Solute segregation and classification of [100] tilt grain boundaries in α-iron: consequences for grain boundary engineering

A complete classification of [100] tilt grain boundaries into the categories of special, vicinal and general resulting from measurements of grain boundary segregation in α-iron is presented. In contrast to the coincidence site lattice approach at least one special grain boundary was found to exist for each misorientation of adjoining grains irrespective of the value of the reciprocal density of coincidence lattice sites. This finding raises a new challenge to grain boundary engineering. It is suggested that a configuration of typically brittle general boundaries in a polycrystal can be transformed into another one consisting of non-brittle special boundaries under suitable annealing conditions by boundary inclination via boundary migration without any change of grain orientations.