An Effect of Damage Rate on Mechanical Property Change and Microstructural Evolution in Proton-Irradiated Fe-Cu Alloys

Abstract Damage rate effects have been recognized as being important for understanding the correlation between mechanical property changes and microstructural evolution in neutron-irradiated commercial reactor pressure vessel steels. In this study, the correlation between the irradiation hardening behavior and defect cluster formation in proton-irradiated Fe-Cu model alloy is investigated using nanoindentation tests and transmission electron microscopy with a variety of damage rates for the proton irradiations. A wide range of damage rates across three orders of magnitude is adopted for the proton flux in a single irradiation experimental system. The hardness in the low damage rate case is higher than in the high damage rate case in the initial stage of damage level when hardening behavior was not saturated. From transmission electron microscopy observations, it is found that a low density of large dislocation loops is formed under lower damage rate conditions. According to the irradiation hardening estimation based on the classical dispersed barrier hardening model, it is indicated that the damage rate effects on the hardening contribution are weak for dislocation loops but dominant for Cu-rich precipitates.