航空材料学报

Preparation of Al₂O₃/Ni cermet by the coating rocess

LI Guo-jun, CHEN Da-ming, HUANG Xiao-xian, GUO Jing-kun

2002, 22(1): 1-5.

[Abstract](1775) [PDF 1263KB](259)

Abstract:
Al2O3/5vol%Ni ceramets were prepared by hot pressing Ni coated Al2O3 powders which were synthesized through the heterogeneous precipitation method XRD patterns showed the amorphous coating layer was crystallized to NiO at 550℃ in air,then NiO was completely reduced to Ni at 700℃ in hydrogen atmosphere And TEM micrograph showed Ni with the size of about 20nm in the coating layers was spherical and weakly agglomerated Microstructure studies on Al2O3/5vol%Ni cermets prepared at 1400℃ found that Ni particles were uniformly dispersed in Al2O3 matrix,and the most of Ni particles were located at the Al2O3 boundary Compared with monolithic Al2O3,bending strength,fracture toughness and thermal conductivity of cermets are markedly enhanced The mechanisms of improvement were discussed.

Effect of minor Sc and Zr joint additions on microstructure and tensile properties of Al-Mg alloy

PAN Qing-lin, YIN Zhi-min, ZhANG Chuan-fu

2002, 22(1): 6-10.

[Abstract](1837) [PDF 1031KB](368)

Abstract:
The effect of the addition of minor Sc and Zr on microstructure and tensile properties of Al-Mg alloy has been studied The results show that the addition of minor Sc and Zr significantly increases the strength of Al-Mg alloy,and results in superior combination of strength and ductility The Al-Mg alloy containing Sc and Zr may form primary Al3(Sc,Zr)composite particles during solidification,which can substantially refine the grain size of aluminum alloy castings More secondary Al3(Sc,Zr)dispersoid phase precipitate in Al-Mg-Sc-Zr alloy,they are much more effective in inhibiting recrystallization and dispersoid strengthening Due to the price of Sc is much expensive than that of Zr,less Sc is required to produce Al alloys containing Sc by the joint additions of Sc with Zr.

Modeling of gas transport and calculation during CVI processing

XIAO Peng, Li Di, XU Yong-dong, HUANG Bo-yun

2002, 22(1): 11-15.

[Abstract](1648) [PDF 1282KB](270)

Abstract:
Transport velocity of reactant species within pores of the preform is one of the key factors determining matrix deposition rate during chemical vapor infiltration processing On the base of establishment of geometry modeling for three typical net structure of pores(body centered structure,cubic structure,stacking)and numerical calculation modeling for transport of reactant species,the effect of net structure of pores on the gaseous permeability and densification were investigated The results revealed that net structure and shape of pores were two of the key factors determining gaseous permeability and final densification of composites.

Research on tensile fracture mechanism of hybrid CARBON-CARBON composites at ultra high temperature

YI Fa-jun, LIANG Jun, MENG Song-he, DU Shan-yi

2002, 22(1): 16-21.

[Abstract](1753) [PDF 481KB](210)

Abstract:
The present paper is concerned with the evaluation of microstructure and interior defects of hybrid carbon-carbon composites with increasing temperature The fracture mechanism of hybrid carbon-carbon composites is also investigated from SEM photographs of fractured surfaces of specimens experienced ultra-high temperature under tensile load,the conclusion is therefore obtained that the porous and cracks coalescence,growth and propagation and the fiber/matrix interfaces degeneration under the combination of ultra-high temperature and load cause strength descend,composite would fractured from a weak section.

Research on laser direct deposition of nickel base superalloy

ZANG Yong-zhong, SHI Li-kai, ZHANG Ping-zhi, XI Ming-zhe, CHENG Jing, XU Jun

2002, 22(1): 22-25.

[Abstract](1754) [PDF 254KB](491)

Abstract:
Laser direct deposition of metallic components is a new manufacturing technology Driven by the solid CAD model directly,fully dense metallic parts with complicated shape can be rapidly obtained through melting the coaxially fed powders with a high-power laser in a layer by layer manner The processing of laser direct deposition of nickel super alloy,the obtained microstructure and properties are introduced in this paper The results show that the as-deposited Rene' 95 nickel superalloy is dense,with directional solidificationmicrostructure along the direction of deposition height The formed materials tend to crack due to the existence of hight residual stress during deposition,preheating the base table is benefit for for residual stress reduction By choosing the suitable processing parameters,Rene'95 nickel superalloy component With complex shape and good dimensional accuracy has been fabricated successfully.

Research on in-situ formation of tiC particles reinforced nickel base alloy coating Produced by laser cladding

YANG Sen, ZHONG Min-lin, LIU Wen-jin

2002, 22(1): 26-30.

[Abstract](1682) [PDF 1032KB](317)

Abstract:
In order to improve resistance to thermal fatigue,wear and corrosion resistance of carbon steel,the laser cladding experiments were conducted on a 3kW continuous wave CO2 laser The diameter of the laser beam is 3-5mm,the scanning velocity is 3-10mm/s,and the powder feeding rate is 3 26g/min The experimental results showed that a composites coating with TiC particles of various shapes and sizes embedded in nickel based alloy can be in-situ synthesized from the mixture of nickel based alloy powder,graphite enwrapped nickel and titanium powders by powder feeding laser cladding An excellent bonding between the coating and the carbon steel substrate was ensured by the strong metallurgical interface The coating is uniform,continuous and free from cracks,however there existed some pores in coatings The microstructure of the coating is mainly composed of γ Ni dendrite,a small amount of CrB,TiB2,M23C6 and dispersed TiC particles The average microhardness of the coating is about HV0 21100 after laser surface remelting,4 5 times larger than that of the steel substrate.

Manufacturing A2017 semisolid materials by SCR Process and thixoforming property research

GUAN Ren-guo, WEN Jing-lin, LIU Xiang-hua, MENG Xian-yun

2002, 22(1): 31-35.

[Abstract](1718) [PDF 263KB](221)

Abstract:
material manufactured by SCR process excelled conventional casting slab in microstrueture;Under the temperature range from 530℃ to 570 ℃,A2017 material manufactured by SCR process could be thixoformed Yeild strength in semisolid forming process was much smaller than in hot forming process;Thixoforming process of A2017 material was divided into four steps,in static thixoforming step A2017 semisolid material forming property was fine,Semisolid formation should be carried out within proper deformation rate from 64% to 72%.

Investigation on compression strength after impact of carbon fiber reinforced bismaleimide resin matrix composites

ZHANG Bao-yan, CHEN Xiang-bao, LI Min, XING Li-ying, WANG Liang, JIANG Shi-cai

2002, 22(1): 36-40.

[Abstract](1740) [PDF 221KB](603)

Abstract:
Compression Strength After Impact(CAI)is the most important parameter of characterizing the toughness of carbon fiber reinforced resin matrix composites Influence of bismaleimide(BMI)resin matrix,carbon fiber and fiber matrix interface on the CAI of BMI resin matrix composites was discussed in this paper Decreasing cross linking density and producing two phase micro structure in BMI resin are two typical ways to enhance the CAI of carbon fiber/BMI composites A suitable resin content is necessary to obtain high CAI of a composite system Carbon fibers with excellent toughness and mechanical properties contribute significantly to increase the CAI of composites Proper fiber resin matrix bond is also necessary to achieve high CAI value.

Interphase and its formational mechanism of GF/PVC composite prepared by aqueous suspension impregnation

YI Chang-hai, TAN Bien, XU Jia-rui, ZENG Han-min

2002, 22(1): 41-45.

[Abstract](1669) [PDF 234KB](217)

Abstract:
Interphase and its formational mechanism of GF/PVC composite prepared by aqueous suspension impregnation was studied by FT IR,microscopy,electron probe and so on,The result showed that the interfacial adhesion and interaction of the composites prepared by the suspension containing I II,III or V latex were due mainly to the physical interaction between the binder and fibers On the other hand,the interfacial binding and interaction of the composite prepared by the suspension containing IV latex were evidenced to involve dominantly chemical interaction and bonding between the fibers and matrix For the composites prepared by the systems of which the fibers were coated with KH 550 or KH 560/LCM or LCB complex surface coating,the interfacial binding and interaction were due mainly to the chemical interaction of the functional groups of the coupling agent with the LCM or LCB coating and PVC matrix.

Influence of cure temperature on performance of SY-H2 adhesive

QIAO Hai-tao, ZOU Xian-wu, LAI Shi-hong

2002, 22(1): 46-50.

[Abstract](1409) [PDF 224KB](332)

Abstract:
An experimental study was undertaken to determine the effects of cure temperature on shear strength of SY H2 paste adhesive.Firstly,curing reaction kinetics of SY H2 paste adhesive was researched by differential scanning Calorimeter(DSC).According to Kissinger and Ozawa method,the apparent activation energy of curing reactions was determined to be 102.3kJ/mol and 103.9kJ/mol respectively.Kinetic order of curing reactions calculated according to Crane method was 0.943.Furthermore,correlation of scanning rate Φ with peak temperature Tp from DSC data was found that Tp and lnΦagree with linear relation.Finally,influence of cure temperature on shear strength of SY H2 paste adhesive was discussed.Increase of cure temperature in a given time can improve the bonding strength.Optimal curing parameter was suggested to be from 130℃to 140℃for two hours.

Mechanism of refining microstructure of isothermally forged Ti-47Al-2Cr-1Nb alloy

WANG Shu-yun, LI Hui-qu, HUANG Zhao-hui, LIN Hai, LI Yuan-chun

2002, 22(1): 51-53.

[Abstract](1675) [PDF 195KB](313)

Abstract:
The microstructure of Ti-47Al-2Cr-1Nb alloy is significantly refined after isothermally forging TMT processing The microstructure of isothermally forged TiAl based alloy was observed by transmission electron microscope(TEM)It is proposed that the main isothermally deformation is due to producing of new deformation twins within gamma grains Most deformation twins are vertical to α2/γ boundary,which can transform into uniform microstructure after annealing treatment.

Rheological behavior of Al₂O₃ aqueous neutral suspensions

TONG jian-feng, CHEN daming

2002, 22(1): 54-57.

[Abstract](1651) [PDF 1036KB](183)

Abstract:
The rhological properties of Al2O3 water suspensions was examined by means of RV-20 rheometer with rheological method The effects of the solid loading,contents of dispersant and milling time on the rhological properties were studied chiefly The research showed:As the solid loading of the suspension increased,the critical shear rate of the "shear thickening" went down from 192 S-1 to 82 S-1 The dispersant content remarkably affects the suspension's critical shear rate of the "shear thickening" The critical shear rate is higher when the content is 1.0wt% So it can be taken as the appropriate contents of dispersant to the suspension with the solid loading of 56vol% Furthermore,the critical shear rate of the "shear thickening" of the alumina suspension increases with the ball milling time,also the stage of "shear thinning" disappears in long time ball milling.

Development of research on damping of fiber reinforced composite-a review

ZHANG Shao-hui, CHEN Hua-ling

2002, 22(1): 58-62.

[Abstract](1809) [PDF 1404KB](707)

Abstract:
Vibration damping is very important to improve dynamic behavior of composite structures There is a strong need for information on damping research in design optimization of composite structures In this paper,the status of research on damping in fiber reinforced composite materials and structure has been reviewed The content can be divided into three parts,such as damping mechanisms,modeling of damping and enhancement of damping At last,the recommendations regarding future research have also been offered.

2002 Vol. 22, No. 1