Solute effects on the Σ3 (111)[1(1)over-bar0] tilt grain boundary in BCC Fe: Grain boundary segregation, stability, and embrittlement

Solute segregation can profoundly affect the thermodynamic stability and cohesive properties of the grain boundaries (GBs) in Fe-based alloys. In the present work, first-principles calculations based on density functional theory (DFT) are performed to understand the atomistic mechanisms of the solute-GB interactions under the dilute limit condition. The segregation effects of six transition metal elements (Cr, Ni, Cu, Zr, Ta, and W) on the Sigma 3 (111)[1 (1) over bar0] tilt boundary in BCC Fe are systematically studied by examining GB energy, solute segregation energy, and GB cohesion. The solute segregation energy is verified to be composed of a combination of the strain and electronic contributions rather than either of them alone, even for the solute elements with large atomic volume. The potential effects of the FCC/BCC polymorphic phase transformations on the solute segregation behaviors are also discussed. The dynamic change in atomic and electronic structures with straining are investigated to provide physical insights into the effects of solute segregation on the properties of the GB cohesion.