航空材料学报

Analysis of laminar flow critical value for TiAl-based alloy during centrifugal casting process

SHENG Wen-bin, GUO Jing-jie, SU Yan-qing, DING Hong-sheng, JIA Jun

1999, 19(3): 1-6,12.

[Abstract](1413) [PDF 259KB](154)

Abstract:
In this paper,the filling process for TiAl based alloy melt poured in permanent mould during the process of centrifugal casting has been analyzed.The relation between the filling speed V and the filling length,as well as the choosing rule of maximum allowing angular velocity ω 0max (r/min) has been obtained.Results show that the filling speed is the function of the filling length during the process of centrifugal casting,and increases with the increase of the filling length.The laminar flow length decreases with the increase of maximum allowing angular velocity.

Tensile creep anisotropy of single crystal superalloy DD3

WEI Peng-yi, YANG Zhi-guo, CHENG Xiao-ming, ZHONG Zhen-gang, LI Cheng, LIU Shi-zhong

1999, 19(3): 7-12.

[Abstract](1405) [PDF 271KB](317)

Abstract:
Tensile creep anisotropy feature of Ni-base single crystal superalloy DD3 with (001),(011),(111) in orientation were investigated under typical conditions(760～950℃,200～800MPa). It was found there is complex and strong creep anisotropy for DD3 under those conditions, such as:the value order of steady creep rate, sensitivity to creep stress and dependence on crystal orientation of this alloy alternate with temperature increasing. Those were due to different crystal slipping(cubic octahedral and combination of them),dislocation movement model and dynamics during those different creep processing, which is determined by composition, ratio between creep stress and tensile strength and crystal orientation of this alloy.

Investigation of X-ray and TEM diffraction of spinodal-decomposition and ordering for Cu-4wt%Ti alloy

WANG Liu-ding, CHEN Chang-le, WEI Ying-hui, KANG Mo-kuang

1999, 19(3): 13-18.

[Abstract](1605) [PDF 249KB](341)

Abstract:
On the basis of lattice wave theory, the several side-band profiles of X-ray diffraction of spinodal decomposition and ordering for Cu-4wt%Ti alloy are simulated by the computer through supposing the rectangle distribution of solute atoms in the alloy,and the profiles are extremely similar to experimental results.Moreover,in the light of the principle of superposition,the composition of above mentioned profiles vertical each other in two directions is carried out and the imitative diffraction patterns obtained are extremely very good consistent with TEM diffraction pattern.

Dislocation structure of spray deposited Ni₃Al-Mo alloy

MI Guo-fa, LUO Zhi-ping, TIAN Shi-fan, LI Qing-chun

1999, 19(3): 19-26.

[Abstract](1488) [PDF 564KB](333)

Abstract:
A Ni3Al-based superalloy of Ni-Al-Mo system has been successfully prepared by using the multifuctional spray atomization and deposition plant.Testing for tensile properties indicated that the spray deposited Ni3-Mo alloy possesses "R"characteristic in the yield strength.Analysis of dislocation structure by TEM has revealed the relationship between the microstructure and yield strength.The results show that the yield strength changing with temperature for the alloy is determined by the dislocation winding condition、pattern and quantity of the dislocation pair and starting degree of the hexahedron slide system inside γ'and γ phases.

Microstructure of the TiC-Al₂O₃-Fe-cermets fabricated by SHS/PHIP

ZHANG Wei-fang, HAN Jie-cai, ZHANG Hua-yu, DU Shan-yi

1999, 19(3): 27-32.

[Abstract](1476) [PDF 282KB](164)

Abstract:
Dense TiC-Al2O3-Fe cermets were produced by self-propagationg high temperature synthesis and pseudo-hot isostatic pressing(SHS/PHIP).The microstructure of the product was analyzed.The results show that the particle size of TiC becomes small and uniform as Fe content increasing.It is favorable to eliminating the small pores between TiC and Al2O3 particles.The interfacial bonding between Fe and Al2O3 was smooth.A thin diffusion layer was found between Fe and TiC.Cellular structure probably being DO3 type alloy as Fe3Al matrix was found in Fe-binder phase.A great amount of dislocations were found in TiC particle dur to the quickly pressing in the processing of SHS/PHIP.

An investigation on oxidation resistance-of DZ22/NiCrAlY coating

JI Yan-ling

1999, 19(3): 33-36.

[Abstract](1315) [PDF 145KB](216)

Abstract:
NiCrAlY coatings on DZ22 superalloy are prepared by magnetic sputtering deposition to improve the high temperature oxidation resistance of DZ22 superalloy. The results of cyclic oxidation test shown that the cyclic oxidation life of DZ22/NiCrAlY system is about 2000h, which is 10 times as the cyclic oxidation life of DZ22. The high temperature oxidation resistance can be improved by increasing the Y and RE in coating.

Investigation on thermophysical properties-of SiO₂-AlN composites

WU Jie-hua, LI Bao-shun, GUO Jing-kun

1999, 19(3): 37-42.

[Abstract](1396) [PDF 282KB](633)

Abstract:
Thermophysical properties of SiO2-AlN composites as a function of temperature and the content of AlN particles were investigated.The theoretical analysis of thermal shock resistance of SiO2-AlN composites was also studied.The results showed that thermal expansion coefficient of SiO2-AlN composites increased with temperature;while in the same temperature thermal expansion coefficient increased with the content of AlN particles above 400℃.Thermal diffusivity and thermal conductivity of SiO2-AlN composites increased with hot-pressing temperature.Retained flexural strength of SiO2-AlN composites decreased abruptly when temperature difference was above 600℃ because of the heavy mismatch of thermal expansion coefficient between SSiO2 matrix and AlN particles.

Microstructure of the C_f/SiC composites by precursor-conversion-hot pressing sintering

HE Xin-bo, ZHANG Chang-rui, ZHOU Xin-gui, ZHANG Xin-ming, ZHOU An-chen

1999, 19(3): 43-50.

[Abstract](1391) [PDF 331KB](277)

Abstract:
The microstructure of the Cf/SiC composites, prepared by precursor conversion-hot pressing sintering with polycarbosilane (PCS) as precursor and binder and AlN-Y2O3 as additives, was investigated using XRD, HRTEM and SEM. The results showed that Y2O3 reacted with the pyrolytic products of the PCS and the oxides on the surface of the AlN and SiC grains, forming the liquid-phase assisting in the densification of the composites, and the fine SiC-AlN solid solution was formed between AlN and the PCS through reaction-dissolution-precipitation at the grain boundaries and the fiber/matrix interface. Due to the presence of the carbon-rich fiber/matrix interphase with a certain of SiC-AlN solid solution, a desirable fiber/matrix interfacial bonding was obtained, which facilitated the debonding and pullout of the fibers. As a result, the composite exhibited excellent mechanical properties.

Analysis on therm alstress of organic-inorganic glass laminate

BAO Yi-wang, ZUO Yan, SHI Xin-yong, MA Juan-rong

1999, 19(3): 51-56.

[Abstract](1409) [PDF 632KB](367)

Abstract:
Thermal stress distribution of unsymmetric laminated structure composed by the materials with greatdifference in expansion coefficient and under uniform tem perature variation was analyzed. The relation between the stress and materialconstant as wellas geom etric size was determ ined. The analytical expression of therm alstress of the laminated glass containing soft prepreg layer in middle was derived. The study provides an investigation and theoretic basis for feasibility oforganic-inorganic glass laminate as the windshield ofaircraft.

Study on BMI/E-glass cloth composite

CHEN Li-xin, SUN Man-ling, ZHOU Xi-zhen, ZHENG Shui-rong

1999, 19(3): 57-62.

[Abstract](1405) [PDF 416KB](320)

Abstract:
With the development of high load and flying speed tactical missile radar,the materials for radome are required to satisfy the demands,such as electric property,thermal property and dynamic property,etc.Therefore,this paper studied the dielectric property,the effect of temperature on dynamic property and the resistance to heat of modified BMI/E-glass cloth composite.Wave penetrating ratio of the radome material was tested by wave guide method.The result shows that the composite can meet the demands of radome because it has enough mechanical strength,good resistance to heat and good dielectric property.

1999 Vol. 19, No. 3