Refractory high-entropy alloys (RHEA) exhibit outstanding strength at room temperature, but their practical applications are often limited due to inherent brittleness. Herein, we design and fabricate dual-phase NixMoVW RHEAs (x=0.25, 0.5, 0.75, 1.0) with tunable body-centered cubic (BCC)/face-centered cubic (FCC) phase fractions via laser melting deposition. Increasing the Ni content promotes the formation of the FCC phase, enhancing liquid backfilling during solidification and thereby mitigating cracking. The rapid solidification inherent to the additive manufacturing process effectively suppresses elemental segregation and promotes microstructural refinement. Compressive tests show that the Ni1.0MoVW alloy achieves an excellent strength-ductility balance, with a yield strength of 1635.5 MPa, an ultimate strength of 2294.7 MPa, and a plastic strain over 14.74% at room temperature. First-principles calculations attribute this superior mechanical performance to the intrinsic stability of both BCC and FCC phases and the strong interfacial bonding at their boundary. This study presents a viable strategy for developing high-performance, crack-resistant RHEAs through compositional tuning and additive manufacturing. The findings provide valuable insights into interfacial strengthening mechanisms in heterogeneous metallic systems.

Abstract Antimony (Sb) thin films are increasingly crucial in semiconductor technology due to their unique electronic and optical characteristics. Pulsed laser deposition (PLD) enhances their production by improving control over film microstructure and addressing uniformity challenges. The mechanical properties of Sb films, especially their behavior under mechanical stress and the associated twinning phenomena, are not well understood. This study employs nanoindentation and electron microscopy to investigate the mechanical properties and twinning behavior of Sb films deposited by PLD. Utilizing SEM and TEM, we analyze the structural changes these films undergo under stress, with a particular focus on deformation twinning, which critically affects their strength. Our findings confirm that deformation twinning, in particular, rhombohedral twinning plays a key role in determining the mechanical properties of Sb thin films. Nanoindentation reveals an activation volume of (2.75–3.85)b3 and a strain rate sensitivity of about 0.05 for Sb films. This research not only fills the existing knowledge gap about the mechanical behaviors of Sb thin films but also highlights the potential of PLD in producing high-quality films for high-performance applications, such as phase change materials, highlighting the transformative potential of PLD in tailoring the mechanical properties of thin films, crucial for next-generation electronic and optical devices.

In this work, a newly developed RAFM steel designed for future advanced reactors was subjected to systematic investigation to elucidate the effects and underlying mechanisms of Si addition (0-1.0 wt%) on the evolution of microstructure and mechanical properties after normalizing and tempering. The results indicate that as an austenite-restricting element, more Si additions effectively reduce grain sizes of prior austenite after normalizing, resulting in refined martensitic lath structures and higher dislocation density as well. The normalized specimens contain a small fraction of MX precipitates (only similar to 0.07%), with their sizes and volume fractions almost independent of Si content. After tempering, dislocation density is markedly reduced due to the occurrence of recovery, while abundant short rod-like M23C6 precipitates (fraction of similar to 3%) appear with gradually reduced sizes with more Si additions. With increased Si content from 0 wt% to 1.0 wt%, the ultimate tensile strength of both normalized and tempered specimens increases from 1105.3 MPa and 801.2 MPa to 1220.1 MPa and 891.3 MPa, respectively, while the uniform elongation slightly decreases by similar to 0.7% and similar to 1.1%, respectively. Theoretical calculations suggest that the added Si has a solid-solution strengthening effect of similar to 46.3 MPa/wt% to yield strength (YS). The dominant strengthening contributions to YS of the normalized specimens are determined to be solid-solution and dislocation strengthening. For the tempered specimens, all classical strengthening factors are able to contribute notably to their YS, with dislocation strengthening remaining the predominant one.

To simulate the actual operating temperature environment of cladding materials in reactors, the effects of aging time (0-5000 h) at 400 degrees C on the mechanical properties and microstructure of Fe-13Cr-3.5Al-2.0Mo-1.5Nb alloy were investigated. During the initial aging stage (500 h), the alloy exhibited a slight decrease in hardness, ultimate tensile strength and yield strength, which was attributed to the reduction in dislocation density and insufficient precipitation of secondary phases. When the aging time reached 2000 h, the alloy showed significant improvement in hardness, ultimate tensile strength and yield strength and then kept stability. The total elongation consistently maintained at a relatively high level, with the fracture mode predominantly exhibiting ductile fracture. Through quantitative calculations, it was determined that the cooperative strengthening contribution from both Cr-enriched alpha' phases and NbMo-rich nanoclusters was the primary mechanism for enhancing the alloy's strength. The alpha' phase formed through spinodal decomposition, exhibiting an initial increase followed by stabilization in both equivalent radius and number density with prolonged aging time. The NbMo-rich clusters gradually transformed from spherical to rod-like or elongated morphologies, accompanied by size coarsening but a reduction in number density. Additionally, the segregation of Nb and Mo at grain boundary and Laves phase interfaces induced the formation of precipitate-free zone (PFZ), which subsequently influenced the alloy's mechanical properties.

This study demonstrated that the optimized AlTiFeCrMoSi0.2 high-entropy alloy (HEA) coating can significantly improve the corrosion resistance of the T91 steel in high-temperature liquid lead-bismuth eutectic (LBE) environment. Compared with the commercial T91 steel, the thickness of oxide scale on the HEA-coated steel after 1000 h of corrosion in oxygen-saturated and low-oxygen LBE environment was reduced by factors of 5.7 and 13.11, respectively. Under saturated oxygen conditions, the oxide scale on T91 steel was dominated by Fe3O4 and FeCr2O4 spinel phases. In contrast, the coating system developed additional protective layers of TiO2 and continuous Al2O3.Under low oxygen environments, the oxide structure on T91 steel transitioned to a mixture of Cr2O3 and FeCr2O4, while the coating consistently formed TiO2 and continuous Al2O3 layers. The oxide layer of the coating effectively prevented the penetration of lead and bismuth, thereby suppressing the occurrence of localized dissolution corrosion. Theoretical calculations confirmed the critical roles of TiO2 and Al2O3 in enhancing the coating's resistance to liquid LBE corrosion. This study provides new insights into the development of LBE-corrosion-resistant approaches.

This study investigates the corrosion behavior of 9Cr1Si ferritic/martensitic steel after pre-irradiation with 2.4 MeV Fe2 + ions at 550 degrees C and subsequent exposure to stagnant lead-bismuth eutectic (LBE) at 550 degrees C under low (10-7 wt% O2) and high (10-3 wt% O2) oxygen conditions. Pre-irradiation accelerates corrosion, leading to a thicker duplex oxide scale (outer Fe3O4 and inner Fe3-xCrxO4) and eliminating Cr-rich precipitate chains through M23C6 amorphization and subsequent Cr redistribution. Under oxygen-saturated LBE, defect-assisted oxygen transport and Si segregation promote formation of Si-rich oxides that impede outer layer growth; under oxygen-depleted LBE, pre-irradiation enhances intergranular oxidation and microcracking. These results demonstrate the distinct roles of pre-irradiation generated defects in altering diffusion pathways and oxide stability under variable oxygen potentials.

Molybdenum (Mo) alloys are promising cladding materials for advanced nuclear reactors due to their high melting point, excellent thermal conductivity, low expansion coefficient, and good compatibility with liquid metals. However, their practical use in nuclear energy systems is limited by several drawbacks, including room-temperature embrittlement, irradiation embrittlement, and poor oxidation resistance. To address these challenges, the strategy of achieving intragranular dispersion of oxide nanoparticles while enhancing oxide/matrix interfacial bonding has been employed. This review summarizes the current progress on oxide dispersion-strengthened (ODS) Mo alloys in terms of fabrication technologies, microstructure characteristics, mechanical properties, irradiation resistance, and oxidation behavior. Although the development of ODS-Mo alloys for nuclear applications has not been fully explored, the current research findings provide a good basis for understanding the relationship between fabrication technologies, microstructure, and performance. Further efforts should focus on elucidating degradation mechanisms and characterization of material properties under conditions more closely simulating actual reactor environments.

FeCrAl alloys pre-corroded (PC) in PWR water with 5 or 200 ppb dissolved oxygen for 2000 h were oxidized in steam at 1200 degrees C. PC produced a duplex scale (inner alpha-Al2O3, outer FeAl2O4), unlike the single alumina on the fresh alloy. Oxidation resistance improved after 5 ppb PC but degraded after 200 ppb PC. Multiscale analyses show that protection is governed by crystallographic compatibility at the alpha-Al2O3/FeAl2O4 interface, which controls the continuity and adhesion of the duplex scale. Poor compatibility triggers early interfacial microvoid nucleation and crack-like cavity growth, creating fast oxygen pathways and accelerating internal oxidation. These results demonstrate that the pre-corrosion environment decisively governs the accident-tolerant performance of long-served FeCrAl cladding.

The development of 700 degrees C advanced ultra-supercritical power plants has created a critical demand for structural materials that bridge the performance gap between conventional stainless steels and costly superalloys. The purpose of this investigation was to evaluate the correlation among precipitate evolution, deformation behavior, and creep damage at 700 degrees C of a 5 wt% Al alumina-forming austenitic (AFA) steel. Creep tests conducted under stresses ranging from 120 to 250 MPa yielded an apparent stress exponent of 5.77. The creep deformation is consistent with a dislocation climb-controlled mechanism, a process significantly influenced by interactions between precipitates and dislocation. However, the alloy exhibits a conspicuous microstructural trade-off at this elevated aluminum level. The NiAl phase undergoes a progressively coarsening during creep, while the Fe2(Nb, Mo)-type Laves phase remains relatively stable. The formation driving force of the sigma phase is calculated to increase as the volume fraction of the NiAl phase increases. Moreover, the precipitation of these brittle sigma phases contributes to a reduction in matrix stability. The ensuing interfacial incompatibility has been demonstrated to promote local stress concentration and damage accumulation, the finding is consistent with the measured creep damage tolerance factor (2 = 9.15). Consequently, the ultimate failure can be more reasonably interpreted as a damage process associated with microstructural degradation and cavity coalescence. The aforementioned results suggest that the addition of 5% aluminum (Al) does not effectively balance antioxidant properties and structural stability during the creep. However, systematic compositional validation remains imperative in the future.

Bulk W-1 wt%Ta-0.5 wt%ZrC (W-1Ta-ZrC) and W-3 wt%Ta-0.5 wt%ZrC (W-3Ta-ZrC) alloys were fabricated and subsequently irradiated with 500 keV He2+ ions at 400 degrees C. Microstructural analyses indicated that the defect clusters were predominantly nano-sized dislocation loops and He bubbles. The average size of He bubbles in W-1Ta-ZrC (1.2 +/- 0.1 nm) is slightly larger than that in W-3Ta-ZrC (1.1 +/- 0.1 nm), along with an approximately 6.9% reduction in number density. Conversely, the number density of dislocation loops in W-1Ta-ZrC was about 9.1% higher than that in W-3Ta-ZrC. Irradiation-induced hardening was evaluated using the nanoindentation test and dispersed barrier hardening (DBH) model. The DBH hardness increments agree well with those obtained from nanoindentation measurements. The results demonstrated a significant increase in the hardening rate of W-1Ta-ZrC, reaching 30.7%, which is nearly 7.7% higher than that of W-3Ta-ZrC. This work systematically investigated the influence of Ta content in the evolution of He-induced defects, irradiation swelling, and hardening in Ta-containing W alloy, providing valuable insights for the development of advanced plasma-facing materials.

ABSTRACT Chemically homogeneous intermetallic nanoprecipitates (INPs), despite their high strength, are intrinsically hard and brittle and often suffer from glide‐plane softening, which can strengthen alloys but severely degrade uniform elongation. This strength–ductility trade‐off is further exacerbated at cryogenic temperatures by the inherent brittleness of bcc‐based phases in precipitate‐strengthened fcc/bcc duplex alloys. Here we propose a strategy that overcomes these limitations through the design of structurally complex INPs, i.e., the ductile B2 multicomponent INPs (MINPs) assembled with dispersive nanocores and a chemical‐heterogeneity shell, in duplex fcc/bcc Fe 58 Ni 16 Cr 16 Al 10 (at%) medium‐entropy alloys (Fe‐MEAs). Within the bcc constituent, these coherent core–shell B2 MINPs serve the dual role of dislocation sources and obstacles, analogous to the ordinary incoherent B2 MINPs that trigger twinning‐induced plasticity in the fcc constituent, yet they are substantially more effective in load transfer for high yield strength and in self‐hardening for large uniform elongation. Critically, the core–shell nanostructure suppresses the glide‐plane softening typical of conventional INPs and promotes the activation of unusual ⟨111⟩ dislocation multiplication and interactions under cryogenic conditions. This work demonstrates a structural complexification strategy for designing self‐hardening MINPs, opening a pathway to ductile, high‐strength materials for advanced cryogenic structural applications.

In this work, nano-sized TiN particle-reinforced FeCrAl alloys were prepared by mechanical alloying (MA) and spark plasma sintering (SPS). The effect of nano-sized TiN content on the microstructure and mechanical properties was systematically investigated by XRD, EBSD and TEM. The results indicate that TiN nanoparticles are uniformly dispersed within the matrix, achieving significant grain refinement through the Zener pinning effect, which synergistically enhances the mechanical properties through dispersion strengthening, dislocation strengthening and grain boundary strengthening. The FeCrAl-5 wt.

This study investigates the regulatory mechanisms of stress-relief by annealing heat treatment on the microstructure and fracture behavior of Ni 2.1 CrAlFe high-entropy alloy fabricated via laser metal deposition (LMD). The microstructural changes induced by heat treatment was examined through characterization techniques including OM, SEM/EDS, XRD, and EBSD, as well as mechanical testing and fracture analysis. The study reveals that heat treatment disrupts the non-equilibrium inherited structural chain dominated by columnar grains, strong texture, and residual stress formed during the LMD process. This leads to grain equiaxialization, randomization of crystallographic orientation, and significant stress relief. XRD and EDS results indicate a structural evolution from metastable A2 phase to an ordered B2 structure, accompanied by a uniform distribution of solute elements. Mechanically, the material exhibits a moderate decrease in yield strength but a notable increase in ductility. The dominant strengthening mechanism shifts from dislocation-based to synergy of grain boundary and solid-solution strengthening. Fractography shows a transition from brittle cleavage fracture to ductile dimple coalescence. Based on these findings, this study proposes a non-equilibrium structural regulation mechanism for additively manufactured high entropy alloys, which explains how heat treatment reconstructs the LMD-induced microstructure through diffusion, ordering, and recovery processes. These findings provide theoretical support for residual stress control and fracture toughness optimization in additively manufactured high entropy alloys.

Ultrasonic-assisted soldering technology offers an efficient and highly promising solution for achieving high-reliability interconnections in space applications. Through analysis, investigated the impacts of ultrasonic soldering time (300W, 0s, 4s, 8s, 12s) on the microstructural modification, grain orientation, and mechanical properties of Cu/Sn58Bi-0.3Co/Cu solder joints were studied. The results demonstrated that the introduction of ultrasonic energy significantly optimizes the microstructure of the composite joints. It effectively eliminated the agglomeration of intermetallic compounds (IMCs) in the matrix and promoted the uniform distribution of elements. As ultrasonic treatment duration increased, the IMC layer thickness at the interface showed a clear increasing trend. Notably, the IMC thickness at the cold end consistently exceeds that at the heat end, which may be related to the temperature gradient induced by ultrasonic cavitation. Electron backscatter diffraction analysis revealed that ultrasonic processing markedly refined the grain size of the solder joints. The grain size of (Cu, Co)6Sn5 decreased from 0.504 μm to 0.339 μm. The Sn and Bi phases transition from an initially random orientation to a preferred crystallographic orientation, while the (Cu, Co)6Sn5 phase retains its random orientation. Shear tests showed that the ultrasonically treated welds exhibited higher strength, with a maximum value of 61.24 MPa, representing a 24% increase compared to the untreated solders. Additionally, fracture consistently occurs within the matrix, displaying a fracture with ductility morphology, indicating that ultrasonic treatment enhanced strength. The findings of this study deepen the understanding of ultrasonic-assisted soldering mechanisms but also offered fundamental theoretical for optimizing composite soldering processes.

This study explores the synergistic effects of laser metal deposition (LMD) and CeO2 nanoparticles in fabricating corrosion-resistant 316L stainless steel (SS) coatings for severe oil and gas operating conditions. The results show that an LMD-fabricated 316L SS coating containing 0.20 wt% CeO2 possesses the best electrochemical performance, involving a decrease in passivation current density (ipass), an increase in pitting potential (Ep), an increase in charge transfer resistance (Rct), a double-logarithmic slope close to −1 and a decrease in point defect concentrations (ND and NA), suggesting further inhibition of electrochemical reactions and enhanced corrosion resistance of passivation films. In addition, XPS analysis reveals that the LMD-processed sample with 0.20 wt% CeO2 obtains the highest fraction of Cr2O3 associated with a lower defect density, higher thermodynamic and chemical stability instead of the hydrated/soluble component dominated by Cr(OH)3, thereby enhancing corrosion resistance of passivation films under harsh oil and gas environments, particularly in the presence of high Cl− concentrations. Our focus on developing coatings for demanding oil and gas environments, characterized by concentrated chlorides, provides a crucial practical relevance. The observed improvements in pitting potential and charge transfer resistance directly address critical failure mechanisms in this industry.

The long-term corrosion behavior of FeCrAl alloys with varying Cr contents (7, 10, and 13 wt%) was investigated in oxygenated pressurized water reactor (PWR) primary water at 360 degrees C and 20.0 MPa. Despite forming similar duplex oxide scales, the alloys exhibited distinct nucleation and growth modes in the outer oxide layer: the lean-Cr alloy (7 wt% Cr) developed a single-oriented Fe2O3 outer layer through single-site-triggered epitaxial growth, while higher-Cr alloys formed polycrystalline oxides via multi-site nucleation and random growth. This transition, linked to differences in early-stage Fe ion supersaturation in the solution, resulted in significantly enhanced corrosion resistance for the 7-Cr alloy, contradicting the conventional view that higher Cr content improves corrosion resistance. Moreover, the Fe2O3 outer layer was shown to play a significant protective role in suppressing further inner oxidation. These findings offer a new mechanistic understanding of oxide evolution and present a novel strategy for designing corrosion-resistant alloys.

For advanced liquid metal-cooled nuclear reactors, one of the primary materials challenges is the degradation of structural component performance caused by high-energy neutrons. This degradation is substantially exacerbated by helium generation via nuclear transmutation reactions. While silicon addition to martensitic steels represents an established strategy for mitigating liquid metal corrosion, its multifaceted influence on the fundamental mechanisms of irradiation damage-encompassing defect evolution, microstructural stability, and helium accumulation-necessitates systematic investigation to ensure long-term reliability and safety. In light of these factors, four series of Fe9Cr1.5 W martensitic steels containing silicon at 0, 0.4, 0.7, and 1.0 wt.% was designed, and were performed dual-beam irradiation experiments with helium injection concentrations of 0,5 and 100 appm/dpa at 550 degrees C. After irradiation, transmission electron microscopy was employed to characterize the dislocation loops and cavities in the irradiated materials, while nanoindentation was used to evaluate the irradiation-induced hardening behavior. Under various dual beam irradiation, the size of irradiation-induced dislocation loops increases with rising silicon content, while the numerical density exhibits the opposite trend. Additionally, at high helium concentrations, silicon addition significantly reduced irradiation swelling. Specimens containing 0.4 wt.% silicon exhibited the lowest average cavity size and number density. As silicon content further increased, changes in irradiation cavities and number density tended toward saturation. Simultaneously, specimens with 0.4 wt.% silicon demonstrated superior resistance to irradiation hardening under all irradiation conditions.

Multicomponent alloys possess excellent comprehensive properties, but the high-strength ones still suffer from insufficient strain hardening ability and unsatisfactory ductility. Synergistical control of grain and precipitates can realize both high yield strength and strong strain hardening, but the conventional multi-step thermomechanical processing method is overly complex to operate. In this work, a facile route of spark plasma sintering (SPS) and subsequent annealing is utilized in Co34Cr32Ni27Al3.5Ti3.5 multicomponent alloy to co-construct fine grains and matrix/boundary precipitates, achieving high yield strength (similar to 1108 MPa), high ultimate tensile strength (similar to 1575 MPa), and good uniform elongation (similar to 15%). High-density coherent L1(2) nanoprecipitates are uniformly distributed within the FCC matrix with an average grain size of similar to 4.8 mu m. The L1(2) phase, as well as two types of sigma phases, are located at grain boundaries (GBs). The high yield strength mainly comes from the contributions of precipitation strengthening and fine-grain strengthening. The remarkable strain-hardening capacity and uniform deformation ability are attributed to the synergistic effects of enhanced dislocation multiplication via intragranular L1(2) precipitates and dislocation accommodation through fine grains and precipitates at GBs. The present study provides a compelling approach for optimizing both grain and precipitates and enhancing the mechanical properties of high-strength alloys.

The decomposition of amorphous SiCxOy phase is a critical step and technical bottleneck for fabricating highly crystalline SiC fibers. In this work, a one-step high-temperature sintering strategy was proposed to directly convert low-oxygen boron-doped amorphous Si-Al-B-C-O fibers into highly crystalline SiC fibers. Boron is incorporated into the fibers in the forms of BxCy, BCxOy, and B(OSi)3 phases, and synergizes with aluminum to promote sintering densification, inhibit SiC microcrystal growth, and enhance the graphitization degree of free carbon. The Si-Al-B-C-O fibers exhibit a tensile strength and modulus of 3.5 GPa and 256 GPa; the resultant SiC fibers achieve a tensile strength of 2.4 GPa and a modulus of 337 GPa, with a strength retention of 70% (10 percentage points higher than undoped SiC fibers). For electromagnetic wave absorption, the boron-doped SiC fibers exhibit a minimum reflection loss of -47.73 dB at 3.6 GHz with a thickness of 4.6 mm, and a maximum effective absorption bandwidth (EAB) of 2.95 GHz. The enhanced absorption performance originates from the elevated graphitization degree of free carbon and multiple heterogeneous interfaces boost dielectric polarization loss and conductive loss. This work provides a feasible technical route for preparing structural-functional integrated SiC fibers, and thus holds significant application potential in extreme environments.

Zintl-phase materials exhibit great potential in thermoelectric applications owing to their high electrical conductivity and low thermal conductivity induced by unique structural and electronic characteristics. In this work, we investigate the electrical and thermal transport properties and evaluate the thermoelectric performance of Zintl-phase tellurides XYTe2 (X = Na, K, Rb, Cs; Y = Al, Ga, In) through systematic analysis based on density functional theory, the Boltzmann transport equation, and unified transport theory. Results show that these tellurides can exhibit ultralow lattice thermal conductivity kappa L; in particular, NaInTe2 shows a value as low as 0.33 W/mK, which is mainly attributed to strong anharmonicity introduced by bonding heterogeneity and the rattling vibrations of the weakly bonded X-site cations. The multiband degeneracy and flat band characteristic near the valence band maximum (P-* M, Z-* P) render into a high power factor of 1.5-2.3 mW/mK2 (p type). By optimizing carrier concentration, exceptional thermoelectric performance with ZT values up to 4.0 (p type) is achieved at 900 K. In contrast, NaGaTe2 shows inferior thermoelectric performance due to the narrow band gap induced bipolar effect that reduces the Seebeck coefficient significantly. In addition, by considering wavelike tunneling effects and higher-order phonon scattering, the tellurides XYTe2 maintain favorable thermoelectric performance with ZT values around 3.3. This work showcases the importance of bond heterogeneity and rattling mode induced ultralow lattice thermal conductivity for enhancing thermoelectric performance in Zintl-phase tellurides.