First-principles investigation of grain boundary structure effects on hydrogen solubility and segregation in tungsten
Wenhao He, Xing Gao, Liangfu Zhou, Dongyan Yang, Zhiguang Wang, Juntao Liu, Zhiyi Liu, Yuhong Li
Abstract
Hydrogen (H) solubility, segregation, and hydrogen-induced intergranular fractures in eight symmetric tilt grain boundaries (GBs) in tungsten (W) are investigated through the first-principles calculations. The results show that there is an equilibrium distance, about 1.95 Å, between the H inserted in interstitial sites and its nearest W. Interactions between the inserted H and GBs are rather localized, thus the local environments of interstitial sites are responsible for the hydrogen solubility. The hydrogen solution energy decreases as the hard-sphere radius r0 of the interstitial site increases. But the trend slows significantly down as the r0 is larger than 0.57 Å, which is corresponding to the equilibrium H-W distance of 1.95 Å, due to the ignorable contributions from lattice distortions induced by the inserted H to the hydrogen solution energy. It is found out that the GBs with smaller interstitial site are more resistant to hydrogen segregation as well as the hydrogen-induced intergranular fractures. Among all GBs studied here, the twin GB ∑3(110)[111] has the smallest interstitial site; hence, it has the weakest capability to trap H and it is also the most resistant to hydrogen-induced intergranular fractures. Our results provide a sound guide to design GBs to suppress hydrogen-induced intergranular fractures.