Analysis of Thermal-Induced Microstructural Changes in Nanoscale Zr/Nb Metal Layers after Proton Irradiation

Abstract

The effect of annealing on the microstructure, defect structure, and mechanical properties of nanoscale metal systems consisting of alternating layers of Zr and Nb is considered. The effect of annealing was studied on coatings pre-irradiated with protons. Nanoscale Zr/Nb metal layers were prepared using the magnetron sputtering method, each layer was 50 nm thick, and the total thickness of coatings was about 1 μm. Using electron microscopy and glow discharge optical emission spectrometry, it was shown that the multilayer structure was preserved after both irradiation and annealing of irradiated Zr/Nb samples. After annealing at 300°C, a decrease in hydrogen luminescence intensity and proton redistribution were observed. Using X-ray phase analysis, it was shown that at an annealing temperature of 200°C, the interplanar distances for Zr and Nb decreased. At an annealing temperature of 300°C, a sharp increase in the interplanar distance in Zr layers and a slight decrease in the interplanar distance in Nb layers were detected. Layer-by-layer analysis of defects in nanoscale metal layers using variable-energy positron beam and Doppler broadening spectroscopy showed that increasing the annealing temperature stimulated the migration and annihilation of defects at interfaces. Regions of reduced electron density at the interfaces on the zirconium side remain the predominant positron capture centers.