From forest hardening to strain hardening in body centered cubic single crystals: simulation and modeling

In body centered cubic (b.c.c.) crystals at low temperature, the thermally activated motion of screw dislocations by the kink pair mechanism governs the yield properties and also affects the strain hardening properties. The strain hardening is studied through two steps, i.e., through forest hardening and dislocation density evolution. The forest hardening has been previously numerically simulated and analyzed by a simple model that applies generally to all b.c.c. metals at low temperature. For the dislocation density evolution, the very first, but crucial, attempt in simulation consists of the development of a boundary condition with dislocation flux balance, which is shown to increase the dislocation density significantly during the early stage of deformation.