Segregation of Carbon in alpha-Fe Symmetrical Tilt Grain Boundaries Studied by First-Principles Based Interatomic Potential

TD Pham and TQ Nguyen and T Terai and Y Shibutani and M Sugiyama and K Sato, MATERIALS TRANSACTIONS, 62, 1057-1063 (2021).

DOI: 10.2320/matertrans.MT-M2021054

Carbon segregation is known to have an extreme influence on the cohesive energies and mechanical properties of grain boundaries (GBs) in steel. In this paper, the stability of a series of alpha-Fe(110) symmetrical tilt grain boundaries (STGBs) with C was systematically investigated based on first-principles calculations. We used the newly-developed Tersoff/ZRL potential of Fe-C interaction constructed from the forces and disolution energies of various defect complexes with C in Fe calculated from first-principles. This potential shows a great effectiveness in considering large complex systems of STGB and determining the segregation sites of various STUB configurations. The stable location of C was analyzed from the view point of free volume formed by the GB systems. We found that the compact GBs were less attractive to C than the open ones. The GBs exhibited a strong attractive interaction with C compared to vacancies, therefore, a higher solubility of C can be expected in GB systems. The present simulation results are consistent with the experimental observations by TEM and APT method, and qualitatively explains the behaviour of C in Fe.

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