Carbon fiber reinforced resin matrix composites (CFRP) and titanium alloys (Ti6Al4V) are widelyfavored in the aviation field for their excellent high specific strength, high specific stiffness, excellent corrosion resistance and thermal shock resistance. However, the significant mechanical properties differences between the two materials often lead to poor machining quality and increase tool wear during the process of making holes in composite/titanium composites. This paper summarizes the research progress of cutting parameters, advanced tool design and cutting environment at home and abroad. In view of the fact that vibration perforation as an advanced machining mode has achieved remarkable technological results in complex/titanium laminated structure perforation in recent years, the key technical problems such as cutting force, cutting heat, hole quality and tool wear in complex/titanium laminated structure ultrasonic and low frequency vibration perforation are analyzed in detail. The new fine and strong integrated wave ultrasonic hole making technology is summarized, and the development direction of future research is prospected. The results of this study will provide an important technical reference for high quality and efficient pore preparation of composite/titanium laminated structures.

With the rapid development of stealth technology, the microwave absorbing properties of composite materials are increasingly required. In this paper, SiC_f /SiC 2D woven fabric was prepared by precursor impregnation and pyrolysis (PIP). The absorbing properties of SiC_f /SiC 2D woven fabric, such as reflection loss, absorbing mechanism and influencing factors, were studied by means of experimental test and numerical simulation. The results show that the SiC_f /SiC 2D woven laminates prepared in this paper have an effective absorption bandwidth of 3 GHz and a maximum reflection loss of –19.2 dB at the absorption peak of 9.7 GHz in the frequency range of 4–18 GHz. Its microwave absorbing performance is closely related to the electromagnetic parameters of the fiber, the microstructural parameters and the incidence Angle of the electromagnetic wave. In addition, it is found that the absorption properties of the composites are mainly due to the special braided structure and the interaction between the fibers and the matrix. These interactions cause electromagnetic waves to be reflected, scattered and absorbed several times inside the material, thus achieving efficient electromagnetic wave attenuation. This paper not only helps to promote the application of SiC_f /SiC composites in stealth technology, electromagnetic shielding and other fields, but also provides a useful reference for the research of other highperformance composites.

As modern aircraft engines advance towards higher thrust-to-weight ratios, increased reliability, and longer lifespans, greater demands are placed on the temperature-bearing capacity and comprehensive service performance of superalloys in hot-end components of engines. In the preparation process of cast superalloys, minor alloying elements in the master alloy play a crucial role in optimizing the microstructure and mechanical properties. This paper focuses on the extensively used K417 and K417G casting superalloys, analyzing the function mechanisms of typical minor element Zr and characterization methods of its distribution features. The analysis mainly includes the influence of minor element Zr on the solidification characteristics, microstructure, and stress-rupture life of casting superalloys. Research shows that the addition of Zr element can effectively reduce the liquidus and solidus temperatures of the alloy and promote the formation of eutectic structure. At the same time, the addition of an appropriate amount (mass fraction of 0.07%–0.09%) of Zr can help improve the stress-rupture life of K417G superalloys; In addition, the time-of-flight secondary-ion-mass-spectrometry and transmission electron microscopy analysis results show that the Zr element is distributed along the interface between the eutectics and alloy matrix in the form of Ni₁₁Zr₉ intermetallic compounds, instead of being only enriched at the grain boundaries as previously believed. The above research provides theoretical basis and data support for the control of minor alloying element content in cast superalloys.

The vacuum arc remelting (VAR) process of 300 mm diameter γ-TiAl alloy ingot was studied by numerical simulation methods. The influence of the melting pool shape, temperature field, and stress field during VAR process of TiAl alloy under different conditions was obtained. The results showed that at the initial stage of VAR, the melting pool had a flattened shape, and it became deeper and V-shape during the stable melting stage. During the melting process, there were tensile stress zones on the surface of the solidified region of the ingot, and the tensile stress increased with the progress of melting, reaching a maximum of 430 MPa. During the subsequent cooling process, the tensile stress decreased, and at 400 s after the end of melting, the maximum tensile stress decreased to 180 MPa. The melting process was simulated separately at melting speeds of 3 kg/min, 6 kg/min, 9 kg/min, and 12 kg/min. As the melting speed increased, the melting pool became deeper, and the shape of the melting pool changed from V-shaped to U-shaped. At 500 s after the end of melting, the maximum tensile stress on the surface of the ingot prepared at a melting rate of 3 kg/min is 120 MPa, and the maximum tensile stress on the surface of the ingot prepared at a melting rate of 12 kg/min is 235 MPa. The heat transfer coefficient had a certain influence on the shape of the melting pool, with the increase of heat transfer coefficient, the shape of bottom of the molten pool changes from wide to shape, but it has little effect on the depth of the melting pool and a relatively small impact on the stress field in the ingot.

The intermediate casing is an important component in aero-engine. Investment casting with high dimensional accuracy, controllable metallurgical quality, and characteristics of integral forming is currently the most widely used special casting method. Shell making is a key process in investment casting. Reasonable control and adjustment to process parameters during shell making can greatly reduce the rejectrate. This study applied joint arm scanning to observe partial deformation of wax patterns, studied the influence of different parameters on the surface quality of wax patterns through pouring experiments. The technical challenges of investment casting for titanium alloy intermediate casings were analyzed, the influence of physical parameters on casting quality was introduced, revealing the phenomena and mechanisms of interactions between different parameters. The results indicate that the influence of physical parameters on casting quality is complex and interrelated. For large, thin-walled and complex structural parts, using higher-strength mold materials to make wax pattens can reduce surface shrinkage and deformation of the wax molds. Surface flow mark defects on wax molds can be eliminated by adjusting wax injection parameters, but this may introduce other defects. Increasing the temperature can reduce the size of the wax pattens and may exacerbate deformation in complex and unstable structures.

Casting defects such as gas and shrinkage porosity are common in aluminum alloys, which seriously affect their performance. In this study, a multi-scale prediction model for defects in cast aluminum alloys based on cellular automaton models was developed independently. To verify the accuracy of the model, X-ray computed tomography (XCT) was utilized to characterize the size and morphology of the microporosities in different parts of the components in three dimensions. A comparative analysis of the predicted and experimental results revealed that the model was capable of efficiently predicting the microporosities sizes in various parts of the components, with the most accurate predictions for the equivalent diameter of the microporosities, exhibiting an average relative error of approximately 25%. This multiscale prediction model can effectively accelerate the optimization of the wheel casting process, improve wheel production efficiency and reduce production costs.

In this study, the microstructures of the directionally solidified FCC/B₂ dual-phase high-entropy alloy were tailored based on different heat treatment processes to improve the mechanical properties in a wide temperature range. The microstructure evolution mechanism under different heat treatment regimes was clarified, and the influence of microstructures on the mechanical properties of the alloy was analyzed. The results show that high-density near spherical L1₂ precipitates can be obtained in the FCC matrix, while lath-like L1₂ precipitates can be obtained in the B₂ phase after solution treatment followed by double aging at high-temperature 800 ℃ and low-temperature 650 ℃. High-density precipitates effectively strengthen the alloy, and the L1₂ phase can promote dislocation movement in the B₂ phase, which is beneficial to improve the plasticity of the alloy at the same time. Compared to the as-cast sample, the comprehensive hightemperature mechanical properties of the alloy after heat treatment are improved.

Metal additive manufacturing technology is an advanced manufacturing technology based on the discrete–accumulation principle, which has brought a subversive progress to the design and manufacture of liquid rocket engines. As the core component of liquid rocket engine, the thrust chamber can realize the lightweight and integrated design and manufacturing of the structure, as well as the overall manufacturing of the flow channel structure of the hot end components such as the combustion chamber, improve the product performance and reliability, shorten the manufacturing cycle and reduce the manufacturing cost. In this paper, the application of metal additive manufacturing technology in the thrust chamber of liquid rocket engine is reviewed, and the future development of the technology is discussed.

For the problem of surface roughness and depth of countersink of weakly rigid CFRP/aluminum alloy laminated members, an experimental study on rotary ultrasonic countersinking of laminated members was carried out. The experiments focused on the comparison of countersinking with and without ultrasonic vibration under different rigidity conditions, and revealed the influence of process parameters, ultrasonic field energy and rigidity of hole-making position on axial force and surface roughness of countersinking. The experimental results show that ultrasonic vibration effectively reduces the axial force and improves the wall quality of the countersink, with an average reduction of 12% in axial force and 10% in roughness R_a. The axial force and wall roughness of the countersink in the hole with the lowest transverse stiffness are the highest, while the axial force and wall roughness of the countersink in the rest of the holes increase with the decrease of axial stiffness. Meanwhile, the rotary ultrasonic machining can achieve effective chip breaking of aluminum alloy and avoid secondary damage to CFRP countersink hole wall by long chips.

Affected by the dynamic disturbance of the workshop, a single scheduling rule cannot consistently obtain good scheduling results in the shop scheduling problem. To this end, a scheduling method based on dueling double DQN (D3QN) is proposed in this paper to solve the flexible job-shop scheduling problem. Firstly, by transforming the scheduling problem into Markov decision process, a mathematical model of reinforcement learning task was constructed, and 18 state features of production system, 9 scoring actions for evaluating machines and jobs, and reward functions related to scheduling objectives are designed respectively. Then, based on dueling double DQN algorithm, during the interaction of machine agent and job agent and workshop production system, the two agents are continuously trained to select the machine and job with the highest score at each scheduling decision-making time, so as to complete the resource allocation task of jobs and machines. Finally, through simulation experiments, the proposed method is compared with the scheduling method which directly selects the machine tool number and selects the scheduling rules. The results show that this method can obtain better scheduling results.

The connection between aircraft composite panels and metal panels is an important research topic in the fuselage structure design. Due to the differences in properties between composites and metals, resulting in the stress of hybrid connectors during service being difficult to predict. Novel carbon nanomaterials represented by carbon nanotubes (CNTs) and MXene films possess unique nanoscale structures and excellent physical properties. In this paper, by improving the preparation process of MXene/CNT composite film sensors and applying them to the health monitoring of composite/metal joint structures, a whole process tracking test of the hybrid joint structures during service is carried out. The results show that the monitoring responses of the thin film sensor throughout the process coincide with the stress–strain curve of the hybrid structure connectors, and it can give accurate early warnings of the failure of the hybrid connection structure, which has certain engineering significance.

Laser powder bed fusion (L-PBF) technology has been widely used in the integration forming of complex parts. However, the thermal stress generated by the rapid heating and cooling during the printing process affects the forming quality of parts. In this study, a two-scale model of TC4 alloy L-PBF forming process was established based on finite element method (FEM) at micro and macro-scale. At the micro level, the real-time temperature fields and stress distribution during three-layer scan process were evaluated, and the effects of process parameters and printing layers on the microscale such as melt pool size were explored. It was found that the growth of the melt pool size was more sensitive to power, and high power could release the accumulated thermal stress in the lower layers, but it also had a higher cooling rate which would increase the maximum thermal stress. At the macro level, the overall printing model of the part was constructed,  and the forming parameters were adjusted based on the microscopic scale results. The residual stress distribution and deformation results were predicted, and good agreement was found between the two. Based on the actual printing results of the component, by constructing a compensation model, the maximum displacement was reduced from 0.626 mm to 0.027 mm, a decrease of approximately 95.7%; The average displacement was reduced from 0.595 mm to 0.024 mm, a decrease of approximately 95.97%, and the calculation time was controlled within a reasonable range.

To solve the problems of low detection efficiency and subjectivity in defect identification during the current manual welding defect detection process, a welding defect image detection and recognition scheme based on Halcon was proposed. The scheme involves preprocessing X-ray images of welding seams, enhancing the display of fish scale patterns through high-frequency enhancement, and extracting the ROI through mean filtering and binarization. Discrimination conditions have been added to the ordinary region growing algorithm to automatically select the most suitable parameters for identifying pores and tungsten slag. The ordinary opening convolution kernel has also been improved to identify unfused parts. Compared with machine learning, this approach does not require a large number of training sets. In experiments, a total of 222 images were detected with an accuracy of 89.19%. The results show that the welding defects DR image automatic identification to improve the efficiency and quality of enterprise parts inspection is of great significance: The computer recognition of weld defects can eliminate the error caused by subjective factors in the workers’ determination of defects; Can be a long time, high-intensity identification of weld defects; Can realize real-time preservation and long-distance transmission of weld defects.