| Research Abstract |
Electical resistivity and micro-hardness measurements have been applied to elucidate the embrittlement mechanisms of pressure vessel steels. Fe-Cu model alloys were irradiated with energetic protons and from annealing experiments, models of production, growth and annihilation of various defects were discussed. Irradiation correlation to estimate radiation effects has also been studied. The results are summarized as follows :
1.Studies with electrical resistivity measurements
Automatic measurement system of electrical resistivity with high precision has been established. It has been found that the resistivity decreases after proton irradiation in Fe-Cu alloys due to association of copper or other impurities with radiation induced defects. Re-analysis of preliminary annealing experiments suggests the presence of clustering process of defect, copper and carbon atoms, defect annihilation processes with liberation of these impurities and so on. A model of post irradiation processes has been p
… More
resented. To further confirm the model, it will be necessary to obtain activation energies and frequency factors for these stages and the dependence of the stages on impurity concentrations.
2.Studies of ageing processes of Fe-Cu alloys by means of micro-hardness measurements.
To elucidate the behavior of copper atoms in Fe-Cu, age-hardening experiments have been performed. The alloys show typical age-hardening. The maximum hardness depends on copper concentration, indicating that the hardening is explained by supersaturation of copper concentration at the ageing temperatures. It is important to note that copper in solution, not the total concentration should be considered in discussing the effect of copper in radiation embrittlement.
Apparent activation energy obtained from time to reach maximum hardness is 154kJ/mol, which is much less than the activation energy of diffusion of copper in iron. This seems to indicate the presence of quenched-in vacancies or association of copper with vacancy
3.Irradiation correlation
Irradiation correlation is a mechamism-based methodology to estimate radiation effects. As a part of irradiation correlation, defect clustering mechanisms, application of in-situ observation of radiation damage with energetic heavy ions, hierarchical structure of irradiation correlation and modeling have been studied. Less
|
