Abstract
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.
Fig. 4 Scanning planes (colored in pink on the left-hand side figures) and dissolution energy landscapes (right-hand side figures) of Fe–C systems of (a) Σ3(112) STGB and (b) Σ9(221) STGB. The location of GB is indicated by green dashed line.
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