Fundamentals of mobile tilt grain boundary faceting

Deformation facets form from relaxation of a disconnection pile-up that builds up at an interface under stress. The misorientation differences between facets are mediated by interfacial disclinations. Any disconnection entering a facet through the disclination transforms. Faceting between {101¯2} twins and the basal–prismatic boundary in hexagonal metals illustrates that twinning disconnections transformed across the disclination are glissile. This increases twin mobility. Here we present a formal description of deformation faceting using three-colored symmetry groups.