中文摘要：

为了研究He在材料中的行为,借助10B的（n,α）核反应,通过反应堆热中子对Al-B合金进行辐照,引入He原子密度达6.2×1025 m-3。采用同步辐射X射线小角散射法（Synchrotron small angle X-ray scattering,SAXS）原位测试了不同温度下合金中He的状态变化,并结合透射电镜（Transmission electron microscope,TEM）对试样进行了观察;采用X射线衍射和中子衍射法分析了合金晶格参数的变化。SAXS分析表明,随着温度升高试样内部的颗粒和孔洞消失,He泡数量不断增多、尺寸增大。700 oC下He泡的半径大约增大到10 nm,与室温时颗粒和孔洞相当。衍射分析表明,B原子引入使得Al晶格常数增大,但不存在可见的第二相,中子辐照使得生成的Li和He原子进入Al晶格,进一步加大了晶格常数。辐照后的样品加热使得He从晶格间隙位置扩散到晶界形成He泡,从而缓解了对晶格的挤压,导致了晶格常数的回复减小,第一性原理计算得到的间隙原子B、Li、He引起的晶格肿胀解释了这一结果。

英文摘要：

Background： Understanding of helium state is important for the materials used in radiation surroundings. Most mechanical damage starts with a change in the microstructure of the material. Purpose： To study the behavior of helium in the material, a helium contained Al-B alloy Al0.4wt%B was prepared using 10B（n, α） nuclear reaction by reactor thermal neutron irradiation. The helium atoms density reached to 6.2×1025 m-3. Methods： The synchrotron small angle X-ray scattering（SAXS） was employed to study the helium state at different temperatures. The X-ray and neutron diffraction were used to inspect the lattice change. The tempered samples were observed with transmission electron microscope（TEM） to confirm the helium bubbles. Results： SAXS analysis shows the volume fraction of helium bubbles significantly increased with temperature. The radius of helium bubbles increased to about 10 nm at 700 oC, which is the similar size of scatters at room temperature. TEM results show some obvious pores and particles existed in the sample at room temperature and disappeared after 500 oC, and helium bubbles appeared increasingly with temperature. The results of SAXS and TEM are consistent. X-ray and neutron diffraction analysis show there is no visible second phase, the doped B increased and the produced Li and He further increased the lattice constant. The heat treating makes He atom escape from the lattice to form He bubble at grain boundaries and results in a drop of lattice. The first-principles calculation gave the volume changes because of introducing B, Li and He and explained this lattice decline. Conclusion： A helium contained Al-B sample was successfully prepared and there is no observable helium bubble in the irradiated sample. Heat treating promoted the helium atom aggregation and helium bubble formation, and removed defects and damages. The SAXS information for helium bubble is observed only in tempered sample.