[SY-I4] Thermodynamic properties of bcc Fe grain boundaries with segregation of 3d-transition-metal solutes
Grain boundaries (GBs) are one of the key factors to manipulate the material properties. The solute segregation and solute drag effects are remarkable for the thermodynamic properties of GBs, where the microscopic atomic and electronic structures affect the macroscopic behaviors of GB evolution. We have developed the local analysis method to get the local-energy and local-stress of each atom [1], which is of assistance to unveil the microscopic mechanism. In the present study, we firstly focused on the Σ11(332) and Σ3(111) <110> symmetrical tilt GBs in bcc Fe with 3d-transition-metal (TM) solutes. We performed ab-initio calculations together with the local analysis, and observed that the segregation behaviors of 3d-TM solutes can be classified into early TMs (Sc, Ti and V), middle TMs (Cr and Mn), and late TMs (Co, Ni and Cu). The early and late TMs prefer to segregate at the looser and tighter sites of GBs, respectively. The local-energy decomposition indicates that the segregation of early TMs is dominated by the stabilization of surrounding Fe atoms at a GB, while that of late TMs is dominated by the repulsion from the bulk as well as the stabilization of a TM-atom itself. Furthermore, corresponding to the segregation energy of each 3d-TM segregated to the looser or tighter site of GBs, by the multiscale modeling, we estimated the solute drag effects on the mobility and interface energy of GBs, and the grain growth rate. Finally, we discuss the cases of general GBs, and compare the results with experiment.
[1] Y. Shiihara et al., Phys. Rev. B 81, 075441 (2010). S. Bhattacharya et al., J. Mater. Sci. 49, 3980 (2014).
[1] Y. Shiihara et al., Phys. Rev. B 81, 075441 (2010). S. Bhattacharya et al., J. Mater. Sci. 49, 3980 (2014).