Structure Changes Of Binary Fe-Cu Systems Containing Cu Clusters Within The Fe Matrix On Heating At Atomic Scale

As the main factor of irradiation embrittlement of nuclear reactor pressure vessel steel,since 60s of last century,nano-rich Cu clusters has aroused researcher's intensive interest.By using various kinds of computer simulations,the formation and growth of Cu clusters and the structure evolution of Cu precipitates were obtained.In this paper,the molecular dynamics method based on classical Newtonian mechanics is adopted.As the temperature increases,atomic packing changes occur in the Fe-Cu binary systems,where small size Cu nano-particles are within in BCC Fe lattices.By calculating the mean square displacement of Cu atoms,the distribution function of Cu atom and the radial density distribution function,the atomic packing structure of the pure Cu atomic region,the Fe-Cu interface region and the pure Fe matrix region are discussed,the structure evolution and movement mechanism of nano-rich Cu clusters in the heating process were also analyzed.It is very important to understand irradiation embrittlement of RPV materials.The results are shown in the following:1.In the Fe matrix,the size of the Cu clusters and the size of the clusters can be occupied in the Fe matrix have effects on the atomic packing structure of Cu clusters and Fe matrix at different temperatures.For the Febulk-Cu135 system,because the Fe matrix can provide small space to accommodate the Cu atoms,packing patterns in many Cu atoms are disordered.For the Febulk-Cu141 system,although the Cu cluster containes more atoms,the Fe matrix can accommodate Cu atoms in larger space,the majority of these Cu atoms are located at the BCC crystal lattice.2.The structural changes present apparent differences for the Fe matrixes containing confined Cu clusters having different atom number on heating.For the Febulk-Cu135 system,strain regions in the Fe matrix are adjacent to the Cu cluster.In the meantime,there are a lot of vacancy defects and the strain regions among the Cu clusters.For the Febulk-Cu141 system,with increasing the temperature,the changes can be observed that the amount of the strain regions decrease,whereas the sizes of some strain regions increase.3.When the acco mandat ion region for the Cu atoms is fixed in the Fe matrix,the Cu atoms can be at the BCC lattice positions by reducing the number of Cu atoms in the Cu clusters.The atom packing structures in the Fe matrixes present similar change patterns on heating.