Ti₂AlNb alloys，as representative TiAl-based alloys designed for long-term use in the temperature range of 650-750 ℃，exhibit promising potential for applications in typical aero-engine components. However，their susceptibility to oxide scale instability，interfacial embrittlement，and degradation of mechanical properties under high-temperature oxidation，molten-salt corrosion，and water-vapor environments constitutes one of the key factors restricting their practical engineering application. The Ti₂AlNb alloy primarily consists of O，B2，and α₂ phases，introducing a high density of grain boundaries and phase interfaces within the alloy，accompanied by pronounced compositional partitioning and electrochemical heterogeneity. As a result，Ti₂AlNb alloys exhibit significant interface sensitivity and non-uniform environmental responses under complex working conditions. This review paper focuses on the significant role of the multiphase microstructure in governing high-temperature oxidation and corrosion behavior and systematically summarizes the research progress on Ti₂AlNb alloys. Particular emphasis is placed on the formation and evolution of complex oxide scales characterized by TiO₂，Al₂O₃，and Nb-related oxides. The dual role of Nb in regulating oxygen diffusion and determining oxide types is clarified，and the effects of selective oxidation among different phases and the associated interfacial stress concentration on the long-term stability of oxide scales are discussed. Considering complex working conditions，this work outlines the coupled corrosion-oxidation behavior of Ti₂AlNb alloys in molten salts containing Cl^－ and SO {}_{\mathrm{4}}^{\mathrm{2}-} as well as in water-vapor atmospheres. It clarifies the localized corrosion sensitivity arising from the electrochemical differences between the B2 and O phases， the destructive effects of corrosive ions such as Cl⁻ and SO {}_{\mathrm{4}}^{\mathrm{2}-} on the continuity and compactness of the oxide scale， and the critical impact of hydrogen ingress-induced intergranular embrittlement in water vapor on application reliability. On this basis，various surface protection technologies developed in relation to the multiphase microstructure and the active diffusion behavior of Nb are introduced. These include aluminizing treatments that construct α-Al₂O₃-dominated selective oxide scales，silicide and Si-rare-earth composite coatings that form SiO₂ barrier layers，and MCrAlY-type metallic coatings with diffusion-barrier designs. The stability of coating/substrate interfaces under complex interdiffusion conditions is also analyzed. From the perspective of engineering applications，key challenges remain in understanding multi-interface coupled oxidation and corrosion mechanisms，establishing reliable long-term environmental stability evaluation methods，optimizing integrated coating-system design，and improving service-life prediction. Future research focuses on multiphase interface regulation and the synergistic design of advanced protection systems.

Titanium alloys， owing to their high specific strength， excellent toughness， and outstanding corrosion resistance， are widely used in aerospace， defense， marine engineering， and medical applications. However， their high production cost remains a major barrier to large-scale adoption. This review summarizes the current research status and future development trends of low-cost titanium alloys， with a focus on both conventional design strategies and emerging technological pathways. In conventional approaches， the replacement of expensive alloying elements （e.g.， Mo，V） with more economical alternatives （e.g.， Fe， Cr， O， N）， combined with optimized melting techniques and processing routes， has significantly reduced material costs. In terms of emerging technologies， high-throughput diffusion techniques， machine learning， and transformation-induced plasticity/twinning-induced plasticity （TRIP/TWIP） mechanisms provide a crucial theoretical foundation for the rapid development of high-performance， low-cost titanium alloys that can be fabricated via short-process routes.Near-net-shape forming techniques， with their high material utilization and short processing cycles， have become key tools for cost control.Looking forward， integrating TRIP/TWIP-based alloy design with advanced processing and manufacturing techniques， along with the strategic optimization of interstitial elements （e.g.， O， N）， is expected to further reduce production costs. Such progress will accelerate the large-scale application of titanium alloys in fields such as automotive light-weighting and military armor， ultimately promoting their widespread adoption across multiple industries.

The dispersion uniformity of titanium alloy/graphene oxide （GO） mixed powder is crucial for the preparation of high-quality graphene-reinforced titanium matrix composites. The mechanism of GO adsorption onto the surface of titanium alloy particle is revealed by theoretical analysis and a quantitative evaluation method is established based on image segmentation using deep learning and statistics analysis. The results show that the SEM secondary electron images of the mixed powder dried for 12 h after solution stirring mixing exhibit high imaging contrast and strong GO adsorption state. The additional pressure generated by the pressure difference between the inside and outside of the liquid bridge is the dominant part for GO adsorption force onto the surface of titanium alloy particle，which is ten orders of magnitude higher than the force of GO. The U-Net network model demonstrates superior segmentation performance for the mixed powder and GO compared to DeepLabV3+ and PSPNet. Under the optimal training parameters，the segmentation accuracies of U-Net for the mixed powder and GO reach relatively high values of 0.9433 and 0.8774， respectively. The stirring blades shape，stirring speed， and stirring time are optimized by numerical simulation of stirring process and the established quantitative evaluation method. The paddle with three inclined blades is the preferred stirring paddle shape for preparing titanium alloy/GO mixed powder. For the mixed powder containing 0.15% （mass fraction， the same below） GO， the preferred stirring process is 400 r/min for 40 min， where the standard deviation and range of GO content are 0.82% and 2.15%， respectively. For the mixed powder containing 0.30%GO， the preferred stirring process is 300 r/min for 80 min， and the standard deviation and range of the GO content are 1.03% and 3.40%，respectively.

Continuous SiC fiber-reinforced Ti₃Al（SiC_f/Ti₃Al） composite combines the advantages of high damage tolerance and ease of forming for Ti₃Al matrix and high-strength for SiC fibers. It is an ideal candidate material for lightweight， high-strength， and high-temperature resistant fasteners in the aerospace field. However，complex residual stresses are inevitably introduced during the thread machining process of SiC_f/Ti₃Al composites. Therefore，analyzing the residual stresses in the threaded regions of SiC_f/Ti₃Al composites is of great significance for enhancing the service safety and reliability of fasteners. Given the complex geometric structures of the threaded regions in turned SiC_f/Ti₃Al composites and the close relationship between their stress distribution and core diameter， the characterization and analysis of stress are challenged by the intricate thread profile and limited dimensions. Residual stress measurements and analyses are conducted on the thread crest and radial cross-sections of the threads using side-inclined X-ray diffraction and nanoindentation method，respectively. The results show that the thread crest is in a state of compressive stress after turning. When the core diameter increases from 3.0 mm to 4.0 mm，the compressive stress increases from 387.6 MPa to 540.6 MPa. The radial cross-sections of the thread are also under compressive stress. As the core diameter increases from 3.0 mm to 4.0 mm，the compressive stress at the same location 100 μm from the thread crest increases from 326.9 MPa to 430.8 MPa. Furthermore， the compressive stress decreases with increasing distance from the thread crest.

To precisely control the thermally/stress-induced products in β-type titanium alloys and overcome the limitations of traditional design methods relying on parameters such as d-electron alloy theory and molybdenum equivalent， a design approach based on specific orientation moduli （Young’s modulus E ₁₀₀， tetragonal shear modulus C′， and shear modulus G ₁₁₁） is proposed. Three Ti-Mo-based multi-component alloys with significant twinning-induced plasticity（TWIP） effect， namely Ti-13.5Mo-3.6Nb（mass fraction/%， the same below）， Ti-13Mo-4.5Nb-1.6Zr， and Ti-12.5Mo-6.5Nb-1.5Zr-0.9Al， are successfully designed. By means of optical microscopy（OM）， transmission electron microscopy（TEM）， electron backscatter diffraction （EBSD）， and tensile testing， the cold workability， thermally-induced metastable phases， and stress-induced deformation modes of the designed alloys are systematically analyzed， and the regulation of specific orientation moduli on thermally/stress-induced products is investigated. The results show that all three designed alloys exhibit excellent cold workability with a cold working rate of over 90%， and the solution-treated microstructure consists of a β-phase matrix and trigonal thermally-induced ω-phase. Their yield strength ranges from 370 to 428 MPa， total elongation from 46% to 50%， and the deformation mode is dominated by ｛332｝_β〈113〉_β twinning. The high Young’s modulus E ₁₀₀（22.9 GPa） of the three alloys completely suppresses the thermally/stress-induced α″-martensitic transformation； the low tetragonal shear modulus C′（7.8 GPa） facilitates ｛332｝_β〈113〉_β twinning， resulting in a twin area fraction of 28.8%-30.1% at 5% deformation； the high shear modulus G ₁₁₁（10.6-10.7 GPa） inhibits the collapse process of the thermally-induced ω-phase， thereby maintaining the trigonal structure of the thermally-induced ω-phase. The design approach based on specific orientation moduli proposed in this study enables the efficient design of Ti-Mo-based multi-component TWIP titanium alloys， combining innovation and practicality. It provides a new pathway for the research and development of high-performance titanium alloys，and possesses broad engineering application prospects.

The rotorcraft structures have typical characteristics such as small batches， multi-specifications， complex shape and high-performance requirements. Additive manufacturing technologies have the ability to integrally form complex shapes and structures and produce on demand， which can achieve lightweight and rapid preparation of structures. It is an ideal process preparation solution for rotorcraft structures. However， although additive manufacturing technologies originating from rapid prototype preparation have been used in rotorcraft structures for more than 10 years， due to many challenges such as the stability of additive manufacturing technology structural parts preparation， extremely high R&D certification costs and rapid technology iteration， for rotorcraft structures， additive manufacturing technology still belongs to the category of new materials， new processes and new technologies. In order to meet the efficient application demand of additive manufacturing technology in domestic rotorcraft structures， based on the application status and development trend of additive manufacturing technology in foreign rotorcraft structures are reviewed and examined， development suggestions for the engineering application of additive manufacturing technology in domestic rotorcraft structures are proposed： constructing quantitative evaluation criteria for the application of additive technology in rotorcraft structures， establishing structural design optimization technology for additive manufacturing， developing high-performance materials， new additive manufacturing processes and high-quality post-processing methods for additively manufactured structural parts， realizing real-time monitoring and process parameter control of additive manufacturing process and universal and efficient airworthiness.

As the demand for aerospace vehicles to withstand high temperatures， ultra-high speeds， and extremely harsh service environments becomes increasingly prominent， there are higher requirements for thermal protection materials in terms of temperature resistance， durability， and reliability. Surface coating technology has become one of the effective ways to improve the oxidation and ablation resistance of composite materials in high-temperature environments. Among these， ceramic coatings， with advantages such as high melting point， high hardness， good chemical stability， and excellent oxidation and ablation resistance， have become a key research direction in the field of surface coating technology. Well-performing ceramic coatings can protect the substrate from harsh external environments such as high temperatures， oxygen-rich conditions， and strong airflow， thereby extending the service life of composites and promoting their application in fields such as aerospace and marine. Addressing the extreme service environments faced by high-Mach-number vehicles， this paper systematically reviews the research progress in high-temperature performance testing technology for ceramic coatings， based on current advancements in testing performance. It focuses on a comprehensive comparative analysis of three core evaluation technologies： static oxidation resistance， thermal shock resistance， and dynamic oxidation ablation， including their testing methods， principles， applicable ranges， and limitations. To address some of the bottlenecks faced by antioxidant ablation ceramic coatings in performance evaluation， future efforts should focus on developing multi-field coupled simulations， establishing performance prediction frameworks， and promoting standardization of testing， to overcome technical barriers and accelerate the research， development， and application of high-performance coatings.

Grain-oriented silicon steel stands as the cornerstone soft-magnetic material for ultra-high voltage transformers and high-efficiency energy-saving distribution transformers. Its outstanding magnetic properties， characterized by high magnetic flux density and low core loss， are mainly ascribed to the well - defined Goss texture in the final microstructure. Nevertheless， the mechanism governing the abnormal grain growth （AGG） of Goss grains during annealing is exceedingly intricate and remains incompletely understood， posing a significant bottleneck that impedes the further enhancement of its magnetic performance.This review comprehensively summarizes the nucleation and growth behaviors of Goss grains throughout the entire manufacturing process， spanning from hot rolling to high-temperature annealing， and delineates the optimization strategies for key production processes. It also systematically synthesizes the typical features of abnormally grown Goss grains， such as grain size， orientation deviation， and internal island grains， with a particular emphasis on analyzing how these features influence magnetic properties and the corresponding regulatory approaches. Moreover， a thorough review is conducted on various theoretical models proposed for the AGG mechanism of Goss grains， covering their fundamental principles， applicability， and limitations. Finally， key research directions for future investigations into the Goss AGG mechanism are proposed， aiming to offer a valuable reference for promoting the development of high-performance grain-oriented silicon steel.

Stainless steel is mainly used for components such as thermal molten salt tanks， heat transfer pipes， heat exchangers， valves， and pumps in solar thermal power generation systems. Molten salt， with its excellent thermophysical properties， serves as the heat transfer and storage medium in solar thermal power generation. However， molten salt exhibits strong corrosive properties towards metal materials. This paper provides an overview of the corrosion assessment and mechanisms of stainless steel in molten salt environments. Firstly， the application of stainless steel in solar thermal power generation systems and its corrosion evaluation in molten salt are introduced. Subsequently， the main corrosion types of stainless steel in molten salt， as well as the corrosion mechanisms in nitrate， carbonate， and chloride salts， are summarized. Austenitic stainless steel meets the corrosion rate requirements for structural materials in solar salt， aluminum-containing stainless steel exhibits superior corrosion resistance in carbonate salts， and 310 stainless steel is suitable for use in purified chloride salts under inert atmosphere protection. The corrosion of stainless steel in molten salt mainly depends on the types of salt anions. Corrosion in salts containing oxygen anions and halide salts is categorized under the molten salt acid-base theory， while chloride salt corrosion also involves the activation-oxidation theory. Finally， the electrochemical corrosion behaviors of atmosphere， impurities and temperature that affect the corrosiveness of molten salt are discussed， and it is pointed out that chloride salt purification can greatly reduce the corrosion of metal materials. Aluminum-containing stainless steel can form a more stable A1₂O₃ passivation film in the oxygenated anionic salt， which can effectively prevent the dissolution of chromium and iron and the penetration of corrosive impurities， which is the main research direction of molten salt corrosion-resistant stainless steel.

Hydrogen energy is known as the “ultimate energy of the 21st century”， and the production of hydrogen is also one of the focuses of attention in the 21st century. Semiconductor photocatalysts offer a promising approach to producing hydrogen under visible light. Vanadium oxide has the characteristics of multiple oxidation states， multiple coordination numbers， high stability， and a narrow band gap， so it has a wide application prospect in the field of photocatalytic hydrogen production. However， vanadium oxide has defects， including a small specific surface area， insufficient visible light absorption， and rapid photogenerated carrier recombination， resulting in low photocatalytic performance. Therefore， it is crucial to optimize the photocatalytic performance of vanadium oxide to improve the efficiency of photocatalytic hydrogen production. In this paper， the application of vanadium oxide in photocatalytic hydrogen production at home and abroad in recent years is reviewed， and the optimization strategy to improve the photocatalytic hydrogen production performance of vanadium oxide is discussed and analyzed. That is， the photocatalytic hydrogen production activity is improved by surface modification， element doping， and heterojunction construction to increase the specific surface area， enhance light absorption， and inhibit the rapid recombination of photogenerated carriers. The hydrogen production performance of vanadium-based photocatalysts prepared by different optimization strategies will be improved continuously in the future. Industrial production is expected to be achieved， which can efficiently convert solar energy into hydrogen energy and replace fossil fuels.

With the increasing emission of CO₂，the harm to the environment is gradually increasing. Reducing CO₂ emissions and reducing the concentration of CO₂ in the atmosphere is a hot topic of current research. CO₂ is not only a greenhouse gas but also a rich and cheap carbon resource. The green and efficient conversion of CO₂ into high-value-added carbon and the realization of CO₂ resource utilization can help solve environmental problems and bring economic benefits. Carbon dioxide has good chemical stability and requires a significant amount of energy to decompose. Therefore，it is extremely challenging to use CO₂ to produce high value-added carbon. However，oxychloride-containing molten salts and molten carbonates can effectively absorb CO₂ to form carbonate ions，and carbon products can be obtained by electrochemical reduction of carbonate ions. In this review，the CO₂ capture and electrochemical reduction of CO₂ by molten salt are analyzed and summarized，and the effects of molten salt electrolyte system，electrode materials，and electrolysis temperature on electrochemical reduction of CO₂ are expounded，the preparation of carbon nanotubes，carbon nanospheres，graphene，and other high value-added carbon by molten salt electrolysis is summarized and prospected.

With the development of aero-engine technology， the rising operating temperature makes the service environment of environmental barrier coatings （EBCs） increasingly severe， imposing higher demands on their comprehensive performance. EBCs have evolved from the first-generation mullite/YSZ system to the fourth-generation thermal/environmental barrier coatings （T/EBCs）， among which rare-earth silicates have become a research hotspot owing to their excellent high-temperature stability and matched thermal expansion coefficient. This paper reviews typical EBCs preparation processes including APS， EB-PVD and PS-PVD， analyses the influence of process parameters on coating quality， and elaborates the typical failure mechanisms under water-vapor corrosion， CMAS attack and thermal cycling stress. Future development of EBCs will focus on high-entropy materials， multi-scale structural design and intelligent process optimization to further improve their service performance and lifetime.

The enormous number of vehicles and the industrial system generate large quantities of waste tires， and pyrolysis is considered to be an effective means of treating waste tires. This paper focuses on the current research status of waste tire pyrolysis technology， summarizes the composition and formation mechanism of waste tire pyrolysis products， and analyses the factors restricting the resource utilization of pyrolysis products and the methods to enhance the resource utilization of pyrolysis products， and puts forward the bottleneck problems that need to be broken through for the industrial application of waste tire pyrolysis technology in the future. Pyrolysis of waste tires produces a range of products such as fuel gas， oil and carbon， as well as other valuable chemicals such as limonene， benzene， toluene， ethylbenzene and others. Existing studies have indicated that the distribution of pyrolysis products from waste tires is determined by the degree of primary and secondary reactions in the pyrolysis process， and the degree of primary and secondary reactions is affected by process parameters such as temperature， heating rate， volatile retention time， pressure， reactor structure， catalysts and material particle size， among which temperature has the greatest influence on the distribution of pyrolysis products. The increase of temperature is conducive to the formation of H₂， CH₄， CO， benzene， toluene， ethylbenzene and xylene， and promotes the conversion of limonene to aromatics and the conversion of sulfur from pyrolysis oil and gas to pyrolysis carbon. In order to realize the industrial application of waste tire pyrolysis technology， further research work should be carried out in the accurate construction of pyrolysis kinetic models， the development of highly selective catalysts and the design of pollutant treatment schemes.

Additive manufacturing of nickel-based superalloys holds significant promise for applications in aero-engines and gas turbines. Evaluating the mechanical properties of these materials is crucial for facilitating their use in load-bearing components. This study investigates the high-cycle fatigue performance of the GH3536 alloy， which is fabricated via laser powder bed fusion and then undergoes solution heat treatment， with the assessment carried out at room temperature.By utilizing X-CT technology and performing fracture analysis， the defect characteristics of the material are comprehensively characterized. Furthermore， a quantitative analysis is conducted to explore the relationship between defect size and fatigue limit. The results reveal that the alloy contains porosity and lack-of-fusion defects， with surface and subsurface defects being the main contributors to fatigue fracture. The defect density in vertical samples is lower， leading to a slightly higher fatigue limit compared to that of horizontal samples.By using the effective defect size in the fracture source region of the fatigue sample， a more accurate and conservative prediction of the fatigue limit can be made. This is achieved by enhancing the Kitagawa-Takahashi （K-T） diagram with the El-Haddad model. The fatigue life of the alloy can be predicted by integrating this approach with the fatigue life characterization method based on the ratio proposed by Murakami， in combination with the El-Haddad model. This combined method provides higher prediction accuracy， especially for vertical samples with low defect density.

Selective laser melting （SLM） technology can fabricate components with highly intricate geometries. Nevertheless， due to its layer-by-layer construction process，SLM inevitably leads to variations in microstructures and mechanical properties along the building direction，which in turn undermines the service stability of the fabricated components. Heat treatment is generally employed to enhance the homogeneity of microstructures and reduce the disparity in mechanical properties along the building direction. This study delves into the influence of building heights on the microstructures and mechanical properties of GH4169 alloy produced via SLM and sheds light on the mechanisms governing microstructure evolution during heat treatment. The key findings indicate that the microstructures of the as-built GH4169 alloy consist of the γ phase and Laves phase. The geometrically necessary dislocation density of the alloy demonstrates a decreasing trend as the building height increases， primarily attributable to the thermal cycles and heat accumulation that occur along the building height. After heat treatment， the recrystallization degree of the alloy at the bottom and middle sections reaches approximately 87.8%， while that at the top section is a mere 34.1%. This significant discrepancy in recrystallization is mainly due to the higher dislocation density at the bottom， which boosts the recrystallization driving force. The yield strength of the as-built GH4169 alloy at the bottom and middle sections is around 850 MPa， whereas that at the top section is approximately 780 MPa. Following heat treatment， the yield strengths of the alloy at different heights all approximate 1150 MPa. Owing to the variation in recrystallization， precipitation at the bottom is more pronounced than that at the top， resulting in a stronger precipitation strengthening effect. On the other hand， the finer grain size and higher dislocation density at the top contribute to enhanced grain boundary strengthening and dislocation strengthening. As a consequence， the strength of the alloy at the bottom and top sections after heat treatment is comparable.

This work studies the microstructure and mechanical properties of K439B nickel-based superalloy castings with a wall thickness of 1-10 mm. The results show that the melt feeding capacity in thin-walled castings is poor， there are many shrinkage porosity in the 1 mm and 3 mm thin-walled castings， and the 10 mm thick-walled casting has the lowest porosity. Due to the increase of melt solidification rate， all of the secondary dendrite arm spacing， grain size and γ' phase size of the castings increase with the increase of thickness. The tensile tests at room temperature show that the mechanical properties of thin-walled castings are significantly affected by the evolution of microstructure. Due to the synergistic effect of the fine grain strengthening mechanism and precipitate shearing mechanism， the 1 mm thick casting exhibits the highest ultimate tensile strength （1037 MPa） and elongation to fracture （5.6%）.The 3 mm thick casting shows the poorest tensile strength and ductility，with values of 890 MPa and 4.1%， respectively， which can be attributed to its highest porosity level and the resulting severe stress concentration. Although the coarsening of grains and γ' phase reduces the grain boundary strengthening effect of the 10 mm thick casting， the reduced porosity and limited dislocation localization effectively impede the crack propagation，thereby preventing a pronounced deterioration in elongation to fracture.

The grain-boundary microstructure of Inconel 617 alloy hot-rolled rods during cold drawing and subsequent solution treatment is investigated using the electron backscattering diffraction （EBSD） technique. The results reveal that the microstructure of the hot-rolled rods contains a substantial number of coincidence site lattice （CSL） grain boundaries， predominantly Σ3 grain boundaries. Following cold drawing， the proportion of CSL grain boundaries decreases significantly， while the proportion of low-angle grain boundaries experiences a sharp increase. After solution treatment at 1120 ℃， low-angle grain boundaries are almost entirely replaced by high-angle and CSL grain boundaries. As the solution temperature rises， the proportion of Σ3 grain boundaries increases， whereas the proportions of Σ9 and Σ27 grain boundaries decline. Within a specific grain-size range， the proportion of Σ3 grain boundaries rises with an increase in grain size. During the solution treatment process， annealing twin boundaries with “cluster” and “island” morphologies emerge， and there exists a Σ3 ⁿ orientation relationship between adjacent grains.

The Al-6Si-0.75Mg-0.2Sc-0.15Zr-0.12Sb alloy is prepared using the smelting process. This study investigates the impacts of solution and aging temperatures， as well as their durations， on the microstructure and mechanical properties of the alloy. Additionally， it analyzed the morphology， size， and distribution of Si and precipitated phases.It is observed that the as-cast microstructure comprises α-Al， eutectic Si， Mg₂Si， Al₃Sc， and Al₃（Sc， Zr） phases. As the solution and aging temperatures and times increase， the morphology of the Si phase transforms from plate-like and fibrous to worm-like and nearly spherical. Prolonged holding times lead to the segregation and coarsening of the Si phase， which turns into short rod-like structures. The tensile strength and elongation initially rise and then decline with increasing solution temperature. During single-stage aging at 170 °C， the strength and hardness first increase and then decrease with the extension of the holding time， eventually reaching a stable state. The interface between the β´´ and α-Al phases evolves from coherent to semi-coherent and then incoherent， and the fracture mechanism shifts from intergranular fracture to typical dimple fracture.Pre-aging at 110 ℃ promotes the precipitation of β´´ and Al₃（Sc， Zr） phases， significantly spheroidizes the morphology of the Si phase， and refines its size. The length and precipitated surface density of the β´´ phases are （29 ± 1.8） nm and 3.52 × 10³ μm⁻²， respectively. After dual-stage aging at 110 °C/2 h + 170 °C/6 h， the tensile strength， yield strength， and elongation can reach 363， 301 MPa， and 7.9%， respectively.

The microstructure evolution in Al8.79Zn2.16Mg2.11Cu0.12Zr alloy ingot during the one-step low-temperature homogenization and three-steps high-temperature homogenization is investigated by the scanning electron microscopy （SEM）， differential scanning calorimetry （DSC）， X-ray diffraction （XRD）， and the transmission electron microscopy （TEM）. The results indicate that the microstructure of the cast Al8.79Zn2.16Mg2.11Cu0.12Zr alloy is similar to that of traditional commercial Al-Zn-Mg-Cu alloys， consisting of η′（Mg（Zn， Cu， Al）₂）， η（MgZn₂）， and Fe-rich （Al₇Cu₂Fe） phases. The θ（Al₂Cu）， T（Al₂Mg₃Zn₃），and S（Al₂CuMg） phases are not present. The redissolution effect of the second phases is not enough after one-step homogenization heat treatment at low temperature（380 ℃/2，8，16，24 h） and the change of redissolution effect is not obvious even if the homogenization heat treatment time is prolonged. A large number of the eutectic organization of the second phases still remains in the original mesh structure. However， the redissolution effect is improved by increasing the homogenization heat treatment temperature to 475 ℃（430 ℃/12 h+470 ℃/4 h+475 ℃/15 h）， except for a small amount of Fe-rich （Al₇Cu₂Fe） phases that are difficult to redissolution， the other phases are almost completely redissolution， no η′ phase transformation of S phase is detected during the one-step low-temperature homogenization and three-steps high-temperature homogenization heat treatment processes. The appearance of quench cracks occurs during the three-steps homogenization heat treatment at 475 ℃， which severely deteriorated the mechanical properties of the region near the crack in the alloy.

Based on the in-situ fatigue test technique of scanning electron microscope （SEM），the small crack behavior of selective laser melting （SLM） TC4 alloy is studied. The focused ion beam （FIB） technique is used to manufacture the simulative initial defects in the process of additive manufacturing，and the initiation and propagation behavior of small cracks induced by defects are observed under cyclic loading. The results show that under cyclic loading，small cracks are easy to initiate at the surface defect，and the crack fatigue initiation life is short. The fatigue life of SLM TC4 alloys is mainly consumed in the small crack propagation stage. Affected by the microstructure，the small cracks are more likely to propagate along the α/β interface. Due to the random orientation of α laths，the path of small cracks is deflected several times in the initial propagation stage，exhibiting a mixed mode of propagation along α lamellae and through α lamellae within grains， resulting in significant scatter in crack growth rates. At the stable crack propagation stage，the plastic slips of the crack tip are obvious，the influence of microstructure is reduced，and the propagation path tends to straighten. Comparative analysis with long crack growth data indicates that SLM TC4 alloy exhibits a significant “small crack effect”.

The microstructure， tensile fracture morphology and initial residual stress of ZTC4 titanium alloy repair welding are analyzed by stereomicroscope， optical microscope （OM）， scanning electron microscope （SEM）， X-ray residual stress analyzer and tensile testing machine， and their effects on room temperature/high temperature tensile properties and fatigue properties are studied. The results show that the microstructure of ZTC4 titanium alloy after repair welding is mainly composed of equiaxed grains （with a grain size of about 1.5 mm） and grains with a large aspect ratio （5∶1）. Different repair welding diameters and annealing treatment can affect the properties of residual stress， thus affecting the mechanical properties. The residual stress at the center of the original state of the room temperature/high temperature tensile and fatigue specimens is mainly tensile stress， which is 115.9， -24.6 MPa and 55.6 MPa， respectively. In the high temperature （350 ℃） tensile test， the larger the initial residual tensile stress （173.3 MPa） at the center of the repair welding diameter 4 mm specimens， the lower the tensile strength （710.7 MPa）； the larger the initial residual compressive stress （-159.1 MPa） at the center of the repair welding diameter 4 mm and annealing specimens， the higher the tensile strength （749.3 MPa）.The residual tensile stress significantly shortens the fatigue life of titanium alloy， whereas residual compressive stress increases it. The initial residual stress at the center of the original state， repair welding diameter of 2 mm， repair welding diameter of 2 mm and annealing， repair welding diameter of 4 mm， and repair welding diameter of 4 mm and annealing specimen is 55.6，109.9， -189.1，61.4 MPa， and -64.3 MPa， respectively. The fatigue properties of the specimens with initial residual compressive stress is better.

To improve the high-temperature performance of GH5188 cobalt-based superalloy， 10%（volume fraction） TiC particle-reinforced GH5188 composites are fabricated by laser melting deposition （LMD）. The microstructure and tensile properties are investigated， and the interfacial forming mechanism and the cause of the high-temperature performance degradation are discussed. The results show that the composite consists of TiC， （W，Ti）C_{1 -x}， and the austenitic γ phase. The submicron-thick （W，Ti）C_{1 -x} interfacial layer forms between the TiC particles and the matrix. The interfacial layer originates from the partial dissolution of TiC and the diffusion and substitution of W elements during the laser melting deposition process. At room temperature， the ultimate tensile strength （UTS） of the composite reaches 1198.9 MPa， which is 24.3% higher than that of the matrix alloy （964.3 MPa）. However， at 1000 ℃， the UTS of the composite is 128.7 MPa， which is lower than the 162.5 MPa of the matrix alloy， with a decrease of 20.8%. The degradation in high-temperature strength is mainly due to the consumption of W elements in the matrix by the （W，Ti）C_{1 -x} interfacial layer， resulting in decrease in its mass fraction and weakening the solid-solution strengthening and dislocation-pinning effects on the matrix.

The 316L/Q370qE stainless steel clad plates with a thickness of （3+32） mm are studied by using X-groove welding process. The effects of welding current on the microstructure and properties of the welded joints of clad plate are analyzed by means of optical microscopy， scanning electron microscopy， transmission electron microscopy， energy dispersive spectroscopy. The results show that the weld metal microstructure of the stainless steel cladding layer and transition layer is austenite and skeletal δ ferrite. The microstructure of carbon steel weld metal is proeutectoid ferrite， acicular ferrite， and ferrite side-plate. And a fine-grained bainite is formed in the area adjacent to the stainless steel transition layer. As the welding current increases， the content of δ ferrite in the weld metal of stainless steel decreases and its shape becomes more irregular. The microstructure in the local weld metal of the carbon steel coarsens. There is extensive mutual diffusion of elements in the interface between the weld metal of transition layer and carbon steel. At the same time， the microstructure in the heat-affected zone of the stainless steel and carbon steel coarsens. However， the change in the original layered interface of the clad plate is not obvious. The tensile fractures of the welded joints of clad plate with different currents all occur in the heat-affected zone. When the current is 230 A， the tensile properties are the best， and the tensile strength and elongation reach 557 MPa and 23.9%， respectively. The low-temperature impact absorption energy of both the carbon steel weld metal and fusion zone near the stainless steel cladding layer is about 20 J lower than that at the position keeping away from the stainless steel cladding layer. The impact energy difference in the heat-affected zone at the two positions is more significant. The change of welding current in the range of 210-280 A has little influence on the intergranular corrosion performance of stainless steel cladding layer. Therefore， when using 230 A and 30-31 V parameters to weld the stainless steel transition layer and cladding layer， the impact performance difference of the weld metal of carbon steel on both sides of the X-groove is the smallest， and the tensile properties of the welded joint of clad plate are the best.

Impact tests are carried out with cylindrical，conical and spherical punches respectively，and the response characteristics of specimens under different punch impact are discussed. The internal damage of the specimen is detected by ultrasonic C-scan instrument，and the law and process of damage expansion under impact are analyzed. The experimental results show that the shape of the punch is an important factor affecting the damage mode of the specimen. In the impact test，the spherical punch cause the most serious damage to the material，comparing to the columnar punch cause less damage，but the damage range is larger. The impact response of the conical punch to the specimen is similar to that of the spherical punch，and the damage area of the two punch to the specimen is not much different，but the damage of the conical punch to the specimen is light. The weaving angle of the material also obviously affects the impact resistance of the material. The impact resistance of the material increases with the increase of the weaving angle. In terms of damage expansion on the specimen，materials with small weaving angles tend to be damaged along the longitudinal direction. The damage of large woven angle materials tends to spread to all sides. In the impact test，the damage process of the specimen includes the longitudinal tensile failure of the fiber bundle，the transverse tensile failure of the fiber and the matrix，and the transverse compression failure.

Porous polyimide materials （PPI） have interconnected pore structures that can effectively store lubricating oil. However，the presence of these pores will reduce the strength and wear resistance of PPI，resulting in a mutual constraint between its oil content and wear resistance，making it difficult to balance. Therefore，a sandwich type density layered porous polyimide material is prepared using the method of layered cold pressing and constant volume sintering. The outer and inner layers of the material can have different porosities. The outer layer uses a high porosity to increase oil content，while the inner layer uses a low porosity to improve material strength and wear resistance，in order to overcome the problem of difficult balance between oil content and wear resistance. Based on the study of uniform PPI performance with different densities，the pore structure of density layered PPI is designed，and two types of layered PPI are prepared. Their mechanical properties，oil content properties，and friction and wear properties are studied. The results show that compared with uniform PPI，density stratified PPI has a higher oil content （>15%） and excellent oil retention rate （94.06%） due to the synergistic effect of different porosity in the inner and outer layers，and maintains excellent mechanical and tribological properties. The tensile strength and compressive strength of the 1.0-1.1-1.0 layered material are 41.7 MPa and 374 MPa，respectively. Its friction coefficient （0.078） is close to that of a uniform PPI density of 1.1 g/cm³ （0.07），but the oil content of the layered material （15.5%） is much higher than that of the uniform material （11.1%）. This sandwich type density layered PPI can balance oil content and wear resistance，providing a new approach for the design of porous materials.

Environmental barrier coatings （EBCs） are a key protective technology for the ceramic matrix composites （CMCs） hot end components of high-performance aircraft engines， which can significantly improve the service stability and reliability of the components. In this paper， Si/Yb₂Si₂O₇/Yb₂SiO₅ tri-layer structural EBCs are prepared by air plasma spray， and their corrosion behavior and degradation mechanism under 1350 ℃ and cycling water vapor conditions are investigated. The results show that the as-annealed coating is mainly composed of monoclinic Yb₂SiO₅ phase and cubic Yb₂O₃ phase， with nano-sized Yb₂O₃ phase dispersed in Yb₂SiO₅. The surface of Yb₂SiO₅ coating exhibits a ridge-like structure accompanied by a certain number of pores after cyclic water vapor corrosion， and the content of corrosion products Yb₂Si₂O₇ increases with the number of cycles. The formation of Yb₂Si₂O₇ is related to the alternating wet to dry corrosive environment and the gaseous substance Si（OH）₄. Penetrating cracks exist within the Yb₂SiO₅ coating but terminate at the Yb₂SiO₅/Yb₂Si₂O₇ interface， and the SiO₂ film generated from the oxidation of the Si bond coat is well bonded to the Yb₂Si₂O₇ interlayer and the Si bond coat in general. The tri-layer EBCs system in this paper exhibits excellent resistance to cyclic water vapor corrosion at 1350 ℃.

The in-plane uniaxial magnetic anisotropy of thin-film materials is intricately linked to high cutoff frequencies. With the growing demand for high-integration electronic components， there is an increasing need for thin-film materials with high in-plane magnetic anisotropy. In this study， FeCoNiMnHf high-entropy soft magnetic thin films with varying Hf concentrations have been fabricated at room temperature using constant-voltage electrodeposition technology. The influence of Hf concentration on the microstructure， soft magnetic properties， and magnetic anisotropy of these high-entropy soft magnetic thin films is thoroughly investigated.The results reveal that as the Hf concentration increases， the grain size of the thin films expands from 240.94 nm to 383.36 nm， and the crystallinity improves from 11.68% to 24.72%. Moreover， the in-plane uniaxial magnetic anisotropy field of the thin films rises from 47.846×10⁴ A/m to 66.2074×10⁴ A/m， and the saturation magnetization increases from 2.763×10⁴ A/m to 10.630×10⁴ A/m. The FeCoNiMnHf thin films exhibit outstanding magnetic properties at room temperature， indicating significant potential for applications in areas related to high cutoff frequencies and magnetic anisotropy.

Converting CO₂ into C1 chemicals such as CO，CH₄，and CH₃OH using solar energy as the driving force is an effective strategy to alleviate the greenhouse effect and energy shortage crisis. However，single-component catalysts face challenges in photocatalytic CO₂ reduction including limited light absorption capacity，easy recombination of photogenerated carriers，and low overall catalytic efficiency. Constructing high-efficiency catalysts to improve photocatalytic CO₂ reduction performance is therefore crucial. In this study，CdS-0.25 with sulfur vacancies and CdS-2 with cadmium vacancies are successfully synthesized via a hydrothermal method by adjusting the ratio of cadmium and sulfur precursors. Characterization analysis shows that compared with CdS-2 with cadmium vacancies，CdS-0.25 with sulfur vacancies exhibits stronger solar light absorption capacity and effectively suppresses the recombination of photogenerated electrons and holes. First-principles calculations demonstrate that sulfur vacancies have better adsorption capacity for CO₂ reactant molecules. The production rates of CO，CH₄，and H₂ from CO₂ reduction over CdS-0.25 are 1.69，0.41，0.11 µmol/（g·h），respectively. These values are 15.8，2，and 1.2 times higher than those of CdS-2. This work provides insights for the design of high-efficiency defective materials for photocatalytic CO₂ reduction.