| Research Abstract |
The most superior method of direct observation of defect reactions is to utilize high energy electron irradiation in a high-voltage electron microscope : (a) A systematic investigation has been performed on the effect of solute addition to defect structure evolution, (b) A method of the identification of the nature of small point defect clusters in neutron irradiated materials was established by superimposing electron irradiation and applied to representative materials, (c) Effect of strain field around dislocation on cascade defects was elucidated, (d) Detection of stochastic fluctuation of point defect reaction processes was successfully made during the growth of electron irradiation-induced dislocation loops, (e) Measurement of short relaxation phenomena was made by newly designed intermittent irradiation technique. As for the defect microstructures induced by high energy neutron irradiation : (f) The role of electron microscopically invisible small defect clusters in iron was eluci
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dated, (g) Relation between the destination of cascade collision induced point defects and the microstructure evolution was studied, (h) Effect of solute elements to the defect microstructure evolution was systematically investigated, (i) The mechanism of defect reaction during neutron irradiation with temperature variation was also studied. Plastic deformation of crystalline metals without dislocation was the most important and new subject in this research project : (j) Absence of the operation of dislocations was confirmed by direct observation of the progress of deformation in an electron microscope, (k) From the dynamic observation of the appearance and disappearance of point defect clusters, point defects are concluded to be introduced as dispersed point defects, but not as point defect clusters, (l) Local strain was successfully measured by the deformation of plastically deformable precipitates, (m) Deformation mode was examined by using samples containing various kinds of secondary defects, (n) all of these experimental results lead to the proposal of a new mechanism of deformation with glide elements which replace dislocations, under the condition of extremely high internal stress. Investigation of high-speed deformation achieved the strain rate of 10^7/s, and (o) Defect structures were found to change drastically by the deformation with strain rate over 10^5/s. Less
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