Recent progress on radiation damage and effects in nuclear materials at the Department of Technical Physics, Peking University

Ensuring the long-term structural integrity of materials under intense radiation is one of the most critical challenges for advanced fission, fusion, and space nuclear systems. High-energy neutrons and ions create collision cascades that generate primary point defects, vacancies and interstitials, which further evolve into dislocation loops, helium bubbles, and voids. The accumulation of such defects causes hardening, swelling, creep, and embrittlement, eventually degrading the mechanical reliability of core components. Traditional structural materials such as zirconium alloys, austenitic stainless steels, FeCrAl alloys, and reduced-activation ferritic/martensitic steels exhibit varying degrees of degradation at high temperature and dose, highlighting the urgent need for novel radiation-tolerant materials and design concepts. The research in this paper systematically addresses this challenge through three major strategies. First, the interface-engineering strategy uses interfaces to serve as efficient defect sinks. In Fe/MgO heterostructures, the periodic misfit dislocation arrays at semicoherent interfaces generate stress fields that drive defect clusters to migrate and annihilate, resulting in an interface-mediated self-healing process, which means continuous defect absorption and annihilation. In nanoporous Cu films, abundant free surfaces accelerate helium diffusion and release, greatly reducing bubble density and radiation hardening. Moreover, dispersion-strengthened systems such as W-Ti-ZrC alloys, ODS steels, and Zr-modified FeCrAl alloys emphasize the cooperative role of particle and interface networks. Their synergistic effects stabilize microstructures, enhance defect trapping efficiency, and suppress radiation-induced swelling and hardening. Second, studies on high-entropy alloys (HEAs) reveal that chemical complexity and multiphase architectures offer unique pathways for defect regulation. In Pd-alloyed FeCrNiCo systems, Pd addition increases local lattice distortion and modifies defect energetics, suppressing dislocation-loop growth at low doses but facilitating helium-bubble coarsening at higher doses. Al-based HEF-strengthened alloys introduce high-entropy fibers rich in Fe, Co, Ni, and Cr into an aluminum matrix, achieving an optimal balance between lightweight and radiation resistance. A Cr-Al atomic exchange mechanism occurs during irradiation, effectively relieving vacancy accumulation and preventing void formation. Furthermore, dual-phase FeCrNiMnAl alloys show clear phase-dependent behaviors. The B2-NiAlMn phase exhibits strong resistance to helium-bubble nucleation, whereas the FCC-FeCrMn matrix tends to accumulate larger bubbles, accompanied by irradiation-induced Fe segregation near phase boundaries. These results collectively highlight how element selection, coherency control, and interphase chemistry can be harnessed to tailor radiation responses in complex alloys. Third, the concept of dynamically stable nanoprecipitates introduces a new paradigm for long-term radiation tolerance. Unlike conventional static dispersoids that coarsen or dissolve under high temperature and dose, these coherent nanoprecipitates remain stable by undergoing reversible disordering-ordering and dissolution-reprecipitation cycles. This dynamic evolution allows them to continuously absorb and annihilate defects, achieving a self-healing capability even under extreme irradiation conditions. Superlattice steels containing Ni(Al,Fe)-type nanoprecipitates exemplify this approach, exhibiting negligible void swelling up to 2350 dpa under Au ion irradiation, which is far beyond the limit of conventional ODS steels. Overall, these studies integrate experimental characterization, ion-beam irradiation, and multiscale simulations to establish a mechanistic framework linking microstructural evolution with defect dynamics. The convergence of interface engineering, chemical complexity, and dynamic phase stability provides powerful design principles for next-generation nuclear structural materials. Future efforts will focus on in-situ irradiation, data-driven modeling, and the quantitative correlation between ion and neutron damage, thereby enabling the predictive design of lightweight, high-strength, and long-lifetime materials for advanced nuclear and space power systems.