Experimental advances in hardening, embrittlement and micro-mechanisms of metals under coupled irradiation, pre-stress and impact loading

During service, numerous structural metals in nuclear reactors are subjected to high-energy particle irradiation under prestressed conditions and may also experience unpredictable impact loads. These conditions can lead to significant degradation of the mechanical properties of structural metals, including irradiation hardening, irradiation embrittlement, irradiation swelling, and irradiation creep, thereby reducing reactor safety and reliability. However, existing studies have predominantly focused on the effects of either irradiation or impact loading on the mechanical properties and deformation mechanisms of metals. A limited number of studies have investigated the degradation behavior of irradiated metals under dynamic loading, whereas the coupled effect of prestress, which is a typical reactor service condition, has been considered even less frequently. The current status of experimental research on the hardening and embrittlement behavior and underlying micromechanisms of metals subjected to the coupled effects of irradiation, prestress, and impact loading is reviewed and summarized. Shortcomings and major challenges in current research are identified, and perspectives and recommendations are proposed regarding the key scientific issues requiring further attention and the critical technological bottlenecks that must be overcome in future studies. Specifically, the following issues should be addressed: (1) the necessity and sufficiency of the causal relationship between dislocation channels and irradiation-induced hardening and embrittlement mechanisms require thorough investigation; (2) equivalent dose-rate assessment methods for metal hardening and embrittlement induced by different irradiation particle sources need to be strengthened; (3) the hardening and embrittlement mechanisms of structural metals in nuclear reactors under prestress and neutron irradiation conditions require further investigation; and (4) research on the impact behavior of prestressed and neutron-irradiated metals urgently needs to be initiated, while safe and efficient experimental techniques for characterizing the dynamic properties of neutron-irradiated metals must be developed immediately. This review is expected to provide a scientific basis and research methodology for future investigations into the hardening and embrittlement behavior and mechanisms of metals under irradiation-prestress conditions, as required in major national projects such as nuclear reactor life extension and the development of advanced reactors.