The effects of boron impurity atoms on nickel 5 (012) grain boundary by first principles calculations
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abstract
Purpose: Impurity atoms in the grain boundary can be responsible for embrittlement or they can strengthen a material. In this work, we have modeled the effect of B impurity on 5 (012) symmetrical tilt grain boundary in Ni by using first principle quantum-mechanical calculations. The grains can either be pushed apart or pulled together depending on the size of the impurity and nature of the local relaxations. Design/methodology/approach: The calculations were carried out by using the Vienna ab-initio simulation package VASP with the projector augmented wave (PAW) potentials within generalized gradient approximation (GGA). K-space sampling is performed using a 2x2x1 Monkhorst Pack scheme for Brillouin-zone integration in all model systems. The Methfessel-Paxton smearing method with 0.1 eV smearing width is used for the determination of partial occupancies for each wave function. Findings: It is found that the extension of the nickel grain boundary is due to the repulsion of the segregated and neighboring B atoms. Moreover, the effects of tensile strength loaded uniaxially along the (012) direction are analyzed when the impurity atoms of B are substituted into the 5 (012) symmetrical tilt grain boundary in Ni. Our calculations are compatible with the other first principle calculations. Research limitations/implications: Cohesive energy calculations indicate that interstitial sites are preferred to substitutional sites and that B leads to cohesive enhancement. Originality/value: The effects of boron impurity atoms on nickel 5 (012) grain boundary by first principles calculations were evaluated.
