The Analysis Of Cu Enrichment And Microstructure In Fe-Cu Model Alloys

One of the main reason induced RPVS (Reactor pressure vessel steel) embrittlement is that trace elements were gathered as nano-particles precipitates in high temperature and strong irradiation conditions. This trace elements like Mn, Ni, Cr, Cu, etc added in alloy in order to improve the ductility, mechanical strength and anti-radiation performance. As trace elements mixed in alloy can enhance the toughness and plasticity. Therefore, for the safe of nuclear reactors operation, it is very important to study the process and the principle mechanism of trace elements precipitates. As Cu for example, in RPVS, high-intensity radiation induce large amounts of micro defects like vacancy, dislocation, vacancy clusters. Cu atoms will migrate together with micro defects as Cu precipitates clusters. Microstructure varies which influence the ductility and mechanical of material properties. To research the interaction of micro defects with Cu precipitates, it can be provided a scientific basis for the early embrittlement mechanisms in RPVS. In order to exclude the influence of other element and simplify the model, experiments adopt the Fe-Cu model alloys as the research object. By using HR-SEM, XRD, TEM and PAT to studying the interaction mechanisms of micro defects and Cu precipitates. The main experimental content are as follows.Heat treatment with high Cu content Fe-Cu alloys in high temperature, to investigate the recover process of micro defects and Cu precipitates in different annealing temperature. By using PAL, DBS and SEM method to characterization the recover of micro defects and obtain the size, concentration of Cu precipitates with different annealing temperature. As Cu atoms can not fully solid solution in alloy in air-cooled conditions. So next experiment to study the state of Cu atoms in alloy which was quenched. Elaborate Cu atoms solid solution state in air-cooled and quenched conditions.Well annealed alloys which contain Cu precipitates and pure Fe have cold rolling deformation experiments. PAL and DBS were used to study the effect of Cu precipitates on micro defects in deformed Fe-Cu alloy, such as the migration and aggregation of vacancy and dislocation by Cu precipitates. As deformed samples, further annealing was carried out to investigate the Cu precipitates and micro defects varies with different temperature. The size and positron of Cu precipitates also can obtained by SEM. As deformed samples which after quenched have TEM analysis to study the evolution mechanism of micro defects. High-resolution function and EDS (Energy dispersive spectroscopy) were taken advantage to characterization of Cu precipitates with different temperature. Samples annealed at different temperatures which after deformed, PAL measurement were used to characterization migration and aggregation of micro defects with different temperature. DBS measurement carried out at the same time, it can reflect the Cu atom clusters varies with different temperature. Different types of micro defects which migration and disappear process can be illustrated Combined with PAL results.H and Fe ion irradiated samples were studied by slow positron beam technology to investigate the defects with different depth. Annealing experiment was carried out after irradiated to illustrate the interaction with the process of Cu precipitates and recovery of micro defects. The study were focus on varies of Cu precipitates and micro defects with different radiation dose, Cu content and different ion. SEM measurement was used to study the surface morphology changes of samples after different annealing temperature.