In order to solve the problems of high volume fraction silicon carbide particle reinforced aluminum matrix composite (SiC_p/Al) machining difficulty and poor surface quality, the longitudinal torsional ultrasonic vibration assisted milling composite process was proposed. Taking ultrasonic amplitude, cutting speed, feed per tooth and cutting depth as variables, a four-factor and five-level orthogonal experimental study was designed. By using response surface method and artificial neural network, the prediction models of cutting force, cutting temperature and surface roughness are established, the interaction effect of two indexes among the four parameter variables is analyzed, and the accuracy of the prediction models is compared and verified. Finally, the multi-objective parameters of cutting force, cutting temperature and surface roughness are optimized by genetic algorithm. The results show that both the response surface method and the artificial neural network have better predictive ability, but the artificial neural network is more accurate. The optimal parameter combination optimized by genetic algorithm is ultrasonic amplitude A=1.84 μm, cutting speed v_c=20 m/min, feed per tooth f_z=0.015 mm/z, cutting depth a_p=0.8 mm. After verification experiment, it is found that the optimal parameter can effectively reduce the cutting force, cutting temperature and surface roughness, and the values are F_t=7.23 N, T=40.18 ℃, R_a=2.4673 μm, respectively. And the prediction errors were 6.91%, 6.53% and 2.53%, respectively, which proved the accuracy of the prediction model and the effectiveness of the optimization parameters.

In response to the problem of chatter and deformation during the precision machining process of the aircraft engine blisk, research on deformation control technology of the blisk was carried out, and a light-curing auxiliary support fixture based on reverse segmented machining was designed. Firstly, the effectiveness of reverse segmented machining in reducing deformation of the workpiece is explained based on the principle of piecewise rigidity during the machining process. Secondly, a three-section auxiliary support fixture was designed, including a compression block, a profiling block, and a fixing plate. The gap between the profiling block and the blade was filled with photosensitive resin to provide support for the machining of the blisk. And the support of the fixture was tested to verify the reliability of the fixture design. Finally, a validation experiment was conducted on reverse segmented machining using a blisk simulation component. The results show that the designed fixture reduced the machining error of the blade disc cross-section line, and the maximum tool deformation was reduced from 0.1 mm to 0.05 mm. This verified that the auxiliary fixture has a good deformation control effect on the blisk.

Due to the long-term service in extreme environments such as high temperature and high stress, the surfaces of nickel-based powder superalloy turbine disk usually needs to be shot peened to meet its stringent performance requirements. Based on this, this paper systematically investigates the effect of different shot peening intensities on the surface integrity of nickel-based powder alloy FGH96. The results show that after shot peening, grain refinement occurs in the near-surface layer of the alloy, producing a hardened layer and introducing large residual compressive stresses in the surface layer. In addition, a plastic deformation layer was produced near the surface, the depth of which deepened with the increase of shot peening intensity from 5 μm in the original state to 117 μm at a shot peening intensity of 0.25 mmA. With the increase of shot peening intensity, the alloy's surface roughness, surface hardness value, depth of the hardened layer, residual compressive stresses in the surface layer, and the depth of the residual stresses layer all showed an increasing trend. The results of this study can provide some data reference for the design and selection of the shot peening process of powder metallurgy superalloys.

Total strain-controlled low-cycle fatigue tests and sustained peak low-cycle fatigue tests with load-holding at maximum tension strains were conducted on powder metallurgy (PM) FGH4096 superalloy at 700 ℃. The influence of the dwell time on the hysteresis loops, stress relaxation, cyclic stress response, fatigue life and damage mechanism were discussed. As shown in test results, tensile strain holding reduce fatigue life. PM FGH4096 superalloy exhibits cyclic softening with different dwell time at the total strain range of 0.9%. The saturation phenomenon of holding effect is found when dwell time increases. Stress relaxation and creep deformation occur during the tensile strain holding period. The stress decreases sharply in the first few seconds of the tensile strain holding period and much slowly later. The low-cycle fatigue fracture and sustained peak low-cycle fatigue fracture are composed of fatigue source area, fatigue crack propagation area and instantaneous fracture area. The fatigue source area is located on the specimen surface. No obvious creep fracture characteristics are found in sustained peak low-cycle fatigue fracture and low-cycle fatigue fracture.

Focus on the requirements of aero-engine turbine guide vane manufacturing, the joining of directionally solidified IC10 superalloy was studied. The results show that, when using Ni–Nb–W–Co–Cr–Al based filler alloy, combined with superalloy power pre-filled into the brazing seam, the IC10 joints with good quality can be obtained under the brazing condition of 1225 ℃/30 min. With the thickness of brazing seam of 0.2 mm, the average creep rupture life can reach up to 44.56 h at 980 ℃/75 MPa. As the brazing gap increases, creep rupture life of the joint gradually decreased. According to the fracture of the joint after creep rupture test, it can be seen that the brittle phases within the joint was the weak link, and the crack easily initiated from these phases.

Aiming at the problem of thermal damage layer on the surface after traditional short electric arc machining, the short electric arc–electrochemical hybrid machining of titanium alloy TC4 was studied, and the material removal mechanism of short electric arc-electrochemical hybrid machining was analyzed. The key parameters affecting the composite machining speed and surface quality were discussed through theoretical models. That is, the processing voltage, the resistivity of the working medium and the feed speed. The effects of key parameters on the surface quality of short electric arc–electrochemical hybrid machining were studied by single factor experiments. The experimental results show that the surface thermal damage layer after short electric arc machining can be well removed by using the electrochemical effect of the bottom surface gap. When the feed speed is 4 mm/min, the thermal damage layer can be completely removed. The machining efficiency is 354 mm3/min, and the surface roughness S_a is 17.982 μm.

The high surface roughness of selective laser melting GH4169 alloy is a challenge that need to be resolved in its application. To replace the traditional acid based electrolyte, choline chloride-ethylene glycol system (Deep eutectic solvent, DES) was used for electrochemical polish GH4169 alloy fabricated by selective laser melting. In order to explore the ethanol addition effect on the electrochemical polishing behavior of the alloy, surface morphology, roughness, glossiness, wetting angle and electrochemical properties before and after electrochemical polishing have been investigated. The result indicates that the surface quality of the specimens after electrochemical polishing has been significantly improved. Among them, when the molar ratio of choline chloride∶ethylene glycol∶ethanol is of 1∶1.9∶0.1, and the processing parameters are of temperature 60 ℃, time 30 min, voltage 3 V, magneton rotation speed 240 r/min and electrode spacing 13 mm, the surface of the specimen shows much more smooth and bright, and the roughness R_a is (0.403 ± 0.010) μm, and the glossiness is (357.9 ± 2.2) GU. The wetting angle and electrochemical properties have also verified that the surface of the sample after electrochemical polishing is more beneficial to corrosion resistance. Meanwhile, the mechanism of the alloy electrochemical polishing in choline chloride-ethylene glycol system has also been discussed.

Nickel-based superalloy Inconel 718 is a typical difficult-to-machine material due to its physical and mechanical properties such as high strength, high toughness, and low thermal conductivity. It easily generates a large amount of cutting heat during the cutting process, which leads to increased tool wear and affects the machined surface quality. As a clean cooling medium, dry ice has the characteristics of low critical temperature, high latent heat, and no residue after sublimation. Such superiorities make dry ice have great application potential in efficient quasi-dry cutting of difficult-to-machine materials. This research applies the assisted method of dry ice particle jet cooling to the machining process for Inconel 718. The beneficial effects of this green manufacturing process are explored on improving the cutting performance of Inconel 718 through reducing cutting temperature. The dry ice particle jet cooling-assisted milling experiments of Inconel 718 are performed. The effects of cooling process parameters on the cutting temperature, cutting force, and machined surface roughness of Inconel 718 are analyzed. The results show that the cutting temperature and cutting force during the milling process of Inconel 718 are significantly reduced under dry ice particle jet cooling conditions, while the machined surface roughness can be reduced. The research proves that the dry ice particle jet cooling can effectively enhance the cutting performance of high-temperature alloys.

Closed blade ring is a type of integral component with superior weight reduction performance, however, it is difficult to machine due to its closed structure, poor openness, narrow and twisted channels, and limited tool feed space. Electrochemical machining (ECM) is a non-traditional machining method, which has the advantages of not being affected by material mechanical properties, no loss of tool cathode, and high machining efficiency. It is one of the important methods for machining closed blade rings. However, there is relatively little research on the flow field of closed blade ring slotting ECM, and the stability of the flow field requires to be improved. Thus, a forward flow liquid supply flow method was proposed for closed blade ring slotting ECM, and flow field simulation and optimization studies were conducted under 1 mm, 2 mm, and 3 mm outlet slot widths. The results show that: (1) The cathode with a slit width of 2 mm had better uniformity and accessibility of flow field in the gap. (2) After adjusting the position of the liquid gap and designing the drainage groove structure according to the principle of equal process, the local liquid shortage phenomenon at the edge of the blade has been effectively improved. Three experiments of closed blade ring slotting ECM were conducted under different liquid outlet slot widths. The results show that the cathode with optimized flow field structure can realize stable machining, and the relative feed speed between the tool cathode and the workpiece was increased from 0.79 mm/min to 0.98 mm/min. The surface quality of the channel was relatively optimal, the roughness of the convex surface decreased from 2.681 μm to 1.641 μm, the roughness of the concave surface decreased from 2.482 μm to 1.243 μm. This verifies the effectiveness of the flow method and the correctness of the flow field simulation results.

To solve the difficult problem of non-interference movement path planning of electrodes of complex cavity-type parts in electric discharge machining (EDM), an electrode movement trajectory search algorithm is proposed. The algorithm is based on the non-uniform rational B-splines (NURBS) parametric curve surface method, which is used to fit the blade profile and establish the accurate mathematical model of the blade. The method of calculating the runner centerline is given, and the trajectory search algorithm is proposed based on the expression of the runner centerline. A special computer aided manufacturing (CAM) system for multi-axis linkage EDM machining of complex cavity parts was developed using the proposed algorithm. The electrode movement path planning and non-interference machining process simulation of 4-axis, 5-axis and 6-axis complex cavity-type parts are carried out, and the machining experiment of the integral turbine disc with blade crown is conducted. The results show that the machining accuracy of the blade shape is less than 0.03 mm, and the total time is 249.3 h, which satisfies the index requirements of the closed integral blisk parts. Experiments show that the algorithm can quickly search for the motion trajectory of non-interference electrode, effectively avoid electrode interference, thereby improving the efficiency of trajectory search, and strong adaptability to working conditions, which can be used to search for trajectories of electrode motion of complex cavity-type parts such as impellers and blisks under various working conditions of 4–6 axes.

There are a lot of deep holes in aero-engine parts, which are not only small aperture, large aspect ratio, but also require no recast layer on the surface of the hole. These characteristics bring a lot of difficulties to the machining of the hole. Electrochemical machining (ECM) is an effective machining method. In view of the difficulties in preparing the side wall insulating layer of cathode used in ECM of small holes with extra large aspect ratio and the problems that it is easy to be damaged in the process of use, a variety of materials and methods for preparing the insulating layer were tried, and the performance stability during the processing was experimentally studied. Finally, a new preparation method of multilayer composite insulating layer based on fused silica capillary column was proposed, and the tube cathode was fabricated by this method. A deep hole with a diameter of 1.1 mm and a depth to diameter ratio of 181 was successfully fabricated on stainless steel material.