Single-crystal GaN epilayers were irradiated with heavy inert gas ions (2.3-MeV Ne^8+ , 5.3-MeV Kr^19+ ) to fluences ranging from 1.0× 1.0^11 to 1.0× 1.0^15 ions/cm^2 . The strain-related damage accumulation versus ion fluences was studied using high-resolution X-ray diffraction (HRXRD) and ultraviolet–visible (UV–Vis) spectroscopy. The results showed that the damage accumulation was mainly dominated by nuclear energy loss. When the ion fluence was less than ∼ 0.055 displacement per atom (dpa), the lattice expansions and lattice strains markedly increased linearly with increasing ion fluences, accompanied by a slow enhancement in the dislocation densities, distortion parameters, and Urbach energy for both ion irradiations. Above this fluence ( ∼ 0.055 dpa ), the lattice strains presented a slight increase, whereas a remarkable increase was observed in the dislocation densities, distortion parameters, and Urbach energy with the ion fluences after both ion irradiations. ∼ 0.055 dpa is the threshold ion fluence for defect evolution and lattice damage related to strain. The mechanisms underlying the damage accumulation are discussed in detail.

Molybdenum rhenium alloys are primary candidates for structural components in space nuclear reactors. However, their degradation mechanisms under the combined influence of irradiation, temperature, and mechanical stress remain poorly understood. In this study, 240 MeV argon ions were used to generate a damage layer of approximately 23 & micro;m in a Mo-14Re alloy, with doses ranging from 1.25 to 10 dpa. Microstructural characterization using GIXRD and TEM revealed significant lattice expansion, reaching a maximum swelling of 0.956% at 3.75 dpa, and a high density of dislocation loops. These microstructural changes resulted in pronounced hardening. Crucially, this study demonstrates that the macroscopic performance degradation is not merely a result of thermal creep in the bulk material but is significantly accelerated by the premature cracking of the brittle surface layer. These surface cracks act as geometric notches that induce severe stress concentrations and propagate into the substrate. This failure mechanism, characterized by damage propagation from the surface to the interior, provides a critical new perspective for evaluating the irradiation tolerance and service life of refractory alloys.

This study investigates the influence of nanoscale oxide dispersoid characteristics on irradiation hardening in FeCrAl-based oxide dispersion strengthened (ODS) ferritic steels. Four ODS alloys with systematically varied oxide size and number density-achieved through Al and Zr additions-along with a conventional HT9 steel, were irradiated with Fe-56 ions to 0.8 dpa at 563 K. Vickers micro-hardness tests revealed that the Zr-added and Al-free ODS steels exhibited significantly lower irradiation hardening than their Al-containing counterparts, while HT9 showed the highest hardening. This enhanced radiation tolerance is attributed to the high number density of fine (similar to 2-10 nm) oxide particles, which act as efficient sinks for point defects, suppressing dislocation loop formation. A power-law correlation was established between the oxide-related sink strength and the irradiation-induced hardness increment. The improved irradiation resistance is primarily attributed to the increased sink strength. Assuming interstitial-type dislocation loops govern hardening, the dispersed barrier hardening (DBH) model yielded predictions consistent with experimental data, confirming the critical role of microstructure in defect mitigation.

A comprehensive investigation of the superconducting response to disruptions is essential for elucidating the mechanisms underlying performance enhancement. Here, we systematically study the effects of Xe-ion irradiation in BaHfO3-doped EuBa2Cu3O7−δ films. Our results show that irradiation significantly modifies intrinsic superconducting parameters. Analysis of critical current density Jc and pinning energy reveals that the degradation of intrinsic properties is a primary factor driving performance decline, and we highlight that enhancing depairing current density Jd is more effective than defect engineering alone, particularly within the quantum critical region. Raman spectroscopy indicates that the degradation arises from disorder at the chain oxygen sites. These findings emphasize that a thorough understanding of both intrinsic superconducting properties and extrinsic pinning structures is critical for optimizing high-temperature superconductor performance.

In this study, Molecular Dynamics (MD) and Object Kinetic Monte Carlo (OKMC) simulations are adopted to explore the long-term defect evolution behavior of Fe-9Cr alloys. The effects of injected Fe ion concentrations (0–1000 appm/dpa) on irradiated microstructures are systematically evaluated at two typical irradiation temperatures of 573 K and 673 K. The results reveal that the modulation effects of injected self-ions are more prominent under high-temperature and high-dose irradiation conditions. At irradiation doses below 1 dpa, injected ions exert a minor influence on matrix defects. As the irradiation dose increases, such an effect becomes considerable: at 10 dpa, the density of large defect clusters varies by more than one order of magnitude under different injected ion concentrations. High-concentration injected ions substantially promote the nucleation and growth of self-interstitial atom (SIA) clusters while inhibiting the formation and evolution of voids. At high irradiation doses, high ion injection concentrations significantly raise the production ratio of <100>-type SIA loops. Furthermore, this work also elucidates the fundamental mechanisms by which injected ions affect the diffusion and segregation of solute atoms.

FeCrAl ODS steel is the promising candidate cladding material for the advanced nuclear systems. The effects of alloy compositions on oxides and the strengthening are vital to materials design and development, which deserve in-depth investigation. Here, detailed crystal structures and interface coherency of totally more than 1000 oxides in Fe-15Cr-3.3Al ODS model alloys with 0.51 wt% Zr and 0.46 wt% Hf addition (denoted as P1 and P2, respectively) were investigated. The oxides in P1 are mainly trigonal Y4Zr3O12 and Y4Al2O9 (YAM, yttrium aluminum monoclinic) while in P2, they are Y2Hf2O7 (pyrochlore) and YAM. The Y2Hf2O7 oxides occupy 74.5 % of oxides in P2 while Y4Zr3O12 oxides account for 65.9 % in P1, manifesting that 0.46 wt% Hf addition can greatly suppress the formation of YAM oxides than 0.51 wt% Zr addition. The mean diameter of oxides in P2 is smaller than P1 due to the formation of smaller Y2Hf2O7 and YAM oxides. Almost all Y4Zr3O12 and Y2Hf2O7 oxides are coherent with the matrix whereas some YAM oxides show a semi-coherency relationship. The semi-coherent YAM oxides take a percentage of 5.0 % in P2, in contrast to that of 8.9 % in P1, indicating an improvement of oxide coherency by Hf addition. A size dependence of coherency of YAM oxides was observed in both specimens. The strengthening mechanism of ODS model alloys is analyzed by using dispersion barrier hardening (DBH) model. The calculated barrier strength factor, alpha for coherent oxides is 0.20, which is smaller than that for semi-coherent oxides, 0.36.

Oxide dispersion strengthened copper (ODS-Cu) alloy is considered as a candidate of heat sink materials for divertors, and Ti doping is regarded as an effective strategy to improve the performance of Cu-Al2O3 (a common ODS-Cu). In order to evaluate the stability of the oxide nano-particles dispersed in Ti-doped ODS-Cu, irradiation was conducted using multiple-energy Fe ions at 350°C on two types of Ti-doped ODS-Cu with identical composition and oxide volumetric fraction while different size of oxide nano-particles. Ultimately, a 24 μm-thick quasi-homogeneous damaged layer of ∼ 1.35 dpa was induced in the specimens. Nano-hardness measurements were used to assess variation in the mechanical properties of the irradiated ODS-Cu. The results showed that both specimens experienced irradiation-induced softening, and softening in the specimen containing smaller sized particles is more pronounced. Microscopic observations reveal that the size of irradiated oxide nano-particles somewhat increased, which can be mainly explained by Ostwald ripening under irradiation, and this ripening effect is more pronounced in the smaller oxide nano-particles.

Effective subsequent heat treatment is crucial for achieving the desired microstructure and excellent mechanical properties in laser-deposited high-performance maraging steel. In this paper, we systematically investigate the synergistic relationship and tuning mechanism of different solution treatment times on the microstructureproperty synergy of new maraging steels fabricated using laser direct energy deposition (LDED). To determine the optimal heat treatment process, solution treatment was conducted at 840 degrees C for varying durations, followed by aging at 530 degrees C for 2 h to induce precipitation strengthening. The results indicate that after 2 h of solution treatment, the alloy exhibits optimal ductility with an elongation of 7.90 % +/- 0.15 %, attributed to the refinement of the martensitic matrix and precipitated phases, along with the formation of a small amount of residual austenite. When the solution treatment time is extended to 4 h, the alloy achieves its highest tensile strength, reaching 1958 +/- 24 MPa. However, the elongation decreases to 7.31 % +/- 0.12 % due to the coarsening of the martensite and secondary phase particles. After 6 h of solution treatment, significant coarsening and aggregation of the martensite and Fe2Mo intermetallic compounds markedly reduce the hardness, strength, and toughness of the alloy. By adjusting the solution treatment time, the size, morphology, and distribution of the martensitic matrix, Fe2Mo, and nanoscale precipitated phases play a critical role in the strengthening and fracture processes. Therefore, optimizing the precipitation behavior of the martensitic matrix and Fe2Mo intermetallic compounds through rational solution heat treatment is key to enhancing the mechanical properties of laser-deposited new maraging steels.

Oxide dispersion strengthened (ODS) steel is considered a promising candidate material for advanced nuclear systems. The stability of oxides plays a critical role in maintaining mechanical properties during service. In a fission environment, structural materials experience damage not only from neutrons but also from fission products. This study focuses on the impact of electronic energy loss on the structural damage of ODS steel MA956 under 345 MeV Fe ion irradiation at fluences of 1012-1014 ions/cm2 at different temperatures. Detectable hardening was observed at an extremely low fluence of 2.0 x 1012 ions/cm2 and lower temperature (-70--50 degrees C). An evident hardening was observed under the irradiation at a fluence of 4.5 x 1014 ions/cm2 and a temperature of 160-185 degrees C. The hardness values of the irradiated samples at low temperatures showed only a slight increase or no changes after annealing at 500 degrees C compared to the as-irradiated samples, indicating that the damaged structures slightly extended or survived the annealing treatment. TEM results indicated that the size and density of oxides slightly increased in the irradiated samples, accompanied by a narrower size distribution. The proportion of oxides smaller than 12 nm decreased, while a higher proportion was observed in the size range of 12 to 20 nm in the irradiated samples, with no apparent differences in matrix damage, except for the irradiated samples at 160-185 degrees C, where dislocation loops were observed. Estimations based on the dispersed barrier hardening (DBH) model suggested that the detectable hardening observed at such low irradiation fluence was attributed to changes in the oxides, due to the electronic energy loss. The evident hardening in the irradiated samples at 160-185 degrees C resulted from the changes in the oxides and the formation of dislocation loops.

This research investigated the anisotropy of creep properties of a low-cost third-generation Nickel-based single crystal superalloy under two conditions of 760 degrees C/800 MPa and 1120 degrees C/137 MPa. The microstructures and deformation mechanisms of the [011] and [111]-oriented specimens were studied in depth and the determinants of anisotropy were analyzed. The low critical resolved shearing stress and the single activation of the <112> {111} slip system synergistically led to the formation of tremendous continuous stacking faults in the [011]oriented specimen, which resulted in its extremely poor creep life under condition of intermediate temperature and high stress. In contrast, high critical resolved shearing stress of <112> {111} slip systems led to the formation of a large number of microtwins in the [111]-oriented specimen. The microtwins dispersed in the gamma' phase could well hinder the movement of dislocations and produce a favorable work-hardening effect, which led to the excellent creep life of the [111]-oriented specimens under condition of intermediate temperature and high stress. Under the condition of high temperature and low stress, the deformation mechanism was transformed to the dislocations slipping on the <110> {111} slip system and climbing. At this point, the anisotropy of the two oriented specimens was significantly weakened. Importantly, the creep behavior was compared with that of other SX superalloys, a specific reason for the anisotropy under the condition of intermediate temperature and high stress was proposed. That was [111]-oriented specimens exhibited significant orientation sensitive to forming microtwins, which induced the different creep anisotropy in this low-cost [111]-oriented Nickel-based single crystal alloy.

Herein, we used a multiscale simulation method to investigate the variation rule of the long-term feature of irradiation defects versus primary knock-on atom (PKA) energies (5 keV–100 keV) in dilute FeMnNi alloys. Simulation results presented a significant effect of PKA energy on irradiation microstructure, the density of large defect clusters increases significantly with increasing PKA energy, and the difference in the number density of visible defect clusters can reach several times to about one order of magnitude at the dose rate of 1 × 10−4dpa/s. The migration events of point defects (PD) decrease significantly with increasing PKA energy, suggesting that a higher PD flux at lower PKA energy could probably enhance the radiation-induced segregation (RIS) in alloys. Additionally, since the generation mechanism involves specific SIA-cluster sizes, the production ratio of <100>-type SIA loops could also influenced by PKA energies. Our simulation results align with experimental differences in the microstructure of light and heavy-ion irradiated alloys. This work clarified the mechanism of PKA energy effects in dilute alloys and provides a certain scientific basis for the comparison and emulation of different particle irradiation.

Nickel aluminum bronze alloy is designed and fabricated by cold metal transfer additive manufacturing (CMTAM) through feeding ERCuNiAl wires with the addition of trace nickel and titanium powders, aiming at improving the wear and corrosion performance. Experimental results show that the α-Cu + γ2(Cu9Al4) + κ(Fe,Ni)Al phases formed for the sample without nickel and titanium addition and 0.3 wt

Silicon carbide (SiC) and its composites are promising structural materials for advanced nuclear energy applications. Due to the lack of advanced nuclear energy devices, ion beam irradiation is widely used to emulate reactor neutron irradiation. At the same time, different types of ion beam irradiation could produce different primary knock-on atom (PKA) energy spectra. PKA energy determines cascade damage sizes and defect clustering distributions, which may influence the irradiated materials' long-term microstructural evolution and mechanical properties. This work used SRIM and Geant4 software to investigate the PKA characteristic produced by 1 MeV different noble gas ions and neutrons in the silicon carbide. The PKA energy spectra and weighted energy spectra of C and Si are calculated, respectively. The simulation results show that the PKA energy spectra calculated by the two kinds of software have obvious differences, but the weighted average PKA energies are close to each other. Simulation results verified that the weighted average PKA energy of Kr and Xe ion irradiation is close to that weighted average PKA energy spectrum for neutron irradiation of advanced reactors. The simulation results provide scientific references for understanding the difference in irradiation effects of different types of ions and also provide fundamental bases for the simulation of primary defect damage and long-term defect evolution in irradiated SiC.

FeCrNiMnAl high entropy alloy (HEA) coatings are prepared on the surface of 304 stainless steel (304 SS) by laser cladding. The effects of laser energy density on the residual stress, microstructure, nanoindentation behavior, the resistance to wear, corrosion and cavitation erosion (CE) of FeCrNiMnAl HEA coatings are studied. Experimental results shows that when the laser energy density decreases from 40 J/mm2 to 24 J/mm2, the phase composition of the FeCrNiMnAl HEA coatings remains unchanged with a single BCC solid solution and the elements are uniformly distributed without obvious segregation. The average grain size of the HEA coatings is refined from 73.5 to 41.7 mu m. When the laser energy density is 28 J/mm2 for S3 sample, the coating displays good forming quality and excellent comprehensive performance. The specific wear rate is only 8.2 % that of the 304 SS substrate. In addition, S3 exhibits the highest corrosion resistance as indicated by the highest corrosion potential (Ecorr) and the lowest corrosion current density (Icorr) in 3.5 wt% NaCl solution. After 10-h CE, the mean depth erosion rate (MDER) of S3 is the lowest (1.69 +/- 0.03 mu m/h), which is much lower than that of 304 SS (4.96 +/- 0.13 mu m/h), and the pure mechanical damage plays a dominant role in CE, followed by the synergistic damage effect. The excellent CE resistance of S3 is attributed to its excellent combination of corrosion resistance, mechanical properties and the self-recovery ability of passivation film.

Slurry erosion and cavitation erosion are the primary causes of failure in pass flow components, and preventive maintenance can effectively extend their service life. In this paper, 17-4PH stainless steel was prepared using laser metal deposition (LMD) technology and aged to investigate the effect of solution treatment on its microstructural transformations. The microhardness, electrochemical corrosion behavior, slurry erosion resistance, and cavitation erosion behavior of the as-built and solution-treated, aged samples were analyzed, with traditional forged specimens used as controls. During heat treatment, the microstructure fully transformed to martensite, and NbC precipitated as a second phase. Solution treatment led to microstructural coarsening, while aging significantly refined the microstructure and produced partial reverted austenite. Micro- hardness analysis showed that the microhardness of the solution-treated and aged samples increased to 465.5 +/- 8.6 HV 0.2 due to the combined effects of finer and more uniformly distributed NbC precipitation and grain refinement. The solution aging samples exhibited the lowest corrosion current density and the highest corrosion potential, influenced by the presence of reverted austenite. Slurry erosion results indicated that the corrosive environment accelerated mass loss due to the synergistic effects of mechanical abrasion from gravel and brine corrosion. Meanwhile, the solution aging samples demonstrated superior resistance to slurry erosion, with mass losses in clear water and brine slurry of only 69 % and 63 % of those observed in the traditional forged samples. In the cavitation erosion experiment, the solution aging sample showed the lowest cumulative mass loss (3.54 +/- 0.18 mg), and the work-hardening of the reverted austenite further enhanced the cavitation erosion resistance of the solution aging sample.

In the past decade, researchers have shown much interest in laser cladding metal matrix composites (MMCs) for its excellent hardness, wear resistance, and high-temperature performance. Nevertheless, the poor corrosion resistance typically exhibited by MMCs limits its further practical applications. To address the issue of reduced corrosion resistance in composite coatings, this study successfully fabricates an austenitic stainless steel (ASS) composite coating reinforced with in-situ synthesized (Ti,Nb)C particles using laser cladding techniques. The production of this complex carbide significantly influences the microstructural characteristics, microhardness, and anti-corrosion properties of the coating. By incorporating Ti, Nb, and Cr3C2 into austenitic stainless steel, the phase structure of the composite coating transforms into alpha-Fe, gamma- Fe, Cr23C6 and (Ti,Nb)C. Thermodynamic analysis and organizational observation indicate that TiC preferentially precipitates and it can serve as a nucleation site for NbC, thereby promoting the in-situ synthesis of complex carbide (Ti,Nb)C. The microhardness value of composite coating containing (Ti,Nb)C is more than twice that of ASS coating. Additionally, the corrosion tests reveal that the composite coating, enriched with elements that promote passivation film formation, exhibits enhanced corrosion resistance compared to the traditional ASS coating.

Cr-based coatings, as protective coatings of Zr-alloy fuel claddings, inevitably suffer from irradiation damage under actual nuclear operating conditions. Here, Cr/CrAlSiN multilayer coatings were deposited on Zircaloy substrates by magnetron sputtering, followed by the evaluation of irradiation resistance using Fe ions. The insertion of nanochannel-CrAlSiN layers refined the columns/grains in Cr layers and increased the interface density, contributing to the greatly enhanced irradiation tolerance and mechanical properties. A low average swelling rate of Cr layers was estimated to be similar to 0.015 %/dpa after the irradiation of Fe ions at 400 degrees C. Moreover, the coating became compacted with strengthening columnar boundaries after low-dose irradiation (similar to 0.8 dpa). Both nanoindentation and micropillar compression test showed the transformation of the deformation mechanism for the multilayer coating, as the irradiated samples relieved stress mainly depending on the plastic deformation under loading, while many cracks formed in the as-deposited ones. Furthermore, in 1200 degrees C steam, a significantly thinner and denser oxide scale formed on the irradiated Cr/CrAlSiN coating, indicative of improved oxidation resistance. The mechanism of radiation-decelerated oxidation was briefly discussed.

This study aims to explore the role of entropy in the radiation resistance of high-entropy pyrochlores by combining experimental results and theoretical calculations. A carefully designed compositional strategy was crucial for reducing the impact of element differences on the radiation resistance of pyrochlore. This approach enabled the acquisition of direct experimental results regarding the influence of entropy on radiation performance. The high-entropy pyrochlores were irradiated with high-energy (352.8 MeV) Fe ions to evaluate their radiation resistance. The results indicate that as entropy increases, the sensitivity of high-entropy pyrochlores to amorphization decreases. Bader charge analysis reveals that increasing entropy at the A-site significantly alters the bonding environment of A-site cations and reduces the covalency of the bond. Further calculations of cation antisite defect formation energy indicate that increasing entropy lowers the defect formation energy. These findings provide new insights for the potential application of high entropy materials in extreme environments.

The FeNiCoCr + xNbC (x = 0, 5, 10 and 15 wt%) composite coatings were fabricated using laser cladding (LC), their phase composition, microstructure, crystallography, corrosion and corrosive wear behavior in 3.5 wt% NaCl solution were investigated. In the FeNiCoCr + 5 and 10 wt% NbC coatings, the ceramic particles remained small, while at 15 wt%, NbC formed polygonal clusters due to continuous melting and coalescence. NbC significantly reduced the grain size by 56 %, 71 %, and 68 % compared to the NbC-free coating. The LC process induced random grain orientations, and NbC increased the proportion of low-angle grain boundaries (LAGBs) and geometrically necessary dislocations (GNDs), with the FeNiCoCr + 10 wt% NbC coating achieving LAGBs of 69 % and rho GND of 1.24 x 1015 m2. In electrochemical test, the FeNiCoCr + 10 wt% NbC coating demonstrated superior corrosion resistance, achieving an Icorr value of 1.45 x 10-2 mu A/cm2, which is attributed to the reasonable dispersion of NbC ceramic particles. Due to the combined effect of multiple strengthening mechanisms, the average microhardness of the composite coating with NbC reinforcement was significantly improved, and the average microhardness of the FeNiCoCr + 10 wt% NbC cladding layer was 440.8 HV0.2. During corrosive wear, the addition of NbC improved wear resistance, and FeNiCoCr + 10 wt% NbC exhibited a specific wear rate of only 1.89 x 10-5 mm3/Nm, with abrasive wear becoming the dominant mechanism.

Slurry erosion is a significant cause of overflow components failure. To enhance the slurry erosion resistance of 0Cr13Ni4Mo martensitic stainless steel used in overcurrent components, this paper employs laser fusion cladding technology to apply carbide-reinforced iron-based composite coatings on its surface. The study examines the microstructure, microhardness, and slurry erosion behavior of these coatings. The findings reveal a robust metallurgical bond between the fusion cladding layer and the substrate. The inclusion of Nb effectively prevents porosity and defects. Thermodynamic theory confirms the formation of NbC in the coating, which acts as a heterogeneous nucleation point during solidification, promoting grain refinement. Additionally, the Nb element facilitates the solid solution of Cr in the fusion cladding layer, enhancing solid solution strengthening. The microhardness of the 9Nb coating increased to 650 +/- 7.2 HV, largely due to the strengthening effect of the in situ synthesized NbC. NbC also fosters the development of small-angle grain boundaries and geometrically necessary dislocations, with the proportion of small-angle grain boundaries in the 9 Nb coating reaching 83.72 % and the rho GND reaching 3.054 x 1016 m-2 The combined effects of fine-grain strengthening, solid-solution strengthening, second-phase strengthening, and dislocation strengthening mechanisms result in improved microhardness and slurry erosion resistance. In a 200-hour slurry erosion test, the weight loss of the 9 Nb coating was minimized to 0.22 +/- 0.02 mg, representing a reduction of 148 % compared to the substrate and 41 % compared to the 0 Nb coating, demonstrating exceptional slurry erosion resistance. The addition of Nb increases the volume fraction of carbides in the coating, which enhances the "protrusion effect" of these carbides and thereby significantly reduces weight loss due to slurry erosion. Furthermore, while the substrate primarily exhibits ductile fracture under erosion, the two coatings display a damage mode that combines both brittleness and ductility.