Effects of alloying on the behavior of B and S at Σ5 (2 1 0) grain boundary in γ-Fe

Abstract

To get the atomic scale understanding of impurities induced intergranular embrittlement or enhancement and the control of these effects on austenitic stainless steels, behavior of impurities B and S at γ-Fe grain boundary (GB) and effects of alloying elements (Cr, Ni, Mn, Co, Mo) additions on the cohesive properties of the γ-Fe GB doped by impurities are investigated by performing density functional theory (DFT) calculations. The results showed that, as the GB enhancer and embrittler respectively, impurities B and S tend to stay at the interstitial sites of γ-Fe GB, while alloying elements also can segregate at the GB studied. The presence of all the alloying elements considered can inhibit B GB segregation to some extent due to the higher segregation energies and can impair the enhancement effect of B on GB cohesion. However, these elements almost have no impact on GB segregation and embrittlement effect of S, except for Ni, Mn and Mo:Ni and Mo inhibit and improve S GB segregation, respectively; Mn and Mo strongly enhance and reduce S-induced GB embrittlement, respectively. Moreover, the remedial effect of (Cr+Ni), (Cr+Mn) on S-induced GB embrittlement is also discussed. Additional atomic structure and total valence charge density analysis demonstrated and explained our conclusions.