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

我们以前报道的实验结果表明，空洞可以在中子辐照铜在高温下移动。为了研究空洞的详细行为，我们在中子辐照的铜中进行了退火实验和原位观察。在KUR的温控舱中进行了中子辐照。（京都大学反应堆）。在300℃下进行中子辐照，损伤水平在10 <-4>~ 10 μ <-3>dpa之间。中子辐照铜的退火温度为250℃，退火时间依次为10、20、30 min.退火后，在室温下进行TEM观察。实验结果表明，空洞沿[110]方向沿着移动。在250℃退火过程中，空洞发生了移动，但小的层错四面体（SFT）没有发生变化。我们观察到37个空洞，其中8个空洞发生移动，其他空洞在退火过程中消失。将原位观察图像、空隙对比图像记录在VTR磁带上，逐帧分析。在室温下观察时，空隙是静态的，并被视为白色圆圈;然而，在300℃下，对比度变为椭圆形，有时消失。7秒后，对比度为白色圆圈，并轻微移动，在300℃下经常观察到类似现象。结果表明，在高温下，空穴随动态结构弛豫而移动。

We reported previously an experimental result which shows that voids can move in neutron-irradiated copper at elevated temperature. To study the detailed behavior of voids, we carried out annealing experiments and in-situ observations in neutron-irradiated copper. Neutron irradiation was carried out in the temperature controlled capsule at KUR.(Kyoto University Reactor). Neutron irradiation was performed at 300℃ to damage levels between 10^<-4> to 10^<-3> dpa. The annealing temperature was 250℃ for 10, 20, 30 min sequentially for neutron- irradiated copper. After annealing TEM observation was carried out at room temperature. Experimental results show that voids moved along the [110] direction. Voids moved during 250℃ annealing but small stacking fault tetrahedra (SFT) were not changed. We observed 37 voids and 8 voids moved, the others vanished during annealing. The images of in-situ observation, void contrast images were recorded on VTR tape and analyzed frame by frame. At room temperature observation voids were static and were seen as white circles ; however at 300℃ the contrast changed to an oval shape and sometimes disappeared. After 7 sec contrast was a white circle and moved slightly and similar phenomena were observed quite frequently at 300℃. It is concluded that void moved with dynamical structural relaxation at elevated temperature.