航空材料学报

2021, (4): 1-2.

[Abstract](173) [FullText HTML] (88) [PDF 328KB](46)

Abstract:

2021, 41(4): 1-1.

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Abstract:

Research progress on formation mechanism of surface integrity in titanium alloy machining

SHEN Xuehong, ZHANG Dinghua, YAO Changfeng, TAN Liang

2021, 41(4): 1-16.

[Abstract](639) [FullText HTML] (166) [PDF 1550KB](100)

Abstract:
Titanium alloy is the main application material for the key components of aero-engine due to its excellent properties, such as light weight, high strength, high temperature resistance, and fatigue resistance. Because of its small elastic modulus, low thermal conductivity, and strong chemical affinity, it produces greater cutting force and higher cutting temperature in the machining process. Different thermal mechanical coupling effects can change the surface structure, composition, and mechanical properties of the material, resulting in different surface integrity state characteristics. This paper expounds the effects of process parameters, tool materials and properties, and lubrication methods on cutting force, cutting temperature, surface roughness and morphology, residual stress, microhardness, and microstructure based on the formation mechanism of surface integrity. It is pointed out that the existing researches mainly focus on the description of phenomena and laws. The research on the formation mechanism of surface integrity based on the thermal-mechanical coupling on the processing interface is lack, and the qualitative characterization system of surface integrity is not perfect. Therefore, the object of titanium alloy machining needs to be upgraded from test block to component, and the influence of the change of contact state of the processing interface caused by the time-varying machining trajectory on the surface integrity should be considered. Moreover, the quantitative evaluation of plastic deformation and grain characteristics is completed to accurately predict the gradient distribution of surface integrity. Taking fatigue performance as the goal, the surface integrity distribution meeting the service performance of components is deduced and designed, and then the processing conditions meeting the requirements are determined to realize the surface integrity processing.

Research progress of aero-engine blade materials and anti-fatigue grinding technology

HUANG Yun, LI Shaochuan, XIAO Guijian, CHEN Benqiang, ZHANG Youdong, HE Yi, SONG Kangkang

2021, 41(4): 17-35.

[Abstract](1124) [FullText HTML] (477) [PDF 1502KB](163)

Abstract:
With the development of advanced aviation engines in the direction of high thrust-to-weight ratio and lightweight, a series of lightweight aviation materials such as titanium alloys, nickel-based high-temperature alloys, and ceramic-based composite materials have emerged and been widely used for the key components in the aerospace field, and have also become the main production materials for aero-engine blades. However, due to the stress concentration sensitivity of carbide and the anisotropy and brittle mechanism of composite materials, the fatigue failure problem is gradually highlighted. Existing studies show that the fatigue resistance performance of aero-engine blades has important relationship with its processing process, which in turn affects the service performance and service life of the equipment. Grinding, as the final material removal process for aero-engine blades, directly determines the final surface integrity and fatigue resistance of the blades while obtaining precise profiles. In order to understand the characteristics of blades processed by new lightweight aviation materials, and provide guidance for the processing of aero-engine blades for optimization of fatigue performance, the application of typical aero-engine blade materials and the research status of anti-fatigue grinding technology are summarized. Firstly, the characteristics of typical lightweight and high-strength aeronautical materials and their application in the production of aero-engine blades are briefly described. Secondly, the method of high surface integrity grinding and the key technology of anti-fatigue processing of aero-engine blades are analyzed. Finally, the research on anti-fatigue grinding of aero-engine blades is prospected.

Recent progress on surface integrity of grinding difficult-to-cut metal materials

DING Wenfeng, LI Min, LI Benkai, XU Jiuhua

2021, 41(4): 36-56.

[Abstract](590) [FullText HTML] (276) [PDF 1395KB](75)

Abstract:
Nickel-based superalloys, titanium alloys, stainless steel and other metal materials are widely used in high-end equipment manufacturing, especially in the field of national defense and military industry. Grinding process is an important method to machine these difficult-to-cut metal materials. However, the thermomechanical coupling effect in grinding process has a significant effect on surface integrity, while the surface integrity contributes to the service performance of parts. In this paper, the formation mechanism, contributing factors, prediction and control of the core elements (such as surface roughness, residual stress, micro-hardness and microstructure, etc.) of surface integrity were comprehensively summarized. The development trend of surface integrity control technology is also prospected.

Evolution of surface integrity of turning TA19 titanium alloy end face under low cycle fatigue

DING Xiaocen, HE Ning, SONG Yingdong, SUN Zhigang, SHI Yaowen, YANG Yinfei

2021, 41(4): 57-65.

[Abstract](316) [FullText HTML] (107) [PDF 1353KB](29)

Abstract:
The purpose of this paper was to reveal the evolution law and mechanism of surface integrity parameters of TA19 titanium alloy end face, and to provide a basis for the process control of blisk surface integrity. Taking faced TA19 titanium alloy fatigue specimens as the research objects, the fatigue tests were carried out at 20 ℃ room temperature and 400℃ high temperature. The evolution law of surface integrity parameters during the whole loading process was analyzed by setting detection nodes in the total fatigue cycle number range. The results show that under the action of low cycle fatigue at room temperature, the fracture is near brittle, and under the action of low cycle fatigue at high temperature, the fracture is obviously ductile. The amplitude and frequency of surface waviness increased sharply with the increase of fatigue loading cycles at room temperature and 400℃. Surface roughness is rarely changed under room temperature fatigue tests, but decreased with the increase of fatigue cycles at 400℃. At room temperature, the surface residual compressive stress almost does not change significantly with the increase of fatigue loading cycles, but decreased exponentially at high temperature, which is in accordance with Zener-Wert-Avrami model. Therefore, in the process of material preparation and machining, it is necessary to improve the internal material uniformity of the blank, reduce the corrugation of the machined surface, and increase the amplitude of residual compressive stress on the machined surface, in order to prolong the fatigue life under the action of high temperature fatigue.

Simulation of residual stress and fatigue test in hole extrusion process for Ti₂AlNb alloy

WANG Yanju, WANG Xin, SHA Aixue, LI Xingwu

2021, 41(4): 66-74.

[Abstract](351) [FullText HTML] (101) [PDF 1674KB](43)

Abstract:
In order to study the effect of hole extrusion strengthening process on the fatigue performance of Ti₂AlNb alloy, a simulation analysis model of residual stress of hole strengthening process was established. The distribution law of surface residual stress and strengthening mechanism after hole extrusion process were discussed. In this work, the hole extrusion experiments were carried out. The high temperature and low cycle fatigue performance of the compressed and un-compressed specimens were tested respectively. Meanwhile, the microstructure characteristics of the fatigue fracture of the two specimens were compared. The results show that the hole extrusion process can produce a strong residual compressive stress layer around the small hole, which effectively delays and inhibits the initiation and propagation of fatigue cracks, and significantly improves the high temperature and low cycle fatigue performance of Ti₂AlNb specimens.

Effect of lead angle of hole expansion mandrel on surface integrity and fatigue performance of TC17 titanium alloy hole structure

MA Shicheng, WANG Xin, SONG Yinggang, WANG Qiang, LUO Xuekun, XU Chunling, TANG Zhihui

2021, 41(4): 75-82.

[Abstract](430) [FullText HTML] (149) [PDF 1044KB](26)

Abstract:
For the TC17 titanium alloy, the influence of the leading end angle of the mandrel on the expansion strengthening effect of the hole structure was studied, the surface integrity of the hole expansion strengthened under different process parameters was characterized, the high temperature and low cycle of the original and strengthened samples were tested. Fatigue life and the morphological characteristics of fatigue fracture are analyzed. The results show that the lead angle of the mandrel has a significant effect on the surface roughness after expansion. The uneven plastic flow of the metal on the surface of the hole wall during the expansion process leads to uneven residual stress distribution on the hole wall after expansion, and the residual stress amplitude at the exit end of the expansion is the largest, and the hole wall has a certain depth of residual compressive stress gradient field after expansion. When the interference of the core rod is constant, the fatigue life increases with the increase of the rear lead end angle of the mandrel. When the rear lead end angle is 8°, the median fatigue life gain after strengthening can reach 1.74 times, and the strengthening effect is the best, its minimum cycle life is 16331 times, which is higher than the longest cycle life of the original sample (13965 cycles). After strengthening, the origin of the cracks is changed from the multi-source type in the middle of the hole wall to the single-source crack initiation at the inlet end of the expansion.

Research progress of rare earth doped thermal barrier coatings

ZHAO Pengsen, CAO Xinpeng, ZHENG Haizhong, LI Guifa, GENG Yongxiang, WU Yi, HU Wei

2021, 41(4): 83-95.

[Abstract](570) [FullText HTML] (299) [PDF 15988KB](85)

Abstract:
Thermal barrier coating (TBC) is a kind of thermal insulation and protective ceramic material, which can effectively improve the working temperature and service life of aero-engine. It has important economic value and strategic position in this field. With the further improvement of thrust-to-weight ratio, the traditional YSZ coating no longer can meet the technical requirements of the new generation engine. In recent years, scholars both at home and abroad have shown that rare earth doping can improve the performance of TBCs to a certain extent. Therefore, rare earth doping modification has become the focus of the development of new high-performance TBCs. In this paper, the applications of rare earth doping in high-performance TBCs are summarized, with emphasis on the effects of rare earth doping on the mechanical, thermal-physical and corrosion resistance of TBCs to molten CMAS. The problem of performance deterioration of TBCs when rare earth is over doped and the deficiency in rare earth selection standard is discussed. Moreover, it is considered that the selection basis of rare earth doping amount and type will be the research focus of TBC materials in the next generation. How to further improves the performance of TBCs is the future development direction of rare earth doped TBCs.

Service damage mechanism and performance attenuation of nickel-based alloy turbine blades

CHEN Cao, HAN Lei, ZHANG Yu, YAN Xiaojun

2021, 41(4): 96-108.

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Multi-scale morphology observations and fatigue performance tests were carried out to study the damage evolution mechanism and fatigue performance attenuation behavior of K403 turbine blades in service. During service in field, the dendrite separation and breakage, γ' phase polymerization and rafting, MC carbide decomposition, harmful phase precipitation and grain boundary weakening are having adverse effects on the fatigue performance of turbine blades. Meanwhile, the loss of alloying elements in matrix causes the alloy matrix to soften. In addition, a large number of pores and microcracks formed in the process of service further deteriorate the service performance of turbine blades. Therefore, after long-term operations, the solid solution strengthening, precipitation strengthening, dispersion strengthening and grain boundary strengthening effects of K403 turbine blades are all weakened, which led to serious degradation of the fatigue performance of these turbine blades with the fatigue life reduced. Besides, the crack initiation source of turbine blade is gradually transformed from subsurface metallic pore initiation to carbide initiation.

Effect of rejuvenation heat treatment on re-service aging stability of γ′phase in directionally solidified superalloy

TANG Wenshu, XIAO Junfeng, NAN Qing, GAO Sifeng, LI Yongjun, ZHANG Jiong

2021, 41(4): 109-118.

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High temperature aging treatment was first conducted on the rejuvenated directionally solidified superalloy to simulate the re-service aging damage of turbine blades and the virgin directionally solidified superalloy respectively. Then re-service aging stability of γ′ phase in the virgin and rejuvenated directionally solidified superalloy was compared and analyzed, and the effect of different rejuvenation parameters on γ′ phase microstructure of the rejuvenated directionally solidified superalloy after the same re-service aging time was studied. The results show that although rejuvenation heat treatment can effectively restore creep microstructure to a nearly ‘‘as-new’’ condition, the re-service aging stability of γ′ phase in the rejuvenated directionally solidified superalloy is worse than that of the virgin directionally solidified superalloy, which is attributed to the decomposition of MC carbide. The rejuvenation heat treatment parameters have a great influence on re-service aging stability of the rejuvenated directionally solidified superalloy. The re-service aging rate of γ′ phase in the rejuvenated directionally solidified superalloy becomes higher, the higher the solution temperature, the shorter the holding time and the greater the cooling rate after solution higher. However, the increased primary aging temperature and holding time cause the decrease of the re-service aging rate of γ′ phase in the rejuvenated directionally solidified superalloy. The second aging condition has no obvious effect on the re-service aging stability of γ′ phase.

Effect of different heat treatment processes on microstructure and mechanical properties of K4169 superalloy

LI Yanjia, LIU Rui, HE Jinshan, HU Pinpin, TANG Xin, WANG Xitao, XIAO Chengbo

2021, 41(4): 119-127.

[Abstract](457) [FullText HTML] (142) [PDF 1756KB](41)

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The microstructure and mechanical properties of different heat-treated K4169 alloys after standard heat treatment (SHT), hot isostatic pressing + standard heat treatment (HIP + SHT) and hot isostatic pressing + heat treatment without homogenization (HIP + HTWH) were compared. The feasibility of heat treatment without homogenization of K4169 alloy after HIP was analyzed. A suitable heat treatment system for casting K4169 alloy was proposed. The results on microstructure show that the hot isostatic pressing (1170 °C/140 MP/4 h) can basically eliminate the Laves phase and δ phase of the alloy. Compared with the alloys after HIP + SHT, discontinuous short rod-like δ phase is existed at some grain boundaries of the sample without homogenization heat treatment (HIP + HTWH), which has no substantial influence on the uniformity of microstructure. The results on mechanical properties show that compared with the alloys after SHT, the yield strength at room temperature of alloys after HIP + SHT and HIP + HTWH is increased by 73 MPa and 91 MPa, and the stress-rupture life (704 °C / 448 MPa) is increased by 35% and 32% respectively. Although the dispersion of stress-rupture life and plasticity for alloys after HIP + HTWH are higher than that of HIP + SHT, the mechanical properties meet the requirements of AMS5383 for K4169 alloy. The HIP+HTWH heat treatment process has the practical application potential for K4169 alloy structure by comprehensive analysis of various factors such as reduction of process cost, the increase of production efficiency and the improvement of mechanical properties.

Fabrication and properties of silica-based ceramic cores modified by mullite powders with different particle sizes

WU Xiaofei, LI Xin, XU Xiqing, NIU Shuxin, FAN Hongna, YANG Xiaowei

2021, 41(4): 128-133.

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Abstract:
Ceramic cores provide complex internal cavity structures in the investment precision castings of hollow blades for aero-engine. The silica/mullite ceramic cores were fabricated by hot injection molding, adding fused mullite powders with different particle sizes as mineralizers. The particle size of mullite mineralizers on the crystallization and properties of ceramic cores was investigated in the paper. The result shows that the mullite mineralizers promote the crystallization of cristobalite in ceramic cores, and finer mullite powders can further improve the heterogeneous nucleation, and generate larger quantities of cristobalite. Mullite mineralizers with large particle size can lead to low sintering degree, poor mechanical properties and creep resistance of ceramic cores. While the particle size of mullite mineralizers is too small, the core contains too much quartzite crystal phase, and the microcrack occurs during the phase transformation during cooling, which also causes the deterioration of the strength at room temperature and the high temperature deformation resistance ability. The ceramic cores with mullite powders in particle size of 19 μm show excellent comprehensive performance, with linear shrinkage of 0.65%, porosity of 31.8%, room temperature strength of 17.8 MPa, high temperature creep deformation of 0.4 mm, and leaching rate of 0.06 g/min.

Effect of annealing atmosphere on optical, electrical properties and microstructure of ZnO∶Al films

HAO Changshan, PENG Jingjing, LEI Pei, ZHONG Yanli, ZHANG Xuan, JI Jianchao, HUO Zhongqi

2021, 41(4): 134-140.

[Abstract](469) [FullText HTML] (172) [PDF 707KB](33)

Abstract:
In this study, the effect of annealing atmosphere on the electrical properties, optical properties, microstructure and defects of ZnO∶Al films was investigated in detail. The crystallization, surface and fracture morphologies, electrical properties, resistivity, transmittance, Raman vibration and photoluminescence of ZnO∶Al films were characterized by SEM, XRD, Hall effect test instruments, ultraviolet-visible spectrophotometer, Raman spectra and PL spectra. The results show that after annealing in air atmosphere, the carrier concentration of AZO films decreases from 1.63 × 10²⁰ cm⁻³ to 7.1 × 10¹⁸ cm⁻³, the optical band gap varies from 3.51 eV to 3.37 eV, the transmittance in NIR increased and the band edge emission in PL spectrum shifted from 3.49 eV to 3.34 eV. On the other hand, while the carrier concentration of AZO films annealing in H₂ atmosphere was 5.3 × 10²⁰ cm^-3, the optical band gap increases to 3.78 eV, the transmittance in NIR decreases remarkably, the emission intensity of the band edge increases by more than 10 times and the band edge emission in PL spectrum shifts to 3.57 eV. Furthermore, the 4 order LO phonons are observed in ZnO:Al films annealed in air.

Preparation and low-frequency absorbing properties of flaky FeSiAl alloy

YIN Yichao, YANG Nannan, ZHANG Hang, GAO Lu, YUAN Fangli, WEI Guoke

2021, 41(4): 141-148.

[Abstract](1321) [FullText HTML] (553) [PDF 4788KB](58)

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The spherical FeSiAl alloy powder was used as the raw material absorbent, and the flakes were made by extrusion under the action of ball milling to obtain excellent low-frequency adsorbing performance. The phase composition, microstructure and electromagnetic characteristics of the flaky FeSiAl alloy were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and vector network analyzer (VNA), the microwave absorption performance was studied. The results indicate that the absorption peaks of FeSiAl alloy absorbent are located in X and Ku bands. The flaky FeSiAl alloy containing 70%(mass fraction) as filler with the thickness of 4.00 mm exhibits strong dielectric and magnetic losses as well as a good impedance matching property. It displays extremely strong electromagnetic wave absorption with reflection loss of –32.8 dB at 2.25 GHz, and the low frequency wave absorbing performance is improved significantly compared with spherical FeSiAl alloy.

Post-buckling analysis method of stiffened composite panels and test verification

LIN Guowei, LI Xinxiang

2021, 41(4): 149-156.

[Abstract](378) [FullText HTML] (130) [PDF 789KB](41)

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Post-buckling analysis methods of fiber-reinforced T section stiffened composite panels were investigated. In this paper, the Finite Element Model was presented. In the model, the progressive damage analysis (PDA) and the cohesive zone model (CZM) were used to simulate the damage progression in skin and stiffener and interface failure between them. Therefore, the failure mode and buckling load and damage load were obtained. Besides, the engineering calculation method was also improved to get buckling load and damage load. Finally, an excellent agreement was found between the analytical prediction and the experimental data, and the effectiveness of these two analysis methods was also verified.

Bending properties and failure mechanism of fiber rare earth magnesium alloy super hybrid laminates

ZHAO Zong, ZHENG Xingwei, QIAN Renfei, WANG Wei, YIN Haohao

2021, 41(4): 157-166.

[Abstract](1156) [FullText HTML] (447) [PDF 1620KB](31)

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The fiber metal laminate is mainly used in the fuselage wall board, wing skin and other key parts of the aircraft. The structural parts mentioned above bear a large bending moment during the service, which requires that the fiber metal laminate should have the ability to resist bending deformation. In this study, fiber rare earth magnesium alloy super hybrid laminate, a new type of fuselage structure material was used as the research object. Three-point bending was used to test the bending strength of unidirectional and cross-ply rare earth magnesium alloy super hybrid laminates under different span-to-thickness ratios (L/h). SEM was used to observe the bending failure morphology of the laminate, and the progressive damage behavior of the laminate during the bending process was analyzed with finite element simulation. The research results show that the different L/h values have a certain effect on the bending strength of rare earth magnesium alloy super hybrid laminates. The effective bending failure L/h values of unidirectional and orthogonal rare earth magnesium alloy super hybrid laminates are 16-22 and 16-20 respectively. Through SEM observation and finite element analysis, it is concluded that the bending failure modes of laminate include elastic stage, plastic stage, fiber and epoxy resin matrix fracture stage, rare earth magnesium alloy fracture stage and laminate delamination stage.

2021 Vol. 41, No. 4