Interstitial filling with non-metallic small atoms (SAs) provides a crucial pathway for tuning the structure and properties of high-entropy films. Owing to their small atomic size, SAs preferentially occupy interstitial sites and, through their distinct chemical interactions with constituent metallic elements, induce changes in local chemical order (LCO). With increasing SAs content, high-entropy films exhibit a progressive transition from disordered interstitial solid solutions to locally ordered states, and eventually to ordered crystalline or amorphous structures, accompanied by pronounced property variations. Accordingly, this review focuses on high-entropy films and systematically summarizes the effects of SAs filling on crystal structure, LCO, and mechanical, magnetic, and electrical properties. A percolation-theory framework is introduced, in which different LCO types are treated as percolating units with characteristic properties, thereby establishing intrinsic correlations between LCO content and macroscopic property evolution. On this basis, the commonalities and distinctions among different SAs in regulating material properties are summarized and compared. Finally, an outlook on future research directions is provided.

Heat treatment has been widely shown to substantially influence the microstructure of selective laser melted Al alloys and composites, enabling precise tuning of their mechanical properties. While extensive research has addressed the optimization of selective laser melting (SLM) process parameters, alloy composition, reinforcement content, and strengthening mechanisms, comparatively limited attention has been paid to the evolution of microstructure and mechanical properties of selective laser melted Al alloys and their composites during heat treatment. A critical knowledge gap remains regarding the mechanisms by which secondary phase particles govern microstructural evolution and mechanical property modifications under thermal processing. To address this gap, an Al12Si alloy modified with an AlCrCuFeNi high-entropy alloy (HEA) was successfully fabricated via SLM. Subsequent solution treatment enabled synergistic control over the microstructure and mechanical properties of the Al12Si-HEA alloy. Comprehensive microstructural characterization and mechanical testing were conducted to systematically investigate the role of HEA particles in influencing microstructural evolution and mechanical behavior during solution treatment. The results showed that the as-built Al12Si alloy exhibited a microstructure composed of primary α-Al and continuous cellular eutectic Si. The addition of HEA particles significantly modified the microstructure, promoting the formation of Si + α-Al(Fe, Cr)Si phases instead of the continuous eutectic Si observed in the unmodified Al12Si alloy. Solution treatment dissolved the cellular eutectic structure, leading to fragmentation and spheroidization of Si into granular phases diffusely distributed within the matrix. With increasing solution treatment time, these Si phases gradually coarsened due to Ostwald ripening, resulting in larger average sizes and reduced number density. Notably, the α-Al(Fe, Cr)Si phases inhibited Si atom diffusion within the matrix, substantially slowing the coarsening rate of the granular Si phases. Under all solution treatment conditions, the Al12Si-HEA alloy exhibited superior performance compared with the Al12Si alloy. This enhancement is attributed to the formation of dual-sized in situ reinforced phases after solution treatment, comprising finer micron-sized Si particles and nano-sized α-Al(Fe, Cr)Si phases. This unique microstructure enabled the Al12Si-HEA alloy to achieve both high str-ength (ultimate tensile strength > 300 MPa) and appreciable plasticity (~14%).

Low-expansion alloys are essential structural-functional materials for advanced technologies requiring stringent dimensional stability. They are key components in precision metrology, electronic and microwave devices, cryogenic systems, and ultraprecision manufacturing equipments, where thermal deformation must be strictly controlled. However, conventional Fe-Ni Invar alloys possess insufficient mechanical strength despite their exceptionally low coefficient of thermal expansion, which limits their applicability in load-bearing environments. Design concept of high-entropy alloys offer a promising pathway to overcome this limitation through multiprinciple element alloy design and the associated synergistic effects. In this work, a novel low-expansion alloy, Al₁Cr₁(Fe₆₅Co₄Ni₃₁)₉₈, was developed by introducing Al and Cr into the multicomponent system and applying thermomechanical processing to tailor and refine its microstructure. This design strategy aims to achieve the synergistic optimization of thermal expansion behavior and mechanical performance. Additionally, in situ XRD during heating was employed to elucidate the underlying mechanism and monitor phase evolution. After thermomechanical processing, the alloy exhibited pronounced grain refinement and an increased martensite volume fraction of 8.91%. The microstructure further contained abundant deformation twins and a high density of lattice defects, which collectively enhanced the mechanical strength and thermal stability. Within the temperature range of -60 ^oC to 100 ^oC, the coefficient of thermal expansion decreased to 1.10\times10^-6-2.04\times10^-6oC^-1. In addition to the Invar effect, this ultralow expansion behavior is attributed to the partial compensation of lattice thermal vibrations by the volume contraction associated with martensite reduction during heating, together with the suppression of anharmonic lattice vibrations induced by interfaces and defects. Meanwhile, the refined microstructure delivered an excellent combination of strength and ductility, achieving a yield strength of 324 MPa, an ultimate tensile strength of 452 MPa, and a fracture elongation greater than 20%. Compared with conventional Invar alloys, the designed alloy exhibited a higher specific strength while maintaining a low coefficient of thermal expansion. These results demonstrate that the synergistic optimization of compositional design and thermomechanical processing enables the exceptional integration of low thermal expansion with robust mechanical properties, offering valuable guidance for developing dimensionally stable structural alloys.

There has been a relentless pursuit for high thrust-to-weight ratio development in the aeroengine field. To tackle this, the study successfully achieved high-quality joining of GH4065A/IN718 dissimilar superalloys via inertia friction welding that demonstrated excellent interfacial bonding and no significant welding defects. A systematic investigation was performed on the influence of post-weld heat treatment on the microstructural evolution at the joint interface. The results indicated that post-weld heat treatment increased the width of the weld nugget and thermomechanically affected zones via dynamic recrystallization and grain boundary migration, which confirmed its regulatory effect on the microstructure. Heat treatment promoted uniform precipitation of γ′ and γ′′ phases on the GH4065A and IN718 sides, respectively, thereby increasing the volume fraction and average size of the γ′/γ′′ strengthening phases. After heat treatment, minor grain coarsening was observed in all the joint regions, along with a considerable reduction in local misorientation in the thermomechanically affected zone, indicating effective alleviation of stress concentration. Moreover, fine γ′/γ′′ phases precipitated in the heat-treated weld nugget zone, and dislocations that cut through these strengthening phases resulted in the formation of stacking faults, which further impeded dislocation motion and enhanced deformation resistance.

Aero engines serve as a critical indicator of national comprehensive strength and technological advancement. However, their performance enhancement poses considerable challenges to the manufacturing technologies of hot-end components. Hot-end structures undergo inertial friction welding, which effectively avoids the defects associated with fusion welding and has been widely adopted for high-quality joining of these structures. This study addresses the inherent process limitations of inertial friction welded joints, including strengthening phase dissolution within the welding zone (WZ), along with axial and radial microstructural heterogeneity, and proposes a customized post-weld heat treatment (PWHT) strategy for inertial friction welded joints of FGH96 superalloys. A systematic investigation was conducted on the effects of solution aging and double aging on microstructural evolution and mechanical properties. The results indicated that increasing the solution temperature leads to grain coarsening and enhanced recrystallization, accompanied by pronounced precipitation and growth of the γ′ strengthening phase, a more uniform carbide distribution, and intensified grain boundary serration within the WZ compared to joints at low solution temperature. At a solution temperature of 1140 ^oC, abnormal grain growth occurred, along with coarsening and inhomogeneous distribution of the γ′ strengthening phase. After solution aging, the impact toughness of the joints improved with increasing solution temperature, whereas the tensile strength initially increased and then decreased. At the solution temperature of 1080 ^oC, the grain size and γ′ strengthening phase were moderate and uniformly distributed, the degree of recrystallization and grain boundary serration were relatively high, carbides were uniformly dispersed, and microstructural inhomogeneity was notably improved. Under this condition, the ultimate tensile strengths of the joints at room temperature and 750 °C were 1455 and 1042 MPa, respectively; and the impact toughness reached 41 J/cm², demonstrating an optimal strength-toughness synergy. Double aging promoted the uniform precipitation of tertiary γ′ strengthening phase in the WZ, resulting in tensile strengths of 1574 and 1279 MPa at room temperature and 750 ^oC, respectively, approaching base metal levels. Meanwhile, the hardness was considerably enhanced beyond the base metal, although the impact toughness was slightly reduced compared with the as-welded joints.

NiCoCrAlY coatings offer good resistance to high-temperature oxidation and corrosion, making them an effective protective layer for gas turbine blades. However, in marine environments, these coatings are susceptible to hot corrosion damage, considerably affecting service lifespan and safety. With the development of modern gas turbines with high efficiency and power, the service temperatures of their blades have increased. An in-depth understanding of the hot corrosion mechanisms of NiCoCrAlY coatings above 900 ^oC is crucial for developing advanced gas turbine blade materials suitable for marine applications. This study investigates the hot corrosion kinetics using conventional gravimetric analysis while considering the quality effect of molten salt volatilization. XRD, SEM, and EDS were used to analyze the surface and interface microstructures, as well as the compositional characteristics of the NiCoCrAlY coating on the DZ411 alloy. These analyses were performed after exposure at 950 ^oC under a Na₂SO₄ salt film and a mixed salt film comprising Na₂SO₄ and NaCl. Results demonstrated that after modifying conventional hot corrosion mass-loss kinetics to consider molten salt volatilization, the hot corrosion mass change becomes a mass gain. The mass gain rate was higher in mixed salt environments than in pure sulfate environments. The hot corrosion mass gain of the alloy is attributed to cyclic oxidation-sulfidation reactions in the coating. Cross-sectional analysis of the corrosion product layer revealed a similar structure under both salt conditions: an outer layer of Al₂O₃, a middle layer of porous oxides dominated by Al₂O₃ and Cr₂O₃, and an inner interdiffusion zone. In addition, Al₂S₃ and Cr₂S₃ precipitates were present at the coating-substrate interface. Furthermore, the presence of chloride salt in the mixed salt environment facilitated chlorination reactions, promoting the diffusion of sulfur and oxygen, and accelerating the degradation of the coating compared with the pure sulfate condition.

Mo and its alloys exhibit considerable potential for aerospace high-temperature components, electronic thermal management systems, and high-temperature power-generation structures due to their high melting point, excellent elevated-temperature mechanical strength, and good creep resistance. However, their application is severely limited by rapid oxidation at temperatures above 700 ^oC, where the formation and volatilization of MoO₃ lead to accelerated material loss and structural degradation. This oxidation susceptibility can ultimately result in disintegration and catastrophic failure under extreme service conditions. The application of silicide-based coatings is an effective strategy to mitigate high-temperature oxidation by forming a protective barrier that isolates the substrate from the environment. Nevertheless, monolithic silicide coatings often suffer from premature failure caused by thermal expansion mismatch with the substrate and inward silicon diffusion during prolonged high-temperature exposure. In this context, silicide-boride composite coatings have emerged as a promising alternative for further improving oxidation resistance. Despite their potential, the mechanisms governing gradient microstructure formation and the origins of performance variability in such composite coatings remain insufficiently understood. In this study, silicide and silicide-boride composite coatings were fabricated on pure Mo substrates using halide-activated pack cementation, and their microstructural evolution and high-temperature oxidation behavior were systematically investigated. The results demonstrate that B element incorporation promotes the formation of a silicide-boride composite coating with a five-layer graded structure: MoSi₂/(MoSi₂ + MoB)/Mo₅Si₃/MoB/Mo₂B. Notably, B facilitates the preferential formation of an initial MoB interlayer at the coating-substrate interface. This interlayer not only inhibits the directional diffusion of Si but also induces a displacement reaction between Si and MoB to form MoSi₂, thereby suppressing the (001) preferred growth orientation of MoSi₂. In addition, volume contraction associated with MoB formation within the MoSi₂ + MoB mixed layer generates pores and a roughened interface, which act as high-density nucleation sites and significantly refine the surface MoSi₂ grain structure. The refined grain structure accelerated the formation of a dense and continuous SiO₂ protective film, thereby effectively inhibiting O diffusion. After 30 h of oxidation at 1200 ^oC, the silicide-boride composite coating exhibited an oxidation mass gain of 1.28 mg/cm² and an oxidation rate constant of 0.29 mg/(cm²·h), representing a 53% reduction relative to the silicide coating. Moreover, the MoB interlayer suppressed inward Si diffusion into the substrate, thereby enhancing long-term stability under high-temperature oxidative conditions.

The cyclic damage behavior of TC4 alloy, which is widely utilized in aerospace and other fields, is critical to the structural integrity of its components. The aim of this study is to elucidate the underlying microstructural damage mechanisms, from the aspect of microstructural evolution, slip activity, and dislocation configurations, during cyclic loading through advanced characterization techniques including EBSD and TEM. The results indicate an initial rapid hardening stage, during which strain is highly localized in microtextured regions due to deformation incompatibility with the surrounding grains. The material subsequently reaches a quasi-steady state, which is marked by accumulated plasticity. Influenced by crystallographic texture and loading direction, the pyramidal \left\{\mathrm{10}\overline{\mathrm{1}}\mathrm{1}\right\}<c + a> slip system exhibits the highest Schmid factor and is preferentially activated, dominating the deformation process and promoting a gradual grain reorientation toward the <\mathrm{11}\overline{\mathrm{2}}\mathrm{0}> direction. TEM analysis indicates that dislocations multiply and align parallel to α/β phase interfaces during cyclic deformation. These interfaces function as both dislocation sources and barriers, thereby enhancing the material's fatigue life. The synergistic coupling between dislocation activity at α/β interfaces and pronounced strain localization within microtextured regions is identified as the dominant mechanism governing cyclic deformation damage in TC4 alloy.

High-performance materials are in strong demand in the electronics and automotive industries. Cu-Ni-Si alloys are widely used owing to their excellent combination of strength and electrical conductivity, whereas 1010 steel provides superior formability, high elastic modulus, and cost-effectiveness. Integrating these materials into laminated bimetallic composites represents a promising strategy for achieving structural-functional integration, thereby overcoming the trade-offs inherent in single-component metals. However, fabrication of such composites remains challenging, primarily due to poor wettability and limited mutual solubility between Cu and Fe, which often result in weak interfacial bonding and coarse as-cast microstructures. Therefore, the development of effective fabrication methods and appropriate post-processing routes to tailor microstructure and optimize mechanical properties is essential for industrial application. In this study, Cu-Ni-Si/1010 steel laminated bimetallic composite was successfully fabricated via continuous solid-liquid bonding method. To investigate the effects of annealing and cold rolling followed by annealing on microstructural evolution and mechanical behavior, the composites were subjected to four conditions: as-cast (sample S1), direct annealing at 450 °C (sample S2), 70% cold rolling followed by annealing at 450 °C (sample S3), and 70% cold rolling (sample S4). Microstructural and mechanical characterization was performed using OM, SEM, TEM, and tensile testing to elucidate the relationships among processing parameters, interfacial characteristics, and strengthening mechanisms. The Cu-Ni-Si layer in sample S1 exhibits coarse columnar grains, with a minor β-Ni₃Si phase located at α-Cu grain boundaries. Direct annealing promotes the formation of nanoscale δ-Ni₂Si precipitates within the α-Cu matrix, contributing to strengthening. In contrast, the combined cold rolling and annealing treatment induces more pronounced microstructural evolution: severe plastic deformation increases dislocation density and refines the grain structure into the fibrous morphology due to incomplete recrystallization. No brittle intermetallic compounds are observed at the interface under any condition. Samples S3 and S4 exhibit wavy, well-bonded interfaces, indicating enhanced interfacial diffusion and metallurgical bonding. Tensile testing shows that sample S3 achieves the highest ultimate tensile strength (613 MPa), significantly exceeding those of sample S1 (379 MPa) and sample S2 (415 MPa), which is attributed to the synergistic effects of work hardening, precipitation strengthening, and hetero-deformation induced strengthening. Although ductility decreases slightly in sample S3, the elongation remains relatively high at 18.4%, whereas sample S4 exhibits the lowest elongation (12.6%), which is detrimental to subsequent forming. Importantly, all samples fracture within the matrix without interfacial delamination, confirming robust metallurgical bonding. These results indicate that direct annealing enhances both strength and ductility in Cu-Ni-Si/1010 steel laminated bimetallic composites, while cold rolling followed by annealing is an effective strategy for substantially increasing strength while preserving interfacial integrity.

Owing to their excellent corrosion resistance and weldability, 5xxx series Al-Mg alloys are widely used in marine and offshore structures. However, research on the sensitization behavior and reversion treatment of Al-Mg alloy welded joints remains underdeveloped with regard to base materials, despite welded joints being critical zones for failure. To address this limitation, the present study systematically investigated the microstructure and corrosion behavior of the base metal (BM), heat-affected zone (HAZ), and weld zone (WZ) of 5A06 alloy tungsten inert gas (TIG) welded joints under as-welded, sensitized (isothermal treatment at 175 °C for 100 h), and reversion-treated (isothermal treatment at 310 °C for 1 and 24 h) conditions. Various microstructural characterization techniques, along with the nitric acid mass loss test (NAMLT), were employed to clarify the sensitization-induced precipitation characteristics in different regions of the welded joints, as well as the effect of reversion treatment on corrosion performance. The results indicated that the as-welded BM consists of uniform, recrystallized grains formed by annealing. Due to welding thermal cycle, the grains in the HAZ were slightly coarsened, whereas the WZ exhibited equiaxed dendritic structures with notable Mg interdendritic segregation. After sensitization, continuous β' phase precipitates formed along the grain boundaries in the BM and HAZ, leading to severe intergranular corrosion during the NAMLT. In the WZ, additional acicular β' phase formed within the interdendritic regions, further inducing interdendritic corrosion and resulting in higher corrosion susceptibility. Reversion treatment at 310 °C for 1 h successfully dissolved the grain boundary β' phase; however, complete dissolution of the interdendritic acicular β' phase required a longer duration. Thus, to ensure the overall intergranular corrosion resistance of the joint, the reversion treatment parameters should be established based on the complete dissolution of the interdendritic acicular β' phase in the WZ.

The indentation technique imposes high requirements on the accuracy of testing equipment in practical applications and is susceptible to disturbances from the testing environment and factors such as sample preparation quality. To optimize the key parameters of indentation experiments and enhance the reliability and scientific validity of this method, this study investigates the influence of experimental conditions on the indentation relaxation behavior of Sanicro25 austenitic heat-resistant steel using the finite element method. The simulation results indicate that the friction coefficient has an obvious impact on the test results. When the friction coefficient increases from 0 to 0.30, the corresponding maximum force increases by 18.41%. At the same time, the surface morphology of the indentation changes significantly. As the friction coefficient increases, the material stacking height decreases. However, when the friction coefficient exceeds 0.15, the change in stacking height becomes less pronounced, and the results under different friction coefficients tend to be consistent; the indentation response is also affected by the ratio of sample thickness to indentation depth (thickness-to-depth ratio). The results show that when the ratio is ≥ 20, the relaxation curves are essentially consistent. Further increasing the thickness-to-depth ratio does not lead to significant changes in the relaxation curve. Under the same indentation depth conditions, a quadrangular pyramid indenter produces a larger equivalent creep strain and a faster initial relaxation rate than a conical indenter.

The development of third-generation semiconductors has increased power density in electronic devices while increasing demands for high-frequency performance of internal soft magnetic materials. Fe-based nanocrystalline alloys are among the most promising candidates for high-frequency applications owing to their excellent comprehensive soft magnetic properties, including high saturation magnetic flux density (B_s), high permeability, and low core loss per unit mass (P_cm). However, further improvements in their high-frequency properties are required. This study prepared Fe_75.2Si₁₃B₈Cu₁Nb_2.8 nanocrystalline alloy ribbons with 15-23 μm thicknesses by adjusting the Cu wheel speed. The effects of ribbon thickness on the structure and static/high-frequency magnetic properties of the nanocrystalline alloys were investigated. Furthermore, the high-frequency magnetization mechanisms of nanocrystalline alloys with varying ribbon thicknesses were examined through magnetic domain structure characterization. Results indicate that all as-spun alloy ribbons exhibit an amorphous structure and transform into a similar amorphous + α-Fe nanocrystalline dual-phase structure after annealing at 843 K for 60 min, with average α-Fe grain sizes of 11.0-11.6 nm. The static magnetic properties of all ribbons are nearly identical, with B_s and coercivities of 1.35-1.36 T and 0.5-0.6 A/m, respectively. On the contrary, the high-frequency soft magnetic properties improve with decreasing ribbon thickness. The effective permeability (μ_e) of thinner ribbons remains stable and exhibits milder attenuation with increasing frequency. At 100 kHz and 1 MHz, the 15-μm ribbon has μ_e of 17000 and 5200, respectively, which are substantially higher than the values of 14000 and 2900 for the 23-μm ribbon. Moreover, the thinner ribbons demonstrate reduced P_cm. At 0.2 T, 100 kHz and 0.2 T, 500 kHz, the 15-μm ribbon shows P_cm of 67 and 811 W/kg, representing reductions of 38.0% and 41.9%, respectively, compared with the 23-μm ribbon. Loss separation analysis indicates that the reduced P_cm of the thin ribbon is primarily attributed to decreased eddy current loss and residual loss. The decreased ribbon thickness refines the magnetic domains, facilitating domain rotation at high frequencies and improving high-frequency permeability while reducing residual loss.

The low electrical conductivity exhibited by CuInTe₂, coupled with its relatively high lattice thermal conductivity, results in a suboptimal thermoelectric figure of merit (ZT) and conversion efficiency, thereby hindering its potential for commercial application in the field of thermoelectricity. A series of Al-doped CuInTe₂ compounds were successfully prepared using solid-state reaction and spark plasma sintering techniques in this study. The influence of aluminum doping on the structure and thermoelectric performance was systematically investigated. Al doping remarkably enhances electrical transport performance by increasing carrier concentration. Meanwhile, Al doping induces substitutional point defects, dislocations, strain fluctuations, and nanoprecipitations of CuInAl₄Te₈, which act as additional barriers to phonon transport, leading to a reduction in the lattice thermal conductivity. Consequently, a minimum lattice thermal conductivity of 0.72 W/(m·K) at 823 K was obtained for CuIn_0.8Al_0.2Te₂ sample, and a maximum ZT value of 0.88, an enhancement of 115% than pristine CuInTe₂. The average ZT values at 323-823 K and 523-823 K were 0.34 and 0.60, respectively, representing approximately 127% and 122% compared with pristine CuInTe₂. The remarkable enhancement of ZT and average ZT values for CuIn_1-xAl_xTe₂ compounds demonstrates the efficacy of In-site doping in CuInTe₂.