The study investigated the impact of heat treatment on the microstructure and tensile properties of GH4061 alloys fabricated by selective laser melting. Findings demonstrated that the as-built columnar grains experienced epitaxial growth spanning multiple molten pools, resulting in the formation of cellular substructures. Following heat treatment, as the solid solution temperature increased, there was a gradual shift in grain orientation towards the (101) and (111) crystal planes. The Laves phase transitioned from elongated chains to granular forms and dissolved at approximately 1060 ℃. The δ phases that precipitated at grain boundaries transformed from coarse bulk structures to disc-shaped, and eventually to short rod-shaped configurations. The average sizes of γ′ and γ″ phases are 23.53 nm, 24.43 nm, 25.34 nm and 25.66 nm at solution temperature of 980 ℃, 1020 ℃, 1060 ℃, 1100 ℃, respectively. The mechanical properties of the alloys after heat treatment show significant improvement at both room temperature and 650 ℃. Specifically, the tensile strengths at room temperature and 650 ℃ for the sample subjected to the 980 ℃ solid solution aging heat treatment are 1342 MPa and 1120 MPa, respectively. As the solid solution temperature increases, the room temperature tensile strength at 1020 ℃, 1060 ℃ and 1100 ℃ decreases by approximately 6.4%, 8.3%, and 10% than that at 980 ℃, respectively. At 650 ℃, the tensile strength at 1020 ℃, 1060 ℃ and 1100 ℃ decreases by approximately 7.9%, 8.8%, and 11% than that at 980 ℃, respectively, while the plasticity increases.

The thin-wall structure of the second generation single-crystal superalloy DD405 was fabricated by laser directed energy deposition technology. The mechanism of hot crack formation in the process of laser directed energy deposition was analyzed and explored by combining experiment and theory. The formation of hot cracking was determined by stress concentration, liquid film stability and carbide precipitated phase. The residual stress in deposition region increased with the deposition height due to the layer-by-layer stacking of the laser directed energy deposition process, so there is a high-level tensile stress in the deposition region. Significant stress concentration occurred at the grain boundary of the deposition region, and the liquid film was teared under the tensile stress on both sides, leading to crack initiation. The stability of liquid film was closely related to the angle of grain boundary between adjacent grains. When the high angle grain boundary is larger than 40°, thermal cracks will be formed under the drive of tensile stress. MC-type carbide precipitates promoted crack initiation by a pinning effect on the liquid feed and weakening interface bonding strength with the substrate.

Powder metallurgy near net shaping (PM-NNS) technology can prepare complex PM components with excellent comprehensive mechanical properties. The principle and advantages of hot isostatic pressing are introduced. The research status of PM-NNS technology in aerospace engines at home and abroad is reviewed. The influencing factors and defect control of the component preparation process are briefly described from the aspects of process route and component development. Some research work and application of PM-NNS in aerospace engine by Institute of Metal Research, Chinese Academy of Sciences are reported. Finally, the main problems and development directions of PM-NNS were summarized, in order to further expand the application of this technology.

Powder metallurgy through hot isostatic pressing (HIP) route, which is a promising near-net forming method, can fabricate high-performance titanium alloy components with complex structure for applications in the aerospace field. In this study, TC11 pre-alloyed powder was made by electrode induction melting gas atomization method, and the asreceived powder was characterized. The powder compacts were HIP at 940 ℃/140 MPa /3 h from the pre-alloyed powder. The microstructure of as-HIPed powder compact was observed by OM and SEM, and the mechanical properties were evaluated by tensile, impact and high-cycle fatigue tests. The effect of residual micro-pores induced by the hollow powder with gas bubbles on fatigue life of as-HIPed powder compact was also investigated. The results show that the TC11 powder compact is approaching to full density, and the microstructure is fine and homogeneous. The quasi-static mechanical properties of as-HIPed powder compacts are close to or even better than those of wrought alloys. The rotating bending fatigue strength is about 590 MPa at 107 cycles. However, the duality of the high-cycle fatigue S – N curve is observed. The micro-pores located at the surfaces of specimens will preferentially become crack initiation sites under fatigue loading conditions, which will further significantly reduce the high-cycle fatigue life of the powder compacts.

Ti₂AlNb pre-alloyed powders were prepared by plasma rotating electrode process (PREP) and electrode induction melting gas atomization (EIGA) respectively, and the pre-alloyed powders were characterized. Ti₂AlNb alloy was prepared by hot isostatic pressing (HIP) process, and the effects of powder preparing process on microstructure and mechanical properties of Ti₂AlNb alloy were investigated. The experimental results show that the compaction density of Ti₂AlNb powder prepared by EIGA method is higher than that of PREP method. The forming research of Ti₂AlNb impeller was carried out under the regime of 1030 ℃/140 MPa/3 h based on the powder metallurgy HIP near net shape technology. The finite element simulation results show that the higher the powder compaction density, the smaller the deformation degree of the HIPed component. Ti₂AlNb pre-alloyed powder prepared by EIGA with higher compaction density is preferred to prepare powder metallurgy complex components.

Al–Mg–Li alloy was prepared using powder metallurgy and hot extrusion methods. The microstructure, fracture morphology and mechanical properties of the alloy were analyzed using metallographic microscopy, scanning electron microscopy, transmission electron microscopy, and a tensile testing machine. The effects of different Mg/Li ratios (1.3, 1.8, 2.5) on the microstructure and mechanical properties of the alloy in the sintered, extruded, and T6 heat-treated states were investigated. The results revealed that an increase in the Mg/Li ratio led to an increase in the relative density of the sintered alloy, indicating the promoting effect of Mg on the sintering process. For the extruded Al–Mg–Li alloy, as the Mg/Li ratio increased, the precipitation of Mg-containing phases gradually increased and clustered near the grain boundaries, resulting in improved mechanical properties, the tensile strength of which increased from 285 MPa to 407 MPa. After T6 heat treatment, the second phase in the Al–Mg–Li alloy mainly consisted of δ′ phase and T phase. The δ′ phase, as the main strengthening phase, was uniformly distributed in the aluminum matrix, while the T phase exhibited a chain-like distribution along the grain boundaries. Increasing the Mg/Li ratio enhanced the tensile strength and yield strength of the alloy, but it may lead to a decrease in elongation. For instance, the Al–5Mg–2Li alloy after T6 heat treatment exhibited a tensile strength of 532 MPa, a yield strength of 473 MPa, and an elongation of 4.5%.

Inconel 718 pre-alloy powder was prepared using the electrode induction melting gas atomization (EIGA) and vacuum induction melting gas atomization (VIGA) methods. Inconel 718 alloy was prepared using hot isostatic pressing (HIP). The effects of milling process, powder particle size, and capsule structure on the microstructure and mechanical properties of Inconel 718 alloy were studied. The results show that EIGA powder has better sphericity, and the mechanical properties of the forming alloy are better than those of VIGA powder. Considering the mechanical properties, powder yield and other factors, the powder with particle size range of 15–106 μm was selected as the hot isostatic pressing powder. The wall thickness of the capsule has a shielding effect on the effective stress acting on the powder. The change of cavity volume has little effect on the densification process. Long term vibration during the powder filling process can lead to particle size segregation, and it is necessary to control the vibration frequency and time during the powder filling process.

The assembly station is the basic management unit of the aircraft assembly line. Due to the complicated process of aircraft assembly and a large number of random disturbances, its managers need to frequently optimize the material configuration of the aircraft being processed. To this end, an optimization method based on the gated recurrent unit (GRU) neural network and genetic algorithm was proposed. In order to overcome the limitation of discrete event simulation in terms of efficiency, a simulation agent model of material configuration evaluation based on GRU neural network was constructed by taking the simulation historical data as the learning sample. The model took the material configuration as the input, and took the estimated completion time and the average residence time of key materials as the output. The simulation agent model was combined with the genetic algorithm as the objective function evaluation model to realize the global optimization of the material configuration. The simulation verification results show that the simulation agent model based on GRU neural network can accurately and efficiently evaluate the material configuration, and the output optimization configuration can effectively shorten the estimated completion time and average residence time.

In order to solve the problem of poor processing quality caused by uneven distribution of flow field during the process of square holes by electrochemical machining (ECM) with tube electrode, a method of workpiece vibration-assisted ECM of square holes with tube electrode is proposed. The results of flow field simulation indicate that workpiece vibration-assisted ECM can generate obvious pulsating flow fields at different positions within the machining gap, improve the electrolyte flow state within the machining gap and effectively eliminate the stagnant water area within the machining gap in the traditional ECM of square holes, thus facilitating the discharge of electrolytic products and improving the stability of ECM. The experimental researches were also conducted at the same time, and the results show that the use of workpiece vibration-assisted ECM with tube electrode can improve the contour accuracy and surface quality of square holes machining, and the use of pulse current can further improve the quality of square holes machining. Finally, a square hole with an average width of 1.218 mm, width standard deviation of 0.026 mm, side-wall surface roughness of 0.703 μm was electrochemically machined by using the amplitude of 0.04 mm, the vibration frequency of 20 Hz, the pulse duty cycle of 80%, the pulse frequency of 5000 Hz and the feed speed of 1.5 mm/min.

Two batches of powders with different levels of inclusion were prepared by the same hot isostatic pressing regime to produce FGH97 alloy, and the effect of the difference in the content of inclusion on the mechanical properties of FGH97 alloy was studied. The tensile properties of FGH97 alloys were tested, and the powder characteristics, alloy microstructure, and tensile fracture morphology were characterized. The results show that, the powder prepared by vacuum induction melting gas atomization (VIGA) method is denoted as powder, which has the characteristics of fine powder collection rate, small grain size of prepared alloy and easy to introduce inclusions. The abnormal particle inclusion of Sirich will lead to the formation of poor γ′ zone in alloy, affects the bonding between powders and reduces the plasticity of FGH97 alloy. At hot isostatic state, the FGH97 alloy has an elongation of 9.5% at room temperature and 1% at 650 ℃. FGH97 alloy was heat treated by solid solution + aging heat treatment, the poor γ′ zone in the matrix disappears, and the plasticity of FGH97 alloy is significantly improved, the room temperature elongation of FGH97 alloy is increased to 14.25%, the elongation at 650 ℃ is increased to 6%.

A sub-pixel detection method of riveting height difference based on optimized Hough transform was proposed for the detection of aircraft riveting height difference. Firstly, the collected riveting height difference image was enhanced by gray scale transformation method of point operation in spatial domain, segmented by the local threshold  segmentation method. Then, Canny operator edge detection was used to extract rough edges and the optimized Hough transform was used to extract sub-pixel edge, and the ring region of rivet hole and rivet head is extracted. Finally, the circle fitting was carried out with the RANSAC algorithm to generate the circle contour, and the average height values of the inner and outer ring regions were respectively extracted by the operator get_current_region_z( ). Then the height difference of the riveted surface can be obtained by the difference of the average height obtained by the function height_Z(). Experiments show that the detection method has strong sub-pixel accurate positioning ability, high accuracy, good stability and repeated measurement accuracy of ±10 μm.

Surface heat transfer coefficient is an important boundary condition for numerical analysis of TC17 titanium alloy quenching. Its accuracy will affect the distribution accuracy of quenching temperature and stress field. Based on the dynamic measured temperature drop curve of deep buried thermocouple, the heat transfer coefficient of TC17 titanium alloy quenched surface is calculated by using the improved concentrated heat capacity method, and the reliability of the results is verified by numerical simulation. The results show that there are three main stages in the process of TC17 titanium alloy water bath quenching: Steam film stage, nucleate boiling stage and convective cooling stage. The surface heat transfer coefficient increases rapidly in the steam film stage and nucleate boiling stage, and then decreases gradually in the convective cooling stage. The surface heat transfer coefficient reaches a peak of 1299 W/(m²·℃) at the 50th s, and the quenching surface temperature is 355 ℃. The calculated results are in good agreement with the measured temperature drop curve, and the average relative error is only 1.4%.

Composite materials have high specific strength, specific stiffness and designability, which have been widely used in aircraft manufacturing. However, due to the influence of springback deformation and other factors, the geometric accuracy of parts is low, and the problem of composite material deformation correction urgently needs to be solved. Aiming at how to standardize and rapidly build the mathematical model of composite material deformation correction process, this paper put forward the automatic tracking, the discrete points and so on to assist the generation of contour surface, proposed the merge sort method, interpolation search algorithm and so on to assist the generation of inner surface. Some surface processing methods used in mathematical model construction were listed, and the deformation correction system of composite parts was developed under CATIA environment. The overall efficiency is improved by 734.5% after modification, which shows that the method can construct the technological mathematical model efficiently and normatively, and improve the generation efficiency of technological mathematical model.