(1. 中南大学材料科学与工程学院，长沙 410083；
2. 中南大学粉末冶金国家重点实验室，长沙 410083；
3. 中南大学有色金属材料科学与工程教育部重点实验室，长沙 410083；
4. 清华大学材料科学与工程学院，北京100084；
5. 北京科技大学材料科学与工程学院，北京100083；
6. 东北大学材料与冶金学院，沈阳110819)
摘 要: 基于第一性原理计算研究纳米结构铁素体合金(NFAs)对中子辐照引发的氦的选择性捕获能力。结果表明：与铁基体中的空位相比，氦更容易被NFAs中Y2Ti2O7的八面体间隙和Y2TiO5沿b轴方向的中空通道捕获；被氧化物捕获的氦相互间存在排斥作用，说明氦在NFAs中的分散度将在很大程度上取决于氧化物的析出分数和弥散度；通过计算界面相图推断，铁素体/Y2Ti2O7界面应为富Y/Ti型，与实验观测到的Y2Ti2O7析出相的非化学计量比特性吻合；氦对Fe/Y2Ti2O7界面有较强的偏聚倾向，且可能对氧化物颗粒尺寸敏感。较大尺度的Y2Ti2O7能够将氦捕获在界面和体内，而低纳米尺度的Y2Ti2O7更倾向于将氦捕获在界面。
关键字: 纳米结构铁素体合金；氦；Y2Ti2O7；Y2TiO5；第一性原理
（1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China
3. Key Laboratory of Nonferrous Materials, Ministry of Education, Central South University, Changsha 410083, China;.
4. School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China;
5. School of Materials Science and Engineering, University of Science and Technology, Beijing 100083, China;
6. School of Materials and Metallurgy, Northeastern University, Shenyang 110819, China）
Abstract:First principles was studied for assessing the relative stabilities of transmutant helium trapping in Y2Ti2O7, Y2TiO5 and the ferrite matrix in nano-structured ferritic alloys (NFAs). The results suggest that, helium in NFAs prefers to occupy individual octa-interstitial sites of Y2Ti2O7 and the open channels along the b axis of Y2TiO5. The helium self-interaction in Y2Ti2O7 is essentially repulsive, suggesting that the dispersion of helium in NFAs might, to a large extent, depend on the number and dispersion of Y2Ti2O7 in the iron matrix. The calculated interface phase diagram predicts the ferritic/Y2Ti2O7 interfaces in NFAs as Y/Ti-rich, in agreement with the experimentally observed non-stoichiometric nature of Y2Ti2O7 precipitates in NFAs. Segregation tendency of helium to the ferritic/Y2Ti2O7 interface can be sensitive to the size of Y2Ti2O7.
Key words: nano-structured ferritic alloy; helium; Y2Ti2O7; Y2TiO5; first principle
