Exploration of vacancy defect formation and evolution in low-energy ion implanted pure titanium

Hydrogen behavior and its related property degradation have been long-standing problems for structural materials used in hydrogen energy. The hydrogen atoms can easily interact with vacancy defects, forming hydrogen vacancy complexes which play an important role in the hydrogen-induced structural damage. However, the interaction mechanisms and its evolutions are still unclear. In this work, the hydrogen behavior and the interaction between hydrogen with defects in pure titanium implanted by 30 keV and 50 keV hydrogen ions were studied by positron annihilation spectroscopy. The implantation doses were 5 x 10(16) H/cm(2), 1 x 10(17) H/cm(2) and 5 x 10(17) H/cm(2), respectively. The results show that the structural damage of pure titanium is positively correlated with the ion implantation energy. For the implantation of 50 keV hydrogen ions, a large number of hydrogen atoms are deposited in the samples. With the increase of implantation dose, the formation of hydrogen vacancy complexes (HmVn) reduces the effective open-volume of defects and changes the structural features of defects in implanted samples, thus suppressing the formation of vacancy defects and causing the damage range shifting from the peak damage (PD) region to the near surface (NS) region. Eventually, the movement of hydrogen atoms intensifies, and the "hydrogen peak" becomes more obvious. The chemical information related to deposited hydrogen atoms can be easily identified in the processing and analysis of positron annihilation results. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.