Helium Stability and Its Interaction with H in B2‐FeAl: A First‐Principles Study

Helium stability and its contribution to H blistering resistance in B2‐FeAl are investigated by a density functional theory (DFT) method, and the results obtained are compared with the H interaction with a Fe vacancy (VFe) in FeAl. He is more energetically favorable to occupy a VFe site, forming a He substituent (HeFe), in comparison with H occupying the first‐nearest‐neighbor (1NN) octahedral interstitial site of VFe in FeAl. At most, six H atoms can be trapped in the vicinity of HeFe one by one, forming HeFe–nH complexes (n is the number of trapped H atoms), similar to the case of VFe in the formation of VFe–nH complexes. HeFe–5H is the main species among the HeFe–nH complexes, whereas VFe–6H is the dominant one in the VFe–nH complexes. No H2 molecule forms inside the cluster unit of the HeFe–5H complex, due to the H–H repulsion caused by He. Strategies for H blistering resistance in iron aluminides are thus proposed.