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592 Vol.28 No.3 WU Sujun et al: Effect of Pre-Deformation Enhanced Thermal Aging on Prec...
DOI 10.1007/s11595-013-0736-z
Effect of Pre-Deformation Enhanced Thermal Aging on Precipitation and Microhardness of a Reactor Pressure Vessel Steel
WU Sujun , LIU Bo, CAO Luowei, LUO Shuai
(School of Materials Science and Engineering, Beihang University (BUAA), Beijing 100191, China)
Abstract: Microstructure evolution in neutron irradiated Reactor Pressure Vessel (RPV) steels was experimentally simulated through an improved degradation procedure in this study. The degradation procedure includes austenitizing at 1 150 and water quench, deformation 10% and 30% respectively, and then thermal aging at 500 for different period of time. The microstructure of the specimens was analyzed in details using transmission electron microscopy (TEM). The micro-hardness test results showed that all the hardness curves of undeformed, 10% pre-deformed and 30% pre-deformed specimens have two micro-hardness peaks with the rst peak value corresponding to different thermal aging time of 1 hour, 5 hours and 10 hours, respectively. It was revealed that the hardness curves were inuenced by the precipitation of Cu-rich precipitates (CRPs) and carbides, deposition of martensite and work hardening.
Key words: reactor pressure vessel steels; cu-rich precipitates; pre-deformation; thermal aging
1 Introduction
Reactor Pressure Vessel is one of the most important components in the nuclear power plant, which provides a radiation shielding effect on the intensely radioactive reactor core. The service life of the nuclear power plant actually depends on this vessel because of its irreplaceable. Irradiation embrittlement strongly degrades the mechanical properties of the RPV steels for the radiation-induced or radiation-enhanced formation of the ultrane Cu-rich precipitates (CRPs), vacancies and dislocations during operation at temperature of about 288 .
Many studies[1-4] indicated that the CRPs are one of the major causes in increasing ductile to brittle transition temperature (DBTT). Mathon et al[5] and
Pareige and Miller[6] indicated that the mechanism of the Cu precipitates in matrix after neutron irradiation is similar to the thermal aging at 500 . Miller et al[7]
revealed that the CRPs were found in a Fe-1.1% Cu-1.4%Ni model alloy after aging at 300 for 10 000 hours and aging at 500 for only 10 hours. Zhang et
al[8] also revealed that the CRPs were found in a model A508-3 steel with 0.5 wt% Cu after...