Startsev O. Dynamics of the structural and phase transformations in alloys of titanium VT-1, zirconium Zr1%Nb and aluminum 1933 affected by high-current relativistic electron beams

The thesis is dedicated to the investigation of influence of irradiation in vacuum on the alloys of titanium VТ1-0, zirconium Zr1%Nb and aluminum 1933 by a high-current relativistic electron beam with an energy around 350 keV, pulse length of 5 micro sec, and fluence in the range of 10-200 J/cm2. Experimental studies employing methods of optical microscopy, scanning electron microscopy, electron-probe analysis, electron-positron annihilation analyzes, showed that irradiation of these materials leads to intense ablation of targets and to formation of near-surface microstructures with new physical and mechanical properties. The modified areas of materials are characterized by the growth of grains, mechanisms of destruction changed to more fragile than for the non-modified material. For the modified surface zone there were observed the quenched, melted and heat-affected zones, and a shock wave affected zone, which are characterized by different microstructure not only due to different irradiation effects, but as well due to the post-irradiation fast cooling, solidification tensions and residual heat supply. The quenched zones of materials have an increased hardness compared to the unmodified materials. The irradiation resulted in a significant enrichment of the 1933 surface by alloying elements Mg, Zn, Cu particularly in the subsurface quenched zone, compared to the non-irradiated sample. The long-range effect was observed in terms of the defect concentration outside of irradiated and melted volume of the aluminum target. This phenomenon was assumed to be determined by the influence of the shock-wave effect of the high-current electron beam. The intense electron beam irradiation affected the type of defects towards increasing the number of vacancy defects.