Geometrically necessary dislocation density evolution as a function of microstructure and strain rate

Abstract

The role of microstructure and strain rate on the development of geometrically necessary dislocation (GND) density in polycrystalline copper subjected to compression is assessed via crystal plasticity modelling and electron microscopy. Micropolar crystal plasticity finite element (MP-CPFE) simulations show that GND density is strongly dependent on crystal orientation, with the highest values in grains with a <101> direction parallel to the compression axis. Experimental analysis shows that this relationship breaks down and demonstrates that orientation is only one of many microstructural features that contributes to dislocation density evolution. Texture development as a function of strain rate is also considered, and it is found that the commonly observed <101> compression texture is delocalized from that pole at high strain rate. Furthermore, quantitative analysis of the role of grain boundaries in GND density evolution highlights their role as strong dislocation sources.