High-Angle Tilt Boundary—A Dislocation Core Model

Abstract

The dislocation model of a symmetric tilt boundary is modified to take into consideration the stress field of the cores of the dislocations. It is found that such modification enables discussion of many properties of high-angle tilt boundaries including porosity, strain energy, intergranular fracture, grain boundary shearing, void formation, preferential melting, preferential diffusion, boundary migration, segregation, precipitation, amorphous behavior, continuous and discontinuous transition, etc., in terms of the interaction among the cores of the dislocations and the properties of the cores themselves. This is a first attempt to devise a working model capable of interpreting all the properties of grain boundaries. Unlike other models which are designed to have a few particular properties in a limited angular range, this model has the advantage of reducing to the dislocation model at low angles and of providing for amorphous behavior at high angles. The characteristic of a grain boundary of behaving as an ordered liquid of lower density is pointed out. The picture of a high-angle boundary is that it contains an equilibrium number of jogs which control many mechanical as well as thermochemical properties.