Radiation effects in neutron-irradiated molybdenum studied by gamma-resonance and positron methods

The effect of ionizing radiation on various physical and mechanical properties of Mo was predominantly investigated by conventional methods such as X-ray diffraction analysis, residual electrical resistance, mechanical testing, electron microscopy and others. However, for objective estimation of the material postirradiation state, information on atomic and subatomic levels is required. In this case it must be kept in mind that the results of macroscopic and microscopic methods may sometimes differ considerably one from another. For example, the study of the processes of annealing of electron-irradiated Mo defects using the electrical resistance and the positron lifetime measurement methods1,2 under almost the same conditions brings about the defect return stages varying in temperature by 50 to 60 K which is likely to be the result of the selectivity difference of these methods. Electrical resistance is known to vary under the effect of all types of defects, while the positron annihilation processes are affected mainly by vacancies. Consequently, methods comparable in terms of their selectivity and enabling us to derive mutually complementing data on the physical phenomena, the same or at least similar by their nature, must be chosen for joint application. In this work, to study the radiation damage of Mo, neutron-irradiated at 350 K by 1018-1020 cm-2 fluences, the gamma-resonance and positron spectroscopy methods are used.