航空材料学报

Microstructures and properties of transient liquid phase diffusion bonded joints of DD3 single crystal superalloy

LI Xiao-hong, ZHONG Qun-peng, CAO Chun-xiao

2003, 23(2): 1-5,24.

[Abstract](1426) [PDF 1324KB](319)

Abstract:
The microstructures and the stress-rupture properties of the TLP diffusion bonded joints of DD3, a nickle-base single crystal superalloy, were investigated. Two interlayer alloys developed for DD3 were employed: D1P, a powder alloy and D1F, an amorphous foil. The results show that there existed the obvious microstructral inhomogeneity in the joint diffusion bonded with D1P, and it required a long time diffusion under high temperature to eliminate this inhomogeneity. However, when the DD3 alloy was diffusion bonded with the amorphous foil interlayer alloy, D1F, it is easier to obtain the joint microstructure identical to that of the base metal. Under proper bonding condition, the stress-rupture property at 980℃ of the diffusion bonded DD3 alloy joints reached or surpassed 90% of that of the base metal.

Effect of 1.0wt%Li on ageing hardening of Al-Zn-Mg-Cu alloys

ZHAO Zhong-kui, BAI Pu-cun, ZHOU Tie-tao, LIU Pei-ying, CHEN Chang-qi

2003, 23(2): 6-9.

[Abstract](1465) [PDF 205KB](362)

Abstract:
The 5.6wt%Zn,1.9wt%Mg, 1.6wt%Cu, 0.3wt%Er containing 1.0wt%Li and Li free aluminum alloys is treated by one-step ageing at 110℃,120℃ and 160℃, and alloys containing Li is also treated by two-step ageing at 110℃/5h+160℃/40h. It is retaining effect of Li on GP zones that the hardening effect of aluminum alloys containing Li is lower during ageing comparing with that of aluminum alloys Li free. Whereas the two-step ageing can make the aluminum alloys containing Li hardening excellently since precipitates η′and T′is formed in alloys.

A method of grain refining of TiAl alloy with different strain rate

HUANG Zhao-hui, LI Yuan-chun, WANG Shu-yun

2003, 23(2): 10-13.

[Abstract](1509) [PDF 791KB](199)

Abstract:
A method of grain refining of TiAl alloy with different strain rate is proposed which includes two successive isothemal compressive deformations. By this method a 70 percent of strains is obtained which lead to a good grain refining of TiAl alloy. The true stress-true strain curves shows a flow softening whose mechanism is dynamic recrystallization. After first deformation with low strain rate, the stresses of second deformation decrease and a large strain degree is obtained due to the grain refining through dynamic recrystallization. Inserting a short dwell period between two deformations can yield an increment of static globularization so that the volume fraction of recrystallized grains are increased.

The effect of heat treatment on microstructure and properties of BT36 high temperature alloy

HAO Meng-yi, CAI Jian-ming, DU Juan

2003, 23(2): 14-17.

[Abstract](1519) [PDF 229KB](396)

Abstract:
BT36 is a high temperature titanium alloy designed to be served at 600℃ in Russia. This alloy contained 5% W, were subjected to five heat treatment processes, and the optical microstructure and mechanical properties (including tensile property, creep resistance, thermal stability, etc) have been examined. The results show that the transformed structure from β phase is one essential factor of high creep resistance, since it’s important to control α plate thickness and morphology of transformed β structure by heat treatment process. The five-fold heat treatment process (995℃/0.5h,AC+970℃/2h left in furnace, and cooling to 700℃/2h,AC+500℃/15h,AC+650℃/6h,AC) is preferable for optimum mechanical properties.

Simulation of the fracture behavior of inclusion-matrix interface for particle reinforced composites

GUO Ran, SHI Hui-ji, YAO Zhen-han

2003, 23(2): 18-24.

[Abstract](1512) [PDF 344KB](295)

Abstract:
Based on Voronoi Cell finite element model, a new cell that can describe the debonding of matrix-inclusion interface is developed for particle reinforced metal matrix composites. With a re-mesh strategy, a simulation of fracture behavior of random distributional particle reinforced composites has been realized. A technique of moving critical node is performed to obtain the effects of the interface debonding on the microstructure and macrostructure of the materials. The process of progressive debonding and the variation of stress field are described by the numerical calculation program. The validity and precision of the model is verified by comparing the results obtained from an example of our model with that calculated by the commercial finite element package MARC. It is shown that this model has the advantage of calculating more complex structure of particle reinforced composites.

Molecular dynamics simulations of corrosion resistant alloy Al₃Ni in its solidification

ZHU Chen-fu, ZHANG Xiao-ru, WEI Yun-he, YU Ping, ZHANG Xiu-jie, ZHANG Jin-ling

2003, 23(2): 25-29.

[Abstract](1395) [PDF 883KB](329)

Abstract:
During the hot-dip process of the corrosion resistant alloy Al3Ni on the surface of the steel, it involves the solidification from liquid to the coating. It is found that the cooling rate has great influence on the microstructure. By means of molecular dynamics simulation technique, the solidification process of liquid alloy Al3Ni has been performed. The F-S N-body potentials have been adopted to describe the atomic interactions. The structural features have been revealed with the pair distribution. The variation of energy with the temperature and the relationship between the energy and the microstructure has also been studied. It has been concluded that non-crystal occurs at both different cooling rates,however,the degree of order rises slightly at the low cooling rate.

An approach of graphitizating carbon nanotubes at high temperature

CAO Mao-sheng, LI Chen-sha, ZHU Jing

2003, 23(2): 30-32,38.

[Abstract](1516) [PDF 603KB](349)

Abstract:
The powders of carbon nanotubes (CNTs) are graphitized under condition of high temperature and pressure to transform amorphous carbon in CNTs. Measurement results, which are got through TEM, measurement of specific area, measurement of quality loss after being oxidized by CO2 and air, show that the amorphous carbon has been changed to crystalline carbon.The degree of graphitization of carbon nanotube powders is significant elevated. All these show that the properties of CNTs can be changed by means of the treatment of graphitizing.

Preparation and characterization of nano-SiO₂/PI on-target hybrid composite films

XU Yi-kun, ZHAN Mao-sheng

2003, 23(2): 33-38.

[Abstract](1506) [PDF 264KB](512)

Abstract:
Nano-SiO2/PI on-target hybrid composite films with different contents of SiO2 were prepared by insitu polymerization. Experiments showed that nano-SiO2/PI hybrid film produced by sol-gel insitu polymerization process was still transparent, even when the content of SiO2 amounted to 20wt%. According to the results of scanning electron microscopy (SEM), SiO2 nanoclusters with uniform diameter were dispersed in polyimide matrices homogeneously. The thermal resistance, the dynamic mechanical property and the tensile property were increased to different extent with the increase of the content of SiO2, while the hygroscopicity decreased. All the results indicated that the precursors of SiO2 were ‘fixed’ onto the carboxyl groups (-COOH) of polyamic acid (PAA) macrochains at the beginning of the chemical reaction, and the SiO2 nanoclusters were produced insitu during the following imidization process. There are a lot of silihydroxyl groups (-Si-OH) with high activity on the surface of SiO2 nanoclusters, which can react with carbonyl groups (C=O) of the PI macrochains to form into hydrogen bonds, so it is expected to achieve on-target hybrid composite films.

Filtration condition influencing molten aluminum filtered with actively coated ceramic particles

ZHOU Ming, ZHANG Wei-yu, NI Hong-jun, LI Ke, SHU Da, SUN Bao-de, WANG Jun

2003, 23(2): 39-44.

[Abstract](1356) [PDF 830KB](269)

Abstract:
Active coating ceramic particles were filled in airpermeable micropore tubal firebrick and dense ceramic tube, respectively, which was used to filter molten aluminum at 710℃. For filtered tensile sample under airpermeable tubal firebrick condition, elongation of tensile sample decreases, whose fracture cracks and dimples were lager and inhomogeneous by observing SEM photograph. Quantities and sizes of inclusions were many and large by observing metallographic specimen; For filtered tensile sample under airimpermeable ceramic tube condition, elongation of tensile sample reaches 48.7%, whose elongation increased 16% by contrast to elongation of tensile sample unfiltered. fracture cracks and dimples of tensile sample were fine and homogeneous, and there were only few 8μm inclusions.

The tribological effects of triphenylthiophosphate (TPPT) and α-mercaptobenzothiazole(MBT) as additives on steel bearing balls

XU Min, LI Di

2003, 23(2): 45-50.

[Abstract](1427) [PDF 856KB](235)

Abstract:
The tribological effects of triphenylthiophosphate (TPPT) and α-mercaptobenzothiazole(MBT) as additives in lubricants pentaerithritol ester(PE) by the means of four-ball machine, Ferrography and AES were investigated. It was found that the lubricating oil with TPPT,which possessed of better tribological behavior than that with MBT for TPPT, can increase both antiwear under lower load and extreme pressure under higher load, while MBT can only increase extreme pressure on high loads because of its FeS film formed on the surface of steel ball. Finally,the possibility of MBT was replaced by TPPT in aviation lubricant was also discussed.

The electromagnetic discontinuities of the aircraft surface and an application of the radar absorbing materials

SANG Jian-hua, ZHOU Hai

2003, 23(2): 51-55.

[Abstract](1529) [PDF 766KB](311)

Abstract:
The issue of how to apply Radar Absorb Coating (RAC) to aircraft from the analysis of electromagnetic characteristics and electromagnetic discontinuities of the aircraft surface were discussed. It presents the idea of using RAC and describes the methods of using Radar Absorb Material (RAM) and special conductive material to reduce the Radar Cross Section (RCS) of aircraft. The idea of repairing electromagnetic discontinuities can reduce the need of the amount of RAM, and so the weight and the cost of aircraft, by which it can also improve the performance and maintainability of aircraft. The methods described are testified.

Cure reaction of cyanate ester resins and the catalyst

LI Wen-feng, XIN Wen-li, LIANG Guo-zheng, MA Xiao-yan, ZHU Guang-ming

2003, 23(2): 56-62.

[Abstract](3157) [PDF 966KB](980)

Abstract:
The cure reaction of cyanate ester resins via the auto-catalytic mechanism, or catalyzed by active-hydrogen compounds and by organic-metal complexes, as well as the different kinds of catalyst used were reviewed. The recent progress of catalyst research in photoinitiating organometallic complexes and organic tin compound is also discussed.

2003 Vol. 23, No. 2