航空材料学报

Refining of cast microstructure of Ti46Al8.5Nb0.2W alloy by heat treatment

LIU Zi-cheng, LI Shu-jiang, LIN Jun-pin, CHEN Guo-liang

1999, 19(4): 1-5.

[Abstract](1507) [PDF 235KB](193)

Abstract:
The gas fan cooling/tempering and subsequent(1000℃⇔1200℃)×4 cycles heat treatment,instead of the conventional forging process,was investigated to refine the microstructure of cast Ti46Al8.5Nb0.2W alloy.By tempering the gas fan cooled metastable structure at temperature above α transus,the cast microstrucure can be destroyed rapidly and the fine and homogeneous duplex microstructure was developed in cast Ti46Al8.5Nb0.2W alloy.It has been found that the duplex microstructure can be transformed into the fine and homogeneous NG microstructure by the (1000℃⇔1200℃)×4 cycles heat treatment.The mechanisms involve preventing the existent γ grains from growing anomalously and globularizing the metastable lamellar structure produced during air cooling from 1250℃ into NG microstructure.

Microstructures observation and mechanical properties test of near alpha titanium alloy Ti600

ZHANG Zhen-qi, LUO Guo-zhen, HONG Quan, YANG Guan-jun

1999, 19(4): 6-10.

[Abstract](1473) [PDF 433KB](356)

Abstract:
Mechanical properties of the near alpha titanium alloy Ti600 with composition 6Al, 2.8Sn, 4Zr, 0.5Mo, 0.4Si, 0.1Y, bal.Ti, in wt%,were studied in different heat treatment conditions. The microstructures of the alloy were studied by LM, TEM.The resulting microstructure consists of small regions of aligned alpha platelets (colonies) and some grain boundary beta. After thermal exposure in air at temperature 600℃ for 100h., the precipitate α2 phase (Ti3Al) and silicides(Ti5Si3) decrease the ductility of the alloy.

Contamination of mold materials on TiAl castings

SU Yan-qing, GUO Jing-jie, JIA Jun

1999, 19(4): 11-15.

[Abstract](1392) [PDF 204KB](301)

Abstract:
The paper studied the contamination of some mold materials usually used for steel casting, including Al2O3, ZrO2, ZrO2·SiO2 and CaO on TiAl castings. The contamination depth of those materials on TiAl castings are CaO 16μm, Al2O3 60μm, ZrO2 130μm and ZrO2·SiO2 130μm respectively. All those values are little than that on Ti castings. The conclusion will promote the development of TiAl intermetallics castings.

Influence of stirring technique on microstructure of TiB₂ and tic particulate reinforced aluminum matrix composites fabricated by melt in situ reaction

YANG Bin, WANG Feng, CUI Hua, DUAN Xian-jin, ZHANG Ji-shan

1999, 19(4): 16-21.

[Abstract](1401) [PDF 266KB](242)

Abstract:
A novel technique in which 3vol%TiB2 and 3vol%TiC particulate-reinforced aluminum matrix composites prepared by melt in-situ reaction was introduced. The influence of a mechanical stirring technique on the microstructure of the composites was studied. It was found that a mechanical stirring is necessary for fabricating TiB2/Al and TiC/Al composites fabricated by this technique. By taking advantage of a novel disc vane stirrer, the 3vol%TiB2/Al and 3vol%TiC/Al composites with homogeneous particulate distribution and with sound structure have been produced.

Oxidation behavior of copper thin films by ion implantation

WANG Xiao-zhen, WANG Er-min, ZHAO Xin-qing

1999, 19(4): 22-26.

[Abstract](1478) [PDF 203KB](230)

Abstract:
In order to inhibit the oxidation induced rising in resistance and degradation of mechanical performance of copper thin films, ion implantation was employed for modification of the copper thin film surface. X-ray diffraction and Rutherford Back Scattering techniques were adopted to investigate and analyze the oxidation characteristics of the films. It is indicated that ion implantation has insignificant effect on the rising in electrical resistance. In addition, the oxidation resistance increase with the increasing in dose of ion implantation. It was observed that the oxidation behavior of copper thin films was changed due to the ion implantation. After implantation, the oxide consists of Cu2O and CuO, instead Cu2O prior to implantation.

Fabrication of interface coating for ceramic matrix composites using rotating-CVI

XIAO Peng, XU Yong-dong, ZHANG Li-tong, CHENG Lai-fei

1999, 19(4): 27-31.

[Abstract](1511) [PDF 217KB](171)

Abstract:
Dense pyrolytic carbon interface coating with uniform thickness and regular surface was fabricated using rotating chemical vapor infiltration (RCVI) process on 2-D carbon cloth within optimal parameters, that is, low pressure (5kPa), high temperature (1100℃), high propylene concentration (62.5 vol%) and 3.5 mm·min-1 rotational linear velocity. The results in this paper show that there are more important effect of deposition temperature on the properties of coating surface, and low pressure, optimization of geometric construct of deposition furnace are valid for preventing forming-soot from pyrolytic carbon deposition process on conditions of high temperature and high propylene concentration.

Tensile properties of GB/HDPE composites and their influence factors

CAO Ke, BAI Shu-lin, CHEN Jian-kang, YU Zhong-zhen

1999, 19(4): 32-37.

[Abstract](1503) [PDF 227KB](362)

Abstract:
The effects of particle volume fraction, tensile rate and interface bonding strength on the properties of GB/HDPE composites were studied by tensile test and SEM observation. The results show:when the filler surface treatment is moderate, both the Young′s modulus and tensile strength of GB/HDPE rise with the increase of particle volume fraction, tensile rate and interface bonding strength.

Structure and thermal properties of doped SiO₂ aerogels

DENG Zhong-sheng, ZHANG Hui-lin, WEI Jian-dong, WANG Jue, SHEN Jun, ZHOU Bin, CHEN Ling-yan

1999, 19(4): 38-43.

[Abstract](1468) [PDF 231KB](424)

Abstract:
Nano-porous TiO2 doped SiO2 aerogel insulation were prepared via sol-gel process using tetraethoxysilane (TEOS) as the precursor and followed by ethanol supercritical drying. TEM, SEM and pore size distribution techniques were used to characterize the morphology and pore structure of the doped silica aerogels. The thermal conductivity measurement of the silica aerogels was determined using the transient hot-wire technique. The results show that TiO2 powders can be scattered homogeneously in the silica aerogels; the pore size of the TiO2 doped silica aerogels is 5～70 nm, the average pore size (BJH) is about 20 nm and the size of the silica particles is 5～10 nm; the peak of the pore size distribution of the TiO2 doped silica aerogels shortened with the increase of the TiO2 powders while some pores less than several nm emerged and the thermal conductivity of the TiO2 (20wt%)doped silica aerogel is 0.035 wm-1K-1 at 831K and 1 atm.

Study of temperature and mechanical properties and constitutive equation for modified BMI/DPA and CTBN toughened epoxy

LIU Yuan-yong, XU Ai-rong, NING Rong-chang

1999, 19(4): 44-51.

[Abstract](1603) [PDF 284KB](337)

Abstract:
A study of tensile and compression properties under different temperature and loading rates for CTBN toughened Epoxy and modified BMI/DPA has been carried out. For the CTBN toughened Epoxy, the toughness and fracture elongation are reduced, but the elasticity modulus E is increased with strain rate increasing. Under dynamic tensile, during compression, the E and yield stress σy both are increased with loading rates increasing. For the modified BMI/DPA, under the dynamic compression condition of room temperature, the relation between E or σy versus ln is a linear curve approximately. A compressive stress-strain curve under different loading rates is given. Also, the sensitivity of the temperature/loading rate and the constitutive equation related to yield stress versus temperature/strain rate both are made in the paper.

Study of triaryl-s-triazine ring high temperature resin

WANG Yan, CUI Guang-zhi

1999, 19(4): 52-57.

[Abstract](1373) [PDF 206KB](237)

Abstract:
The major materials and triarye-s-triazine ring (TSTR) resins were respectively synthetized, while the synthesis in one step of 4-cyanobenzoic anhyrdide had been applied the national patent. Infrared ray and thermal analysis such as differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) also were used.The experimental results indicated that the highest working temperature of the resin was about 400℃, comparable to American PMR-Ⅱ-50 resin.

Development of reaction bonded SiC ceramics spacecraft combustion chamher

CHEN Ming-he, FU Gui-long, ZHANG Zhong-yuan, ZHOU Jian-hua

1999, 19(4): 58-62.

[Abstract](1670) [PDF 187KB](843)

Abstract:
The process of the application of reaction bonded SiC ceramics to the manufacture of spacecraft combustion chamber was investigated.The results showed that spacecraft combustion chamber made from reaction bonded SiC ceramics is acceptable and results of the experiment is satisfactory.The strength of parts with reaction bonded SiC ceramics is changing with silicon content.Under the this article testing condition,the optimum silicon content is 10.5%.The method of reaction bonded SiC ceramics is suited for manufacture parts of complicated structure and higher size precision.

1999 Vol. 19, No. 4