Effects of Grain Boundary Characteristics on Its Capability to Trap Point Defects in Tungsten
Wen-Hao He1,2, Xing Gao1**, Ning Gao1, Ji Wang3, Dong Wang4, Ming-Huan Cui1, Li-Long Pang1, Zhi-Guang Wang1**
1Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 2University of Chinese Academy of Sciences, Beijing 100049 3Ningbo Institute of Industrial Technology, Chinese Academy of Sciences, Ningbo 315201 4State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084
Abstract：As recombination centers of vacancies (Vs) and self-interstitial atoms (SIAs), firstly grain boundaries (GBs) should have strong capability of trapping point defects. In this study, abilities to trap Vs and SIAs of eight symmetric tilt GBs in tungsten are investigated through first-principles calculations. On the one hand, vacancy formation energy $E_{\rm V}^{\rm f}$ rapidly increases then slowly decreases as the hard-sphere radius $r_0$ of the vacancy increases. The value of $E_{\rm V}^{\rm f}$ is the largest when $r_0$ is about 1.38 Å, which is half the distance between the nearest atoms in equilibrium single crystal tungsten. That is, any denser or looser atomic configuration around GBs than that in bulk is helpful to form a vacancy. On the other hand, SIA formation energy $E_{\rm SIA}^{\rm f}$ at GBs decreases monotonically with increasing the hard-sphere radius of the interstitial sites, which indicates that GBs with larger interstitial sites have stronger ability to trap SIAs. Based on the data obtained for GBs investigated in this study, it is found that the ability to trap Vs increases as the GB energy increases, and the capability of trapping SIAs linearly increases as the excess volume of GB increases. Due to its lowest GB energy and smallest excess volume among all GBs studied, twin GB $\sum$3(110)[111] has the weakest capability to trap both Vs and SIAs.
2018, Vol. 35 
