Evolution of geometrically necessary dislocations in plastically strained precipitation hardened materials

摘要

There has recently been a strong interest in modelling size-dependent plasticity in metals based on the concept of geometrically necessary dislocations (GNDs). However, the precise manner by which geometrically necessary dislocations interact with second-phase particles remains elusive. Nevertheless no detailed materials characterisation has been performed to quantify these relationships. In the present paper, the evolution of GNDs in the presence of different precipitate morphologies is investigated. Room temperature tensile deformation experiments were performed on the aged specimens of an aluminium alloy and the evolving microstructure was compared with the mechanical response. The precipitate morphologies were characterised using transmission electron microscopy and the dislocation structure was analysed using orientation imaging of deformed specimens. It was observed that structural evolution was a function of the precipitate characters. In general, the dislocation cell size and misorientation angle between dislocation cells evolves systematically with deformation at relatively small strain levels.