Point defects in FeAl Σ[210](-1-20) grain boundary:a first principles study

Abstract. Density functional theory has revolutionized computational material physics and its usage in research has increased annually to this day. This thesis is a first principles computational study on the hydrogen embrittlement of FeAl. Point defects of hydrogen and vacancies were introduced to the Σ5[210](-1-20) grain boundary. The probability of the defect formation was considered by calculating formation energies and the strength of the structure by cohesive energies. Correlation was found between the stability of the structure and the hydrogen defects density of states. All the point defects were probable to form in the grain boundary and increased the structures stability. Therefore the hydrogen embrittlement observed on the macro scale was not present in the case of the point defects used in this study. The structural failure can still be due to larger complexes of defects

Embrittlement analysis of ∑5[210]/(−1−20)∑5[210]/(−1−20) FeAl grain boundary in presence of defects:an ab initio study

Abstract Iron aluminide (FeAl) inter-metallic compounds are potential candidates for structural applications at high temperatures owing to their superior corrosion resistance, high temperature oxidation, low density and inexpensive material cost. However, the presence of defects can lead to reduction in the strength and ductility of FeAl-based materials. Here we present a density functional theory (DFT) study of the effect of the presence of defects including Fe and Al vacancies as well as H dopants at the substitutional and interstitial sites at a Embrittlement analysis of $\sum {{{{5}\left[ {{21}0} \right]} \mathord{\left/ {\vphantom {{{5}\left[ {{21}0} \right]} {\left( {\overline{1}\overline{2}0} \right)}}} \right.} {\left( {\overline{1}\overline{2}0} \right)}}}$ FeAl grain boundary in presence of defects : an ab initio study FeAl grain boundary focusing on the energetics. The plane wave pseudopotential code Vienna Ab initio Simulation Package (VASP) in the generalized gradient approximation (GGA) is used to carry out the computations. The formation energy calculations showed that intrinsic defects such as Fe and Al vacancies probably form at the GB, indicated by their negative formation energies. These vacancies can further form defect complexes with H impurities, indicated by lowered formation energies, compact bonds and charge gain of H atoms. Electronic structure analysis showed stronger hybridization of 1s orbitals of H with Fe and Al atoms, which leads to the stabilization of these defects resulting in degradation of material strength