High temperature dislocation processes in precipitation hardened crystals investigated by a 3D discrete dislocation dynamics

Abstract

3D discrete dislocation dynamics is employed to investigate motion of general mixed dislocation segments subjected to high temperature loadings in microstructures with impenetrable particles. The implementations of the model first address several benchmark processes including shrinkage of a glissile dislocation loop driven by self-stresses and an annihilation of mutually interacting co-axial prismatic dislocation loops. In particular, we show that models of the microstructure with planar and/or translational symmetry improve efficiency, speed and stability of the calculations. Our simulations then focus on migration of low angle dislocation boundaries in an array of particles while taking into account all mutual dislocation-dislocation interactions and the action of an externally applied stress. The results show for the first time that the migration of tilt dislocation boundaries in crystals with particles can be associated with threshold stresses. The calculated thresholds are in a good agreement with experimental threshold stresses that characterize creep behaviour of precipitation hardened alloys.