Statistical Analysis of Grain Boundary Angles in Vapor-Grown Iron Bicrystals

Abstract

Grain boundary energy cusp is a tasic property of theoretical importance. The practical significance depends largely on how strongly the population of the boundary is influenced by the energy cusp. The present work is a statistical analysis of the population in vapor-grown iron bicrystals. During the growth, the disturbing effects of the surroundings appeared relatively weak.
The question investigated first is whether all the bicrystal boundary is in perfect coincidence relationship or only distribute about them with maxima at the coincidence orientations. Electron channeling pattern with an error limit better than 0.1° was applied to resolve the problem. It was concluded that they only distribute about the coincidence orientation.
The observed distribution was very heterogeneous; The major component of the misorientation from the perfect coincidence was of tilt type. The result is explained if the population of the grain boundary is controlled by the energy and the boundary within the enrgy cusp is composed of grain boundary dislocation network superimposed upon the coincidence related boundary.
Near coincidence boundaries were also observed although the population was very small. The boundaries were composed of two densely packed lattice planes joined parallel along the boundary. A general trend in the histogram suggested that the bicrystal is formed by the nucleation of a sister crystal on the {100} stepped surface of a growing single crystal.