The paper presents the domestic and overseas current status of the steel applied to aircraft landing gear in combination of the design concept and requirements for aircraft landing gear. The application features and concept of the steel used for landing gear are summarized and the domestic and overseas status are compared. For the moment, the low-alloy ultra-high strength steel and high-alloy ultra-high strength steel are all being used in the material system for aircraft landing gear steel, and the complete technical system for its anti-fatigue manufacturing is built. At present, China's development and application of high strength steel applied to aircraft landing gear is at the world advanced level. At last, the prospect for future development is analyzed.

Additive manufacturing technology (AM) is a new type of manufacturing technology based on the discrete-stacking principle and processing component with computer model data. Selective laser melting (SLM) is an important technology in the field of additive manufacturing. With its integrated manufacturing characteristics and significant advantages in the field of complex structural parts manufacturing, it has become a key development technology and frontier direction in the field of aerospace manufacturing. This article reviews the material system and application fields of SLM technology, and mainly analyzes the latest process research of SLM technology and typical applications in the aerospace field. It focuses on the research progress and results of SLM iron-based alloys, nickel-based alloys, titanium alloys and aluminum alloys. While SLM technology is widely used in various fields, there are also many problems and shortcomings, such as many internal defects of forming materials, cracks and deformations of high-performance materials, lack of standard systems, and low compatibility of powder materials. Constraints require further in-depth work in these areas.

Magnesium alloys are the lightest structural alloys developed so far and have a great potential for lightweight applications, ranging from portable electronic devices to automobile parts. Comparing to Mg alloys containing no rare earth (RE), Mg-RE alloys attracted more and more attentions due to the higher strengths at both room temperature and elevated temperature. Strengthening methods for Mg alloys with high RE contents and low RE contents were introduced respectively in this paper. For Mg alloys with high RE contents, precipitates of β' lying in the triangular prismatic plates can impede dislocation slip effectively to enhance the strength of the alloy. For Mg alloys with low RE contents, the microstructure containing nano grains in the surface layer and twinning in the center can be obtained by surface mechanical attrition treatment. Thus the Mg alloy can be strengthened by both refinement strengthening of nano grains and twinning strengthening of RE segregated twin boundaries.

With the development of advanced aviation engines in the direction of high thrust-to-weight ratio and lightweight, a series of lightweight aviation materials such as titanium alloys, nickel-based high-temperature alloys, and ceramic-based composite materials have emerged and been widely used for the key components in the aerospace field, and have also become the main production materials for aero-engine blades. However, due to the stress concentration sensitivity of carbide and the anisotropy and brittle mechanism of composite materials, the fatigue failure problem is gradually highlighted. Existing studies show that the fatigue resistance performance of aero-engine blades has important relationship with its processing process, which in turn affects the service performance and service life of the equipment. Grinding, as the final material removal process for aero-engine blades, directly determines the final surface integrity and fatigue resistance of the blades while obtaining precise profiles. In order to understand the characteristics of blades processed by new lightweight aviation materials, and provide guidance for the processing of aero-engine blades for optimization of fatigue performance, the application of typical aero-engine blade materials and the research status of anti-fatigue grinding technology are summarized. Firstly, the characteristics of typical lightweight and high-strength aeronautical materials and their application in the production of aero-engine blades are briefly described. Secondly, the method of high surface integrity grinding and the key technology of anti-fatigue processing of aero-engine blades are analyzed. Finally, the research on anti-fatigue grinding of aero-engine blades is prospected.

As the most representative additive manufacturing method in the field of aviation equipment at present, the laser additive manufacturing supports the structure design innovation, rapid development and verification. Among them, selective laser melting is mainly used for precision near net shape manufacturing of complex precise functional structures, and laser direct metal deposition is mainly used for manufacturing large and complex load-bearing structures. In order to support the strategic layout of the development of additive manufacturing technology in the aviation field, this paper sorts the current situation and development trend of laser additive manufacturing, and points out that the focus of additive manufacturing development is bound to turn to the metallurgical quality, mechanical properties and their stability control of products. The research and development of intelligent functions such as online monitoring, parameter self-tuning control of additive manufacturing equipment are becoming a research hotspot. Either the research on mechanical behavior of additive parts based on damage failure analysis and life prediction or the performance evaluation and verification technology based on components and characteristic structures have begun to attract the attention of engineering application departments. Based on the analysis of the technology development trend, the development goal of laser additive manufacturing technology in the aviation field in 2035 and the corresponding policy and environmental support and guarantee needs are proposed, and the technical development roadmap in 2035 is put forward. In 2025-2035, the control technology of microstructure, property and deformation for additive manufacturing of ordinary metal, intermetalliccompound, Nb-Si and ceramic based material is to be made a comprehensive breakthrough, the performance verification is to be basically completed, the functional assessment has been partially completed, and some products are to be entered mass production. Important load-bearing structures of aircraft and rotating parts of aeroengine made by additive manufacturing are to be widely used.

High entropy alloy is defined as an alloy containing four or more main elements. The atomic fraction of the main elements is greater than 5% and not more than 35%, which has excellent properties such as high strength, high wear resistance and high corrosion resistance. Refractory high-entropy alloy is a new type of superalloy designed and developed based on high-entropy alloy of refractory elements, which has broad application prospects in aerospace, petrochemical and other fields, and is expected to replace traditional superalloys. This paper reviews the composition design of refractory high-entropy alloys from the aspects of element selection and addition of trace elements, and its phase composition has single-phase structure and duplex structure, and the preparation method and performance characteristics of refractory high-entropy alloys are studied, and finally gives the problems and challenges faced by refractory high entropy alloys. This review provides a valuable reference for researchers in the component design, microstructure regulation and performance development of refractory high entropy alloys.

Structural stabilities, mechanical properties and electronic structures of Al₂Cu, Al₂CuMg and MgZn₂ intermetallics in Al-Zn-Mg-Cu aluminum alloys were determined from the first-principle calculations by VASP based on the density functional theory. The results show that the cohesive energy (E_coh) decreases in the order MgZn₂ > Al₂CuMg > Al₂Cu, whereas the formation enthalpy (ΔH) decreases in the order MgZn₂ > Al₂Cu > Al₂CuMg. Al₂Cu can act as a strengthening phase for its ductile and high Young's modulus. The Al₂CuMg phase exhibits elastic anisotropy and may act as a crack initiation point. MgZn₂ has good plasticity and low melting point, which is the main strengthening phase in the Al-Zn-Mg-Cu aluminum alloys. Metallic bonding mode coexists with a fractional ionic interaction in Al₂Cu, Al₂CuMg and MgZn₂, and that improves the structural stability. In order to improve the alloys' performance further, the generation of MgZn₂ phase should be promoted by increasing Zn content while Mg and Cu contents are decreased properly.

The harsh space environment and its influence on the performance of space tribological materials are reviewed. The effects of the harsh space environment on the friction and wear mechanisms of friction materials, anti-wear materials and anti-friction materials are analyzed respectively. Space friction materials which are often used in space docking system and space manipulator should have stable friction torque and excellent adhesive wear resistance. Space anti-wear materials are mainly used in the space bearings, gears and seal parts. For example, The metal elements (e.g. Ce, Cr, Mn, Mo, Nb, W) and solid lubricants are often added for Fe-Al intermetallics to restrain creep at high temperature; the wear resistances of Ti and its alloys are often improved by surface modification; anti-wear coating which has a proper associativity with the matrix can improve the wear resistance of the materials. Space anti-friction materials mainly refer to lubricants and self-lubricating materials which can reduce friction coefficient of the materials, such as soft metals, polymer materials, some oxides, fluorides and sulfides. With the development of aerospace science and technology, it is highly demanded that the novel tribological materials with high performance should be developed for space applications, and the database of tribological materials should be built, in order to meet the international challenge of development of space technology.

Surface integrity state after machining has an important effect on the service life of metal parts and components. The effects of four kinds of surface integration processing methods on the high-temperature fatigue properties of FGH95 alloy were investigated. These four surface processing methods were AR (grinding), GCSSP (grinding and cast steel shot peening), GCSP (grinding and ceramic shot peening) and GDSP (grinding and double shot peening). The surface roughness, residual stress distribution and micro-hardness were characterized by roughness tester, X-ray diffraction (XRD) stress tester and micro-hardness tester. The rotating-bending fatigue life with notched specimens (stress concentration factor, K_t = 1.7) was investigated. The results indicate that the fatigue life of specimens increased largely by GCSSP, GCSP and GDSP compared with AR specimens respectively. Furthermore, GDSP process can obtain the best surface residual stress field distribution, gradient distribution of micro-hardness, surface roughness and improvement of the high-temperature fatigue property.

The AlSi10Mg powder was prepared by supersonic gas atomization. After classified, the powder was fabricated into block by selective laser melting (SLM). The microstructure, phase, and evolutions of powder and block were investigated by optical microscope, scanning electron microscope and X-Ray Diffraction. The tensile properties of SLM block were tested by tensile experiments at room temperature. The results show that the size distribution of AlSi10Mg powder after classified can meet the requirements of SLM technology. The powder always is spherical and spherical-like. Meanwhile, the microstructure of powders is fine and uniform, which contain α(Al) matrix and (α+Si) eutectic. In addition, the melt pool boundaries of SLM block are legible. The microstructure is also uniform and densified, the relative density approaches to 99.5%. On the other hand, only α(Al) and few Silicon phase are detected in this condition, due to the most alloying elements are dissolved in α(Al) matrix. At room temperature, the ultimate tensile strength of SLM block reaches up to 442 MPa.

As a non-conduct and whole field measurement method, 3D DIC (3D digital image correlation) is widely used in mechanical properties test of many types of materials in varies fields. Compared with other optical measurement methods, it has advantages as automation, simple optical path, strong universality and anti-interference and so on. But it has some problems in the process of application, i.e. the measurement accuracy is uncertain, the high temperature test condition seriously affects the experimental results, and the measurable area of large curvature specimen is limited. This paper gives a general introduction to the application of 3D DIC in the conventional mechanical property test of different types of materials, and verifies its accuracy by comparing with the traditional extensometer measurement results and the finite element simulation results. It focuses on some latest technological progress, such as the high-temperature speckle preparation and multi-camera DIC, as the application of 3D DIC in the high temperature and large deformation measurement is mostly studied. Moreover, it is pointed out that 3D DIC should be further studied for the influence of speckle on measurement precision, the effect of environmental factors, the measurement of micro strain scale and the application in fields of military and biomedical materials.

The deformation behavior of the GH4133B Ni-base superalloy in hot working process was investigated by the isothermal compression tests carried out at the temperature of 940-1060℃ and the strain rate of 0.001-1.0 s⁻¹ with the height reduction of 50%. The microstructure of the deformed samples under different processing parameters was observed. Combined with Arrhenius hyperbolic sine equation and Zener-Hollomon parameter, the constitutive model of hot deformation of the alloy was established, and the hot working diagram was drawn. The activation energy of hot deformation of the alloy was 448 kJ/mol. the power dissipation reached its peak at 1020 ℃ and strain rate of 1 s⁻¹. Based on the establishment of constitutive model and processing map, the results of isothermal compression simulation and microstructure test analysis show that the best hot working deformation temperature of GH4133B nickel base superalloy is 1020-1060 ℃ and the strain rate is 0.01-0.1 s⁻¹.

Titanium alloy is the main application material for the key components of aero-engine due to its excellent properties, such as light weight, high strength, high temperature resistance, and fatigue resistance. Because of its small elastic modulus, low thermal conductivity, and strong chemical affinity, it produces greater cutting force and higher cutting temperature in the machining process. Different thermal mechanical coupling effects can change the surface structure, composition, and mechanical properties of the material, resulting in different surface integrity state characteristics. This paper expounds the effects of process parameters, tool materials and properties, and lubrication methods on cutting force, cutting temperature, surface roughness and morphology, residual stress, microhardness, and microstructure based on the formation mechanism of surface integrity. It is pointed out that the existing researches mainly focus on the description of phenomena and laws. The research on the formation mechanism of surface integrity based on the thermal-mechanical coupling on the processing interface is lack, and the qualitative characterization system of surface integrity is not perfect. Therefore, the object of titanium alloy machining needs to be upgraded from test block to component, and the influence of the change of contact state of the processing interface caused by the time-varying machining trajectory on the surface integrity should be considered. Moreover, the quantitative evaluation of plastic deformation and grain characteristics is completed to accurately predict the gradient distribution of surface integrity. Taking fatigue performance as the goal, the surface integrity distribution meeting the service performance of components is deduced and designed, and then the processing conditions meeting the requirements are determined to realize the surface integrity processing.

Thermal barrier coating (TBC) is a kind of thermal insulation and protective ceramic material, which can effectively improve the working temperature and service life of aero-engine. It has important economic value and strategic position in this field. With the further improvement of thrust-to-weight ratio, the traditional YSZ coating no longer can meet the technical requirements of the new generation engine. In recent years, scholars both at home and abroad have shown that rare earth doping can improve the performance of TBCs to a certain extent. Therefore, rare earth doping modification has become the focus of the development of new high-performance TBCs. In this paper, the applications of rare earth doping in high-performance TBCs are summarized, with emphasis on the effects of rare earth doping on the mechanical, thermal-physical and corrosion resistance of TBCs to molten CMAS. The problem of performance deterioration of TBCs when rare earth is over doped and the deficiency in rare earth selection standard is discussed. Moreover, it is considered that the selection basis of rare earth doping amount and type will be the research focus of TBC materials in the next generation. How to further improves the performance of TBCs is the future development direction of rare earth doped TBCs.

The continuously developing infrared detection technology and precise guidance technology pose an increasingly serious threat to the survival and penetration of missiles, hypersonic aircraft and other weapons and equipment. Infrared stealth technology plays an increasingly important role in modern warfare. Traditional low-emissivity coating materials usually have low emissivity characteristics in the entire infrared band and do not have spectral selectivity. This causes a poor effect on radiative cooling, which is not conducive to the reduction of the overall infrared signal of the target. Spectrally selective radiation infrared stealth materials can reduce the emissivity of atmospheric windows (3-5 and 8-14 µm), while using non-atmospheric window (5-8 µm) for radiative cooling. They have more efficient infrared stealth performance, thus attracting a lot of attention currently. This article introduces the research status and progress of three-generation spectrally selective radiation structures, which are based on photonic crystals, frequency selective surfaces and Fabry-Perot cavities respectively, summarizes their advantages and problems. At present, the spectrally selective radiation infrared stealth material is still far from practical application. In the future, it should continuously develop in the direction of simpler technology, stronger high-temperature stability and multiband compatibility.

Nickel-based superalloys, titanium alloys, stainless steel and other metal materials are widely used in high-end equipment manufacturing, especially in the field of national defense and military industry. Grinding process is an important method to machine these difficult-to-cut metal materials. However, the thermomechanical coupling effect in grinding process has a significant effect on surface integrity, while the surface integrity contributes to the service performance of parts. In this paper, the formation mechanism, contributing factors, prediction and control of the core elements (such as surface roughness, residual stress, micro-hardness and microstructure, etc.) of surface integrity were comprehensively summarized. The development trend of surface integrity control technology is also prospected.

The MCrAlY bond coats used for thermally-sprayed thermal barrier coatings applied to aeroengines and industrial gas turbines are reached their temperature limits. The further development is aiming to extend service life, low production cost and compatibility with new fuels. The new MCrAlYs have to be oxidation resistant and spallation resistant, and able to prevent SRZ formation caused by the diffusion with superalloy substrate, and to avoid the damage of thermo-mechanical properties. This paper reviewed recent developments in this area, and proposed a composite structured low-β / near-γ′ type MCrAlY with a very low ϕ value and CTE closed to Al₂O₃ to achieve the target. This approach may be cost effective, and more attractive to aeroengine and industrial gas turbine manufacturers, as well as coating developers and research institutions. Meanwhile, big data analysis will help to design new coating composition, speed up the development process and reduce R&D cost, lead to the findings of more durable thermal barrier coatings for aeroengine and industrial gas turbine applications.

To improve the fatigue resistance of the bolt connecting hole, the effect of double cold expansion (DCE) of the hole on the fatigue life of TB6 titanium alloy was investigated. The fatigue fracture, surface roughness, residual stress, hardness and microstructure of the hole wall were characterized by scanning electron microscopy (SEM), roughmeter, X-ray diffraction (XRD), microhardness tester and optical microscopy. The mechanism of DCE on the fatigue life of the hole was also investigated. The results show that the mean value of the fatigue life of DCE specimen is much higher than that of the interference fit specimen. The surface integrity of the hole wall is improved after DCE. The roughness decreases remarkably. The deep surface-strengthen-layer with high hardness and deep residual compressive stress field are formed around the hole through severe plastic deformation of the microstructure of the hole wall. It is considered that the improvement of surface integrity plays an important role on the enhancement of fretting fatigue life.

The influence of different grades of prior particle boundary (PPB) in PM FGH96 superalloy during high-cycle fatigue test at 550 ℃ was investigated by the in-situ fatigue test in SEM. The results show that the PPB in P/M FGH96 superalloys by plasma rotating electrode process (PREP) + hot isostatic press (HIP) is constituted of large size γ' and carbide. There are no significant effect on the initiation and propagation of high cycle fatigue crack in different grades of PPB. Crack initiation is initiated in the grain interior, and the propagation is transgranular or intergranular, which is influenced by the angle between the grain boundary and the stress axis. In the fast crack growth zone and the transient zone, the fracture characteristics of serious grade PPB FGH96 superalloy are transgranular and along PPB globular surfaces.

The change of fatigue life and microstructure of 2124-T851 thick plate after cold expanded with different deformation was studied by fatigue test, TEM, SEM and X-ray diffraction apparatus. The results show that the fatigue life increases with the increase of expanded deformation until the maximum value is reached, and then decreased rapidly with the increase of expanded deformation. At 0.4 mm expanded deformation, fatigue life reach peak value, which is 12.66 times of the non-cold-worked specimens. The microstructure research results show that the residual compressive stress and dislocation cell structure form around the cold-worked holes during the cold expansion, and increase quickly with the expanded deformation. The strengthened layer retarded the fatigue crack growth rate. The appropriate cold expanded deformation can improve the surface roughness of hole, and retard the initiation of fatigue crack, consequently improving the whole fatigue life.

The influence of Cu content on microstructure and properties of 2219 aluminum alloy was investigated by using tensile tests, welding tests, electrochemical impedance spectroscopy (EIS), cyclic anodic polarization curves (Tafel) combined with optical microscopy (OM) and scanning electron microscopy analysis (SEM). The results indicate that the residual crystal phase in the matrix of 2219 aluminum alloy is reduced with the decrease of Cu content which contributed to effectively suppress the precipitation of Al₂Cu coarse phase during the welding process. Furthermore, with the decrease of Cu content, elongation of the alloy is significantly increased, while the tensile strength and yield strength is slightly decreased. At the same time, Al₂Cu phase formed in the matrix induces localized corrosion which causes the deterioration of corrosion resistance in the alloy, while the corrosion tendency of the alloy can be reduced by the decrease of Cu content and the corrosion resistance of the alloy is improved.

Three continuous silicon carbide fiber reinforced SiBCN composites (SiC_f/PyC/SiBCN) distinguished by different weaving methods of fibers (including two dimensional woven, 2.5 dimensional woven with the fiber tow through the thickness and three dimensional five directional braiding) were fabricated by resin transfer molding (RTM), polymer impregnation and pyrolysis (PIP) technology. In order to study the impact of waving methods, the microstructures of fabricated composites were observed and the mechanical properties such as tensile, compression strength and bending strength of the composites were tested. The results show that different distributions of fibers on different directions lead to anisotropy of mechanical properties for each composite, and fabric preform structure has a significant influence on the mechanical properties of the composites.

Based on the experiments of isothermal forging wedge-shaped samples, Deform-3D numerical simulation software was used to confirm the strain distribution in the wedge-shaped samples. The effect of deforming temperature and strain on abnormal grain growth(AGG) in extruded FGH96 superalloy was examined. It is found that when the forging speed is 0.04 mm/s, the critical AGG occurring temperature is 1100℃, and the critical strain is 2%.AGG does not occur within 1000-1070℃, but still shows the feature of 'critical strain', and the region with strain of 5%-10% has the largest average grain size.AGG can be avoided and the uniform fine grains can be gained when the strain is not less than 15%.

Hardness gradient, residual stress gradient and the organization structure of surface super-hardened M50NiL steel roller and M50 steel roller were studied, the rolling contact fatigue life was measured, and the failure process was analyzed and compared by using surface profiler, Vickers hardness tester, X ray residual stress determinator, optical microscope, scanning electron microscope (SEM), rolling contact fatigue test machine and other equipment. The fatigue failure mechanism of surface super-hardened M50NiL steel was revealed. The results show that the fatigue failure mechanism of surface super-hardened M50Nil steel returns to the Hertz theory and shows typical contact fatigue characteristics. The high surface hardness, residual compressive stress and a good organization structure can completely inhibit the initiation of surface cracks; therefore, the failure mechanism is returned to the Hertz theory.

In order to break through the technical bottleneck of traditional Mo/8YSZ double- layer thermal barrier coating which is easy to peel off at high temperature, the influence of the thickness of matrix, bonding layer, transition layer and ceramic layer on the residual stress of Mo/8YSZ functional gradient thermal barrier coating were studied. The numerical model of plasma spraying Mo/8YSZ functional gradient thermal barrier coating was established by using ANSYS finite element software. In the model, the variation of material thermal and physical parameters with temperature was considered, and the influence of different substrate, bonding layer, transition layer and ceramic layer thicknesses on the residual stress of functional gradient thermal barrier coating was analyzed. The results show that the maximum radial residual tensile stress and maximum radial residual compressive stress decrease with the increase of substrate thickness. With the increase of the thickness of bond layer, transition layer and ceramic layer, the maximum radial residual tensile stress increases and the maximum radial residual compressive stress decreases. Residual compressive stress is the main form of axial residual stress, with the increase of substrate thickness, maximum axial residual compressive stress of coating decreases, and with the increase of bonding layer or transition layer thickness, the maximum axial residual compressive stress increases, however, the change of ceramic layer thickness does not obviously effect the maximum axial residual compressive stress. The effect of changing the thickness of adhesive layer on the interface residual compressive stress is more obvious. The influence of the thickness of the matrix on the interface residual stress between the matrix and coating is within a certain range. When the substrate thickness increases to 12 mm, with the increase of the substrate thickness, the variation difference of the radial residual stress between the substrate and coating interface decreases. With the increase of the substrate thickness, the transition point and stress transition point of the stress form gradually transfer to the upper part of the boundary between the substrate and coating. With the increase of the thickness of the bonding layer, transition layer or ceramic layer, the transition point and stress transition point of the stress form gradually transfer to the lower part of the central area of the interface between the substrate and coating. By designing the functional gradient thermal barrier coating and adjusting the structural parameters of the thermal barrier coating system reasonably, the residual stress and stress mutation of the spraying component can be further reduced and the bonding strength between the substrate and coating can be improved.

Gleeble physical simulation technique was employed to investigate the high-temperature flow stress characteristics of the studied spray forming 7055 aluminum alloy. Simultaneously, the Arrhenius constitutive model which couples the parameter of true strain and the BP artificial neural network constitutive model were contrastingly utilized to predict the flow stress behavior of the experimental alloy. The result shows that the flow stress of spray forming 7075 aluminum alloy is significantly affected by deformation parameter, which is negative correlated with deformation temperature and positively correlated with strain rate. Through the comparison of the two models, the average relative error of the Arrhenius constitutive model lies over 2%. And the error of the model tends to increase with the rising temperature. Moreover, the average absolute error and the average relative error reach the maximum at hot processing temperature (around 450 ℃). It is difficult to precisely predict the flow stress characteristics of the alloy. However, BP artificial neural network constitutive model has higher prediction accuracy, the average relative error δ value is only 0.813% and has higher temperature stability.

Due to the high energy density, long cycling life, excellent Coulombic efficiency, wide working temperature range and low operation cost, Lithium-ion battery (LIB) is widely regarded as one of the most promising candidates for energy storage systems. At present time, LIB has been used in mobile phones, notebook computers, electric vehicles and other consumer fields, but also in civil aircraft, unmanned aerial vehicles, space detectors and the aerospace fields have a broad application prospect. In order to further expand the application field of LIB, a large number of research teams have designed and developed a wide variety of electrode materials with excellent performance for LIB through ingenious ideas. Through in-depth research, the electrolyte with wide temperature adaptability and high pressure adaptability is developed. To further explore and develop LIB with improved property, much research effort has been devoted into this field. After 30 years of technological breakthrough and industrial promotion, LIB-related products have become increasingly mature, and have been widely used in various fields in order to further broaden the application scenarios of LIB, the preparation of high-performance electrode materials and the construction of safe electrolyte system will be the new direction of the development of LIB technology.

Fiber-reinforced ceramic matrix composites have many excellent mechanical properties for their high specific modulus, high specific strength, low coefficient of thermal expansion, high temperature resistance, corrosion resistance and wear resistance. Due to these properties, fiber-reinforced ceramic matrix composites have been widely applied in aerospace and other fields. However, fiber-reinforced ceramic matrix composites are difficult to machine due to their heterogeneity, anisotropy, high hardness and brittleness. Therefore, it is necessary to conduct in-depth research on the machining mechanism of this kind of composites. This paper systematically reviews the research status of conventional machining method and non-conventional machining method of fiber-reinforced ceramic matrix composites. It also generalizes the development trend, advantages and disadvantages, application scope, existing problems, and corresponding solutions of various machining methods. Compared with the conventional machining method, non-conventional machining method has obvious advantages, which is the main direction of development at present.

In order to improve the fatigue performance of TC17 central hole specimen, the hole wall surface integrity was characterized by scanning electron microscopy (SEM), roughness meter, X-ray diffraction, and the influence of hole cold expansion(HCE) parameter on the fatigue performance of the hole specimens was investigated. The results show that the minimum fatigue life (14718 cycle) of the HCE specimens with an expansion value of 0.18 mm is higher than the original specimen (13965 cycle). Compared to the specimens with the expansion values of 0.28 mm and 0.38 mm, the fatigue life dispersion is less, no obvious stress concentration phenomenon is found, and it has the best fatigue performance than the other two. The surface roughness value of hole wall is the lowest after the HCE with 0.18 mm, the inner hole wall forms a certain depth of strengthened layer, the residual compressive stress produced in the hole side effectively suppresses the produce of fatigue cracks in the inner hole wall, so the fatigue performance of hole structure is improved.

Through-thickness microstructure and mechanical property of AA 7055-T7751 aluminum alloy plate were investigated by using electron backscattered diffraction (EBSD), transmission electron microscope (TEM) and small angle X-ray scattering(SAXS). The results indicate an inhomogeneous distribution of microstructure through the thickness. The degree of recrystallization decreases gradually from 69% to 19.1%, as deepening from the surface to the center of the plate. The size of subgrains decreases from 10 μm at the surface to around 2 μm at the center. Strong texture of rolling type is observed near the center but the intensity decreases gradually as nearing the surface and the shear texture becomes the dominant. High density of plate-like η' phases are observed in the alloy, indicating the sufficient precipitation. η' precipitates of this condition are around 3.7 nm in radius, 1-3 nm in thickness and are found coherent with the Al matrix with a coherent strain of 0.0133, showing a strong strengthening effect. The heterogeneity in grain scale does not influence the distribution and the morphology of precipitates. The yield strength (L direction) varies linearly along the thickness direction of the plate, fitting an equation of σ_y=-38.7S+604.8 (0≤S≤1). The variation of yield strength is related to the heterogeneity of grain structure.

The corrosion of aluminum alloy in marine atmospheric environment was an essential electrochemical corrosion under thin electrolyte film, which was different from the corrosion in bulk solution, the corrosion rate was related to the thickness and composition of thin electrolyte film. The relationship among film thickness, relative humidity and salt deposit on aluminum alloy surface was established and verified by experiment. The electrochemical properties of 7B04 Al-alloy under thin electrolyte film with different thickness and different NaCl concentration were studied. The results indicate that the free-corrosion potential of 7B04 Al-alloy under thin electrolyte film is easier to reach steady state than that in bulk solution, both free-corrosion potential and corrosion rate are higher under thin electrolyte film. With the decrease of film thickness, the cathodic polarization current density of 7B04 Al-alloy increases, and the anode reaction is suppressed. With the increase of NaCl concentration in thin electrolyte film, the free-corrosion potential of 7B04 Al-alloy decreases, and the corrosion rate increases, but the polarization of the anode and cathode have little effect on the change of NaCl concentration. The free-corrosion potential of 7B04 Al-alloy is no longer changed when the mass fraction of NaCl reaches 5%.

The morphologies, surface energies and surface chemical properties of the domestic T700 grade carbon fiber and the T700S carbon fiber were characterized by using scanning electronic microscopy (SEM), inverse gas chromatography (IGC) and X-ray photoelectron spectroscopy (XPS) respectively.The mechanical properties of the two carbon fibers/QY9611 composites were also discussed. The results indicate that the surface properties of carbon fibers have an important influence on the interfacial properties of composites. The interfacial properties of domestic T700 grade carbon fibers/QY9611 composite at room temperature/dry conditions are superior to T700S/QY9611 composite. The toughness of domestic T700 grade carbon fibers/QY9611composite is outstanding as well. The value of CAI has reached the level of foreign advanced composite IM7/5250-4. After hydrothermal treatment, the interfacial strength of domestic T700 grade carbon fibers/QY9611 composite is equal to that of T700S/QY9611 composite. It shows that domestic T700 grade carbon fibers/QY9611 composite has good hydrothermal-resistant properties.

In order to ensure the performance of the automated fiber placement forming parts, according to the homogeneity of the image of the prepreg surface along the fiber direction, a defect segmentation algorithm which was the combination of gray compensation and substraction algorithm based on image processing technology was proposed. The gray compensation matrix of image was used to compensate the gray image, and the maximum error point of the image matrix was eliminated according to the characteristics that the gray error obeys the normal distribution. The standard image was established, using the allowed deviation coefficient K as a criterion for substraction segmentation. Experiments show that the algorithm has good effect, fast speed in segmenting two kinds of typical laying defect of bubbles or foreign objects, and provides a good theoretical basis to realize automatic laying defect online monitoring.

Aluminum foam was fabricated by space-holder method with carbamide particles as space-holder material. The effects of forming temperature, porosity and diameter of pores were investigated systematically. During this process, the electronic universal testing machine combined with digital image correlation (DIC) technique was used to test the properties. The results show that the porosity and diameter of pores can be well controlled by space-holder method. The best sintering temperature of forming Al foam is 650 ℃. Under this sintering temperature, the compressive yield strength reaches 10.7 MPa. With the decrease of pore porosity, both of the compressive yield strength and platform stress increase, so the energy absorption of foam is improved remarkably. When the diameter of pores is below 2.0 mm, the energy absorption of foam is improved slightly with the increase of Al foam diameter. DIC technology can be used directly to characterize the mechanical behavior of foam material, which has a good engineering application prospect.

The property of the surface layer of twice hole expansion Ti1023 alloy was analyzed by TEM, X-ray and roughness tester, and the strengthen mechanism of the bushing hole expansion was discussed. The results indicate that the roughness(R_a1.722→0.349 μm), hardness(Hv32→38) and residual stress distribution of the hole are improved by twice hole expansion techniques,and the fretting wear fatigue(fatigue limits 385→619MPa) of Ti1023 alloy is improved.

The strengthening and toughening mechanism of aluminum lithium alloy treated by thermo-mechanical processing have been summarized, and the effect on the evolution of microstructures, grain structure and precipitation, were discussed and analysed deeply. The precipitation sequence and behavior of the main precipitation phase were modified by the thermo-mechanical processing, stimulating the forming of fine dispersion combined particles of δ', θ"/θ', T1, and S"/S' phases, uniformly distributed in the matrix, which significantly improved the relationships of strength and the plastic toughness, with the inhibiting of broadening of precipitate free zones, and of the precipitation and coarsening of strengthening particles at the grain boundary.The density of solute atom and vacancies significantly raised up after solution treating, and retained as supersaturated solid solution after water quenching, which acted as the driving force for the precipitation during subsequent aging. Pre-deformation and pre-aging significantly increased the density of fine dispersion strengthening particles of δ' and G.P. zones, which uniformly nucleated in the matrix, and the combined strengthening phases of δ', θ"/θ', and T1 were obtained after high temperature second aging, controlling the size and volume fraction of these particles.Refined grain and optimal grain structure were achieved by new and typical thermo-mechanical processing, and the proportion, size, and oriented relationship of main strengthening particles of δ', θ"/θ', and T1 phases were optimized.At last, the research direction of new thermo-mechanical treatment on the large scale rolled plates and hot worked forgings is pointed out, such as age forming, to meet the need of light high performance of new aluminum lithium alloys used for the large aircrafs and heavy lift launch vehicles.

Through turning and rotary bending fatigue test, the effect of turning feed on GH4169 superalloy surface integrity, and the effect of surface integrity on fatigue life were studied. The results show that the surface roughness R_a decreases from 1.497 μm to 0.431 μm when the turning feed decreases from 0.2 mm/r to 0.02 mm/r. The surface residual stresses are changed from tensile stress to compressive stress. The depth of plastic deformation layer decreases from 8 μm to 2 μm. The surface stress concentration factor has the most significant effect on the fatigue life of GH4169. With the increase of stress concentration factor, the fatigue life decreases significantly. When f is 0.13 mm/r, the surface stress concentration factor K_st is 1.166; the surface micro-hardness is 405.27HV_0.025; the surface residual stress is 82.08MPa; and the average fatigue life is 6.98×10⁴ cycles. The multiple cracks are initiated at the machined surface defects of GH4169 superalloy specimen.

The friction extrusion additive manufacturing (FEAM) process of aluminum 6061-T651 cylindrical bar was successfully achieved by using independently developed solid-state friction extrusion additive equipment. The forming characteristics, microstructure features and mechanical properties of the final specimen obtained under different rotational speeds were comparatively analysed and discussed. The results show that for a given transverse movement speed of 300 mm/min, a fully dense single-channel double-layer specimen with thickness of 2 mm and 4 mm without any internal defects can be obtained by using the rotational speed of 600 r/min and 800 r/min respectively. The final specimen achieved under the higher rotational speed presents a flat interface, a narrower deposition layer, and a rougher surface because the effects of friction and extrusion experienced by the rotational shoulder are weakened during the deposition process. The plastic deformation and thermal cycle experienced by the bonding interface under 600 r/min are more significant than those under 800 r/min, and the grains are refined to 6.0 μm. The softening degree of the interface obtained under 600 r/min is more serious, and the hardness in this region is only 52.7%-56.2% of the value of the as-received feed rod, while this value can reach 56.0%-61.3% of the hardness of the base material. The final specimen attains a good comprehensive mechanical property. The ultimate tensile strength of the final specimen obtained under rotational speeds of 600 and 800 r/min can reach 66% and 70% of the value of the as-received feed rod respectively, while the percentage elongation after the break can reach 212% and 169% of the value of the base material respectively. The tensile properties of 6061 aluminum alloy prepared in this paper have obvious advantages compared with those of other Al-Mg-Si alloys fabricated by other well-developed additive manufacturing processes.

Continuous silicon carbide (SiC) fiber toughened SiC/SiC composites are composed of continuous SiC tows, interphase and SiC matrix. They possess a series of excellent properties such as high strength, high stiffness, low density, high-temperature resistance and oxidation resistance. They are the ideal materials for hot-section components of aero engines and land-based gas turbines. Under the influence of load, heat, vapor and oxidants, as well as the impact of gas and foreign matter, SiC/SiC composites have complex rupture and erosion failure modes. As SiC/SiC composites are being applied more extensively, the research on the failure mechanism because of fatigue and creep is becoming more and more important. The application of new characterization methods, such as acoustic emission, digital image correlation, electric resistance monitoring, in-situ CT and SEM on the SiC/SiC composites in recent years could facilitate the illumination of the damage evolution and failure mechanism during mechanism tests.

Carbon fiber reinforced silicon carbide ceramic based (C/SiC) composites are widely used in industrial, aerospace and other fields due to their high strength, hardness and wear resistance. However, C/SiC composites are difficult to be removed and processed. In this paper the common preparation methods of C/SiC composites and the performance characteristics of their materials are reviewed. The traditional machining methods, ultrasonic assisted machining, laser processing and other processing methods of C/SiC composites are summarized. The material removal mechanism, processing precision, common defects and problems in the processing are analyzed. Traditional machining needs further optimization cutting tool materials. Ultrasonic assisted machining needs to explore the coupling mechanism of ultrasonic vibration between the tool and the material, and the mechanism of material removal under vibration. The removal mechanism of 2.5-dimensional and 3-dimensional C/SiC composites by laser processing also needs to be studied. On the basis of these studies, the possibility of high efficiency, precision, stability and non-destructive processing of C/SiC composite materials is explored by further adopting the composite machining method.