Application features and research status of alternative 3D-printing materials for six typical 3D-printingtechniques were reviewed. From the point of view of physical forms, four kinds of materials of liquid photosensitive resin material, thin sheet material (paper or plastic film) , low melting point filament material and powder material are included. And from the composition point of view, nearly all kinds of materials in the production and life are included such as polymer materials: plastic, resin, wax; metal and alloy materials; ceramic materials. Liquid photosensitive resin material is used for stereo lithigraphy apparatus(SLA); thin sheet materials such as paper or plastic film are used for laminated object manufacturing(LOM); low melting point polymer filament materials such as wax filament, polyolefin resin filament, polyamide filament and ABS filament are used for fused deposition modeling(FDM); very wide variety powder materials including nylon powder, nylon-coated glass powder, polycarbonate powder, polyamide powder, wax powder, metal powder(Re-sintering and infiltration of copper are needed after sintering), wax-coated ceramic powder, wax-coated metal powder and thermosetting resin-coated fine sand are used for selective laser sintering(SLS). Nearly the same above powder materials are used for selective laser melting(SLM), but the printed parts own much more higher density and better mechanical properties. Powder materials are likewise used for threedimensional printing and gluing(3DP), however, the powders are stuck together by tricolor binder sprayed through nozzle and cross-section shape of the part is color-printed on it. Finally, the development direction in both quality and the yield of 3D-printing materials were pointed out to be a bottle-neck issue and a hot topic in the field of 3D-printing.

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.

Solid propellant is an important source of power for rockets and missiles, and its performance improvement is of great significance for improving the combat capability of missile weapons. 3D printing technology as a focus on advanced manufacturing technology, able to complete high-precision, high-complexity device manufacturing that is difficult to achieve by traditional manufacturing processes, solve the problems of uneven mixing, poor product consistency, and low safety, which are difficult to solve by traditional solid propellant pouring process, has broad prospects in the field of solid propellant manufacture.. The slow progress of the research on the preparation of solid propellant by 3D printing is mainly due to the two major problems of safety and process bottleneck. In view of the safety issues of solid propellant 3D printing, solid propellant 3D printing and related work are divided into three stages: 3D printing of partial energetic components, 3D printing of mixed propellants, and 3D printing of solid propellants. The safe printability of energetic components should be demonstrated step by step. In review of the bottleneck problem of solid propellant 3D printing process, the development progress of 3D printing propellant special slurry and equipment is introduced. From the current achievements and development, the future research on solid propellant 3D printing should focus on the development of special formulation and the realization of large-scale printing.

Key components used in the high-pressure compressor of advanced aero engines operating in the 550-600 ℃ range have an urgent demand for 600 ℃ high-temperature titanium alloy. However, the use of casting, forging, and other traditional processing techniques is not sufficient to meet the requirements for gradient or composite structures, functional integration components and complex components that are difficult to form. Additive manufacturing is an advanced manufacturing technology that offers unique advantages such as material design-manufacturing integration and complex design-customization integration. It provides a new approach to the development of new materials and technologies of 600 ℃ high-temperature titanium alloy. Currently, attention is being paid to the processing of 600 ℃ high-temperature titanium alloy by using additive manufacturing techniques at home and abroad, focusing on the relationship among materials, processing, structures, and properties. Firstly, this paper reviews the research on 600 ℃ high-temperature titanium alloy in brief, introduces the microstructure characteristics of deposited and post-treated states of 600 ℃ high-temperature titanium alloy under different additive manufacturing processes, and analyzes key properties such as tensile properties, creep properties, thermal fatigue properties, and antioxidant properties. Then, the research progress of composite materials based on 600 ℃ high-temperature titanium alloy and gradient structure built by additive manufacturing is discussed. Finally, the prospects are provided for research directions including the development of 600 ℃ high-temperature titanium alloy materials for additive manufacturing, exploration of hybrid manufacturing processes, defect control, and establishment of performance evaluation standards.

Nickel-based superalloy is an essential material to prepare hot-end components in aero-engines and gas turbines, due to its excellent mechanical properties under high temperature. Additive manufacturing（AM） is one of the most important techniques to fabricate superalloy components with complex geometry. In this paper, the research progress of microstructure and defects of AMed superalloy is reviewed. Based on the existing literature, tensile properties of GH3536, GH3625 and GH4169 are summarized. Typical applications of AMed superalloy components in aero-engines and gas turbines are presented. Finally, for the problems in existing investigations, it is suggested that the future research can focus on materials design, heat treatment/hot isostatic pressure process optimization, single crystal preparation, real-time monitoring technique development and internal surface treatment technique innovation.

Additive manufacturing is a new manufacturing technique that integrates laser, digitization, materials and other disciplines. It has the advantages of dimensionality reduction manufacturing, complex forming, and high material utilization. It is one of the most promising techniques in the field of material processing. Metal additive manufacturing technique has been widely studied and applied in the aviation field. The research on the additive manufacturing of aviation metal materials by domestic and foreign scholars continues to deepen. AECC Additive Manufacturing Technology Innovation Center has carried out a quantity of research and obtained some data from the four factors of metal additive manufacturing: microstructure, defects, surface and configuration. Some phenomena and laws have been found, including the characteristics and influencing factors of microstructure continuous growth; influence of the structure on mechanical properties; the characteristics and causes of common defects（pores, cracks, incomplete fusion） in additive manufactured typical materials and their influence mechanism on mechanical properties, especially fatigue properties; the relation between surface roughness and forming angles, and the influence of surface states on fatigue properties; factors influencing configuration of metal additive manufacturing. Finally, the problems existing in the development of metal additive manufacturing are summarized, and the suggestions for future research and development are put forward.

In recent years, as the 3D printing technology growing maturity and commercialization, the researchers have attempted to apply this emerging manufacturing technology to the design and fabrication of wave-absorbing materials. In this paper, the recent progress of 3D printing technology in fabrication of microwave absorbing materials, including 3D printing FSS and metamaterial absorbing materials, 3D printing honeycomb absorbing materials, 3D printing ceramics and other 3D printing microwave absorbing materials are reviewed. Furthermore, the limitations of 3D printing materials, the lack of mechanical properties of materials, the problems of testing and analysis of microstructure of 3D printing technology in microwave absorption materials manufacturing are also systematically expounded, at the same time, the future developing trend of 3D printing technology in the manufacturing field of microwave absorption materials, such as miniaturization, multi-function and intelligent is also prospected.

The microstructure, tensile and damage tolerance properties in different directions of Al-Mg-Sc-Zr alloy fabricated through selective laser melting（SLM）have been investigated. The results show that the YZ plane is a bimodal grain morphology composed of fine equiaxed grains and coarse columnar grains, while the XY plane is composed of fine equiaxed grains. The yield strength and tensile strength in both 0° and 90° directions are over 500 MPa, and the anisotropy is small, while the elongation in 90° direction is significantly lower than the 0° direction due to the lack of fusion（LOF）defects between the deposited layers. The K_IC of the 0° and 90° CT samples are respectively 21.41 MPa·m^1/2 and 20.89 MPa·m^1/2. The resistance to crack propagation in columnar grains region is lower and leading to a smaller K_IC for 90° CT samples. The microstructure and defects are the two main factors that affect the anisotropy of crack propagation performance. The LOF defects play a leading role in the near-threshold regime, and the crack propagation rate is faster when the crack propagation plane is parallel to transverse direction. On the other hand, the microstructure plays a leading role in the steady-state propagation regime. The fracture surface exhibits transgranular fracture when the crack propagation plane is parallel to transverse direction, which provides higher crack propagation resistance and result in lower crack propagation rate.

Based on the traditional manufacturing technology, the “classic” structure, which has a large mass and many weak parts of fatigue is difficult to satisfy the development needs of future fighter aircraft. The innovative structures ( three-dimensional bearing overall structure, bionic structure, gradient metal structure and micro truss lattice structure) based on the advantages of additive manufacturing technology characteristics, breaking through the shackles of traditional structures, with lightweight, long-life, low-cost and other characteristics, can greatly improve the quality of the body platform, providing an effective technical way for the future development of new fighter aircraft. Taking the fuel pipe joint, ring radiators and three-dimensional frame beam integral structure as examples, this paper expounded the whole process of integrated development of new additive structure design and manufacturing, and compared with the original traditional manufacturing scheme, achieved significant benefits, such as substantial weight loss, improvement of finished product rate, and reduction of fatigue weak parts. In addition, the reference significance of cross-domain technologies such as fiber optic sensing and construction structure to the innovation of aircraft structure was also discussed.

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.

In order to clarify the microstructure of Al-Mg-Sc high-strength aluminum alloy prepared by ultra-high speed laser melting deposition, and study the relationship between structure and properties, Al-Mg-Sc high-strength aluminum alloy was prepared by using 7075 aluminum alloy as matrix and self-developed equipment（LDF3000-40 laser melting deposition machine）. The effect of laser scanning rate on the microstructure and tensile properties of the materials was investigated. The results show that there are no obvious defects such as pores and cracks in the samples deposited by ultra-high speed laser melting, but contain a few small keyholes. The samples are composed of fine α-Al equiaxial crystals and dispersed Al₃（Sc, Zr）particles. The effect of scanning rate on mechanical properties is further studied by numerical simulation. It is found that the faster scanning rate of laser in the range of 0.1-1 m/s can reduce the accumulation of powder materials and porosity of the surface of the deposition layer, thus the mechanical properties can be improved. The maximum tensile strength is 303 MPa and elongation at break is 22.5%.

Nickel-based superalloys are important structural materials in turbine engines and gas turbines, but their conventional fabrication processes are complex, costly and have poor raw-material-utilization rate. The electron beam powder bed fusion（EBPBF） technology is a new solution for forming superalloys, which can realize near net forming of complex structural parts. During more than ten years of development, EBPBF technology has realized the high-quality formation of superalloy materials and components represented by Inconel 718 and Inconel 625, and has continuously extended its capability to form crack-free, high-γ'-phase-portion difficult-to-weld nickel-based superalloys, and can even directly prepare single-crystal nickel-based superalloy components. In this paper, the relevant literatures on EBPBF nickel-based superalloys in recent years are reviewed, and the current research status from the perspectives of printability, process optimization, property characterization of EBPBF nickel based superalloy components are analyzed and summarized, and also the future research work is proposed.

The effect of heat treatment on the microstructure and high temperature mechanical properties of SLM GH4169 alloy was studied by using a self-developed in-situ high temperature tensile device. The results show that the grain morphology of as-built alloy changes from columnar crystal to equiaxed crystal after homogenization+solid solution+aging treatment （HSA）, coupling with Laves phase dissolution, and a large amount of γ′ and γ″ strengthening phase precipitates. At 650 ℃, the yield strength and tensile strength of the as-built sample are 574 MPa and 740 MPa, while the yield strength and tensile strength of HSA sample are 818 MPa and 892 MPa respectively, which are 42.5% and 20.1% higher than that of the deposited alloy. The deformation process can be further characterized by in-situ tensile testing. The surface grain undulation of the as-built sample gets larger, the coordinated deformation ability becomes stronger, and the plastic flow ability gets better.The cracks in the as-built sample are originated around the Laves phase, spreading along the dendrite towards the maximum shear stress, and shear fracture occurs after necking of the sample. In HSA samples, the cracks are initiated around carbides and propagating along the grain boundaries. The fracture mode is a mixed type, involving both intergranular and transgranular fractures.

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.

Owing to novel design concepts and their unique properties, high-entropy alloy (HEA) has become a hot topic in material science. At present, the studies and applications of high-entropy alloy are still mainly limited to the preparation and synthesis of materials. With its wide application in industry, it must involve the research of high-entropy alloy in welding field. This paper describes the welding of high-entropy alloy with the same material, welding between high-entropy alloy and dissimilar material, and welding between dissimilar material with high-entropy alloy as filler material. The paper focuses on analyzing the welding method, high entropy alloy components, the initial state of welding and welding parameters, and other factors on the joint organization and properties. While the high-entropy alloy is mainly applied as filler material, the high entropy effect and hysteresis diffusion effect for interface controlling are particularly important. Finally, the high-entropy alloy coatings under different preparation methods are analyzed in detail, introducing the cladding process, the addition of microelements, the effect of post-heat treatment, and comparing the wear resistance high-entropy alloy coatings under the laser melting process. By summarizing the research and application of high-entropy alloy in the welding field, it is pointed out that the current problems are that the corresponding standard between high-entropy alloy system and welding process has not been established and the formation mechanism of defects has not been clarified. The future research directions of high entropy alloy in welding field are proposed.

Selective laser melting（SLM）can achieve nearly net-shape complex parts of GH3536 alloy, and its high temperature mechanical properties are important indicators for safe service. The effect of heat treatment on microstructure and high temperature tensile properties of SLM GH3536 alloy were studied. The heat treatment at 1225 ℃ for 1 h was carried out to explore the regulation mechanism of microstructure and properties. The results show that heat treatment can effectively eliminate the cellular subgrain structure inside the grains, which significantly enhances the dislocation slip ability. The tensile elongations at room temperature, 650 ℃ and 815 ℃ are increased by 75%, 92% and 683%, respectively. In addition, the decrease of the aspect ratio of the columnar grains significantly reduces the anisotropy in the heat-treated sample. The fracture analysis shows that the fracture mode of the heat-treated sample changes from intergranular fracture to mixed fracture with the increase of tensile environment temperature.

K403 nickel-base superalloy is widely used in the manufacture of aero-engine turbine blades because of its excellent properties at room temperature and high temperature. In order to solve the problem of turbine blade crack defects caused by long-term service in complex working conditions, in this work, two different processes of （tungsten inert gas, TIG） welding and laser cladding were used to repair the blade cracks, and the microstructure and properties of the repaired region were studied. The influence of TIG welding and laser cladding repairing on microstructure, mechanical properties and failure behavior was analyzed. The results show that the microcracks tend to occur near the repair interface using the TIG welding repairing process, which are mainly caused by carbides and low melting point eutectic structure. The grain and structure of the repaired area by laser cladding repair technology are more uniform, and the microcrack defects can be easier to control. The comprehensive mechanical properties of the samples repaired by laser cladding are obviously higher than those repaired by TIG welding repairing process, and the samples repaired by laser cladding have better process stability. The tensile strengths of the samples using the laser cladding repair process and the TIG welding repair process at room temperature have reached 87.44% and 69.22% of the strength of K403 base material, respectively. According to the failure analysis results, the tensile fracture at room temperature in the repaired region presents mixed fracture characteristics, and the tensile fracture at high temperature presents intergranular fracture characteristics. Microcracks in the repaired area, local liquid phase deficiency defects and carbide structure are the main reasons of failure. The laser cladding technology has the advantages of heat source concentration and smaller heat affected zone, which can effectively restrain the defects and refine the microstructure. Therefore, the laser cladding repair process is used to repair the edge plate crack damage generated during the blade test run. After fluorescence and kerosene-chalk detection, the repairing process meets the relevant reuse requirements.

GH3536 and GH4169 nickel-based superalloys are widely used in aerospace engines and other hot-end components. In this paper, GH3536 and GH4169 alloy samples were fabricated by optimizing the process parameters using selective laser melting（SLM）, the defect characteristics and microstructure of two alloys, as well as the effects of different homogenization temperatures and holding times on microstructure evolution, average grain size, and properties of two alloys were studied. The defect characteristics and microstructure were investigated by OM, SEM, and EDS, et al. The Vickers hardness meter was used to test the alloy’s microhardness. The results indicate that the as-built GH3536 alloy exhibits more defects, including pores, cracks, and lack of fusion, while only pores are present in as-built GH4169 alloy. The melt pool of alloy is eliminated by homogenization treatment, and the grains grow into equiaxed grains. M₂₃C₆ are found to distribute within grain boundaries and grain interiors of GH3536 alloy, while NbC are found to distribute within grain boundaries and grain interiors of GH4169 alloy, and the amount of precipitates is significantly reduced with the increase of homogenization temperature. The average grain size of GH3536 alloy is increased by 106.8% from 48.5 μm at 1130 ℃/1 h to 100.9 μm at 1250 ℃/4 h. The grain size of GH4169 alloy is increased by 53.3% from 57 μm at 1080 ℃/1 h to 87.4 μm at 1200 ℃/4 h.The homogenization treatment of GH3536 alloy and GH4169 alloy results in a significant decrease in microhardness of the former, from 262HV to 180-190HV, while the latter shows a significant increase, from 313HV to 430-450HV.

GH4169 alloy usually serves in high temperature environment, and the high temperature performance of GH4169 alloy made by additive material is often lower than that of the standard of forgings, which affects its service safety, thus it is necessary to improve its safety by means of heat treatment. In this work, GH4169 alloy was prepared by selective laser melting（SLM）, and the effects of hot isostatic heat treatment process on the microstructure, high temperature tensile properties and high temperature stress rupture properties of the SLM formed GH4169 alloy were investigated by using characterization methods such as optical microscopy（OM）, scanning electron microscopy（SEM）and X-ray energy dispersive spectrometry（EDS）, etc. The results show that, compared with the conventional heat treatment processes, the grains of GH4169 alloy after hot isostatic treatment are equiaxed, the pores and Laves phases are basically disappeared, the short rod-like δ phase is more continuous at the grain boundaries, a large number of granular γ'' phases are precipitated inside the grains, and the grains are significantly refined. After hot isostatic pressing treatment, the ultimate tensile strengths of GH4169 alloy at 650 ℃ are 1053 MPa and 1051 MPa, the elongations after breaking are 8.6% and 8.5%, the high temperature stress rupture properties are 1620 min and 2065 min, and the high temperature endurance time is improved by 90 times and 30 times respectively in scanning and building direction. The high temperature ultimate tensile strength and high temperature stress rupture properties are higher than wrought standard, while the elongation after breaking has not exceeded the wrought standard.

Introducing emerging high entropy alloys materials into advanced intelligent manufacturing for laser additive repair is expected to promote the deep integration of new generation of materials and manufacturing technology and greatly improve the utilization of raw materials and energy, which have broad application fields and excellent development prospects. This paper introduces the application status of high entropy alloys in laser additive repair, and points out that the mismatch of strength and toughness, inaccurate performance control and unclear strengthening mechanism are the key scientific problems that need to be solved urgently in the expansion and application of high entropy alloys in laser additive repair. Exploring the ductile-brittle transition mechanism of the high entropy alloys cladding coating metal, clarifying the basic mapping relationship among the materials, processes, microstructure and coating performance of cladding coatings, obtaining a complete and effective method for predicting the composition of high entropy alloys, innovating the design of alloy powder system, optimizing and adjusting the control processes, and obtaining a high-performance cladding coating suitable for extreme service environment and with low cost are the main research focus and development trends in the future.

Multiple GH4169 samples were prepared with the regulation of the forming process of selective laser melting（SLM）, particularly in laser power and scanning speed. The microstructure including defect morphology and distribution was observed by using metallography. The sample porosity was acquired using X-ray computed tomography（XCT）, and the three-dimensional characteristics of defect were also statistically studied. The correlation of forming process and defect characteristics was finally analyzed. The results show that when the optimized energy input density is 59.1 J/mm³, the forming samples share common features of overlapping melting trace with a tidy morphology, randomly distributed pores with sizes of less than 30 μm and the density is as high as 99.9998%. Within a narrow window of forming process（220-300 W, 700-1300 mm/s）, the scanning speed takes more responsibility for the sample density, and its high value tends to form extremely irregular lack of fusions（LOFs） that distribute in the overlap of melting trace. As deviating from the optimized process, the number of defects has increased, and some defect sizes are also greater than 30 μm. The shapes of pores and LOFs respectively formed by high laser power or high scanning speed are closely related to their own sizes, that is, the larger the size, the more irregular the shape, which produces more detrimental effects than regular pores.

Wire arc additive manufacturing (WAAM) is an additive manufacturing technology with high deposition rate that produces a variety of high-performance metal structures layer by layer stacking. The research on WAAM technology of large and medium complex aluminum alloy and titanium alloy for aviation equipments has been widely concerned. In this paper, the WAAM technical definition, classification, forming system and principle are discussed. The recent research progress in the microstructure properties, metallurgical defects, quality improvement and technical application of typical components of aluminum alloy and titanium alloy formed by WAAM in aerospace field both at home and abroad is reviewed. The key common problems in the WAAM forming large and medium complex components of aviation equipments are analyzed, and the 2035 WAAM forming technology route planning map is proposed. In 2035, the "shape control" and "property control" technology of WAAM aluminum alloy and titanium alloy component is to be mastered; the large and medium complex structure components of aluminum alloy and titanium alloy which formed by WAAM are achieved comprehensive application in aviation equipment.

Additive manufacturing technology has a broad development prospect in the field of aviation equipments. As an important metal additive manufacturing process, the electron beam additive manufacturing is in a rapid development stage. The wire-feed electron beam additive manufacturing can meet the requirements of rapid and low-cost manufacturing of aviation large size structural parts and can be used to repair high-value damaged parts. Electron beam selective melting has obvious advantages in the manufacturing of complex structures and refractory alloy parts. Based on the analysis of the state-of-arts of the electron beam additive manufacturing technology, the roadmap of the electron beam additive manufacturing for aviation equipments in 2035 is comprehensively analyzed and drawn from the five aspects of development needs, objectives, common key technologies, applications, strategic support and guarantee in order to provide reference for the development of the electron beam additive manufacturing technology of aviation equipments. In 2035, a perfect additive manufacturing standard system is to be built; and electron beam additive manufactured key load bearing components for airplane andaeroengine realize mass production and application.

In this study, the third-generation rhenium containing single crystal superalloy was brazed by mixed powder filler, in which the mixed powder filler was consisted of nickel-based powder filler and the superalloy powder with the same composition of the base metal. SEM and EPMA were used to analyze the influence of the proportion of the third-generation single crystal superalloy powder in the mixed filler on the microstructure of the joint, and the high temperature stress rupture properties of the brazed joint with four kinds of solder were tested. The result indicates that the microstructures and phase compositions of the Ni-based powder filler and mixed powder filler are both consisted of γ-Ni, γ′, CrB, Ni₃B and M₃B₂ type boride, but the residue of the mixed powder filler is molten ball-type superalloy. With the thickness of brazing gap constant and increasing the ratio of the third-generation single crystal superalloy powder in the mixed filler, the precipitation of M₃B₂ type boride and low-melting point phases in the joint can be inhibited, and the distribution of borides becomes more uniform and the size becomes smaller, thus improving the uniformity of the composition and microstructure of the joint. When the proportion of alloy powder increased from 0% to 50%, the endurance life of the joint increased from 15 min to 34 hours. However, when the proportion of alloy powder increased to 60%, there are a lot of void defects in the joint, resulting in the endurance life of the joint decreased to 4 hours.

Ti-6Al-4V(TC4) titanium alloy is a kind of α+β type two-phase titanium alloy widely used. However, due to the microscopic defects in additive manufacturing titanium alloy, its mechanical properties are lower than the forging level, and post-treatment is usually required. Therefore, it is necessary to further study the additive manufacturing process and post-treatment of TC4 titanium alloy. In this paper, the microstructure and comprehensive properties of titanium alloy were analyzed by the changes of common process parameters such as energy input power and scanning strategy in the additive manufacturing process, and the influence of other process parameters such as protective gas type, substrate thickness, powder size and other factors in the additive manufacturing process was introduced. The influence of common heat treatment methods after additive manufacturing on its microstructure and mechanical properties was also comprehensively analyzed, and the influence of new post-heat treatment methods, such as vacuum heat treatment and cyclic heat treatment, as well as the influence of multiple post-treatment and comprehensive use of heat treatment were summarized. Generally speaking that the reasonable selection of additive manufacturing process parameters and the application of post-heat treatment method are the basis for obtaining titanium alloy components with excellent performance. The comprehensive use of various heat treatment methods or other post-treatment methods and heat treatment are the effective ways to further improve the performance of titanium alloy components in additive manufacturing. To establish a uniform selection standard for additive manufacturing process parameters and post-processing process is the key to the future development of additive manufacturing.

Laser additive repair technology is suitable to repair the metal parts of military aircraft. It is an important thrust to prolong the flight service life and improve the ability of independent maintenance. This paper introduced the characteristics of laser additive repair technologies such as selective laser melting forming, laser direct deposition forming, laser cladding and laser arc composite additive manufacturing. The common types of defects with different scales, such as edge collapse, surface spheroidization, porosity and crack in the process of laser additive repair were described, and the corresponding control methods were proposed. The laser energy density, overlap ratio, feeding speed of filler materials, shielding gas flow, time parameters and scanning path of laser additive repair technology were summarized, and the repair performance was improved by the application of external energy field and optimization design of special filler materials. Finally, the application of laser additive repair technology in the maintenance of aircraft wing beams, turbine blades, single crystal blades, landing gear and other metal parts was listed. The future research trend of laser additive repair technology in auxiliary system design, multi energy field fusion, evaluation standard formulation was emphasized, the research and development of mobile laser additive repair equipment were discussed.

Additive manufacturing provides a new way to develop high-performance superalloys and components. A γ′- strengthened CoNi-base superalloy suitable for additive manufacturing was developed, and a crack-free block material was prepared by optimizing the parameters of electron beam melting（EBM） technology. The experimental results show that the lowest porosity of the alloy is about 0.14% when the scanning speed is 2000 mm/s. The microstructures of the as-printed CoNi-base alloy are columnar grains growing along the <001> direction, the average grain width is about 235 μm, and the volume fraction of γ′ phase is about 30%. After hot isostatic pressing and solution aging treatment, the porosity of the alloy is further reduced to about 0.09% with unobvious change of columnar grains. The average size of γ′ phases is about （70±18）nm with the volume fraction of about （32±3.6）%. The results of room temperature tensile tests show that the additive manufactured γʹ-strengthened CoNi-base superalloy exhibits excellent strength and ductility, showing a good potential of industrial application.

Turbine blades of long-life civil aircraft and gas turbines are affected by high temperature oxidation during service, which greatly reduces the surface strength under complex working conditions and significantly shortens the service life. Therefore, oxidation resistance is one of the most specific properties that must be considered in the application of turbine blades. The influence of the different drilling processes for cooling holes on the oxidation behavior of Ni-based SX (single-crystal) superalloy at 980℃ and 1100 ℃ was investigated. The difference in the oxidation mechanism of the cooling holes under different drilling processes provided a basis for the establishment of the blade life model under service conditions. The results indicate that the film cooling holes processed by millisecond laser exhibit poor oxidation performance, and all oxidation kinetic curves basically obey the parabolic or linear law. In the initial oxidation stage of the millisecond laser specimen, the oxidation reaction is primarily determined by the growth pattern of outer NiO. Subsequently, a three-layer oxide layer（(Ni, Co)O-Spinel phase layer-α-Al₂O₃） gradually formed around the hole. There are relatively micro-holes under the internal α-Al₂O₃ layer and the γ'-free zone, which makes the oxide layer easy to exfoliate. Discontinuous α-Al₂O₃ is rapidly formed in the initial oxidation stage of the picosecond laser specimen, and then connected to each other to form the dense α-Al₂O₃ layer.

IIn order to improve the corrosion resistance of 300M steel surface, NCLT was used in cw-1k solid-state Nd: YAG laser system, Hastelloy C276 coating with 800W laser power and 8 mm/s scanning speed was prepared on the surface of cw-1k solid-state Nd: YAG laser system. The macro morphology, microstructure, phase composition, microhardness, friction and wear properties and electrochemical properties of C276 coating were tested. The results show that the microhardness of C276 coating is increased by 1.4 compared with the substrate. However, the wear resistance of the coating is lower than that of the 300M steel substrate, the corrosion potential of the coating is the highest, the self - corrosion current density is the smallest. The C276 coating is prepared on the surface of 300M steel by laser cladding technology, which significantly improves the corrosion resistance of 300M steel surface, and provides a new scheme for improving the corrosion resistance and corrosion resistance of the material surface.

Thermoplastic composites exhibit high toughness and damage tolerance, as well as good impact resistance. Additive manufacturing offers an effective way for making high-performance complex thermoplastic composite components without molds, which has a broad application prospect in aerospace and other fields. This article introduces the research progress of additive manufacturing process of short-cut fibers/continuous fibers reinforced thermoplastic composites. The processes and mechanical properties of different resins and fibers are compared. For the additive manufactured PEEK reinforced with 10%(volume fraction, the same below) of shortcut carbon fibers, the tensile strength and modulus can reach 109 MPa and 7.4 GPa, respectively, which is 85% higher than the pure PEEK. For the additive manufactured ABS reinforced with 10% continuous carbon fibers, the tensile strength and modulus can reach 147 MPa and 4.185 GPa, respectively, which is 5 times and 2 times of pure ABS. According to different processing routes and material systems, the equipment for fabricating advanced thermoplastic composites becomes larger and more integrated. Finally, from the material, equipment, process and application perspectives, the challenges and opportunities of thermoplastic composites by additive manufacture are identified.

The development of supersonic aircraft has created an urgent demand for heat-resistant aluminum alloy that can serve at the temperatures range from 300 ℃ to 500 ℃. However, the high-temperature mechanical properties of heat-resistant aluminum alloys are still unable to meet practical application requirements. Therefore, further research is needed from the aspects of material composition design and microstructure control to improve the comprehensive mechanical properties of heat-resistant aluminum alloys. In this paper, the research progress of heat-resistant aluminum alloys is reviewed from the aspects of microalloying design and eutectic alloys, and the development trend of heat-resistant aluminum alloys is prospected. The article first systematically introduces the development history and research status of Al-Sc, Al-Cu, Al-Si, and Al-Mg heat-resistant aluminum alloys, focusing on the microalloying design ideas of heat-resistant aluminum alloys, as well as the effects of transition metal elements and rare earth elements on precipitation phases, microstructure, and mechanical properties. Subsequently, the development status of heat-resistant eutectic aluminum alloys in Al-Fe, Al-Ni, Al-Ce, and Al-Si systems is comprehensively summarized, with a focus on the important role of rapid solidification technology and additive manufacturing technology in promoting the development of heat-resistant eutectic aluminum alloys. Finally, the main problems faced in the development and application of new heat-resistant aluminum alloys are analyzed, and the development trends of future research on heat-resistant aluminum alloy is discussed from the perspectives of data-driven composition design, high-throughput experimental verification, engineering application research, and standard system construction.

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.

In this paper, repeated brazing thermal cycles were carried out for the single crystal superalloy DD6 at 1220 ℃ for 30 min. The dendrite segregation was analyzed . The microstructural evolution and mechanical property of the alloy DD6 after thermal cycles were studied in detail. The results showed that the segregation coefficient didn’t change obviously after brazing thermal cycles in comparison with the original state. After one brazing thermal cycle, the γ′ phases grew up visibly, but they still kept a certain degree of cubitization. After two or three brazing thermal cycles, the cubitization of the γ′ phases decreased obviously. Therefore, the brazing repair times should not be more than one in this condition. With the increase of brazing thermal cycles, the original γ′ phases not only became larger and connected, but also a small part of the γ′ phase edge changed from straight state to uneven state, and gradually a large number of serrated state. It was also found that the fine secondary γ′ phases were formed in some of γ matrix during each cycle either in the dendritic core or interdendritic region. After each thermal cycle, the alloy DD6 can keep 100 h at 980 ℃ with the initial stress of 250 MPa. After that, the stress was increased by 25 MPa every 10 h until the sample fractured. The stress rupture life was similar to that without thermal cycle, but the elongation and redution of area were increased gradually.

4D printing technology has attracted people's attention since it came up in 2013. 4D printing is a kind of new manufacturing technology which is based on 3D printing and smart materials. In other word, 4D printing is evolved from 3D printing and aimed at the improvement of structure, property and function. 4D printing predicts that the self-assembly, multifunction and self-healing can be achieved. This paper reviews the whole research progress of 4D printing in time sequence, and summarizes the achievements of this technology in material science, manufacturing industry, bioengineering and medical science. In addition, the application perspectives in this field are also discussed.

According to the repair demand of aircraft 30CrMnSiA high-strength steel pull rod, the laser cladding process research and pull rod repair were carried out using gas atomized 30CrMnSiA powder as cladding material. The effects of different process parameters on forming quality were compared. The microstructure, mechanical properties and wear resistance of the cladding area under the optimal laser process were studied, and the damaged part of the pull rod was repaired by this process and dimensional measurement was carried out. The results show that using the optimal laser cladding process, the cladding layer with good metallurgical bonding with the base metal and dense microstructure can be obtained. The cladding layer is composed of columnar or honeycomb shaped ferrite and surrounding martensite. The microhardness of the cladding layer is about 475HV, about 36% higher than that of the base metal, and the average tensile strength of the joint is about 9% higher than that of the base metal. Compared with forged 30CrMnSiA steel, the depth of wear track of the cladding layer is reduced by 27.7%, and the width of wear track is also reduced by 35.2%, which means better wear resistance. By using this process, a repaired pull rod with good cladding quality, satisfactory dimensional accuracy and basically no thermal deformation is obtained, so the qualified products are delivered.

GH3536 superalloy was fabricated using Selective Laser Melting (SLM) to investigate the effect of process parameters including the laser power and scanning speed on the density, microscopic defects and surface quality of GH3536 samples. According to the measurement of density, it can be found that the density of samples increases rapidly when the laser energy density is less than 57.0 J/mm³, the density of samples fluctuates within the range of 8.30 g/cm³-8.35 g/cm³ as the laser energy density increases from 57.0 J/mm³ to 187.0 J/mm³, while the density of samples decreases slightly when the laser energy further increases. The conclusion is that the inadequate or excessive energy input reduces the density of samples. The metallographic observation shows that there are a large number of lack-of-fusion defects when the laser energy is insufficient. However, when the input laser energy is too much, many evenly distributed microcracks and gas pores appear inside of samples, indicating that defects are the main reason for low density of samples. The optimal process parameters of SLM-processed GH3536 alloy are determined by the statistical analysis of spatter particles which might cause irregular defects. Tensile properties of the sample fabricated under 175 W and 700 mm/s are tested at room temperature and the results show that the SLM-ed GH3536 superalloy has good tensile properties at room temperature.

In the current aviation industry, laser melting is an ideal technique for repairing and surface treatment of TC4 alloy parts, which has advantages over traditional metal repair techniques in terms of process. In this work, laser melting repair processes were performed on the surface of alloy specimens by different laser scanning speeds at a power of 2 kW, and the changes in metallographic organization, electrochemical corrosion properties and mechanical properties of the repaired surfaces were detected and analyzed. The results show that the significant microstructural changes are occurred during the laser repair process. The best corrosion resistance of the repaired surface is achieved at a laser scanning speed of 150 mm/min. The best microhardness and wear resistance of the repaired surface are achieved at 200 mm/min.

Nickel-based superalloy (GH4169) and Si₃N₄ ceramics were connected by AgCuTi composite active filler and high purity W foil which acts as interlayer. The effects of temperature on the microstructure evolution and mechanical properties of GH4169/ Si₃N₄ brazed joint were systematically studied. The results show that the effective connection of GH4169/Si₃N₄ brazed joint can be realized by using AgCuTi+W composite filler. The microstructure of the joint is GH4169/TiNi₃+TiCu+TiCu₂+Ag(s, s)+Cu(s, s)+W+TiN+Ti₅Si₃/Si₃N₄. When the brazing temperature is low, the Ti element in liquid filler diffuses to less of the ceramic interface with the filler, and no obvious reaction layer is formed; when the brazed temperature increases to 880 ℃, Ti is enriched on the ceramic side, forming a thickness of 2 μm TiN and Ti₅Si₃ reaction layer. At this time, the shear strength of the joint is the highest, reaching 190.9 MPa. With the increase in brazing temperature, the content of Ti-Cu compound, which is a brittle compound, increases and the mechanical properties of the joint are greatly reduced. The fracture results show that during the shear process, the crack initiates in the interlayer, and then diffuses into the Si₃N₄ ceramic matrix, and finally breaks on the side of Si₃N₄ ceramic.

Light-curing 3D printing technology stands out as one of the oldest, fastest-growing and most widely used technologies in the field of 3D printing. This technology utilizes ultraviolet or other light sources to rapidly solidify liquid photosensitive polymers, creating products with complex geometrical structures that are difficult to achieve with traditional manufacturing methods. This paper summarizes the latest research progress in photocurable polymer materials for 3D printing, covering various types of photocurable polymers including thermoplastics with high remoldability, thermosets with good structural stability, and hydrogels with hygroscopic network cross-linking structures. Additionally, the applications of photocurable 3D printing polymers in various fields such as biomedical, flexible electronic devices, soft robotics, energy storage, and aerospace are discussed in detail. This review also explores the application of photocuring technology in 4D printing, highlighting the potential of 4D printing in dynamic materials and smart manufacturing. In the future, light-curing 3D printing technology is expected to advance toward the development of high-performance polymer composites, the integration of intelligent and automated printing systems, and the deep integration with cutting-edge technologies such as artificial intelligence, continually driving its applications and innovations in high-tech fields and advanced manufacturing.

The microstructure characteristics and formation mechanism of linear friction welded (LFW) TC4-DT damage-tolerant titanium alloy joint were investigated . The microstructure of each zone of the joint was analyzed in detail by using an optical microscopy and a scanning electron microscopy; the microhardness distribution of the joint was tested by means of a microhardness tester. The results show that dynamic recrystallization occurs in weld zone (WZ); the WZ temperature exceeds the β-transus temperature during welding, and both β→α′ and β→α phase transformation occur in WZ under rapid cooling after welding, resulting in a large number of α′ martensite and secondary lamellar α are formed. Due to the high deformation resistance of TC4-DT titanium alloy, the thermo-mechanically affected zone (TMAZ) of this joint is relatively narrow. The structure of the TMAZ is elongated, deformed and broken seriously under the strong thermo-mechanically coupling effect. Moreover, a few α′ martensite and a large number of secondary lamellar α are formed in TMAZ under the condition of rapid cooling after welding. The microstructure characteristics of α colony with different orientation of the base metal (BM) is basically preserved in the heat affected zone (HAZ). However, due to the influence of heat, the mutual diffusion of elements occurs at the α/β phase boundary in α colony, the interlayer β is consumed, and the primary α grows up. The refined crystalline strengthening and second phase strengthening of the WZ microstructure, the strain strengthening and second phase strengthening of the TMAZ microstructure, and the growth of α phase in the HAZ make the microhardness of above zones higher than that of the BM.