Effect of hydrogen-vacancy cluster on the tensile strength of alpha-titanium twin boundaries: A first-principles investigation

Abstract

This study investigated the formation of hydrogen-vacancy cluster at twin boundaries (TBs) in alpha-titanium and their impact on TB strength. Using first-principles calculations, it is found that a single vacancy (VA) on the {10−12} TB plane can trap up to five hydrogen atoms, while the single VA on the {10−11} TB plane can accommodate up to eight hydrogen atoms. The presence of VA weakens TBs by reducing the number of Ti-Ti bonds near the TBs. However, in the {10−12} TB with VAH5, the enhancement effect of Ti-H-Ti bonds dominates over the weakening effect of electron transfer, resulting in a slight increase in tensile strength compared to {10−12} TB with VA. On the other hand, in the {10−11} TB with VAH8, the weakening effect of electron transfer dominates, leading to a further reduction in tensile strength relative to {10−11} TB with VA. Therefore, the effect of hydrogen-vacancy cluster on the strength of twin boundaries is sensitive to the type of twin boundary. These findings provide valuable insights into the role of hydrogen in the embrittlement of alpha-titanium.