Abstract
Under irradiations, mechanical performance of nuclear alloys would degrade due to irradiation induced defects. Different strengthening methods can play a different role in the evolution of the defects. In this study, the effect of four typical strengthening methods including fine grain strengthening, dislocation strengthening, second phase strengthening and solid solutions strengthening on the defect evolutions in bcc iron-based alloys are investigated with rate theory simulations, a technique capable of simulating a long-term evolution of defects caused by irradiations. Simulations show that at high dose, irradiation induced voids become the dominating factor that affect irradiation hardening. Strengthening methods with the enhancement of sink strength (fine grain strengthening, dislocation strengthening and second phase strengthening) have little effects on the evolution of voids, while strengthening method with impediment of migration of defects (solid solutions strengthening) can effectively inhibit the nucleation and growth of voids. For fine grain strengthening and dislocation strengthening, the irradiation hardening is almost kept unchanged when changing grain size and initial dislocation density. For second phase strengthening, the irradiation hardening can be inhibited to some extent by increasing mainly the number density of precipitates. The solid solutions strengthening is the most proper method to inhibit irradiation hardening of bcc iron-based alloy because it can inhibit the development of voids, especially at high dose.
Highlights
Material problems have been the major challenges for the development of advanced nuclear systems
The mechanical properties of nuclear materials can be affected under high energy neutron irradiation, which leads to irradiation hardening, irradiation embrittlement and the rise of ductile-brittle transition temperature (DBTT)
A large number of voids were found in martensitic steels irradiated in high flux isotope reactor (HFIR) [3]
Summary
Material problems have been the major challenges for the development of advanced nuclear systems. The mechanical properties of nuclear materials can be affected under high energy neutron irradiation, which leads to irradiation hardening, irradiation embrittlement and the rise of ductile-brittle transition temperature (DBTT). Bcc (body-centered cubic) iron-based alloys have become the main candidate materials of advanced nuclear energy systems due to their better irradiation swelling resistances compared to fcc (face-centered cubic) austenitic steel [1,2]. A large number of voids were found in martensitic steels irradiated in high flux isotope reactor (HFIR) [3]. Irradiation hardening is the key factor that affects the application of bcc iron-based alloys. The performance degradation of nuclear alloys is mainly due to various defects and defect clusters induced by irradiation
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