What Is a Grain Boundary?

A grain boundary is an interface between grains with the same structure and different orientations. At the crystal interface, the atomic arrangement transitions from one orientation to another, so the atomic arrangement at the grain boundaries is in a transition state. The contact interface between grains is called grain boundaries. Inorganic non-metal materials are sintered from fine powder. During sintering, numerous fine particles form a large number of crystal centers. Grain boundaries are formed when they develop into grains and gradually grow until they meet.

In polycrystals, due to the different orientation of the grains,

During the growth of crystalline materials, due to the limitation of external space, they failed to develop into crystals with regular morphology, but only

Due to the difference in the orientation of the particles on the grain boundaries between the two grains, both strive to make the arrangement of the particles on the grain boundaries conform to their own orientation. When equilibrium is reached, the

There are two different classification methods. One is to simply classify the angle between two grains. Divided into small-angle grain boundaries and large-angle grain boundaries. The small-angle grain boundary is an angle in which the atomic arrangement and combination of two adjacent crystal grains are small, about 2 to 3 °. The grain boundaries between the two grains are composed of a fully fitted portion and a mismatched portion. When a crystal grain is rotated by a small angle around the axis of the vertical crystal grain interface, it can also be formed by

Trigeminal grain boundary is a line defect formed when three grain boundaries meet, and has unique thermodynamic and dynamic properties different from grain boundaries. The tridental grain boundary, as a preferred location for nucleation, cavitation and corrosion of new phases, and a favorable channel for solute atom diffusion, plays an important role in grain growth and plastic deformation. Therefore, it is of great significance to study the migration process of trigeminal grain boundaries and its influencing factors. ^[3]

Trigeminal grain boundaries have significant effects on grain boundary motion and grain growth dynamics. The migration of the tridental grain boundary and its grain boundary increases with the increase of the deformation amount, and the migration distance of the tridental grain boundary is smaller than that of the grain boundary. Tridental grain boundaries cannot prevent the grains from rotating, but they can significantly slow down the spinning process. ^[4]

The grain boundary curvature at the top of the ring-shaped crystal grains changed partly in the early stage of evolution, and then the grain boundary curvature remained stable. This is because the initial state of the trident grain boundary is unstable (the angle between adjacent grain boundaries is not 120 °). When the angle between adjacent grain boundaries reaches a steady state of 120 °, the shape of the trident grain boundary remains stable. Due to the driving effect of the curvature of the ring-shaped grain boundary, the arc-shaped grain boundary at the top of the ring-shaped grain continuously shrinks toward its center of curvature until the trigeminal grain boundary disappears and becomes a straight grain boundary.

Throughout the evolution process, the straight grain boundaries in grain boundary and grain boundary always remained flat, indicating that the trigeminal grain boundary migration is self-similar. The orientation angles of the three grains remained unchanged during the evolution process, indicating that none of the grains was rotated. Grain boundary curvature affects the trigeminal grain boundary migration rate, and the two are directly proportional. The trigeminal grain boundary has a drag effect on the grain boundary migration. The smaller the grain boundary curvature is, the more obvious the trigeminal grain boundary drag effect is.