航空材料学报

Design and Fabrication of Rhenium-titanium(Re-Ti)Functionally Graded Material

YANG Shang-lei, LOU Song-nian, CHEN Yan, XUE Xiao-huai, LI Shi-min

2005, 25(3): 1-4.

[Abstract](1551) [PDF 944KB](239)

Abstract:
The functionally graded material of Re-Ti was developed using electrod-beam smelting(EBS)technology. Re-Ti graded material was designed based on analysising the physical properties and binary alloy phase diagram of Re, Ti. The component proportion of mixed metal powder and smelting processes was ascertained by simulating temperature field of EBS. The experimentatal results show that the figuration of Re-Ti graded material was fine. The elements distribution in bridge-intergradation layer is progressional uniformity diversification along the thickness.

Thermal-mechanical Properties of Fe₃Al/Al₂O₃ Composite Graded Coatings

LIU Ying-cai, YIN Yan-sheng, WANG Xin, ZHANG Jing-de

2005, 25(3): 5-10.

[Abstract](1426) [PDF 557KB](269)

Abstract:
On the basis of analyzing the formation mechanism of thermal-stress in coatings, according to practical thermal conditions and mechanical principle, the calculating model that can estimate thermal stress of coatings during fabricating process is established, and this type of stress has been calculated. Through observing the microstructure of coatings by SEM, the thermal mechanical behavior and its effect on the properties of coatings are studied. The results show that, in graded coatings, parameters of thermal mechanical behavior and fabrication stress change with the compositions. The highest stress exists in the bottom layer and the thermal stress decrease from the substrate to the surface. In graded coatings, the highest stress and the average stress are both lower than that in single Al2O3 coatings. Thermal discompatibility is the key reason of thermal stress in coatings. The gradient distribution of coatings'composition can effectively reduce thermal stress during fabrication process.

Study on Structure and Mechanical Properties of Epoxy/clay Nanocomposites Prepared by Shear Dispersing Method

LU Hai-jun, LIANG Guo-zheng, ZHANG Bao-yan, CHEN Xiang-bao

2005, 25(3): 11-15.

[Abstract](1432) [PDF 951KB](287)

Abstract:
Two comparative processing methods, general stirring with magnetic bar and high shear dispersing with high-speed emulsifying and homogenizing mixer(HEHM), were used to disperse and pulverize clay particles modified with dodecyl amine(DDA)in order to prepare finely exfoliated epoxy/clay nanocomposites. It can be observed from Transmission Electron Microscopy(TEM)graph that large clay aggregates still exist in the cured epoxy/MMTDDA nanocomposites prepared by general dispersing method, only the small clay particles or the external layers of large clay aggregates can be partially exfoliated. While the fine exfoliation can be achieved by exerting external shearing force on clay aggregates and the mechanical properties are dramatically improved. At a constant shearing speed, the mechanical properties are increased with the dispersing time. Impact strength is enhanced to 43.9kJ/m2 from 32.1kJ/m2, which is about 36.8% higher than that of pristine epoxy. The flexural strength also can be increased. Dynamic Mechanical Analysis(DMA)indicates that store modulus of epoxy/MMTDDA nanocomposites is not improved in glassy region, but have an increase in glass transition region. The glass transition temperature(Tg)of epoxy/MMTDDA(3wt%)nanocomposites is increased up to 214.9℃ from 209.6℃, which is about 5.3℃ higher than that of pristine epoxy, and the increase of Tg will depends on the dispersion and exfoliation of clay particles.

Co-consolidating Thermoplastic Composite Article after Thermoforming Stiffers

WANG Ke-jian, YI Xiao-su, TANG Bang-ming, LI Hong-yun

2005, 25(3): 16-20.

[Abstract](1473) [PDF 434KB](217)

Abstract:
This paper reported an integrated manufacturing process of one thermoplastic composite article with L-shaped stiffers of poly(ether ether ketone)(PEEK)matrix carbon fiber reinforced composites. It was found that the stiffer margins were not well consolidated by directly press forming after laying up the designed number of fabric in mold. However, a matched-die press thermoforming from the preformed blank solved the problem. The L-shaped stiffers were then fixed in mold to co-consolidate with the multiple fabric for cover flat part and finally bonded to each other. When using such quick forming techniques, the fabrication cost could drop dramatically in large volume production of aerospace composites 3-D structural parts.

Fine Microstructure Characteristic in Fusion Zone of Electron Beam Welding of Ti-6Al-4V

WU Hui-qiang, FENG Ji-cai, HE Jing-shan, ZHANG Bing-gang

2005, 25(3): 21-24.

[Abstract](1465) [PDF 962KB](465)

Abstract:
Microstructure characteristic in fusion zone of electron beam welding of Ti-6Al-4V was studied by means of OM, XRD, EPMA and TEM. The results indicated that crystallizing morphology of fusion zone was evolved into columnar crystals from equiaxed grain in base metal. Only α′phase presenting basket-weave microstructure was produced. Lath of fine microstructure in fusion zone present multi-directional distribution. Some β stabilized element such as Fe, V concerntration distribution fluctuation occurred nearby fusion line. Dislocation density in fusion zone obviously decreased than that of base metal.

Effect of Heat Processing on Titanium Alloy(Ti-6Al-4V Ti)Castings Residual Stress

FENG Zhi-hua, WANG Hong-hong, XIE Cheng-mu, YAN Yuan-lin

2005, 25(3): 25-27.

[Abstract](1567) [PDF 620KB](258)

Abstract:
Surface residual stress distribution of duplex phases titanium alloy(ZT4)castings in the case of different successive processing are investigated.The experiment results indicate that surface residual stress of castings after hot isostatic pressing is in lower stress level,surface residual stress of welded castings appears scatter and larger numberal value tensile-compressive stress,Annealing treatment can effectively relieve surface residual stress of castings to certain stress level.The final surface residual stress of annealed castings is related to the off-furnace temperature.

Fatigue Iife Prediction in Argon-arc Welded Joint

HU Ben-run, CHEN bo, WANG li-fa, LIU Jian-zhong, WU Xue-ren, FAN Jin-juan

2005, 25(3): 28-31.

[Abstract](1483) [PDF 807KB](370)

Abstract:
Smooth fatigue specimens of welded joint were made by using argon-arc welding. The material used was TA15 titanium sheet. High cycle fatigue tests were carried out at R=0.5,0.06. SEM analyses found that most of the initiation of cracks at defects of the welded joint. Fatigue life prediction from the initial crack size to failure based on long crack propagation at different zones of welded joint was made by using J.C.Newman′s FASTRAN II code. It was found that predicted results were agreed well with the experiment data by using long crack propagation base line at boundary of the welded joint.

Investigation on Distribution Character of Tensile Strengh of CVD Filament and MMCs

CAI Shan, LI Zhang-yi, DONG Yan, YAN Ming-gao

2005, 25(3): 32-36.

[Abstract](1455) [PDF 219KB](194)

Abstract:
The distribution character of tensile strength of CVD filament are described by single Weibull distribution function and the different mechanism of fracture. The results show that the distribution of tensile strength of intrinsic defects having different mechanism of fracture fit single Weibull distribution and have each particular shape and parameter. The distribution character of tensile strength of CVD filament after hot pressing is also analyzed. The effect of hot pressing on strength property and distribution character of CVD filament is observed. This is ascribed to the change of defects in the process of hot pressing. In this paper, the application in representing and forecasting the production performance of CVD filament and metal matrix composites based on the conclusion of Weibull distribution theory are also discussed.

Studies of Epoxy Resin and Bismaleimide Resin on Not-water Aging and Bending Properties

ZHAN Mao-sheng, ZHANG Ji-hua

2005, 25(3): 37-44.

[Abstract](1535) [PDF 1720KB](379)

Abstract:
Epoxy and bismaleimide resins were treated in hot water at 96℃. After that, the resins that reached water-absorption equilibrium were dried at 60℃. The relationships between water-uptake(water loss)and immersed time were measured, and the equilibrium water-absorption(water-desorption)content M∞, diffusion coefficient Dx, kinetics parameter k,n, and permeability coefficient P was calculated, respectively. The calculated results show that water-absorption(water-desorption)of resins were controlled by diffusion in the range of investigated time. It is found that bending properties of both resins obviously decreased after hot-water aging. Drying contributed to restore the bending properties of resins after aging. However, the bending properties of resins after drying were still lower than those initially.

Study on Speciality of Anti-flat Head Impact for Laminate Composites

JIANG Hai-bin, WEI Bo-rong, CHEN Qing, LI Ming-qi

2005, 25(3): 45-49.

[Abstract](1515) [PDF 587KB](220)

Abstract:
In this The impact resistant against flat head and impact damage of composite materials using column flat impact head(dia.25mm)to impact lamina(1.50~2.50mm)is studied in certain range of impact speed and using acceleration transducer to analyze the dynamic stress change of the back of lamina. The results indicate the main factors affecting impact resistance of composite materials are fabrics characteristics, fiber content and interfacial strength, the impact energy critical value determines the impact damage mode and energy absorption, and enhancing composites stiffness can improve the energy absorption ability.

Damage Identification of Composite Materials Based on Modified BP Neural Network

DONG Xiao-ma, ZHANG Wei-gong

2005, 25(3): 50-52.

[Abstract](1550) [PDF 148KB](176)

Abstract:
A dynamic approach based on modified BPNN for damage identification of composite materials is proposed. By using wavelet series, the features of signals are extracted and input to modified BPNN for training the network and identifying the damages. The results show that the method can exactly identify the faults.

Regeneration of Waste Electroless Nickel Plating Liquor

RONG Xin-ya, WU Chun-su, TAO Guan-hong, HE Jian-ping

2005, 25(3): 53-56.

[Abstract](1525) [PDF 881KB](378)

Abstract:
The method using soluble calcium salt for regeneration of waste electroless nickel plating liquor, in which the lactic acid used as complexing agent and hypophosphite used as redcing agent is studied.Under the condition of pH=5.6~5.8 and temperature between 45℃ to 50℃, after 2h agitation and 0.5h aging, the solute calcium salt made the phosphite content decreased from 158g/L to 23.06g/L and the consumption of nickel salt and hypophosphite were very little in waste liquor, while the plating rate and appearance of the regenerated plating liquor were equivalent to the newly mixed one.

Development of Casting Technology for Superalloy Integral Turbine Wheels

TANG Xin, CAO La-mei, LI Ai-lan, GAI Qi-dong, LIU Fa-xin

2005, 25(3): 57-62.

[Abstract](1587) [PDF 1505KB](467)

Abstract:
The development of investment casting process for integral turbine wheels using higher strength nickel-base superalloy was reviewed in this paper. The progress in materials for integrally cast turbine wheels was presented. Fine grain casting process and the duplex-properties casting for superalloy integral turbine wheels were introduced emphatically. In the end, the development trends and application prospect of superalloy integral turbine wheels were proposed.

2005 Vol. 25, No. 3