High speed impact surface treatment such as shot peening (SP), laser shock peening (LSP) and surface mechanical attrition treatment (SMAT) can effectively improve the fatigue property, stress corrosion cracking performance and wear resistance of metallic materials. These surface modification techniques have been widely employed in aviation, aerospace, automobile, ship and nuclear industries. The basic principles and characteristics of SP, LSP and SMAT are introduced in this paper. The effects of SP, LSP and SMAT on surface integrity parameters of aluminum-lithium alloys, superalloys, titanium alloys and steels such as surface roughness, residual stresses in the surface layers, microhardness and microstructures in the surface layers are summarized. Finally, the research and development of high speed impact surface treatment in China are prospected.

Based on the hybrid reasoning method of rule-based reasoning (RBR) and case-based reasoning (CBR), this paper studies the intelligent design method of aircraft structural parts. Firstly, combined with fuzzy theory and rulebased reasoning technology, processing fuzzy parameters for aircraft structure parts design, and the intelligent selection system of aircraft structural parts is designed to realize the type selection of aircraft structural parts. Secondly, the K-nearest eighbor (KNN) and grey relation analysis (GRA) are used to deal with the numeric parameters of aircraft structural parts  design, and it implements cases retrieval and evaluation. Then the best similar cases are used for variant design to obtain the target case. Finally, the feasibility of the hybrid reasoning intelligent design system is verified by taking the section steel as an example.

Single shoulder friction stir welding was used to achieve a 40 mm thick AZ31 magnesium alloy doublesided butt welding, the microstructure and mechanical properties of the joint were analyzed. The joint can be divided into five zones: base material (BM) zone, heat affected zone (HAZ), thermal-mechanical affected zone (TMAZ), nugget zone (NZ) and overlapped zone (OZ), of which the OZ is unique to Ds–FSW joints. The existence of ultra-fine grains and diffusely distributed precipitated phase Al₈Mn₅ in the OZ significantly increases the ultimate tensile strength (UTS) and elongation (EI) in this zone, respectively 217.7 MPa and 14.65%, resulting in a high joint efficiency ratio of about 85.81% of the base material. The joints are mainly fractured at the junction of NZ and TMAZ on the advancing side, and their fracture mechanism is a mixture of ductile fracture and quasi-cleavage fracture.

In order to study the formation mechanism of laser high-speed rotating welded joint of carbon fiber reinforced thermoplastic composites (CFRTP) and titanium alloy, and explore the influence of process parameters on the joint quality, a mathematical model of laser high-speed rotating welding of CFRTP/titanium alloy was established. The temperature distribution was calculated with finite element method, and the influence of laser power, welding speed and spot size on the weld width and penetration was analyzed. The theoretical calculation results were compared with the experimental results. The results showed that the finite element simulation can predict the temperature field distribution of CFRTP/titanium alloy joints. Through the numerical analysis, the weld penetration and weld width of CFRTP/titanium alloy during laser welding can be predicted. The theoretical calculation results are basically consistent with the experimental results, which means that the simulation can provide theoretical support for high quality laser welding of CFRTP/titanium alloy.

Friction stir lap welding of 6151 aluminum alloy was carried out by using the tip-half-thread pin, and the process parameters were optimized by combining radial basis function neural network (RBFNN) and ant colony optimization (ACO) algorithm, to improve the characteristics of lap interface and maximize the bearing capacity of the joint. The result showed when the rotational velocity, welding speed and plunge depth were 1504 r/min, 207 mm/min and 0.12 mm, respectively, the highest tensile shear load of the joint reached 5.06 kN/mm, which was increased by 6.08% than the highest tensile shear load before optimization. The RBFNN combining with ACO provides an effective way to optimize the welding processing parameters and further enhance the strength of aluminum friction stir lap welding joint.

Porous metal sandwich structure has light weight, high specific strength and stiffness, high temperature and corrosion resistance, sound dissipation, heat insulation and other excellent properties. The application of high-end equipment in the aerospace field is receiving more and more attention. Brazing is the preferred method to realize the joining between core and face sheets of porous metal sandwich structure. However, the process of large area brazing of  core and face sheets is prone to defects such as melting of brazing filler to thin-walled base metals, low brazing rate, large brazing deformation and formation of continuous brittle reaction products at the interface, so large area brazing of porous metal sandwich structure is still difficult, and basic research on brazing of porous metal sandwich structure is urgently needed. Scholars at home and abroad pay attention to the adjusting of joining interface micro-reaction products for the type and distribution, dissolution prediction of thin-walled base metals, welding heat deformation control of thin-walled  core and other challenges. The study about new methods of brazing interface microstructure control, brazing process– morphology of brazing fillet–microstructure of brazed joint–the mechanical properties of the joint was conducted to clarify the microstructure evolution of the brazed joint and optimize the mechanical properties of the joint. It has important scientific significance and the value of application. The progress of domestic and international research is reviewed in terms of the interface micro-zone control of the brazed joint of the metal porous sandwich structure, the micro-morphological design of the brazed joint based on the optimization of mechanical properties, the effect of the brazing process on the mechanical properties of the structure, and the predictive model for dissolution of base metals in molten brazing filler metal, respectively.

The microstructure and fracture toughness of a bimodal and basket-weave TC17 titanium alloys linear friction welded joint were investigated to meet the manufacturing demands of titanium alloy dual-performance blisk. Metallographic examination reveals that fine-grains with metastable phases are formed in the welding zone (WZ), thermoplastic deformed microstructures with partially dissolved primary α_p phases are formed in the thermo-mechanical affected zone (TMAZ). Fracture toughness examination shows that the fracture toughness of the WZ and TMAZ is significantly lower than that of the base metals, resulting in an obvious brittle tendency of the joint. However, the postweld annealing heat treatment can decompose the metastable phases into the equilibrium α+β phases in the joint, which can alleviate the brittle tendency of the joint to a certain extent.

Al/Fe dissimilar metals welding has the advantages of lightweight structure and good comprehensive performance, which has a wide application prospect in aerospace, nuclear power energy, automobile, electronic and electrical appliances and other industries. However, due to the difference of physical properties, there are still many problems in joining methods and processes of Al/Fe dissimilar metals. Electromagnetic pulse welding, a solid-state welding technology, which can effectively overcome the welding problems caused by the different properties of dissimilar metals, is widely used in welding of dissimilar metals such as Al/Fe. This paper briefly analyzes the problems existing in Al/Fe dissimilar metal welding, and the welding principle, process, characteristics of electromagnetic pulse welding technology. Then summarizes and analyzes the new progress of electromagnetic pulse welding technology from the aspects of process research, equipment optimization, joint performance, interface morphology and bonding mechanism, numerical simulation, and the combination of various welding methods, and puts forward corresponding suggestions for the future technological development.

To solve the problems of high temperature, long holding time, vacuum environment and active elements when vacuum brazing porous ceramics, this work used ultrasonic assistance to realize the rapid wetting of porous ceramics, and the effect of ultrasonic power on the wetting effect was studied. The results showed that the Sn9Zn nonactive solder wetted the porous ceramics within 10 s at 230 ℃ under ultrasonication. When the ultrasonic power was 333.3 W, the solder infiltrated the ceramic matrix by a width of 25 μm. The width of the infiltration layer increased with increasing the ultrasonic power. The width of the infiltration layer was 80 μm when the ultrasonic power was 1000 W. Due to the low temperature during the wetting process, the residual stress in the infiltration layer after cooling was low, and thus the ceramic and the solder were closely bonded without cracks. The results of transmission electron microscopy showed that the wetting interface was enriched with oxygen and zinc elements. In this work, the rapid wetting of the porous ceramics can be attributed to the intense cavitation of the solder inside the microchannel of the porous ceramics. The extremely high temperature and pressure caused by the collapse of cavitation bubbles caused the non-active solder to rapidly wet the porous ceramics.

In order to reduce the formation of brittle intermetallic compounds in NiTi/Ti6Al4V dissimilar laser welding and improve the mechanical properties of welded joints, NiTi/Ti6Al4V laser welding was performed by adding Co and Zr interlayers respectively. The effect of Co/Zr interlayer on microstructure, phase structure and mechanical properties of welded joints was studied. The results show that the microstructure of the fusion zone in NiTi/Co/Ti6Al4V and NiTi/Zr/Ti6Al4V joints is composed of equiaxed dendrites, columnar dendrites and some macroscopic segregation zones. Co and Zr can respectively replace Ni and Ti in Ti₂Ni brittle intermetallic compounds, which inhibits the formation of brittle phases. In addition, the maximum hardness of NiTi/Co/Ti6Al4V and NiTi/Zr/Ti6Al4V joints is near the NiTi boundary, 543HV and 467HV respectively. Meanwhile, brittle fracture occurs at the NiTi boundary. The NiTi/Zr/Ti6Al4V joint has a large tensile
strength of 315.9 MPa and fracture strain of 1.74%.

The linear friction welding (LFW) experiment of Ti₂AlNb and Ti60 alloys was conducted. The microstructure evolution of the joint was analyzed by using an optical microscope and scanning electron microscope, and the mechanical property of the joint was tested as well. The results reveal that the microstructures of thermo-mechanically affected zones (TMAZ) on both sides of the joint deform along the direction parallel to weld interface. α₂→B2 and O→B2 transformations occur in TMAZ of the Ti2AlNb side joint in which the fraction of B2 phase is higher than that of base metal; β→metastable β→α transformations occur in TMAZ of the Ti60 side joint, resulting in fine lamellar secondary α precipitation. Dynamic recrystallization happens in weld zones (WZ) on the two sides of the joint. During welding, the WZ of Ti₂AlNb side joint completely transformed into B2 phase and retained after rapid cooling; the WZ of Ti60 side joint is firstly transformed into high-temperature β, and then β→α′ transformation occurs during fast cooling, leading to α′ martensite precipitation. In addition, interdiffusion of solute elements occurs at the weld interface, forming an element diffusion layer about 1 μm in width, and the grains on two sides of the weld interface are intergrowth. Under the coupling effects of strain strengthening and precipitation strengthening of TMAZ and fine grain strengthening and precipitation strengthening of WZ, the tensile strength (939 MPa) of the joint is not lower than that of Ti60 base metal, and the fracture mode is ductile fracture.

The Mg–Al composite heat dissipation structure has a good application prospect in the aviation industry. In view of the key problem that brittle Al₁₂Mg₁₇, Al₃Mg₂ compounds are easily generated in the connection of Mg–Al dissimilar materials, this experiment adopts the ultrasonic-assisted transient liquid phase bonding (U-TLP Bonding), and uses pure Zn as the interlayer, the reliable connection of Mg/Zn/Al joint is realized at 350 ℃ . The effect of ultrasonic time on the microstructure evolution and mechanical properties of the joint is studied. Under the optimal process parameters, the joint is mainly composed of Mg+MgZn eutectoid structure, and the average shear strength of the joint reaches 50.2 MPa.

Due to the coupling effects of various technical process factors on numerical control (NC) machining, varying degrees of NC machining distortion is almost inevitable for most aeronautical monolithic components. This brought critical negative effects on guaranteeing product accuracy, improving machining efficiency and reducing manufacturing cost. The NC machining distortion of aeronautical monolithic component is one of most severe challenges in aviation manufacturing industry. This paper summarizes and analyzes the factors, internal mechanism and prediction technology of NC machining distortion of aeronautical monolithic components. Furthermore, the research progresses of distortion control and distorted components correction technologies were expounded. Finally, prospects for the development trends of distortion prediction and control technologies of aeronautical monolithic components is presented.

In order to solve the problem of accurate forming of asymmetric cross-section truss strip of skin frame of C919 domestic large aircraft, the constitutive model and springback law of materials were obtained based on the performance test and evaluation of 2099–T3 and T83 Al–Li alloys with 2–shaped profile and L–shaped profile. At the same time, a new piecewise constant curvature progressive roll bending process is proposed. Combined with the theoretical analysis and calculation of roll bending forming, the finite element model of constant curvature four-axis roll bending is  established, and the influence factors of roll bending springback and curvature radius of two types of profiles are analyzed. The simulation results determine the reasonable roll bending process parameters of asymmetric cross-section profiles as follows: the friction coefficient between profile and roller is 0.10–0.12, the clearance between profile and roller is 0.2 mm, and the limit lifting heights of left and right rollers of 2–shaped profile and L–shaped profile are 43 mm and 30 mm, respectively. Finally, the qualified variable curvature profile parts were successfully produced by the MC4P431IAS CNC roll bending machine using the method of piecewise equal curvature asymptotic roll bending, and the roll bending process test verification of variable curvature profile was completed. The maximum clearance value is only 0.76 mm, which successfully verifies the feasibility and accuracy of the variable curvature rolling forming scheme. At present, the research results have been successfully applied to the roll bending production of fuselage skin skeleton truss in large aircraft of C919.

In this paper, aluminum alloy single curvature skin is taken as the research object, and the problem of large springback of sheet metal is solved by using the method of combination of tensile and electromagnetic progressive forming. The effects of two predeformation schemes of fixed clearance and variable blank holder on the deformation and springback of sheet metal were studied by finite element method and experiment. Compared with the fixed gap stamping, the springback of the sheet is greatly reduced, and the springback is 47.6 mm. Then the electromagnetic progressive method of skin parts with elastic pad is used to reduce the springback of sheet metal. It is found by simulation that the tangential tensile stress of the sheet decreases and a small plastic strain is produced. The plastic strain energy increases, the elastic strain energy decreases, and the springback decreases. When the coil discharges 8 kV in 6 positions, the springback of the sheet is 10.4 mm, which is 78.1% lower than that of the quasi-static stamping, and the surface of the parts is smooth. The experimental results are consistent with the simulation. The research in this paper provides a reliable means for the accurate manufacture of aluminum alloy skin parts.