The s-d interaction induced hydrogen trapping effect in α-U (130)/[001] twin boundary region

Abstract

Hydrogen embrittlement is a serious obstacle to the safe storage and practical application of metal uranium. In this work, the hydrogen solution characteristics in the (130)/[001] twin grain boundary region in α-U metal are studied by first-principles theoretical and electron backscatter diffraction experimental methods. Our results show that the solution energy of hydrogen atom is the lowest at the (130)/[001] twin boundary plane, and increases as the distance from the twin boundary expands. Hydrogen atoms need to overcome energy barriers to diffuse both along and vertical to the twin boundary plane, i.e., the H atoms are trapped at the interstitial sites in the twin boundary region. It is also found that the s-d interaction between H and U atoms has induced the hydrogen trapping effect. Furthermore, the existence of Nb atom notably lowers the hydrogen solution energy and deepens the hydrogen trap in the region of (130)/[001] twin boundary, which is attributed to the intensified s-d interaction between H and U/Nb atoms. These findings are expected to reveal the underlying mechanism of the microstructural evolution of H atoms in U and provide a theoretical guidance for enlightenment to mitigate or inhibit hydriding corrosion in U metal.