Energetics of segregation and embrittling potency for non-transition elements in the Ni Σ5(012) symmetrical tilt grain boundary: a first-principles study

Abstract

A series of non-transition elements bound to the NiΣ5 (012) symmetrical tilt grain boundary (GB) and the (012) free surface (FS) systems hasbeen studied by first-principles calculation using WIEN2k code, which is based on thefull-potential linearized augmented plane wave method with the generalized gradientapproximation. The multilayer relaxations in the presence and absence of solutes aredetermined by the force minimization procedure. The binding energies at someGB/FS/bulk sites including both interstitial and substitutional sites are calculatedfor all the non-transition elements between H and Rn (from the first-row to thesixth-row elements). The GB/FS segregation energy is obtained by calculatingthe binding energy difference between the GB/FS site and the inner bulk site.The embrittling potency energy is obtained by calculating the difference betweenthe GB and FS segregation energies on the basis of the Rice–Wang model. Thecalculated results show that most of the non-transition elements have negativeGB/FS segregation energies. In our definition, this means that there exists asegregation site in the GB/FS that is more stable for the solute atom than in the bulk.The embrittling potency energies are positive for most of the solutes. However,some exceptions such as Be, B, C, and Si having negative and large embrittlingpotency can enhance the GB cohesion. The calculated results are found to beconsistent with the various experimental findings within the discussion based on thesimple site competition model neglecting the interactions between different solutes.