2014 Vol.34(1)

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2014, 34(1): -.
[Abstract](36) [PDF 3421KB](2)
Applications of Powder Metallurgy Technologies in Aero-Engines
QU Xuan-hui, ZHANG Guo-qing, ZHANG Lin
2014, 34(1): 1-10. doi: 10.3969/j.issn.1005-5053.2014.1.001
[Abstract](89) [PDF 3421KB](3)
An overview of the advantages of powder metallurgy technology is provided. Several typical kinds of P/M materials used in aero-engine, such as Ni-based superalloy, Ti-based alloys, refractory alloys, Ultra high temperature alloys, oxide dispersion strengthened alloys and thermal spraying powder were introduced. The main focus is on the elucidation of the key fabrication technologies and hot topics on the preparation of Ni-based superalloy powder, Ti-based alloy powder and thermal spraying powder. The characteristics and research progress of the main forming technologies of hot isostatic pressing, spay forming, powder injection molding and rapid forming were summarized. The typical P/M components used in aero-engine were listed. The potential applications and research directions of powder metallurgy technologies were put forward.
Effects of Minor Si Addition on Creep Rupture Property of Cast TiAl Alloys with Directional Lamellar Microstructures
ZHANG Xi-wen, ZHU Chun-lei, LI Hai-zhao, ZHANG Ji
2014, 34(1): 11-15. doi: 10.3969/j.issn.1005-5053.2014.1.002
[Abstract](77) [PDF 2668KB](2)
This paper investigates the effect of 0.2 atomic percentage silicon addition on the creep rupture property of cast TiAl with directional lamellar microstructures. The creep rupture life at 800℃ and 220MPa load was significantly improved by adding minor silicon. Moreover, the value of rupture life endanced is even greater at 800℃ and 300MPa and at 850℃ and 220MPa load though the absolute life values of both alloys are descended as usual. Same as the original alloy, the cast TiAl-0.2Si ingots also show the fully lamellar microstructures with a monolithic lamellar orientation although Ti5Si3 type precipitates already presented in the matrix structures. The extent difference of lamellar structures degradation in both alloys after the same creep rupture holding time indicates that the better lamellar stability provided by the Si addition should be an important factor to benefit the longer creep rupture life.
Influence of Solution Temperature on Homogenizing of TIG Weld Composition of C300
YANG Shuai, PENG Yun, ZHANG Xiao-mu, PENG Zhan-nan, TIAN Zhi-ling
2014, 34(1): 16-21. doi: 10.3969/j.issn.1005-5053.2014.1.003
[Abstract](76) [PDF 15654KB](1)
The preliminary calculation and investigation of the homogenizations of segregation alloying elements in maraging steel (C300 grade) TIG (Tungsten Inter Gas Welding, TIG) weld treated at different solution temperatures were carried out by means of OM, SEM and EDS. The results indicate that the main alloying elements in the weld of C300 are Ni, Mo, Ti; Martensite with uniform composition can be obtained by 1200℃/1 h AC (Air Cooling) treatment for the weld. Weld with uniform composition would no longer produce reverted austenite after 480℃/4h AC processing.
Microstructure and Mechanical Properties of Refil Friction Spot Welds in 2195Al-Li Alloy
ZHANG Cheng-cong, SHEN Xiao-li, FENG Xiao-song, GUO Li-jie
2014, 34(1): 22-26. doi: 10.3969/j.issn.1005-5053.2014.1.004
[Abstract](79) [PDF 27728KB](1)
2195 aluminium-lithium alloy was welded with refill friction spot welding process. The influence of welding time on the mechanical properties was studied, microstructure and microhardness of the typical joint were tested. The results show that the shear strength and cross strength of the joint were increased first and then decreased with the worm-up time from 0.2s to 1.4s. Both shear strength and cross strength were increased with the welding time from 1.8s to 3.2s. The joint cross section can be divided into weld nugget zone (NZ), vertical thermomechanical affected zone(vTMAZ) and horizontal thermomechanical affected zone(hTMAZ). The interface between the NZ and vTMAZ is the weak joining area. The microhardness in the NZ decreases obviously.
Self-healing Mechanism of CVD-BCx under Water and Oxygen Environments
ZHANG Wei-hua, CHENG Lai-fei, LIU Yong-sheng, LUAN Xin-gang
2014, 34(1): 27-33. doi: 10.3969/j.issn.1005-5053.2014.1.005
[Abstract](103) [PDF 3709KB](2)
BCx was prepared by Chemical Vapor Deposition (CVD) process, oxidation behavior of CVD-BCx and the kinetic parameters of CVD-BCx oxidation were obtained under water and oxygen environments. The B2O3 formed from the oxidation of CVD-BCx can seal the crack, by using the kinetic parameters of CVD-BCx consumption and B2O3 formation, the self-healing time of the crack can be predicted. The self-healing time of theoretical prediction was verified by the self-healing of the pre-crack in the layered BCx/SiC structure. The resuts show that the theoretical prediction time is matched the experimental results.
Development and Characterization of High-temperature and Laser Ablation Resistant Coating
LI Jing, ZHANG Jin-dong, ZHANG Yu-zhong, GUAN Zhen-wei, WANG Zhi-yong, ZHAO Yan, DING He-yan
2014, 34(1): 34-38. doi: 10.3969/j.issn.1005-5053.2014.1.006
[Abstract](90) [PDF 2784KB](1)
The ablation resistant coating was prepared by using organic silicon resin, polyethylene carbon silane as binder and Al2O3, BN, SiC, ZrO2, SiO2, CF as filler. The physical and mechanical properties of the coating were characterized. The results show that the glass powder and BN play a key role to reduce cracks in the coating, as well as ZrO2 is crucial to improve the heat and ablation resistant capabilities of the coating. The 1mm 30CrMnSiA steel substrate with 600μm coating would not be perforated by the ablation for 4 seconds from 3000℃ oxygen acetylene flame. When radiated from laser with power density of 531 W/cm2 for 4s, the temperature of substrate can decrease more than 1000℃ with the protection of 900μm coating.
Preparation and mechanical Properties of VC/Ni nano-laminated coatings
ZHOU Xiao-jun, YI Jian-hong, NI Cheng-lin, XU Cheng-zhu, HUANG Feng, ZHANG Xue-dong, XU Ying
2014, 34(1): 39-45. doi: 10.3969/j.issn.1005-5053.2014.1.007
[Abstract](77) [PDF 2738KB](1)
VC/Ni nano-laminated coatings with modulation period of 4nm, 12nm, 88nm and pure VC were prepared by alternating dual-target MF pulsed magnetron sputtering deposition. The microstructure of those coatings was analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Nanoindentation and Vickers indentation were used for characterizing the hardness, Indentation modulus and toughness, which show that all the VC/Ni nano-laminated structural coatings have a clear interface and being in a dense structure. The hardness of all coatings are about 20GPa which is less than the hardness of pure VC coating. On the contrary, the toughness of those VC/Ni coatings is better than the pure VC coating.
Synthesis and Properties of m-Carborane-Based Bisphenol-Type Phenolic resin
QI Shi-cheng, WANG Yao-shuang, WANG Hong-rui, ZHANG Xiao-a, JIANG Sheng-ling, LV Ya-fai
2014, 34(1): 46-51. doi: 10.3969/j.issn.1005-5053.2014.1.008
[Abstract](88) [PDF 2326KB](2)
1,7-Bis(4-hydroxyphenyl)-[WTBX]m[WTBZ]-carborane(preP1) was synthesized from m-carborane by Ullmann reaction,demethylation, and reaction with formaldehyde .The effects of catalyst species, phenol/formaldehyde molar ratio, temperature and time on synthetic reactions were carefully studied. The obtained preP1 was characterized with FTIR,1H NMR,13C NMR and MS methods. TGA behavior and structure transformation of cured preP1 was also investigated. The results show that preP1 (Mn=1035) with hydroxymethylcarboranebisphenolA as main component was obtained when NaOH is used as catalyst under the condition of 100℃/8h. The char of cured preP1 at 900℃ in nitrogen and air is 88.9% and 92.9%, which are much higher than that of commercially obtained boron-containing phenolic resin. It is believed that under air B—H bonds in preP1 could react with oxygen and transform to three-dimensional network structure containing B—O—B bonds. Therefore, the cured products gain weight at 685℃.
Influence of Ultrasonic Impact Load on Residual Stresses Distribution of Welded Joints for CP3 Titanium Alloy
HUANG Li-ting, CHEN Ming-he, XIE Lan-sheng, ZHANG Chang-qing
2014, 34(1): 52-55. doi: 10.3969/j.issn.1005-5053.2014.1.009
[Abstract](85) [PDF 1517KB](1)
Residual stresses distribution induced by laser welding for CP3 titanium alloy was predicted by the finite element model. Residual stresses distribution of welded joints after ultrasonic impact treatment(UIT) were obtained. Welded joints were impacted by different magnitude of forces. A hole drilling method was used to determine the residual stresses. It reveals the tensile stresses of welded joints can be transformed into compressive stresses by using UIT. The compressive stresses rise with the increase of impact force. The stresses come to be steady when the impact force reaches 60N.
Study on Measurement of Non-uniform Stress Field and Stress Gradient by Using Ultrasonic
WANG Xiao, SHI Yi-wei, LIANG Jing, HE Fang-cheng, TAO Chun-hu
2014, 34(1): 56-61. doi: 10.3969/j.issn.1005-5053.2014.1.010
[Abstract](67) [PDF 1375KB](1)
Principle of acoustoelasticity related to ultrasonic measurement for stress was introduced briefly. Longitudinal critically refracted (Lcr) ultrasonic wave was used to determine a non-uniform stress field in high strength 7050-T7451 aluminum alloy. Effect of stress gradient on propagation of the wave with frequency of 1MHz and 5MHz was investigated as well. The results indicated that there was a good linear relationship between stress and velocity of Lcr wave, which would be a non-destructive evaluated stress. Temperature and coupling were the main error sources of testing. When temperature maintained invariable, errors of measurement were less than 40MPa in different position. This was tolerable when tested stress was relatively high. Non-uniform stress field mapped by ultrasound had good coincidence with actual stress field. When stress field was gradient distributed, change of velocity of Lcr wave with frequency of 1MHz was larger than that of 5MHz. It showed that Lcr wave represented mean internal stress within a certain depth range that was determined by frequency. It has high potential to reveal subsurface stress gradient in thickness by using ultrasonic.
Microstructure and Mechanical Properties of Welding Joint of Cladding CuSi3 on Q235 Steel substrate using TIG Method
YU Ye-xiao, LI Yu-long, XU Jian-ning, SUN Yu-jie
2014, 34(1): 62-68. doi: 10.3969/j.issn.1005-5053.2014.1.011
[Abstract](68) [PDF 5041KB](1)
Surface cladding of copper on Q235 steel substrate was conducted by using a TIG deposition method. Microstructure characteristic of the cladding layer and the distribution regularity of the Fe in the deposited layer were investigated by using an optical microscopy and a scanning electron microscopy (SEM) installed with an energy dispersive spectrometer (EDS). The results show the dissolution of the steel substrate induces the formation of the Fe-rich phase according to the EDS analysis across the interface. The uniformity of microstructure and the distribution of Fe element have great influence on the hardness. The average microhardness of the deposited layer increases with the enhancing of the welding heat input.
High Cycle Fatigue Failure Mechanism of 300M Ultra-high Strength Steel and its Electron Beam Welded Joints
ZHANG Guo-dong, YANG Xin-qi, HE Xin-long, LI Jin-wei
2014, 34(1): 69-75. doi: 10.3969/j.issn.1005-5053.2014.1.012
[Abstract](61) [PDF 5041KB](1)
The high cycle fatigue properties of 300M steel electron beam welded joints were tested and the high cycle fatigue failure mechanism was analyzed combined with macro/micro morphology of the fracture. Results indicate that the fatigue strength of welded joints is lower than that of the parent metal. The micro defects at the specimen surface and the non-metallic inclusions of Ti(C, N) particles are the two factors which induced the fatigue crack initiation of 300M steel. The reason for why the fatigue strength of 300M steel electron beam welded joints is lower than that of parent metal can be attributed to the following two points. On one hand, the cohesion strength of the columnar grain boundary is low; on the other hand, columnar grains in weld metal is long,grain surface is very flat and the direction of its distribution is different. Under the fatigue loading, the columnar grain boundary which distribute along the maximum shear stress direction facilitate the formation of fatigue crack.
Fatigue Performance of Al-Cu-Mg Aluminum Alloy for Aviation
LIU Ming, ZHANG Kun, DAI Sheng-long, HUANG Min, YI Lin-na
2014, 34(1): 76-81. doi: 10.3969/j.issn.1005-5053.2014.1.013
[Abstract](105) [PDF 4021KB](1)
The fatigue characteristics of 2124-T851 aluminum alloy were studied under cyclic loading in axialon different specimen orientation, specimen shape and experiment stress ratios R. After the fatigue tests, the fracture sections were analyzed by OM,SEM and TEM. The results indicate that 2124-T851 aluminum alloy possesses the excellent properties in fatigue and damage tolerance. The fatigue strength was increased as the stress ratios enhancing. The fatigue strength of smooth specimens (Kt=1)was two times more than notched specimens(Kt=3). The fatigue strength of transverse specimens is higher than longitudinal specimens and the discrepancy in the two orientations is increase as the stress ratios decline. The fractographic analysis of the specimens indicates that the fracture appearances consisted of fatigue crack initiation zone, fatigue crack propagation zone and final fracture zone. The locations of initial fatigue cracks generally were on the surface of stress concentration or on the different defects of this alloy.
High Temperature Mechanical Properties and Fracture Characteristics of 7A12-T7352
HUANG Min, CHEN Yi, LI Chao, CHEN Jun-zhou, RU Ji-gang
2014, 34(1): 82-85. doi: 10.3969/j.issn.1005-5053.2014.1.014
[Abstract](112) [PDF 9837KB](1)
The effect of temperature in range of room temperature-175℃ on mechanical properties and fracture characteristics of 7A12-T7352 was investigated. The microstructures and fracture surfaces were analyzed by using TEM and SEM. The results show that the tensile strength in area is temperature-dependent and decreased with increasing the temperature. The microstructures of precipitates and grain size show nearly stable in high temperature tensile as investigated by TEM. Furthermore,there is remarkable effect slip characteristics and interface of slippage with increasing the temperature from fracture feature.
Evaluation of Anti-fatigue Manufacture for Superalloy Turbine Disc in Aero-engine
YANG Jian, LIU Guo-liang, WEI Lei, LV Jian-xun, ZHANG Shuang
2014, 34(1): 86-93. doi: 10.3969/j.issn.1005-5053.2014.1.015
[Abstract](87) [PDF 3987KB](3)
The surface of superalloy turbine disc was strengthened by machining and shot peening. And the micro surface characterization and its evaluation, the mechanical characterization and its evaluation were investigated by using metallographic analysis and X-ray residual stress measurement.The results show that: (1) the mechanic surface micro morphlogy mainly includes deformation layer, strain line, fold, tear and white layer. And the shot peening surface micro morphology is acute deformation of surface microstructure, lattice distortion and bidirectional cross-slip; (2)the residual stress of shot peening surface is between 725MPa to 850MPa; (3) the surface scratch less than 0.02mm and surface deformation layer less than 10μm have little influence on fatigue life;(4)The evaluation indexes of anti-fatigue manufacture are macro-evaluation, micro-evaluation, and residual stress evaluation. Also, the corresponding evaluation standard should be established along with the total life of parts.

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