Segregation of Carbon in α-Fe Symmetrical Tilt Grain Boundaries Studied by First-Principles Based Interatomic Potential
Thi Dung Pham, Tien Quang Nguyen, Tomoyuki Terai, Yoji Shibutani, Masaaki Sugiyama, Kazunori Sato
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 α-Fe〈110〉 symmetrical tilt grain boundaries (STGBs) with C was systematically investigated based on first-principles calculations. We used the newly-developed Tersoff/ZBL 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 STGB 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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ISIJ International Vol.61(2021), No.8