TiC/Ti6Al4V composites are prepared by synchronous ultrasonic energy field-assisted laser melting deposition. The effects of synchronous ultrasonic energy field treatment on the microstructure and properties of the composites with TiC volume fraction of 5% and 20%， respectively， are studied. The results show that the as-built composites contain inhomogeneous distributed undissolved TiC particles and in-situ TiC particles， among which 5%TiC/Ti6Al4V （volume fraction，the same below）composites contain chain shaped eutectic TiC with larger size， and 20%TiC/Ti6Al4V composites contain dendritic primary TiC with larger size. With the application of synchronous ultrasonic energy field treatment， the distribution uniformity of undissolved TiC particles in the composite is improved. Moreover， the in-situ TiC reinforcing phase is refined， where the chain shaped eutectic TiC transforms to granular eutectic TiC， and the size of dendritic primary TiC decreases. Due to the effect of synchronous ultrasonic energy field treatment， the microhardness of 5%TiC/Ti6Al4V and 20%TiC/Ti6Al4V increases from 406.5HV_0.2 and 498.4HV_0.2 to 414.2HV_0.2 and 539.1HV_0.2， respectively. The wear rates reduce from 1.82 × 10^-6 mm³·m^-1·N^-1 and 1.04×10^-6 mm³·m^-1·N^-1 to 1.78×10^-6 mm³·m^-1·N^-1 and 9.48×10^-7 mm³·m^-1·N^-1， respectively. The tensile strength of the 5%TiC/Ti6Al4V increases from 1075.23 MPa to 1116.31 MPa， the yield strength increases from 1021.51 MPa to 1043.12 MPa， and the fracture strain increases from 1.27 % to 1.45 %， which realizes the simultaneous improvement of strength and plasticity.

SiO₂， TiO₂， NaCl， and KCl are chosen as activating fluxes for laser welding of 5 mm thick TC4 titanium alloy to increase the laser absorptivity of base material and improve weld formation. Based on the influence of activating fluxes on weld formation， the mechanism of action of activating fluxes and their impact on the microstructure and properties of welded joints are analyzed. The experimental results show that the activating fluxes have no significant effect on the macro formation of the weld， and the four activating fluxes can affect the shape size of the weld by increasing the laser absorptivity related to welding heat input. Besides， SiO₂ mainly reduces the absorption and scattering of laser beam by reducing photoinduced plasma， and TiO₂ primarily reflects and propagates laser beam among the fine particles， NaCl and KCl have both. The tensile strength of the joint coated with SiO₂ and TiO₂ has descended by 14% and 10% respectively. It is related to the change of weld microstructure by activating fluxes. The tensile properties of the welded joints coated with NaCl and KCl are not lower than that of uncoated welded joints. They can be used as an effective activating flux for TC4 titanium alloy laser welding.

The Ti/Al dissimilar welded structure combines the high strength and corrosion resistance of titanium alloys with the lightweight and formability advantages of aluminum alloys， providing a broader range of options for product design and manufacturing. Meanwhile， this structure helps reduce component mass and cost， achieving lightweight design and structural-functional integration. Friction stir welding （FSW）， as a solid-state welding method， is one of the most suitable techniques for Ti/Al dissimilar joining. However， conventional Ti/Al FSW still faces challenges such as severe tool wear， non-uniform mechanical properties along the weld thickness， potential lack of penetration at the weld root， and difficulty in precisely controlling intermetallic compounds （IMCs）. This paper reviews the improvements proposed by researchers worldwide to address these issues， exploring various innovative processes to overcome the limitations of conventional Ti/Al FSW and achieve high-quality joints. It analyzes and compares the characteristics and applicability of different modified FSW techniques， including interlayer addition at the interface， application of auxiliary external fields， modification of joint configurations， and stationary shoulder FSW. The study further explores their roles and mechanisms in enhancing weld quality and optimizing interface properties， while systematically summarizing future research directions for Ti/Al dissimilar FSW. Finally， it is pointed out that future research should focus on further optimizing modified welding processes， improving process stability， and enhancing industrial feasibility to promote the engineering application of Ti/Al dissimilar welded structures.

With the development of fields such as aviation， aerospace， and navigation， the service conditions for high-end equipment have become increasingly stringent， placing higher demands on the manufacturing industry. Additive manufacturing technology， also known as 3D printing technology， has significant advantages over traditional manufacturing techniques in producing complex shapes and structures， and it is expected to achieve specific location printing and structural printing with unique properties in three-dimensional space. Wire-based laser directed energy deposition （W-LDED） technology， as an important branch of additive manufacturing， has notable advantages such as high efficiency， high precision， and high material utilization， making it promising for applications in the manufacturing of high-end equipment. Despite the many advantages of W-LDED technology， there are still numerous challenges regarding the selection of process parameters， multiple thermal cycles， and the precise control and repeatability of the manufacturing process. The deposition quality and manufacturing stability are influenced by various factors， and addressing these current challenges is a key focus of research both domestically and internationally. Based on this， this paper provides a detailed introduction to the current research status of W-LDED technology from three aspects： process parameter optimization， deposition quality analysis， and microstructural composition control. It analyzes the impact of different parameters on forming quality and manufacturing stability， proposes optimization strategies， summarizes the current application scenarios of W-LDED technology， and presents ideas for the future development trends of this technology，including material innovation and the development of multifuctional composites，research on forming mechanisms，establishing predictive models for process-defect-microstructure property relationships， new hybrid additive/subtractive manufacturing methods，and the development of large-scale，high-precision，and multifuctional equipment.

NiTi shape memory alloys （SMAs） have found widespread applications due to their unique superelasticity and shape memory effects. However， traditional manufacturing methods face challenges in fabricating complex geometries and precisely controlling the microstructure NiTi alloys. Wire arc additive manufacturing （WAAM）， with its layer-by-layer deposition characteristics， offers a novel solution for NiTi alloy fabrication. This paper reviews the research progress in WAAM NiTi shape memory alloys， with emphasis on the influence of process parameters on microstructure， phase transformation behavior， and mechanical properties. The advantages and disadvantages of different arc processes （such as gas metal arc welding， gas tungsten arc welding， and cold metal transfer） in NiTi alloy fabrication are analyzed， along with recent achievements in forming quality， phase transformation temperature control， and mechanical properties through WAAM technology. Particular attention is given to the significant microstructural heterogeneity and oxidation issues arising from high heat input， low cooling rates， and repeated thermal cycling during the layer-by-layer deposition process， which adversely affect mechanical properties and superelastic performance. To address these challenges， strategies including process optimization， active cooling， third element addition， and heat treatment are proposed to improve material homogeneity. Furthermore， this paper discusses the heterogeneous structure design of NiTi alloys with other metals， highlighting the potential of WAAM in fabricating multi-material composite structures for high-performance devices. While WAAM demonstrates advantages in fabricating complex geometries and multi-material structures， challenges remain regarding oxidation， element vaporization， and poor interlayer bonding. Future research should focus on heat treatment optimization and microstructural control， development of novel multi-metal composites， and exploration of innovative approaches to enhance interfacial bonding and oxidation resistance， thereby further improving NiTi alloy performance and expanding their application domains.

Addressing the need for high-precision shape control and low-damage property control in formed parts， as well as the goal of achieving deep decoupling of thermal， mass， and force aspects of the heat source while increasing the deposition rate， multi-electrode arc welding/additive manufacturing （AM） technology has gradually become a focal point of interest in both academia and industry. This paper systematically reviews the development history of multi-electrode arc processes， comprehensively summarizes the cutting-edge research achievements in the field of multi-electrode arc welding and AM， and categorizes and summarizes different types of coupled arcs in multi-electrode arcs. The multi-electrode arc system achieves finer control over the thermal-mass-force transfer process of the hybrid arc by introducing multiple electrodes， which helps optimize the forming quality of deposited layers， reduce defects， and improve manufacturing precision. This study highlights the differences in heat source and electrode arrangement configurations among various types of multi-electrode arc processes， and their distinct thermal-mass-force decoupling transfer characteristics， summarizes the influence mechanisms of welding process parameters on the stability of hybrid arcs. Finally， this paper proposes multi-electrode arc characteristics suitable for wire arc additive manufacturing， explores the high-performance manufacturing of composite components， and establishes a process database for novel multi-electrode arc technologies， which provide valuable insights for the application and promotion of coupled arc and multi-electrode arc AM technologies.

The oxidation kinetics and microstructure of S30815 heat resistant stainless steel， both in its base material and welded joint， are analyzed at different service temperatures by the constant temperature oxidation method. High temperature oxidation kinetic curves are obtained by the mass gain method. The morphology， composition， and microstructure of the oxide films are studied by using scanning electron microscopy （SEM）， energy dispersive spectroscopy （EDS）， and X-ray diffraction （XRD）， respectively. The results show that under constant temperature oxidation conditions at 780 ℃， there is less mass gain and a relatively lower oxidation rate. The oxidation products are mainly Cr₂O₃， Fe₂O₃， and Fe₃Mn₃O₈， exhibit sheet， strip， and polyhedron shapes. At 880 ℃， the mass gain and the oxidation rate significantly increase. The oxidation product at this temperature comprises a mixed oxide of Cr₂O₃， Fe₃O₄， MnFe₂O₄， and Ni （Cr₂O₄）， which is mainly in thin strips and sheets. The oxidation kinetics curves of S30815 follow a parabolic rule. With the increase of oxidation time， the oxidation rate gradually decreases and eventually tends to be stable， showing a good oxidation resistance at high temperature. A larger amount of dense Cr₂O₃ oxide film is generated on the surface of the welded joint， exhibiting a lower average oxidation rate and better oxidation resistance compared to the base material.

Wire arc additive manufacturing （WAAM） employs an arc as the energy source to melt metal wire layer by layer， making it suitable for the rapid fabrication of medium to large-sized complex metal components. Owing to its high forming efficiency， low manufacturing costs， and exceptional material utilization rates， WAAM has extensive application prospects in the aerospace and defense sectors. The regulation of residual stress and distortion in metal components is a key scientific and technical problem that must be solved to promote the efficient and high-quality development and application of WAAM. The mechanisms and influencing factors of residual stress and distortion in WAAM are explored. The experimental measurement and numerical simulation methods are analyzed and compared， and strategies for reducing residual stress and distortion at different stages of the WAAM process （before， during， and after deposition） are systematically summarized. Finally， it is pointed out that numerical simulations， machine learning， in-situ diagnosis， and control are the key research directions for controlling residual stress and distortion in WAAM in the future.

Multi-wire arc additive manufacturing technology has the advantages of low cost and high efficiency， especially high flexibility in composition design and regulation， and has become the mainstream technology for the preparation of large-scale complex metal structural parts. Multiple wires （same or different） are fed at the same time to realize in-situ alloying in the molten pool. This method provides a feasible path for the preparation of advanced metal materials with complex compositions. This paper discusses the research progress of multi-wire arc additive manufacturing in the preparation of traditional materials such as high-performance titanium alloys， aluminum alloys， and stainless steels， as well as advanced metal materials such as functionally graded materials， high-entropy alloys， and intermetallic compounds. The problems of uneven microstructure， anisotropy of mechanical properties and insufficient forming accuracy of multi-wire arc additive manufacturing components are discussed. The development directions of multi-wire arc additive manufacturing process window， multi-process coupling， and forming process monitoring and control system are proposed， which provide a theoretical basis for the improvement and development of the multi-wire arc additive manufacturing process.

The 18Ni350 maraging steel（M350） straight-wall component is fabricated using wire arc additive manufacturing（WAAM） process. By employing direct aging heat treatment， the microstructure and mechanical properties of M350 are controlled. The effect of different aging conditions （aging temperature and aging time） on the microstructure and performance of M350 is studied. The results show that the solidification microstructure of M350 fabricated by wire arc additive manufacturing consists of columnar dendrites and cellular dendrites， with segregation of Ni， Mo， and Ti elements observed in the interdendritic regions.During the direct aging process， a reverse transformation occurs in the interdendrite region where Ni， Mo， and Ti elements segregate，leading to the conversion of martensite phase to austenite phase. With the increase of aging temperature and aging time， the size and quantity of reversed austenite increase. The microhardness， yield strength （YS）， and ultimate tensile strength （UTS） first increase and then decrease. The peak microhardness （534HV）， YS （1600 MPa）， and UTS （1658 MPa） are achieved at 530 ℃ aging for 3 h. At the same time， the elongation after fracture remains a value above 13%. In addition， the M350 fabricated by wire arc additive manufacturing demonstrates mechanical anisotropy， with the anisotropy difference peaking under the optimal aging conditions， exhibiting a YS difference of 360 MPa and a UTS difference of 287 MPa.

In order to obtain NiTi alloy with excellent properties， dual-wire arc additive manufacturing technology is used to control the wire feed speed of Ni and Ti wires， and precisely adjust the atomic ratio and phase composition of Ni alloy. The results show that when the Ni/Ti atomic ratio is 8∶10 in the center of the longitudinal cladding passage， the deposited NiTi alloy is mainly composed of Ti₂Ni phase accompanied by a small number of Ti-rich particles， and the microhardness and compressive strength reach 560HV and 1600 MPa， respectively. When the Ni/Ti atomic ratio is 11∶10， the Ti₂Ni phase is included in the NiTi phase， and the irrecoverable strain of 1.6% appears in the cyclic compression process. When the atomic ratio of Ni/Ti is 15∶10， the cluster Ni₃Ti phase is formed in the NiTi phase， the longitudinal fracture strain is close to 40%， and the irrecoverable strain is only 1.2% after cyclic compression， showing good superelasticity. In addition， compared with the central region of the longitudinal cladding passage， the microstructures of the transverse lapping region of the samples with different Ni/Ti atomic ratios show obvious grain coarsening and component segregation， and the compressive strength and plastic deformation ability are significantly reduced.

During the wire-arc additive manufacturing process， Al5356 straight-wall components are fabricated by imparting lateral swings of varying frequencies and amplitudes to the welding gun. The impact of these swinging arcs on the forming quality， pore distribution， microstructure， and mechanical properties of the components is evaluated through surface waviness calculations， microstructural analysis， and mechanical tensile tests. The results show that incorporating the arc swing technique in the manufacturing process significantly enhances the forming accuracy， compactness， microstructural uniformity， and mechanical properties of the straight-wall samples. Within the experimental parameters， applying an arc swing reduces the surface waviness of Al5356 straight-wall samples by 60% compared to those produced without an arc swing. Additionally， the porosity and maximum pore diameter are decreased from over 0.65% and 33 µm to below 0.20% and 10 µm， respectively. The average tensile strength in both the X-direction （deposition direction） and Z-direction （build direction） increases by approximately 13% and 15%， respectively， while the average elongation improves by about 27% and 25%， respectively. Notably， the frequency of the arc swing has a more pronounced effect than the amplitude in enhancing surface quality， pore dispersion， and pore diameter reduction in the deposited components. High-frequency arc oscillation exerts a potent stirring effect on the melt pool， leading to a more uniform temperature distribution across the transverse direction of the deposited weld path. The observed enhancement in mechanical properties is primarily attributed to the reduction of pore defects and the homogenization of the microstructure. Therefore， the proper application of the arc swing technique in wire-arc additive manufacturing holds significant promise for improving the forming quality and mechanical properties of components.

To improve the comprehensive mechanical properties of selective laser melting （SLM） TA15 alloy， the microstructure and mechanical properties of SLM TA15 alloy are studied under annealing conditions of 800 ℃+air cooling， 950 ℃+air cooling， and 1050 ℃+air cooling. The microstructure characteristics of TA15 alloy under annealing conditions are characterized by electron backscatter diffraction. The results show that the orientation and texture of the α phase are not changed after the heat treatment at 800 ℃ or 950 ℃， showing the characteristics of a net basket structure. After the heat treatment at 1050 ℃， the texture with the maximum strength of 9.18 appears along the direction ［0001］， showing the characteristic of the weistenite structure. With the increase of annealing temperature： the width of both α' and α phase increases gradually； the aspect ratio of both α' and α phase increases first and then decreases； the geometrically necessary dislocation density of both α' and α phase decreases gradually； the Vickers hardness of the sample decreases first and then increases， with the highest Vickers hardness of （397.2±10）HV for the unheat treated sample； the strength of TA15 sample decreases gradually； and the elongation increases first and then decreases. After tensile tests， the unheat treated samples show mixed fracture characteristics， the samples treated at 800 ℃ and 900 ℃ show plastic fracture characteristics， and the sample treated at 1050 ℃ show brittle fracture characteristics.

As a common additive manufacturing （AM） technology， selective laser melting （SLM） is a great potential manufacturing technology for special-shaped parts，such as porous and thin-walled parts. However， the traditional single beam SLM technology develops slowly due to the problems of lesser forming size and inferior efficiency. On the basis of single-beam SLM， multi-beam selective laser melting （MB-SLM） uses multiple beams and multiple galvanometers to partition scan and perform overlap forming. It greatly improves the forming size and efficiency， perfectly solves the inherent problems of single-beam SLM，and is expected to become an emerging technology to expand the application of metal additive manufacturing. The research progress of multi-beam selective laser melting in forming principle， forming equipment， and formation and control of defects is reviewed. The microstructures and mechanical properties of different alloys manufactured by multi-beam selective laser melting are summarized. Importantly， the main strategies to control defects and mechanical properties are highlighted. Finally， the development trends are forecasted， such as the impact of temporal and spatial difference characteristics between multi-beam on mechanical properties， and the consistency change of process parameters between different regions to reduce defects of formed parts.

As-deposited parts of 2024 aluminum alloy are fabricated by cold metal transfer and pulse （CMT+P） hybrid wire arc additive manufacturing. The distributions of pore defects， grain morphology， and secondary phase precipitation of CMT+P wire arc additive manufacturing 2024 aluminum alloy， and the influence of different process parameters on pore defects， grain morphology and secondary phase precipitation， and corrosion resistance are investigated. The results show that the pores of the as-deposited parts of 2024 aluminum alloy are mainly distributed near the fusion line. In the same heat input， the larger wire feed speed and travel speed result in higher porosity. In a deposition layer， the upper part is the equiaxed grain without preferred orientation， and the lower part is the columnar grain with preferred orientation. In the same heat input， the texture is weakened and the percentage of equiaxed grains is increased due to the fine grain region in the higher wire feed speed and travel speed. The precipitated secondary phases are mainly Al₂CuMg， Al₂Cu， and rich-Fe， Mn phases. The secondary phases distribute continuously along the grain boundaries. In the early stage of corrosion， the main factor affecting the corrosion resistance of as-deposited parts is the precipitation amount of Al₂CuMg. The better local corrosion resistance is mainly caused by lower Al₂CuMg phase fraction in lower wire feed speed and travel speed.

The effects of different heat treatment processes on the anisotropy of TB6 titanium alloy fabricated by laser deposition manufacturing were investigated.The evolution of microstructure was analyzed by using optical microscope （OM）， scanning electron microscope （SEM）， and transmission electron microscope （TEM）. The variation trend and influence mechanism of anisotropy with heat treatment were investigated. The present research shows that the original β grains and the morphology of the primary α phase （α_p phase） are greatly affected by the thermal gradient. The original β grains in the microstructure of TB6 titanium alloy fabricated by laser deposition manufacturing are elongated along the deposition direction and are ellipsoidal. In addition， the relative slender α_p phase parallel to the deposition direction is found. These two factors jointly lead to the anisotropy of room temperature tensile property of the as-deposited samples. The tensile strength in the vertical deposition direction （X-direction ） is 7.3% higher， the yield strength is 5% higher， and the elongation is 32.4% lower than that in the deposition direction （Z-direction）. The low-temperature annealing treatment has little effect on microstructure， only the anisotropy of plasticity is decreased. After high-temperature annealing treatment， the difference in aspect ratio of α_p phase is significantly reduced， leading to the anisotropy of the room temperature tensile property decreases. The strength are still higher in the X-direction， and the elongation is higher in the Z-direction. The strengthening mechanism of the solution-aging treating sample is completely changed due to the precipitation of the secondary α phase （α_s phase）. In addition， there is no obvious preferential growth of α_s phase after heat treatment， so the anisotropy of the room temperature tensile property tends to be eliminated as the strength increases.

3D printing， as a new manufacturing technology， has been widely applied in the forming and manufacturing of various materials with enormous development prospects. Graphite has excellent high-temperature resistance， conductivity， thermal conductivity， thermal stability， and chemical stability， widely used in fields such as metallurgy， energy industry， aerospace， and nuclear industry. Using graphite and its composite materials as the matrix and 3D printing technology to produce graphite products can reduce the graphite production cycle， improve material utilization， reduce graphite dust pollution， and provide an efficient and economical comprehensive solution for personalized customization and industrial application of high-performance and complex shaped graphite. This article focuses on the 3D printing technology of graphite and its composite materials， analyzes and discusses the advantages and disadvantages of each technology， introduces the performance and application of graphite products formed by 3D printing， discusses the opportunities and challenges of graphite and its composite materials in the development process of 3D printing， and puts forward expectations and prospects for this. The development of graphite 3D printing technology needs to develop the types of expansion of graphite composite materials and new printing equipment and its supporting equipment， and conduct 3D printed graphite post -processing technology based on traditional graphite process.

The selective laser melted （SLM） GH4169 superalloy has a significant directional columnar dendritic solidification microstructure， which can cause severe mechanical property anisotropy and increase service risk. The GH4169 superalloy prepared by laser selective melting （SLM） technology is taken as the research object， and two different heat treatment processes are designed： hot isostatic pressing+standard solid solution+double aging and hot isostatic pressing+homogenization heat treatment+standard solid solution+double aging for post-heat treatment of the prepared alloy. The effect of two heat treatment processes on the anisotropy of microstructure and high-temperature tensile properties of GH4169 superalloy prepared by laser selective melting is investigated. The results show that the homogenization heat treatment eliminates the Laves phase， and the columnar crystal structure of the as-built GH4169 alloy transforms into an equiaxed crystal structure. The high-temperature tensile results show that the high-temperature tensile strength ratio and plasticity ratio of GH4169 alloy in the transverse and longitudinal directions without homogenization treatment are 1.10（1145/1040） and 0.83（10.2/12.2）， respectively. The high-temperature tensile strength ratio and plasticity ratio of GH4169 alloy in the transverse and longitudinal directions after homogenization heat treatment are 1.00（1041/1038） and 1.00（8.6/8.6）， respectively. The anisotropy of microstructure and mechanical properties of GH4169 alloy prepared by laser selective melting is eliminated.

The development of advanced aero-engines with high thrust-to-weight ratios in the future has an urgent need for new high-performance lightweight high-temperature compressor blisks. Laser additive manufacturing TC25G-TiAl4822 gradient structure material is an important material system for the blisk of the lightweight high-temperature compressor. The composition selection and solidification structure research of gradient transition layer alloy have a key influence on guiding the structural performance design of related components. To understand the solidification structure evolution behavior of （1-x）TC25G-xTiAl4822 transition layer alloy with the change of TiAl4822 pre-alloyed powder content in powder raw materials， two kinds of single raw material （TC25G or TiAl4822） alloy ingots and alloy ingots with nine kinds of mixed raw materials are prepared by laser melting technology. Material characterization equipment and hardness measurement devices such as optical microscope， scanning electron microscope， XRD， and TEM are used for the study. The research results show that with the increase of the content of TiAl4822 alloy powder in the raw material， the characteristics of solidified grains change to dendrite → equiaxed → dendrite. The microstructure of the alloy at room temperature changes as follows： α_p+α_s+β+α₂→α_p+ α_s+α₂+β/B2 → α+α₂+β/B2 → α₂+B2 → α₂+γ+B2 → α₂+γ. Due to the change of the phase content of different alloy compositions， the Vickers hardness of the matrix first increases and then decreases， the overall hardness value changes in the range of about 450-620HV when the powder proportion is 50%-70%. If the intermediate composition alloy is directly used as the transition layer， the hardness will suddenly change. Therefore， the selection of the transition layer alloy composition should consider the range close to pure TC25G or TiAl4822.The above results provide the basis for the composition selection of bimetallic transition layer alloys to avoid the intermediate proportion of powder content range.

The microstructure control and corrosion resistance of aluminum alloys fabricated by wire and arc additive manufacturing（WAAM） are important issues that must be studied in engineering applications. The 5356 deposited part is produced by a CMT （cold metal transfer） system. The microstructure and hardness are characterized by metallurgical microscope， X-ray diffractometer （XRD）， scanning electron microscope （SEM） and micro-hardness tester， and the corrosion resistance behavior is studied by using electrochemical workstation， slow strain rate stress corrosion testing machine. The results show that the microstructure of 5356 WAAM aluminum alloy is composed of α-Al matrix and β（Al₃Mg₂） phase. The grains in the deposition layer are columnar crystals with an aspect ratio of ≤2， and the β（Al₃Mg₂） phase exists mainly as finely dispersed particles， while the grains in the interface layer are recrystallized equiaxed grains with smaller size， and the β（Al₃Mg₂） phase is predominantly distributed in large discontinuous blocks along the grain boundaries， with fewer fine granular β（Al₃Mg₂） phase within the grains， leading to a reduction in the matrix strengthening effect. The self-corrosion current density of the deposited layer is 23% of that of the interface layer， which may be caused by the content and morphology of β（Al₃Mg₂） phase. The stress corrosion sensitivity index at a slow strain rate of 5356 WAAM aluminum alloy is 0.57， and samples experience fracture and failure at the interface layer in both silicone oil and 3.5%NaCl solution medium. This is attributed to the lower strength at the interface layer matrix and shearing effect played by large intergranular β（Al₃Mg₂） phase in silicone oil inert medium， while the β（Al₃Mg₂） phase dissolves preferentially in the 3.5%NaCl aqueous solution， and intergranular corrosion propagation is accelerated under tensile stress.

Based on the response surface design， the optimal process parameters for single-side friction stir welding（FSW） of 2195 Al-Li alloy sheets are studied. It is found that the higher the rotation speed and the lower the welding speed， the higher the tensile strength of the welded joint. The results show that in the single-side FSW， when the pin length is 2/3 length of the thickness of the plate， the root of the weld appears unwelded defects， the fracture form of the welded joint is between brittle and plastic fracture， and the tensile strength of the joint is poor. Based on the optimum process parameters of single-sided welding， double-sided FSW can overcome the unwelded defects at the root of single-sided welding. Under different tool pressures， when the stirring head speed is 1600 r/min， the feed speed is 150 mm/min， and the pressure is 0.1 mm， the double-sided welding can improve the tensile strength of the welded joint by about 10% and the elongation of the welded joint by 10%. In two-sided FSW， the material flow on the forward side is obvious， and the fracture mode of the welded joint is a plastic fracture. In double-sided welding， the plate is subjected to secondary stirring and heating， resulting in increased softening of the material in the welding area.The microhardness of the double-sided welded joint is further reduced than that of the single-sided welding.

The joining of aluminum/copper dissimilar metals is successfully achieved by ultrasonic-assisted nano-enhanced plasma arc fusion brazing， and a well-formed aluminum/copper lap joint is obtained. The effects of ultrasonic waves and SiO₂ nanoparticles on the macroscopic and microscopic morphology， organizational structure， mechanical properties and conductive properties of lap joints are analyzed and studied by SEM， EDS， XRD， tensile test and conductivity test. The results show that the lap joint is obtained under the coupling action of ultrasonic waves and SiO₂ nanoparticles， and the spreading and wetting effect of liquid aluminum on the copper surface is better， the front side of the weld is well formed， and the joint is mainly composed of intermetallic compound layer region and Al-Cu eutectic region. The thickness of the intermetallic compound layer is reduced obviously，and the mechanical properties of the joint is significantly improved. The relative conductivity of the aluminum/copper joint using SiO₂ nanoparticles and ultrasonic waves is 153.527%IACS， exhibiting improved mechanical properties and electrical conductivity.

To study the static recrystallization behavior of laser additive manufacturing superalloys and their effect on mechanical properties， the solid-solution strengthened nickel-based superalloy GH3536 was investigated.The selective laser melting（SLM）method was used to prepare test blocks and bars， which were subjected to solution treatment at 1175 ℃ for different time. The static recrystallization behavior during heat treatment was investigated by EBSD analysis to explore its influence on the tensile properties. The results show that the as-built state organization is dominated by columnar grain growing along the build direction with 〈001〉 fiber texture. The recrystallization fraction after heating at 1175 ℃ for 1 h is 61.8%. Twinning is the main formation of recrystallization nucleation， and the degree of recrystallization gradually increases with the extension of the heating time. The recrystallization kinetic curve was obtained by fitting the Avirami equation， which matched the experimental results well. Static recrystallization significantly suppresses the anisotropy of the mechanical properties. The change magnitude of mechanical properties is small after the heating times more than 1 h.

Continuous fiber-reinforced resin matrix composites are widely used in aerospace， automotive and marine industries due to their low density and excellent mechanical properties. However， traditional manufacturing processes are expensive and unable to form complex parts due to mold limitations. Additive manufacturing has the advantages of high freedom of design， rapidity， and flexibility，and is considered an important directions for the future production of continuous fiber reinforced composites. At present， the additive manufacturing technology of continuous fiber reinforced composite is still in its infancy. This paper systematically reviews the research status of continuous fiber reinforced resin matrix composite， summarizes the research progress of printing equipment， process and materials， and provides directions for the construction of printing platform and engineering application of continuous fiber reinforced resin matrix composite. The influence of printing process parameters， such as temperature， speed， and layer thickness on printing quality is analyzed， providing a reference for the intelligent additive manufacturing of continuous fiber reinforced composite materials. Meanwhile， the development of the two-dimensional and three-dimensional structural design for continuous fibers for lightweight manufacturing， such as fiber path laying and structural topology optimization is discussed. The research trends of equipment， materials， printing process， and structural design for additive manufacturing of continuous fiber-reinforced composites are summarized and outlooked.

Due to the large temperature gradient in the laser melting deposition process， the coarse primary β columnar grains with preferred orientation are formed along the deposition direction， resulting in significant anisotropy of materials. This study aims to change the morphology of the primary β grains， refine the microstructure and weaken the texture of titanium alloy by adding Cu element in the materials during the process of laser melting deposition. The effects of Cu content on the microstructure and texture of TC4 titanium alloy manufactured by laser melting deposition are studied systematically. The results show that Cu element addition can refine the columnar primary β grains significantly and make the grain size distribution more uniform. The columnar grains are transformed to fully equiaxed grains when 4% Cu （mass fraction， the same as below） is added into the material， and the average size of primary β grains decreases to 385 μm from 1490 μm of TC4 titanium alloy. Basket-weave microstructure composed of α-Ti， β-Ti， and a small amount of Ti₂Cu is obtained inside primary β grains of the samples with Cu addition. The short rod-like Ti₂Cu distributes at the boundary of the α-Ti lath， and its proportion in the microstructure increases with the increase of Cu addition. The average width of α-Ti is 0.44 μm when 8% Cu is added， which is reduced by about 63% compared with 1.18 μm of the sample without Cu addition. When 4% Cu is added， the maximum multiples of uniform distribution（MUD） value of α-Ti pole figure is reduced by about 71% compared with TC4 titanium alloy，which demonstrates that the addition of Cu can significantly reduce the texture strength of titanium alloy manufactured by laser melting deposition.

Single crystal superalloy turbine rotor blade is one of the core hot-end components of the aero-engine， which has a decisive role in the thrust and performance of the aero-engine. Additive manufacturing for repair technology is one of the most challenging tasks in the special machining of aviation equipment. In this paper， the repair processes and their application for single crystal superalloy turbine rotor blades were systematically reviewed. Aiming at the problems of hot cracking defect， the cracking formation mechanism， key influencing factors， and control methods were summarized. In addition， the research progress in microstructure and mechanical properties of single crystal superalloys repaired by additive manufacturing technology are summed up. Furthermore， the prospective developing direction of single crystal superalloy turbine rotor blade repair is indicated. Specific filler material composition design， new process development， and multi-objective collaborative optimization based on deep learning are considered to be important future research directions.

To improve the impact resistance of metal and composite material joint structures， a metal synapse structure was manufactured using metal laser selective melting technology. The structure was co-cured and molded with T300 twill woven carbon fiber-reinforced composite material （CFRP） to form a through-thickness reinforcement joint structure. The impact resistance of the synapse joint structure was verified through Charpy pendulum impact tests. Analysis and optimization of the synapse morphology were conducted based on CFRP damage patterns and impact absorption energy， as well as other influencing factors. Finite element simulations and comparative calculations were performed. The experimental results indicate that the penetration-enhanced joint method can prevent metal stress concentration and carbon fiber cutting caused by drilling holes. The impact absorption energy measures at 68.54 J， with a 216.1% improvement compared to the bolted connections. Increasing the height of the synapses effectively inhibits the composite material impact delamination. The synapse feature size and synapse array density affect internal defects in the composite material. With increasing synapse feature size and synapse array density，the impact absorption energy first increases to a point and then decreases. Finite element simulations based on synapse feature size variations showed that the simulation results deviated from the experimental results by less than 17%， and the damage form is highly consistent.

The novel Ti69NbCrZrX （X=Sn，W，Al，Mo，1%-2%， mass fraction） was used as an interlayer to join TiAl alloy with Ti₂AlNb alloy by pulsed current diffusion welding at 900 ℃/30 min/8 MPa. The post-weld joint microstructure and properties were analyzed by SEM， EDS， EBSD， and room temperature tensile test. The results show that defect-free TiAl/Ti₂AlNb joints can be obtained using Ti69NbCrZrX as the connecting interlayer. The joint interface microstructure is mainly composed of TiAl diffusion affected zone， interlayer diffusion zone， and Ti₂AlNb diffusion affected zone. The TiAl diffusion affected zone structure is composed of white β phase and gray block α₂ phase，the interlayer diffusion zone structure is mainly composed of gray block α₂+ α phase， and white β/B2 phase composition， Ti₂AlNb diffusion affected zone is composed of β/B2 matrix phase with lath and acicular O phase. The average value of room temperature tensile strength of the joint is 642.5 MPa， which reaches 91.57% of the strength of the base material. The fracture mode of the joints is dominated by brittle intergranular fracture， supplemented by brittle transgranular fracture.

Laser melting deposition is more suitable for repairing thin-walled substrates of single crystal alloys compared to argon arc welding and micro plasma arc welding. This article used laser melting deposition technology for additive repair of DD6 single crystal superalloy. The microstructure characteristics of the repaired zone and heat affected zone of the additive repaired joint were analysed by optical microscopy， scanning electron microscopy， and EBSD. And the microhardness distribution and high-temperature tensile properties of the repaired joint were tested. The results indicate that in the heat affected zone adjacent to the repair interface， γ' phase is partially coarsened and dissolved， and the hardness decreases significantly. The microstructure of repaired zone is an oriented columnar crystal structure grown epitaxially， and composed of γ+γ' phase and a small amount of dispersed carbides between dendrites. Many elongated columnar stray grains remain in the repaired zone， mostly distribute near the fusion line. As the height of the repaired zone increases， the dendrite spacing and hardness of the epitaxial growth tissue increases gradually， and the proportion of fine grid γ' phase in the dendrites increases continuously. The tensile strength of the repaired joint at 980 ℃ reaches 102% of the base material， and the yield strength reaches 92% of the base material， but the elongation is relatively poor.

For Ni₃Al-based superalloy IC10 turbine blades， some defects， such as cracks and ablations， would appear after long-term service. To shorten the overhaul period， the turbine blades can be repaired using the brazing technology. In this study， an independently designed Co-based filler alloy （CoCrNi（W，Al，Ti，Mo，Ta）-B） was used to join the IC10 superalloy. The effects of the brazing gap and the brazing time on the joint microstructure and mechanical properties were investigated. The results show that the designed filler alloy has good brazeability at 1220 ℃ for IC10 superalloy. Because of the interreaction and mutual diffusion， the brazing seam is wider than the preset gap. Meanwhile， the matrix of brazing seam is γ＋γ′ dual phase which was similar to the IC10 base material. Because of the boron in the filler alloy， a large number of white borides are formed. The brazing holding time has little influence on the microstructure and strength of the joint， but the brazing seam has significant effect.With the brazing seam wider， the joint strength tested at 1000 ℃ increases gradually. When the brazing seam is set at 0.15 mm， the joint strength is 454 MPa， which is close to that of the IC10 base material. According to the joint fracture morphology， the increase in joint strength is mainly due to the small and diffuse white boride phase in the joint， inducing the tortuous crack propagation path.

The defects on TB6 titanium alloy were repaired using pulsed TIG（tungsten inert gas） additive manufacturing technology， and the effects of process parameters （pulse current and pulse time） and heat treatment on the microstructure and mechanical properties of the repaired TB6 titanium alloy were studied to determine the optimal heat treatment process parameters. The results show that the mechanical properties are relatively better in the as-repaired state when the pulse current is 50 A and the pulse time is 40 ms， with a tensile strength of 1113 MPa and an elongation of 5.26%. These samples are sequentially subjected to solid solution and aging heat treatment. When the samples are solid solution treated for 2 h under different temperatures （740， 760， 780 ℃）， the primary α phase is increasingly dissolved， while the β phase gradually grows and evenly distributes in the matrix. After water quenching， the growth of the β phase is inhibited， and acicular rhombic martensite α'' phase is precipitated in β grains， resulting in a decrease in tensile strength and a remarkable increase in elongation. Under different aging temperatures （500， 520， 540 ℃） for 8 h， the α'' phase continuously grows and gradually transforms to equiaxial grain， and the mechanical properties are greatly improved. The optimal microstructure and mechanical properties are achieved under the conditions of 780 ℃/2 h WC+520 ℃/8 h AC， with a tensile strength of 1119 MPa and an elongation of 7.36%.

The 6061-T6 ultra-thin aluminum alloy with a thickness of 0.5 mm was welded using micro-joint friction stir welding technology. The effects of three kinds of stirring heads with different shaft shoulder morphology on the forming quality， microstructure， mechanical properties， welding thermal cycle， and force process of the 6061-T6 thin-wall butt joint were studied. The flow behavior characteristics of the plastic metal in the three welding cross-sections were analyzed in sequence. The results show that the forming effect of the weld surface is significantly affected by welding heat input. The hardness distribution trend of the joint cross-section formed by three kinds of stirring heads with different shaft shoulder morphology is a “W” shape. The highest hardness values in the center of the nucleation zone and the lowest hardness values in the thermo-mechanical affected zone of the needle-free three-involute diversion groove shaft shoulder welded joint are the highest among the three shaft shoulder welded joints. The mechanical properties of the joint formed by the three-involute guide groove with the needle shaft shoulder are outstanding， and the tensile strength， yield strength， and elongation after fracture are higher than those of the other two. The three tensile fracture forms are mainly ductile fractures. The process parameters of the thermal cycle and force can accurately reflect the changing trend of the welding state. The energy required to maintain the weld metal softening is from the heat generated by friction between the shaft shoulder and the workpiece and the work done by the axial and forward forces of the shaft shoulder. The axial force and forward force changed with the softening degree of the welded metal， playing a dynamic regulating role in the migration of plastic metal in the weld. The shoulder surface has a strong effect on the upper part of the weld， driving the plastic metal migration between the forward side and the backward side. The needle of the stirring head promotes the interaction between the plastic metal and the backing plate， providing a driving force for the flow of the upper and lower parts of the weld metal. The optimal heat generation potential is the combined result of the stirring needle and the involute groove， which work together to form a well-formed weld.

The microstructure evolution of the interface in the simulated heat affected zone （HAZ） of G115 steel was characterized by electron backscatter diffraction （EBSD） and high resolution transmission electron microscopy （HRTEM）. The results show that the size of precipitated M ₂₃C₆ in the fine grain zone is smaller than that in the coarse grain and the critical zone， which is only about 100 nm， and the precipitation strengthening effect is obvious. With the increase in peak temperature， the number of small angle grain boundary increases， hence the grain boundary strengthening effect increases. The highest geometrical dislocation density is 3.19×10¹⁴ m^-2 in the coarse-grained zone. The recovery of the critical dislocation， the pinning of the fine MX precipitates and the appearance of the subgrains make the G115 steel maintain the durable strength for a long time at high-temperature. For the microstructure of the fine grain zone， the increase of welding heat input promotes the transformation of martensitic lath substructure into martensite block substructure， the dislocations are annihilated， the formation of subgrain is inhibited， and the yield strength decreases from 1115 MPa to 947 MPa. When the welding heat input is 14.4 kJ/cm， the microstructure of the fine grain welding heat affected zone has both good strength and toughness.

The SiC/AlSi10Mg composites were fabricated via selective laser melting（SLM）. The phase characteristics， microstructure， anti-corrosion and wear resistance properties of SLM SiC/AlSi10Mg and SLM AlSi10Mg samples were investigated by XRD， SEM， EDS， EBSD， electrochemical test， and friction and wear test. The results show that in the 3.5% （mass fraction） NaCl solution， the corrosion current density of SLM SiC/AlSi10Mg （2.0827 μA/cm²） is lower than that of SLM AlSi10Mg （3.389 μA/cm²）， and the passivation film on the surface of SLM SiC/AlSi10Mg （7.1 nm） is thicker than that of SLM AlSi10Mg （1.9 nm）， indicating the SLM SiC/AlSi10Mg sample has better corrosion resistance than that of SLM AlSi10Mg. The reason can be attributed to that the addition of SiC causes the grain refinement， the increase of high grain boundary， and the interruption of the continuity of Al matrix， leading to the decrease of corrosion rate and the increase of corrosion resistance. In addition， the average microhardness for SLM SiC/AlSi10Mg composites （207.68±16.02）HV_0.2 is twice that of SLM AlSi10Mg alloy （103.58±7.41）HV_0.2， indicating its hardness and wear resistance are improved. Both the wear mechanisms of SLM AlSi10Mg and SiC/AlSi10Mg composites are mainly abrasive wear and oxidation wear.

High-strength aluminum alloy have become one of the most commonly used metal materials for aerospace and automotive application parts due to its high strength， low density， excellent ductility and corrosion resistance. Wire arc additive manufacturing （WAAM） has the ability to rapidly in-situ form and manufacture complex structural parts， and is very suitable for the manufacturing of medium or large high-strength aluminium alloy parts. The current status of high-strength aluminum alloy WAAM processes and equipment， the inherent properties and defects of high-strength aluminum alloy WAAM， and the main performance optimization methods were comprehensively analyzed in this paper. The inherent characteristics of the microstructure and properties as well as the impact of hybrid additive manufacturing technologies on the microstructure and properties were discussed. Opinions are put forward on issues such as metallurgical defects， characteristic performance requirements， the advantages and disadvantages of various optimization processes in WAAM. Development directions such as a comprehensive evaluation system， composition design and wire development， special heat treatment systems and synergy of composite additive manufacturing technology are proposed. Such proposals are expected to provide references for the performance improvement and application promotion of high-strength aluminum alloys manufactured via WAAM.

Laser additive manufacturing （LAM） enables the integrated direct formation of high-performance metallic components with complex geometry. However， the non-uniform distribution of temperature gradients， in-situ heat treatment effects， non-equilibrium solid phase transformations， and heterogeneous microstructure during the process result in intricate residual stresses that significantly affect the quality and overall performance. A comprehensive review of residual stress in LAM by introducing its fundamental definition and classification is provided in this paper. Furthermore， the particularity， formation mechanisms， characterization methods， and regulation techniques associated with residual stress in LAM is systematically reviewed. The subsequent sections introduce various characterization methods for residual stress in LAM components， along with their respective characteristics. Additionally， the applicability， advantages， and disadvantages of each method are presented. Furthermore， the methods for controlling residual stress can be categorized into post-treatment control and in-situ treatment control. Finally， the joint effect of different types of residual stress should be considered in the study of the cause and evolution mechanism of residual stress in LAM. The characterization method of residual stress should be integrated with various methods to facilitate mutual verification. To mitigate the impact of stress concentration on the printing process and resultant quality， as well as minimize the influence of post-processing stress on part accuracy， it is imperative to investigate in-situ control methods for residual stress and explore real-time online monitoring techniques for LAM.

Refractory high entropy alloys have excellent high temperature mechanical properties， but the high temperature oxidation resistance has always been one of the limiting factors in their application. Four kinds of refractory high entropy alloys AlNbTaTiZr， AlMoNbTiZr， AlMoNbTaTiZr and AlMo_0.5NbTa_0.5TiZr were designed and prepared by laser additive manufacturing technology. The oxidation mass gain of AlNbTiZr-based refractory high entropy alloys was measured at 900 ℃ and 1000 ℃， and the oxidation layer structure of different samples was studied. The effects of Mo and Ta on the high temperature oxidation resistance of AlNbTiZr-based refractory high entropy alloys were compared and analyzed. The results show that the four kinds of as-deposited high entropy alloys prepared by laser additive manufacturing are BCC＋HCP dual-phase structures. The dendrites are mainly BCC phases with high melting points， and a small amount of HCP phase rich in Al and Zr is distributed among the dendrites. AlNbTaTiZr shows the best oxidation resistance after oxidation at 900 ℃ and 1000 ℃ for a long time， and Ta instead of Mo to some extent improves the oxidation resistance of refractory high entropy alloys.

Due to the low boiling points of the main constituents of 7075 aluminum alloy and the high surface tension gradient of the molten alloy， combined with the uneven energy distribution of the circular Gaussian （CG） laser beam spot commonly used in directed energy deposition （DED） processes， the forming quality of 7075 aluminum alloy DED specimens is generally poor. This significantly restricts the further application of DED in 7075 aluminum alloy. By regulating the laser mode， it is possible to effectively modify the temperature and flow fields of the melt pool， as well as the corresponding solidification conditions. Thus， the forming quality of laser additive manufacturing specimens and the active control of microstructure are improved. An off-axis parabolic integrating mirror is employed to homogenize the CG laser mode into a circular flat-top （CF） laser mode， which is further tilted to achieve a transversely elliptical flat-top （TE） laser mode. Using these three different laser modes， single-track cladding， single-wall structures， and 7075 aluminum alloy in DED block specimens are prepared. Combined with numerical simulations， the influence laws and underlying mechanisms of the laser modes on the forming quality and solidification structure are revealed. The simulation results indicate that by modulating the laser beam spot from the conventional CG laser mode to the CF and TE laser modes， the uniformity of the heat flux on the surface of the cladding layer is significantly improved， subsequently reducing the temperature gradient of the melt， and increasing the solidification rate. Compared to the CG laser mode， the surface forming quality of single-wall structures and block specimens under the CF and TE laser modes is significantly enhanced. The width variation of the single-wall structures is greatly reduced， and the dimensional accuracy in the horizontal direction of the block specimens is improved. Additionally， the density of the block specimens increases from 95.8% to 97.2% and 97.7%， respectively. In terms of solidification structure， the texture is significantly weakened， the grain size is reduced by approximately 50%， and the number of nano-precipitated η-phase within the grains is also increased.

Wire-arc additive manufacturing is a new type of manufacture using wire as filling material and arc as a heat source， making it easier to manufacture complex-shaped and big-sized parts. The reciprocating and unidirectional process path experiment was conducted. The inclined wall made by unidirectional path has better morphology， less splash， and a smoother surface. The simulation model of AM11 reciprocating and unidirectional manufacturing path was established in finite element software and solved. The simulation results show that the unidirectional path deposition temperature is 267.4 ℃， the deposition thermal stress is 357.4 MPa， the reciprocating path deposition temperature is 307.0 ℃， and the deposition thermal stress is 420.4 MPa， the heat accumulation and thermal stress of unidirectional path are lower than that of reciprocating path. AM11， AM12， and AM21 inclined wall samples with different slope factors by wire-arc additive manufacturing in unidirectional path were prepared， and their microstructure and properties were analyzed. The results indicate that the grain size of AM11， AM12， and AM21 is 35， 39 μm， and 42 μm， there is more precipitated β-Mg₁₇Al₁₂ in AM21 thin-walled grains， which has larger and more dimples than that of the other two samples. The micro-hardness values of AM21 and AM11 are both about 81.5HV， higher than 73.1HV of AM12. The horizontal and vertical tensile strengths of the AM21 inclined wall sample are 255.7，224.4MPa， the yield strengths are 103.8，96.0 MPa， and the elongations reach 13.1% and 8.2%. The tensile strengths and elongations are both greater than those of AM11 and AM12 samples， but the yield strengths are close. The AM21 inclined wall has much better strength and plasticity， and verify that the more perpendicular the inclined wall of magnesium alloy arc additive manufacturing is， the better the mechanical properties such as strength and plasticity.

The stereolithography 3D printing technology provides a new technical solution for the preparation of complex structure SiC ceramic parts， but the characteristics of high light absorption and high refractive index of SiC lead to a common problem that printing is difficult to cure. SiO₂ with low absorbance and low refractive index was added to SiC ceramic matrix powder as filler to improve the curing property and printing accuracy of SiC ceramic paste. The effects of different amounts of SiO₂ on the rheology， stability and curing properties of the slurry and its mechanism were studied. The green body with high precision and good surface quality was prepared by stereolithography 3D printing technology， and the microstructure and properties of the green body were tested and analyzed. The results show that the adding SiO₂ to the SiC slurry can reduce the viscosity， improve the stability， and improve the curing property of the slurry. The addition of SiO₂ can significantly improve the surface roughness of the SiC green body and make the bending strength increase at first and decrease then.