Study of dynamical behavior of point defect clusters in neutron-irradiated metals at elevated temperature by electron microscopy

在GRAND-IN-AID的3年科研支持中，发表了以下7个项目：(1)Silver Sigma-5边界附近驱替损害地层的计算机模拟研究。(2)高温中子辐照下面心立方金属中位错附近的间隙团簇偏析。(3)高温下中子辐照面心立方金属的点缺陷吸收位错吸收效率随注量的变化。(4)中子辐照面心立方金属中的位错在高温下的增殖机制。(5)中子辐照面心立方金属中层错四面体(SFT)和空洞在高温下形核和长大的原子机制。(6)裂变中子辐照面心立方金属高温损伤结构演化的原子机制。(7)D-T聚变14 MeV中子辐照面心立方金属损伤结构演化的原子机制。在这些工作中，最重要的结果是中子辐照的面心立方金属在高温下形成空位团簇和SFT的原子机制。透射电子显微镜观察表明，面心立方金属中同时存在空洞和SFT。空位中包含的空缺数量超过500个，而SFT中的空缺数量不到250个。计算机模拟表明，空位团簇在结构松弛为弦状团簇后，可以通过DamaskDienes-Weizer弛豫以团簇的形式移动。当v-簇中的空位数目小于250个时，该簇松弛为SFT。SFT是铜和镍中最稳定的结构。当团簇中的空位数目超过500个时，由于各向异性，它不会松弛为一(111)个片状。团簇松弛为球状构型，由大量的{111}v晶片组成。它的球状星团最终松弛成一个空洞。

Following seven items were published during 3 years supports of GRAND-IN-AID FOR SCIENTIFIC RESEARCH (1) A computer simulation study on displacement damage formation near sigma-5 boundary in Silver. (2) Segregation of interstitial clusters near dislocations in FCC metals neutron-irradiated at high temperature. (3) Changes of the dislocation sink efficiency of point defect absorption for the fluence in neutron-irradiated FCC metals at high temperature. (4) Multiplication mechanism of dislocations in neutron-irradiated FCC metals at high temperature. (5) Atomistic mechanism of nucleation and growth of stacking fault tetrahedra (sft) and voids in neutron-irradiated FCC metals at high temperature. (6) Atomistic mechanism of damage structure evolution in fission neutron irradiated FCC metals at high temperature. (7) Atomistic mechanism of damage structure evolution in D-T fusion 14 MeV neutron irradiated FCC metals. In these works, the most significant result is the atomistic mechanism of the formation of vacancy clusters of voids and sft in neutron-irradiated FCC metals at high temperature. TEM observations showed that both of voids and sft form in an FCC metal simultaneously. The number of vacancy that is contained in a void is more than 500, while the number of vacancy in an sft is less than 250. Computer simulation shows that vacancy clusters can move as a cluster through Damask-Dienes-Weizer relaxation after the structure relaxes to string-like cluster. When a number of vacancies in a v-cluster are less than 250, the cluster relaxes to an sft. The sft is the most stable structure in Cu and Ni. When a number of vacancies in a cluster are more than 500, it does not relax to a one (111) platelet due to an anisotropy. A cluster relaxes to a spherical configuration, which are composed by a large number of {111} v-platelets. Its spherical clusters finally relax to a void.