Calculation of GB Energies and Grain-Boundary Self-diffusion in Nickel and Verification of Borisov Relations for Various Symmetric Tilt Grain Boundaries

Symmetrical boundaries with tilt axes <100> , <110> and  <111> in nickel have been studied using atomistic modeling methods. The energies of grain boundaries (GBs), as well as the energies of point defects formation in high-angle GBs, have been calculated by the molecular statics method. Dependences of the GB energy on the misorientation angle are given for each of the three axes listed above. The energies of point defects formation are given as a function of energy depending on the distance between the position of the defect and the GB plane. Simulation of self-diffusion in high-angle GBs has been carried out in two versions–for vacancy and interstitial mechanisms of mass transfer. Temperature dependencies of self-diffusion coefficients have been constructed and the activation energies have been estimated. Based on the comparison of activation energies, the dominating diffusion mechanisms have been established. Anisotropy and the dominating diffusion mechanism are completely determined by the type of individual boundary. Based on calculations of the GB energy and self-diffusion simulation data, the Borisov correlation for high-angle GBs is considered, and it is shown that this correlation is quite poor for these grain boundaries.