Reactor Pressure Vessel(RPV)is a key structural component of nuclear reactor.It has to endure high-dose neutron irradiation during service.Neutron irradiation produces defect clusters and solute segregation,causing hardening and embrittlement of the RPV steel.A pretty number of testing and characterization techniques of microstructure and mechanical properties utilizing miniaturized specimens have been developed[1−4].Current experimental studies show that the increase of nano-hardness and micro-hardness of materials is positively correlated with that of macroscopic yield stress and ductile-brittle transition temperature[5;6].Meanwhile,some physical models related to defects,solute cluster characteristics and hardness change of materials have been established[7;8],supposing that the hardness increment in irradiation material mainly comes from the large heterogeneous clusters.
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