Microstructural evolution and hardening effect in low-dose self-ion irradiated Zr–Nb alloys

Abstract

Self-ion irradiation-induced hardening behavior and microstructural evolution in dilute Zr–Nb alloys after exposure to low-dose irradiation have been investigated using nano-indentation measurement, EBSD analysis, and TEM examination. Two types of Zr–Nb alloys, i.e., solute-type Zr0.2Nb with only solute Nb atoms and precipitate-type Zr2Nb with both solute and excessive Nb atoms, are utilized to elucidate how the addition of Nb influences microstructural and mechanical property changes upon irradiation. Significant irradiation-induced hardening was confirmed for both alloys, and the extent of hardening was slightly greater in Zr2Nb relative to Zr0.2Nb. The irradiation-induced hardening at [0001] orientation exhibited the lowest value, which gradually intensified as the orientation deviated from [0001] axis to [101¯0] and [21¯1¯0]axes, irrespective of the concentration of Nb. This tendency is ascribed to the slip-system-dependent loops-dislocation interaction. The signs that the doping of Nb can suppress irradiation defect formation were evidenced by the strong sinking effects verified at the particle–matrix interface and grain boundary. With the application of the dispersed barrier hardening model and quantitative characterization of microstructure features, it is revealed that the <a>-loops are mostly responsible for the hardening in both alloys and a rational obstacle strength of <a>-loop in α-Zr is derived as ∼0.33–0.36.