Study of Self-Diffusion along Asymmetric Grain Boundaries with the Misorientation Axis [100]

A study of grain boundary self-diffusion along asymmetric grain boundaries with a misorientation axis [100] has been conducted using computer simulation methods. The misorientation angle of asymmetric boundaries corresponds to the misorientation angle of the special grain boundary Σ5(013). The calculation was conducted using the coupled Morse potential and the multiparticle Cleri–Rosato potential. The results demonstrate that the structure of asymmetric boundaries can be described within the structural unit model, wherein all boundaries comprise exclusively structural elements that are characteristic of the Σ5(013) boundary. The calculation of grain-boundary diffusion coefficients was conducted and Arrhenius dependences are constructed, from which the diffusion activation energies are determined. High-temperature and low-temperature regions are distinguished in the constructed dependences. The dependences contain two to four linear segments. It is determined that at elevated temperatures, the grain-boundary region undergoes amorphization prior to the adjacent grains. This indicates that the boundaries melt at lower temperatures, ranging from 0.86 to 0.95 of the melting temperature.