Challenges of interfacial classification for grain boundary engineering

Abstract

The most widely used characteristic of grain boundary type in grain boundary engineering (GBE) is the reciprocal density of coincidence sites Σ. Low values of Σ are supposed to indicate special boundaries. A systematic study of segregation at well characterised grain boundaries in Fe–Si alloys resulted in detailed classification of [100] tilt grain boundaries refining the coincidence site lattice (CSL) concept. This classification agrees well with the CSL concept in characterising the low Σ {015}, {013} and {012} symmetrical grain boundaries as special, however, the CSL concept fails in classifying the asymmetrical boundaries. It was clearly proved that general boundaries also exist for the Σ=5 CSL relationship while a special boundary appears in the non-coincidence 45°[100] misorientation. The important result of this classification – the finding that each asymmetrical grain boundary formed by the (011) plane is special – evokes new possibilities for GBE technologies.