Example of a disconnection on a Σ5 grain boundary in a simple cubic lattice, showing the burgers vector and step height of the defect.
Most natural and technologically important crystalline materials are polycrystalline, and therefore contain a network of grain boundaries (interfaces between neighboring pairs of grains with different crystallographic orientations) that strongly influence their material properties. GB properties play an important role in determining many physical and mechanical properties of polycrystals including mechanical strength, ductility, creep rate, etc. Therefore, one effective approach for tailoring material properties is through exploitation of GB structure-property-processing relationships to control the spatial, chemical and crystallographic distribution of GBs. The goal of our group’s research is the experimental verification of a unifying description of GB dynamical phenomena based on a disconnection model. Disconnections are important line defects on GBs that have both dislocation and step height character: they add curvature to otherwise planar GBs. In our studies, we stimulate the migration of grain boundaries by a variety of driving forces (mechanical load, thermal energy, voltage) and observe their dynamic response. Experimental data is used to quantify the properties of specific GBs and the disconnections which mediate their migration.