航空材料学报

Study on laser clad zirconia thermal barrier coatings

GAO Yang, XIE Lun, TONG Bai-yun, LIANG Yong, SHI Chang-xu

2003, 23(3): 1-4.

[Abstract](1505) [PDF 566KB](218)

Abstract:
A new type of thermal barrier coatings is being studied for gas turbine blades by laser cladding on Ni-base super-alloy substrates.A 5KW CW CO2 laser was used to produce NiCoCrAlY bond coatings and zirconia ceramic coatings with double remelting.The results show that during rapid melting and solidification in laser process, the oriented epitaxial growth, closely packed columnar structure could be obtained by controlling laser parameters.An alumina layer which exists between the NiCoCrAlY layer and columnar ceramic layer provides for the adherence of them.The ceramic coatings made by laser remelting were predominantly composed of a mixture of cubic and tetragonal phases, which can be retained by rapid cooling to room temperature.

Effect of quenching temperature and tempering time on grain refinement in TiAl base alloy

HE Shuang-zhen, HE Yue-hui, HUANG Bai-yun, ZHANG Jun-hong, LU Shi-qiang, TANG Jian-cheng

2003, 23(3): 5-10.

[Abstract](1457) [PDF 2157KB](250)

Abstract:
By tempering the quenching samples in the α+γ phase region, a very fine duplex microstructure(18-30μm) was obtained in the as cast Ti-48Al-2Cr-0.5Mo(at%) alloys with an initial grain size of about 1000μm.The refining effect was found to be greatly dependent on the quenched microstructure which is controlled by prior heating temperature.With increasing the quenched temperature, the quenched microstructures become fine and the volume fraction of feather microstructure decreases.During tempering, larger grain was produced with time increasing.The 18μm microstructure in tempering for 3h was obtained in the sample quenched at 1400℃.The mechanism of grain refinement in TiAl base alloy was also discussed theoretically in present work.

The matrix crack spacing distribution of 3DC/SiC composites

ZHANG Jun, XU Yong-dong, ZHANG Li-tong CHENG Lai-fei, DONG Ning

2003, 23(3): 11-14.

[Abstract](1460) [PDF 611KB](248)

Abstract:
Cracks are inevitably brought in matrix since the CTE mismatch between carbon fiber and SiC matrix during the manufacture of C/SiC composites.In this paper, the distribution of matrix cracks in 3DC/SiC composites with different thickness interphase is studied by x2 goodness of fittest, and it is showed that the matrix crack spacing between tows in 3DC/SiC composites obey normal distribution which is determined by the basketry of 3D composites.

Study on the behavior in thermal shock and ablation resistance of TiC-TiB₂/Cu ceramic-matrix composite

ZHU Chun-cheng, LI Yao, HE Xiao-dong, ZHANG Xing-hong, HAN Jie-cai

2003, 23(3): 15-19.

[Abstract](1393) [PDF 1703KB](185)

Abstract:
The TiC-TiB2/xCu ceramic-matrix composites were produced by self-propagating high-temperature combustion synthesis combined with pseudo hot isostatic pressing(SHS/PHIP).The microstructure and the components of the synthesized compacts were analyzed.To investigate their behaviors of ablation resistance, the TiC-TiB2/xCu cermets were heated with plasma torch.The results showed that along with increase of the Cu content,the thermal shock resistance of the TiC-TiB2/xCu was enhanced, but the ablation resistance was descended.The loss mass of the cermet after ablation for 20 seconds was 1.7g and the mass loss ratio was 0.11g/s.The ablation resistance was obtained due to the combined action of both the high strength cermet with the durability to erosion and high temperature and the metal binder, Cu, performing decalescence and volatilization at high temperature.

Effect of temperature parameters of mold-agitation process on grain feature of superalloy blisk

YU Bao-zheng, TANG Xin, LIU Fa-xin

2003, 23(3): 20-22.

[Abstract](1389) [PDF 864KB](183)

Abstract:
The effect of temperature parameters of mold-agitation process on grain feature of different part of superalloy K418B blisk under various experimental condition was investigated.It was found that; the temperature parameter, such as mold temperature Tmold and superheat of melts ΔT,has no obvious effect on grain feature(size and configuration) of disk part of the blisk, but has significant effect on that of blade part.The grain feature of disk part is mainly decided by mechanical parameters of mold agitation.

Dynamic restoration mechanism during hot compression of high purity α-Fe

LIN Zhi, WANG Yan-li, LIN Jun-pin, KIM K N, CHEN Guo-liang

2003, 23(3): 23-26,32.

[Abstract](1423) [PDF 1320KB](166)

Abstract:
Specimens of high purity α-Fe were deformed in the GLEEBLE-1500 at temperatures of 550℃,700℃, 800℃ and 900℃ at strain rates ranging from 0.001 to 10s-1.The microstructural changes, which occur during the hot compression, have been investigated by optical microscopy and related to the true stress-true strain curves.The experimental results show that the dynamic recrystallization is accelerated with increase of deformation temperature and decrease of strain rate.The relation between the dynamic recrystallization and Z-parameter has been investigated.Dynamic recrystallization takes place approximately in a certain range of Z-parameter, i.e.25lnZ 37.

Study on pulsed TIG welding of aluminium matrix composites

WANG Shao-gang, XU Jiu-hua, JIANG Cheng-yu

2003, 23(3): 27-32.

[Abstract](1559) [PDF 1108KB](229)

Abstract:
The weldability of A12O3P/6061A1 was investigated in the condition of pulsed TIG welding.Results of tensile test, microhardness test and metallographic structure observation show that the quality of the joint is rather good, the mi-crostructure of joint is dense, no gas holes, no inclusion or crack etc can be found, the joint strength is about 80 percent that of the parent material.The analyses of X-ray diffraaction(XRD) and scanning electronic microscopy(SEM) indicate that in the joint there are Al,Al2O3,MgAl2O4 etc phases and tensile specimens manifest the mechanism of toughness cracking.The possible problems of the aluminium matrix composites in TIG welding and the ways of improving joint quality are finally discussed in this paper.

Effect of aging time on the performance of coating

FANG Bing-yan, HAN En-hou, WANG Jian-qiu, ZHU Zi-yong, KE Wei, HU Jian-ping, XU Zhi-gang

2003, 23(3): 33-37.

[Abstract](1190) [PDF 441KB](259)

Abstract:
The resistance to corrosion of an epoxy coating containing the pigment of zinc chrome yellow was studied using electrochemical impedance spectroscopy(EIS).The results showed that the coating had the best performance when it was aged for 4 weeks.However, when the aging time was longer or shorter, the coating would exhibit bad anti-corrosion performance.Electrochemical impedance spectroscopy could be used in the study of aging coating.

Research on self-cleaning coating of organic Ti-Si compound resins

FENG Yan-wen, LIANG Jin-sheng, LIANG Guang-chuan, JI Zhi-Jiang, WANG Jing

2003, 23(3): 38-41.

[Abstract](1522) [PDF 507KB](174)

Abstract:
The self-cleaning thin films were made of the organic Ti-Si compound resins which were prepared by hydrolysis, polycondensation and distillation of organic silane coupling agent(SG-Si900), titania alkoxide and tetraethoxysilanes(TEOS) in the presence of acetic acid, with dipping-drawing technology on the surface of glass.Further study focused on the factors effecting capability of the self-cleaning thin films.Studied found that the length of chain of the organic Ti-Si compound resins can be controlled by the blocking function of the SG-Si900, and the hydrophilic ability and the adhesion of the thin films of the compound resin can be improved by increasing the content of the TEOS, controlling the content of the SG-Si900 and Ti, rising the heat-treatment temperature and painting times, etc.Hence a conclusion can be drawn, when Si/Ti is 9, SG-Si900/TEOS is 1, painting times is 3, heat-treatment temperature is 200℃, thickness of the thin film is about 80nm, the capability of the thin film of the compound resin is excellent, there is 0 degree for it with water without presence of ultraviolet radiation.

Study on friction coefficient of a aodified phenolic basis composition

ZHUANG Guang-shan, WANG Cheng-guo, WANG Hai-qing, SUN Yi

2003, 23(3): 42-45.

[Abstract](1432) [PDF 2593KB](205)

Abstract:
A hybrid fibers reinforced modified phenolic basis composition used for disc brake equipment of para-high speed train was studied,and its tribologic characteristics under dry condition with different initial braking speeds and normal stresses were studied on the Friction & Wear Tester for Railway Rolling Stocks, the morphology of friction surface after braking was studied by SEM, the results show that the change of instantaneous friction coefficient vs instantaneous velocity influenced by initial speed and the friction coefficient went down with contact stress increasing; the critical condition for application under dry friction and brake to stop condition was 0.82 MPa contact stress and 27.3 m/s initial speed; the main reason for change of friction coefficient was the friction film formed on friction surface.

Study on parameter matching performance between low thermal infrared emitting coating and microwave absorbing materials

XIE Guo-hua, ZHANG Zuo-guang, WU Rui-bin

2003, 23(3): 46-49.

[Abstract](1422) [PDF 355KB](207)

Abstract:
This paper has investigated the parameter matching performance between low thermal infrared emitting coating and microwave absorbing matereial.The research results can be described as follows:with the increase of filler particles of low thermal infrared coating, thermal infrared emissivity of material system decreases gradually, its permeability hardly changes and holds its value low, and its permittivity increases steeply and later hardly changes and holds its value high.The thermal infrared emissivity of the coating composed of laminar filler particle is lower than that of the coating composed of globular filler particle when above two coatings have the same filler particle content.The resulting material has two stealthy properties stated above when these two materials having exact parameter and content of the filler form a layer-structure material system.

pH effect on the performance of Alumina ceramic slurry for gelcasting

TONG Jian-feng, CHEN Da-ming

2003, 23(3): 50-52.

[Abstract](1520) [PDF 273KB](306)

Abstract:
The effects of pH on the performance of ceramic slurry during preparing aqueous alumina concentrated suspension with low viscosity and high solids volume loading are studied.The results shows:the Zeta potential is zero when pH of slurry is abound 5, which the viscosity of slurry is densest and dispersed effect is worst.However, The Zeta potential is biggest when pH of slurry is about 9, which stability of alumina in suspension is best.

Modified equivalent stress model for high cyclic fatigue curves

HAN Xi-peng, XU Chao, DUAN Zuo-xiang, LIU Shao-lun

2003, 23(3): 53-57.

[Abstract](1585) [PDF 467KB](259)

Abstract:
The reduction method of equivalent stress model for median S-N curves and modified equivalent stress model or three parameter power function for P-S-N curves has been proposed based on data of high cyclic fatigue obtained by discrete test.In comparison with traditional standard method, this method not only save number of specimen but also can give the new S-N curves with other stress ratios by interpolating,so it is more appropriate for engineering application.

Progress in design theory and methods research on radar absorbing materials

PENG Zhi-hui, CAO Mao-sheng, YUAN Jie, XIAO Gang

2003, 23(3): 58-63.

[Abstract](1501) [PDF 549KB](501)

Abstract:
The principle methods and optimization technique of computation design towards radar absorbing materials(RAM) through 10 years were summarized, and the design techniqus in existence were briefly evaluated.In addition, the problems in RAM design are described and the RAM development direction are predicted.

2003 Vol. 23, No. 3