Microstructural and mechanical property evolution of Ar9+ ion irradiated Zr-based alloys - effect of initial microstructure and alloying addition

This work endeavours to bring out the role of initial microstructural features and alloying additions in the irradiation response of a material. Three Zr-based binary alloys, namely Zr-0.17 wt.% O, Zr-0.33 wt.% Sn and Zr-2.5 wt.% Nb, with starting microstructures exemplifying annealing, hot-extrusion and cold-pilgering operations, respectively, were selected. The alloys were irradiated at room temperature using 315 keV energy Ar9+ heavy ion. Depth-dependent microstructural evolution of the alloys upon irradiation was assessed through positron annihilation Doppler broadening spectroscopy and grazing incidence X-ray diffraction, while nanoindentation probed the mechanical behaviour. Irradiation responses of the alloys garnered in terms of S-parameter, coherently scattering domain size, microstrain, dislocation density and hardness were compared. The observed differences were rationalized on the basis of (i) starting microstructural attributes of the alloys, which posed as sinks to the irradiation-induced point defects, and (ii) impact of alloying additions on diffusion and annihilation of these defects.