Solubility and Anisotropic Migration Behaviors of Helium in bcc Iron Under Strain

作     者：Yue Yu Ben Xu Hao Chen Zhi-Gang Yang Chi Zhang 

作者机构：Key Laboratory of Advanced Materials of Ministry of Education School of Materials Science and EngineeringTsinghua University 

出 版 物：《Acta Metallurgica Sinica(English Letters)》 (金属学报（英文版）)

年 卷 期：2018年第31卷第2期

页      面：199-207页

核心收录：

学科分类：07[理学] 070205[理学-凝聚态物理] 0702[理学-物理学] 

基　　金：supported by the National Basic Research Programs of China (Nos. 2015GB118001  2015CB654802  20151080369 and 20141300796) 

主　　题：Strain Point defects Migration Density functional theory (DFT) Iron Helium embrittlement 

摘      要：The different solution and migration behaviors of tetrahedral and octahedral interstitial helium in bcc iron have been investigated by using first principles calculations. We showed that the tetrahedral site has less charge transfer and less redistribution of the density of states but stronger bonding and a lower solution energy. This is due to the coupling between the symmetrical facts of the two interstitial atoms and the 3 d orbitals of Fe atoms. The solution energies of both sites are not significantly influenced by applied normal strains of 2% and 4%. In contrast, the migration barriers have the reverse trends for different migration directions under strain, which can be explained by an anisotropic elastic energy change and charge transfer. The lower migration energy along certain directions under strain can facilitate the segregation of helium and the formation of helium bubbles.