Dislocation density distribution at slip band-grain boundary intersections

TL;DR

This study uses advanced 3D X-ray micro-diffraction to analyze dislocation density distributions at slip band-grain boundary intersections in titanium, revealing micro-plasticity and the influence of grain boundary ledges on dislocation behavior.

Contribution

It provides new insights into the dislocation mechanisms at grain boundaries using 3D characterization of Nye tensor and GND density in titanium.

Findings

Dislocation pile-ups occur at grain boundaries hindering slip transfer.

Grain boundary ledges act as secondary dislocation sources.

Local micro-plasticity is observed near slip boundary intersections.

Abstract

We study the mechanisms of slip transfer at a grain boundary, in titanium, using Differential Aperture X-ray Laue Micro-diffraction (DAXM). This 3D characterization tool enables measurement of the full (9-component) Nye lattice curvature tensor and calculation of the density of geometrically necessary dislocations (GNDs). We observe dislocation pile-ups at a grain boundary, as the neighbor grain prohibits easy passage for dislocation transmission. This incompatibility results in local micro-plasticity within the slipping grain, near to where the slip planes intersect the grain boundary, and we observe bands of GNDs lying near the grain boundary. We observe that the distribution of GNDs can be significantly influenced by the formation of grain boundary ledges that serve as secondary dislocation sources. This observation highlights the non-continuum nature of polycrystal deformation and helps us understand the higher order complexity of grain boundary characteristics.