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2021 Vol. 64, No. 9
Published: 2021-05-01
FEATURE
FORUM
RESEARCH
C0NTENTS
COVER STORY
APPROACHING SCIENCE
 
       FEATURE
14 Effects of Particle Size on Microstructures and Properties of GH4169 Alloy by SLM Additive Manufacturing
CHEN Shiqi, LIU Lianping
DOI: 10.16080/j.issn1671-833x.2021.09.014
To investigate the influence of raw GH4169 alloy particle size on microstructures and properties of AM moldings, two kinds of alloy powder with different particle size range were selected for selective laser melting experiment, and samples were heat treated under the same conditions. Density and tensile properties were analyzed for both as-deposited and heat-treated samples. All samples’ microstructures, fracture morphologies and precipitates were observed by OM and SEM. The results indicate that the density of coarse powder in as-deposited samples is higher than that of fine powder, and samples with fine powder have higher yield strength R p0.2 and tensile strength Rm in heat-treated. However, as-deposited and heat-treated samples with coarse powder exhibit higher elongation. What’s more, the as-deposited samples’ molten pool has a configuration of fish scales along the deposition direction, and samples with fine powder have more irregular molten pools than coarse powder. Meanwhile, solidification of molten pool starts from interface and inherits the structural characteristics of solidified molten pool, possessing structure genetic characteristic. Microstructure of both samples shows no significant difference, indicating the size of powder particles has no obvious effects on their microstructures. The equiaxed grain microstructures formed after the heat treatment reduce defects, meanwhile precipitated phase appears, which are main factors for the increasing of R p0.2 and Rm.
2021 Vol. 64 (9): 14-20 [Abstract] ( 193 ) HTMLNew PDF (40528 KB)  ( 367 )
       COVER STORY
22 Electro Stream Machining Technology of Multi-Station
ZHANG Mingqi, PAN Zhifu, FU Junying, CUI Haijun
DOI: 10.16080/j.issn1671-833x.2021.09.022
In modern aero-engine manufacturing, high quality and high efficiency are simultaneously required for gas holes machining in turbine blade. Solutions and application results of multi-station electro stream machining technology is described, including the design of multi-station layout and equipment, the technology of blade positioning and automatic detection, the automatic setting of machining gaps and the technology of precise alignment and penetration detection. Through the automatic alignment and detection of blade, correcting the deviation of blade profile is realized. Through the replaced probe, the problem of determining the initial clearance is solved. By monitoring the processing fluid, the automatic transposition machining after penetration is realized.
2021 Vol. 64 (9): 22-29 [Abstract] ( 186 ) HTMLNew PDF (7900 KB)  ( 118 )
       FORUM
32 Research on Aero-Engine Rectifier With Precision Electrochemical Machining Process
HUANG Mingtao, FU Junying, LIU Meng, CHENG Xiaoyuan, ZHANG Mingqi,CHU Yucheng, WANG Xizhong
DOI: 10.16080/j.issn1671-833x.2021.09.032
Aero-engine rectifier is characterized by dense cascades, narrow channel space and poor structural openness. A series of studies with precise vibrating electrochemical machining process were carried out for nickel-base superalloy rectifiers. By coupling high-frequency pulse with low-frequency vibration, batch optimization of cathode surface profiles, physical model of flow field simulation and analysis, uniform and stable machining state of small gap was obtained. The optimized process parameters were obtained by orthogonal test. The parameters are voltage of 15V, cathode vibrating frequency of 20Hz, opening angle of 160°–190°, pulse frequency of 3000Hz. Rectifier blades were produced with profile tolerance of – 0.023 ~ + 0.025mm and roughness Ra of 0.55μm. No intergranular and pitting corrosion was observed by SEM. And no matal elements were selectively removed by EDS. The manufactured nickel-base superalloy rectifier had passed the high cycle fatigue test and had been successfully applied to aero-engine. This provides provides technical support for the manufacture of complex monolithic components with difficult-to-machining materials.
2021 Vol. 64 (9): 32-38/59 [Abstract] ( 137 ) HTMLNew PDF (6540 KB)  ( 427 )
39 Research on Correlation of Micro Groove Machining Parameters and Groove Width in Tube Electrode Electrochemical Milling
ZHAO Ziqi, QU Ningsong
DOI: 10.16080/j.issn1671-833x.2021.09.039
The micro groove machining process of micro tube electrode milling is affected by a variety of processing parameters. It is the basis of theoretical research to explore, quantify and summarize these laws through scientific tools, which is very important for the research of practical engineering problems. The locality of micro groove machining is an important criterion to evaluate the electrochemical milling process of micro tube electrode, and the selection of machining parameters plays a decisive role in the localization of micro groove machining. In this paper, Pearson correlation analysis method is used to explore the correlation of the main processing parameters and the groove width. It is discovered that the influence of current density is significantly higher than the initial machining gap and cathode scanning speed. Based on that, the adjustment strategy of each processing parameter is formulated. Thus, the parameters of high locality micro-groove machining can be optimized quickly
2021 Vol. 64 (9): 39-44 [Abstract] ( 133 ) HTMLNew PDF (13108 KB)  ( 65 )
45 Optimization of Electrochemical Machining Process of Blade Based on DOE Design
ZHAI Lulu, LIU Haibo, HUAN Heng
DOI: 10.16080/j.issn1671-833x.2021.09.045
For the electrochemical machining of super-alloy blades with complex curved surface, the requirements of high precision for the size and shape of inlet and exhaust sides should be met. The process parameters of blank thickness, margin, electrolyte conductivity and voltage have important effects on the machining accuracy of the front and rear edges. In order to find out the four main process parameters on the influence law of machining accuracy and machining time, the processing surface and processing time of a compressor were studied. In this paper, DOE test design was used to optimize the electrochemical machining process of the blade, eight samples were designed by using partial factors, and the performance of all samples was compared and analyzed by using Minitab software. The results show that the main parameters affecting the machining accuracy of the front and rear edges of the blade are blank thickness, margin and electrolyte conductivity. The main parameters that affect the processing time are blank thickness, electrolyte conductivity and voltage. After optimization, the process parameters were blank thickness 10mm, margin 0.99mm, electrolyte conductivity 134.7mS/cm2 , voltage 20V, respectively. The precision of the front and rear edges obtained under this parameter is stable at 0.06mm, and the processing time is stable at 20min.
2021 Vol. 64 (9): 45-52 [Abstract] ( 103 ) HTMLNew PDF (6563 KB)  ( 215 )
53 Experimental Investigation on Wire Electrode Electrochemical Machining Square Slotted Torsional Spring
TANG Cheng,FANG Xiaolong,XU Chongchang,ZENG Yongbin
DOI: 10.16080/j.issn1671-833x.2021.09.053
Square slit torsion springs are widely used in various types of fighters and helicopters to trim steering gears, and their mechanical properties are significantly affected by manufacturing accuracy. Combination of low-speed rotation and linear feed to perform wire electrochemical machining square slotted torsional spring was proposed, analyzing its combined kinematics, designing a special motion device, and establishing a test system for wire electrochemical machining square slotted torsional spring. The experimental research on the electrochemical machining of the wire hole tube electrode to explore the influence of the feed speed and processing voltage parameters on the hole diameter and hole type was studied, and selecting the processing parameter with a feed speed of 0.6mm/min and a processing voltage of 14V, an array of machining holes with a hole diameter of 0.96mm is provided. The process of applying an insulating coating is used to avoid the corrosion of the non-machined surface of the torsion spring during the wire electrochemical machining process. The influence of the processing voltage on the feed speed is explored. Using optimized process parameters and improved process flow, a square slit torsion spring sample with an average slit width of 1.006mm, a size deviation of ±0.05mm, and a good surface quality was processed.
2021 Vol. 64 (9): 53-59 [Abstract] ( 88 ) HTMLNew PDF (14067 KB)  ( 94 )
       APPROACHING SCIENCE
60 Focus on High Performance Machining for Aerospace
2021 Vol. 64 (9): 60-61 [Abstract] ( 109 ) HTMLNew PDF (1055 KB)  ( 160 )
       RESEARCH
62 Research on 3D Surface Topography in Milling of CFRP
FAN Wentao, CHEN Yan, CHEN Yijia, XIE Songfeng, JI Junjie, JI Daohang
DOI: 10.16080/j.issn1671-833x.2021.09.062
Carbon fiber reinforced polymer (CFRP) is a typical difficult–to–machining material. There are still some problems in its milling process, such as the poor surface quality and difficulty in fully characterizing the surface topography. In this article, slot–milling tests were carried out with different feed speeds, and the surface topography and machining mechanism of CFRP milling was studied. It was found that there was a big deficiency using two–dimensional surface roughness parameters, three–dimensional surface roughness can more comprehensively reflect the surface topography of CFRP milling. The surface topography of CFRP was jointly characterized by arithmetic mean height Sa, root mean square height Sq, skewness Ssk and kurtosis Sku. With the increase of the feed speed, Sa and Sq increase gradually, but Ssk and Sku decrease. In order to guarantee the machined surface quality, the down milling method is used, and the feed speed should be less than 1200mm/min.
2021 Vol. 64 (9): 62-67 [Abstract] ( 143 ) HTMLNew PDF (8341 KB)  ( 94 )
68 Structures and Properties of Nano–Precipitates in Al–Li Alloys
WANG Shuo,ZHANG Chi,WANG Junsheng
DOI: 10.16080/j.issn1671-833x.2021.09.068
The structure and performance of the third and fourth generation Al–Li alloys depend on the type, size, shape, distribution and sequence of the nano–precipitates within them. In this review paper, typically nano–precipitates generated by additions of Mg, Ag, Si, and Mn elements were reported. In particular, in Al–Li–Cu system: stabilities of δ′ (Al3Li) and δ′(Al3Li)/Al3Sc core–shell structures with non–equilibrium composition; the coherent and semi–coherent interfaces of θ′(Al2Cu)/α–Al and the segregation behavior of Cu at the interfaces; the origin of the relationships including “in–phase” and “anti–phase” for opposite δ' phases in the δ′/θ′/δ′ composite precipitation; and various crystal structure models of T1 (Al2CuLi). In Al–Li–Cu–Mg system: the interface of S(Al2CuMg)/α–Al; the good resistance of Ω(Al2Cu) phases to grain coarsening and the nucleation induced by vacancy. In the Al–Li–Cu–Mg–Si system: the competitions for σ(Al5Cu6Mg2) – S' and σ–Ω due to non–component Si and Ag atoms; and phase transition from Q(Al3Cu2Mg9Si7) to B'(Al3Mg9Si7) because of the intrinsic point defect in Q. By using X–ray diffraction (XRD), high–resolution transmission electron microscopy (HRTEM), high–angle annular dark–field scanning transmission electron microscopy (HAADF– STEM), and first–principle calculations, it is able to provide inspiration for us to understand the performances of these nano precipitations.
2021 Vol. 64 (9): 68-76 [Abstract] ( 295 ) HTMLNew PDF (3430 KB)  ( 508 )
77 Simulation Study on Residual Stress and Fatigue Life of TB6 Titanium Alloy Hole After Double Cold Expansion
JIANG Tingyu,WANG Yang,WANG Peng,WAN Zhicheng,ZHANG Quanli,SU Honghua
DOI: 10.16080/j.issn1671-833x.2021.09.077
The double cold expansion strengthening technology can ensure that the hole has enough strengthened effect, and realize the close fit between bushing and the hole edge, so as to improve the fatigue life of connectors effectively. Residual stress distribution and fatigue life of double cold expanded hole were studied by simulation method. Firstly, a finite element model for the double cold expansion of TB6 titanium alloy components was established to analyze the accuracy of the simulation model. Secondly, based on the simulation results, the fatigue life of the double cold expanded hole was analyzed by MSC.Fatigue software. Finally, the effect of the hole diameter deviation and the expansion lubrication condition on the fatigue performance was taken into consideration. The results show that the stress concentration on the hole wall can be effectively alleviated by the double cold expansion process. The fatigue failure position transferred from the hole edge to the position far away. Furthermore, a constant stress level in the direction of the smallest cross-section with different apertures occurs. It is also found that the excessive diameter deviation has a negative effect on the fatigue life, where good lubrication condition is beneficial to the fatigue performance.
2021 Vol. 64 (9): 77-84 [Abstract] ( 134 ) HTMLNew PDF (9244 KB)  ( 268 )
85 Effects of Automated Fiber Placement Heating Uniformity and Temperature on Mechanical Properties of Composite
DENG Linwei,PU Yuanzhu,ZHANG Shaoqiu,YANG Heng,HAN Miaoling
DOI: 10.16080/j.issn1671-833x.2021.09.085
Automated fiber placement (AFP) is one of the most advanced high-performance aerospace composite manufacturing technology. In order to further study the influence of heating temperature on the properties of composite in AFP technology, a heat transfer model of infrared heating system in AFP process was established. Based on this model, the temperature control method of AFP and the uniformity of temperature distribution in the prepreg layers were analyzed, and the influence of heating temperature on the mechanical properties of composite was studied experimentally. The results show that the heating temperature is the key process parameter affecting the mechanical properties of the composite. When the heating temperature was set at 35℃ , the tensile strength, bending strength and interlaminar shear strength of the composite specimens made in this paper increased by 20.9%, 12.4% and 4.9%, respectively. Pre-curing of prepreg tows due to over-high local temperature of the prepreg caused by uneven heating, and the resin-poor regions caused by resin flow under the combined action of local high pressure and temperature probably is the one of reasons leading to the deterioration of composite properties.
2021 Vol. 64 (9): 85-92 [Abstract] ( 159 ) HTMLNew PDF (13793 KB)  ( 344 )
93 Influences of Second–Phase Particles on Recrystallization Processes of Al Alloys
LI Zhiqiang,WANG Junsheng
DOI: 10.16080/j.issn1671-833x.2021.09.093
The recrystallization processes of Al alloys under the influences of second–phase particles are investigated. There are many second phase particles in the microstructures of aluminum alloys. These second–phase particles can be formed in the solidification processes or precipitated in the solid phase transformation processes. They have great influences on the recrystallization processes of the Al alloys. Firstly, in the nucleation processes, the fine dispersed second phase particles prevent the dislocation movement, thus slowing down the recrystallization nucleation processes. However, when the sizes of the second–phase particles are large, the dislocations concentrate around the second– phase particles with high density, which leads to nucleation near the second phase particles. Secondly, in the process of recrystallization grain growth, the second–phase particles pin the grain boundary movement, thus slowing down the recrystallization processes. The influences of the size and distribution of second phase particles on the recrystallization processes are very important foundation of the composition and processing technology design of Al alloys. The influence factors of the second–phase particles on the recrystallization processes of Al alloys mainly focus on the analysis of the size and distribution of the second–phase particles. The morphologies of second–phase particles and the particle/matrix interfacial energies also have great influences on the recrystallization processes.
2021 Vol. 64 (9): 93-101 [Abstract] ( 110 ) HTMLNew PDF (2293 KB)  ( 351 )
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· 'Aeronautical Manufacturing technology ' is included in EI database
· China Science Citation Database (CSCD)
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· Aeronautical Manufacturing Technology ranked No. 3 in Chinese S&T Journal Citation Reports (CJCR)
· High Quality Sci-tech Journal Classification Catalogue in Aerospace Field （2023）
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