantalum allow the model to reproduce experimental plate-impact data with a very good match.