Effect of Irradiation with a Pulsed Electron Beam on the Defect Structure Formation and the Properties of the Surface Layer of Zr-Nb-H System Alloys

he effect of pulsed electron beam (PEB) irradiation modes on the structure and defect formation and the mechanical strength in the near-surface layer of a Zr-1 wt % Nb alloy with a hydrogen content of 0.0016 and 0.21 wt % (hereinafter, Zr-1Nb and Zr-1Nb-0.21H alloys, respectively) has been studied. By using optical and electron microscopy, as well as X-ray diffraction analysis, it was established that irradiation of the Zr-1Nb and Zr-1Nb-0.21H alloys in the mode without surface melting did not change the morphology and phase composition of their structure. After irradiation with a PEB in the surface melting mode, the dissolution of particles of the beta-Nb phase and the formation of a lamellar structure were observed in the near-surface layer of the alloys regardless of the hydrogen concentration. It was shown by positron annihilation that irradiation in the mode without surface melting led to the formation of dislocations and vacancies in the near-surface layer. In the near-surface layer of the alloys irradiated with a PEB in the surface melting mode, in addition to dislocations and vacancies, defects of the "vacancy-impurity" type were formed. The presence of hydrogen in the alloy contributed to the formation of complex hydrogen-vacancy complexes in the surface layer during irradiation with a PEB. The mechanical strength of the near-surface layer of the alloys was determined depending on the mode of irradiation with a PEB. It is shown that the formation of a lamellar structure in the near-surface layer led to an increase in the strength characteristics of the Zr-1Nb and Zr-1Nb-0.21H alloys under tension in the temperature range of 293-673 K by 25-10%.