Ion Irradiation Enhanced Helium Atoms Re-Solution and the Related Hardening in Hastelloy N Alloy
AUTHORS: Liu, JZ; Huang, HF; Liu, RD; Gao, J; Zhu, ZB; Li, Y
Transmission electron microscopy (TEM) and nanoindentation were performed in Hastelloy N alloy with three kinds of irradiation mode: single He ions, He + Xe (3 dpa) ions and He + Xe (10 dpa) ions. TEM results showed the presence of nano-sized irradiation-damage defects, such as helium bubbles, xenon bubbles, dislocation loops and precipitates. It was found that the helium bubble can grow up via absorbing vacancies, and the helium bubble shrinkage will be also occurred due to the helium atoms re-solution. In the case of He + Xe (3 dpa) ions irradiation, the helium bubble growth via absorbing vacancies induced by subsequent Xe ion irradiation was more noticeable. As for the sample irradiated by He + Xe (10 dpa) ions, the ion irradiation enhanced helium atoms re-solution played an important role. Moreover, the helium atoms were more easily dissolved from small helium bubbles and the mechanisms behind them have also been shed light on. In addition, the dispersed barrier hardening and strengthening superposition models were used to predict the nanohardness increments produced by the different irradiation defects. The nanohardness increments measured by nanoindentation for irradiated samples were basically consistent with the calculated nanohardness increments. Graphic Both the ballistic recoil re-solution and the damage assisted re-solution make it easier for helium atoms to dissolve from small helium bubbles.