Nuclear Materials and Energy (Sep 2023)
Strengthening/embrittlement effects induced by segregation of transmutation He and Li at Be {101̄1} grain boundary by first-principles calculations
Abstract
First-principles calculations have been performed to investigate the effect of segregation of transmutation helium and lithium atoms on the strength of beryllium {101̄1} grain boundary. For the stability of transmutation lithium and helium atoms in bulk beryllium, both of them preferentially occupy the substitutional site with the lowest formation energy. In the investigation of segregation behavior of multiple transmutation lithium and helium atoms at the grain boundary, it has been found that more helium atoms tend to segregate at the {101̄1} grain boundary compared with the limited segregation of lithium atoms. Meanwhile, the equilibrium concentration of both helium and lithium atoms decreases with the rising of temperature. The segregation of one lithium atom could improve the stability of grain boundary, while the stability of grain boundary could be degraded due to the segregation of more lithium and helium atoms. In addition, the segregation of lithium and helium atoms has different effects on the strength of grain boundary. On the one hand, the transmutation lithium atoms exert a strengthening effect on the strength of grain boundary, which could be beneficial for the improvement of properties of beryllium grain boundary. On the other hand, the segregation of transmutation helium atoms could impose an embrittlement effect which reduces the strength of grain boundary. Besides, it has also been verified that the co-segregation of transmutation lithium and helium atoms weakens the stability and strength of {101̄1} grain boundary. Moreover, the influence of helium atoms on the stability and strength of grain boundary is more obvious than that of lithium atoms. The theoretical work will hopefully provide some insights into the segregation behavior of transmutation atoms at the grain boundary of beryllium, which could be significant for the improvement of strength of grain boundary of beryllium by the grain boundary segregation engineering.
