Bin Cai

Gen-IV nuclear systems demand structural materials with superior high-temperature mechanical integrity, corrosion resistance, and irradiation tolerance. Nickel-based alloys, owing to their excellent high-temperature properties, chemical stability, and irradiation resistance, have become leading candidate materials for key components in advanced reactors such as molten salt reactors and very-high-temperature gas-cooled reactors. This review comprehensively surveys typical reactor-grade nickel-based alloys—Hastelloy N/GH3535, Inconel 718, and Inconel 617—covering their in-service behavior, key properties, processing–microstructure relationships, and irradiation damage research. Special attention is given to irradiation-induced microstructural evolution, including point defect generation and migration during cascades, formation of dislocation loops and voids, helium bubble nucleation and growth, precipitation, and phase transformations, as well as their links to macroscopic property degradation (hardening, embrittlement, swelling, and creep). Recent advances in ion-irradiation experiments, microstructural characterization, nanomechanical testing, and computational methods (first-principles and molecular dynamics) are critically discussed. It is shown that irradiation resistance can be significantly enhanced through compositional optimization, grain-boundary and dislocation engineering, oxide-dispersion strengthening, and the design of heterogeneous interfaces. Finally, future research directions are proposed, emphasizing advanced characterization, multiscale modeling, and data-driven approaches for accelerating the development of next-generation irradiation-resistant nickel-based alloys.

To optimize the overall performance of as-cast 8021 aluminum alloy billets for power battery foil, this study explores how Ce addition (0–0.4 wt.%) regulates microstructure, mechanical properties, and corrosion resistance via second-phase reconstruction. Microstructure characterization, mechanical property testing and electrochemical corrosion tests were performed. The results show that Ce addition first refines, then stabilizes, and finally coarsens α-Al grains. The addition of 0.2 wt.% Ce promotes the formation of tentatively identified dispersed Al–Ce–Fe ternary phases, achieving the optimal combination of ductility (elongation: 42.7%) and strength (tensile strength: 95.0 MPa), as well as superior corrosion resistance (i_corr = 2.79 × 10⁻⁷ Acm⁻²). Excessive Ce led to possible precipitation of the Al₂Ce phase and grain coarsening, deteriorating alloy properties. In conclusion, 0.2 wt.% Ce is the optimal content to balance the microstructure, mechanical and corrosion properties of 8021 aluminum alloy, providing a theoretical basis for its compositional optimization of as-cast billet for battery foil applications.

The mismatch of the coefficient of thermal expansion (CTE) between the reinforcement and the matrix leads to thermal residual stresses and defects upon cooling from the processing temperature to room temperature. The residual stresses and defects have a significant impact on the mechanical properties of metal-matrix composites. To investigate the effect of cooling temperature on the residual stresses’ distribution and mechanical properties of SiC/Al, we investigated the cooling process of SiC/Al from different initial temperatures to room temperature. We found that residual stresses mainly distributed in the interface of SiC/Al composites after cooling, and the higher the initial temperature of cooling, the higher the value of residual stresses and the greater the degree of atomic displacement. During the cooling process, the Shockley partials and stair-rod dislocations were the two dominant dislocation structures. After cooling, the length of Shockley partials was about 80% and the length of stair-rod dislocations was about 18%. The mechanical properties of SiC/Al composites reduced after cooling. These results have filled the gap in understanding the mechanism of defect evolution in SiC/Al composites under cooling conditions, as well as the influence of cooling conditions on the mechanical properties of the material.

Based on the acid etching strategy proposed in 2022, a novel treating method is developed and employed in the Sm_0.2Ce_0.8O_2−δ (SDC) based SOFC. After 25 min acid treatment, the surface roughness of SDC increases by 60% while the peeling strength of cathode/electrolyte interface can be enhanced by 129%. The peak power density at 923 K reaches 1.392 W·cm⁻², 30% higher than that (1.067 W·cm⁻²) without treatment. Compared with little degradation observed during working at 873 K for 200 h, apparent performance degradation of single cells can be observed during thermal cycling at 673–873 K. However, the thermal cycling stability can be markedly improved by the 25 min acid etch. Combined with the electrochemical impedance spectroscopy and microstructure observation, this suggests that the significantly enhanced performance should be caused by the synergy effect of both revitalized interface and increased bonding area between cathodes and electrolytes.

Molten salt reactors (MSRs) offer advantages such as enhanced safety, reduced nuclear waste, and cost effectiveness. However, the corrosive nature of fluoride-based molten salts challenges the longevity of structural materials. Ni-based alloys, like Hastelloy N, have shown resistance to fluoride salt corrosion but suffer from issues like helium embrittlement caused by neutron irradiation. To address these concerns, the incorporation of graphene (Gr) into Ni-based alloys is being explored. Gr’s superior mechanical properties and irradiation tolerance make it a promising reinforcement material. In this study, a Ni-17Mo alloy, a simplified model of Hastelloy N, was combined with reduced graphene oxide (RGO) using powder metallurgy. The effects of milling time and sintering temperature on the microstructure and mechanical properties were systematically studied. The results indicated that optimal sintering at 1100 °C enhanced tensile strength and ductility. Additionally, RGO incorporation improved the alloy’s strength but reduced its elongation. This research highlights the potential of Gr-reinforced Ni-based alloys for advanced MSR applications, offering insights into fabrication techniques and their impact on material properties.

Negative thermal expansion (NTE) ceramics Sm_0.85Zn_0.15MnO₃ (SZMO) and ZrMgMo₃O₁₂ (ZMMO) were selected to prepare Sm_0.85Zn_0.15MnO₃-ZrMgMo₃O₁₂/Al-20Si (SZMO-ZMMO/Al-20Si) composites using ball milling and vacuum heating-press sintering processes in this study. The synergistic effect of the SZMO and ZMMO NTE ceramic reinforcements on the microstructure, mechanical properties, and coefficient of thermal expansion (CTE) of the composites was investigated. The results show that the processes of ball milling and sintering did not induce the decomposition of SZMO or ZMMO NTE ceramic reinforcements, nor did they promote a reaction between the Al-20Si matrix and SZMO or ZMMO NTE ceramic reinforcements. However, the excessive addition of SZMO and ZMMO NTE ceramics led to their aggregation within the composite. Adding a small amount of SZMO in combination with ZMMO effectively increased hardness and yield strength while reducing CTE in the Al-20Si alloy. The improvement in strength was primarily provided by SZMO, while the inhibition effect on CTE was primarily provided by ZMMO. An evaluation parameter denoted as α was proposed to evaluate the synergy effects of SZMO and ZMMO NTE ceramic reinforcements on the mechanical properties and CTE of the composites. Based on this parameter, among all composites fabricated, adding 2.5 vol% SZMO NTE ceramic and 10 vol% ZMMO NTE ceramic resulted in an optimal balance between CTE and strength for these composites with a compressive yield strength of 349.72 MPa and a CTE of 12.55 × 10⁻⁶/K, representing a significant increase in yield strength by 79.20% compared to that of Al-20Si alloy along with a notable reduction in CTE by 26.44%.