Grain boundary classification and its consequences for Grain Boundary Engineering

Based on detail study of solute segregation at individual grain boundaries in α-iron, a new classification of [100] tilt grain boundaries was developed.

Individual grain boundaries were divided into the categories special, general and vicinal (Fig. 1). In contrast to the classification based on the coincidence site lattice model we found special grain boundaries for each misorientation of two adjoining grains, supposing the grain boundary plane is formed by the densest plane (110) at least from one side. This finding provides new possibilities for Grain Boundary Engineering: we suggested that the required increase of special grain boundaries is not necessarily reached exclusively by complex reorientation of individual grains inside polycrystal (Fig. 2, up) but can be obtained by simple reorientation of the grain boundaries, i.e., their migration/inclination between existing grains (Fig. 2, bottom). In this way, the path of an easy brittle fracture could simply be eliminated by another configuration of inclined gran boundaries that is not prone to such behavior (Fig. 3).

P. Lejček, V. Paidar: Challenges of interfacial classification for grain boundary engineering, Mater. Sci. Technol. 21 (2005) 393–398. doi:10.1179/174328405X39716

P. Lejček, S. Hofmann, V. Paidar: Segregation based classification of [100] tilt grain boundaries in α-iron and its consequences for grain boundary engineering, Acta Mater. 51 (2003) 3951–3963. doi:10.1016/S1359-6454(03)00219-2