航空材料学报

Spark plasma sintering and mechanical properties of Al₂O₃-ZrO₂ nanocomposites

CHEN Guo-qing, ZHANG Kai-feng, WANG Guo-feng, HAN Wen-bo

2004, 24(1): 1-6.

[Abstract](1369) [PDF 285KB](383)

Abstract:
The nano-sized powders of Al2O3/ZrO2 with excellent chemical homogeneity were synthesized by heating of ethanol-aqueous salt solutions method. Alumina-zirconia ceramic nanocomposites were superfast densified using spark plasma sintering(SPS) from nanoscale Al2O3/ZrO2 powders. The effect of zirconia nanophase on the densification, sintering behavior, mechanical properties, and microstructure of the composites was investigated. The composites are a typical intra/inter granular nanocomposites, where the maximum bending strength and toughness of the composites are 1070MPa and 10.42MPa°m1/2, respectively. The reasons that ZrO2 particles inhibit the densification and also retard the matrix alumina grain growth were explained from the activation energy. The microstructure observed indicate that lots of intergranular nanoparticles are more effective to pin dislocations, hence, complex dislocation morphology appears in the matrix grains of alumina. It can be deduced that intragranular fracture mode and multiple interfaces are the main characteristics of the samples.

Influence of the materials on the solidification microstructure of laser multi-layer cladding

FENG Li-ping, LIN Xin, CHEN Da-rong, LI Yan-min, YANG Hai-ou, HUANG Wei-dong

2004, 24(1): 7-11.

[Abstract](1333) [PDF 630KB](363)

Abstract:
316L stainless steel and Ni35 self-melt alloy were selected to perform laser multi-layer cladding experiments on the Ni-base superalloy directional solidification substrate. Mechanisms of microstructure formation were investigated. Results show that directional solidification cladding layers of 316L stainless steel with fine crystallography orientation under the processing parameters mentioned in this paper were obtained. While for the nickel-base self-melted alloy Ni35 which is not easy to acquire columnar dendrite tend to appearing equiaxed grains in the cladding layers under similar processing condition.

Processing technology of high Nb containing TiAl alloy

LI Shu-jiang, WANG Yan-li, LIN Jun-pin, LIN Zhi, CHEN Guo-liang

2004, 24(1): 12-16.

[Abstract](1930) [PDF 669KB](612)

Abstract:
The processing technology of high Nb containing TiAl alloy was studied. The results show the mass gain during the consumable electrode arc melting is much less than that during the vacuum induction melting. The mass less of high Nb containing TiAl alloy comes from the vacuum induction melting. The mass less during the vacuum induction melting mainly depends on the skull size and evaporation of alloy. The fluctuation of alloy compositions during melting primarily results from the change of skull size. Al content of alloy after the vacuum induction melting is dependent on the composed effect of skull size and evaporation of alloy melt. Nb content of high Nb containing TiAl alloy gradually increases during melting. The homogenization treatment at 1200℃ for 24 hours eliminates the dendrite segregation of as-cast structure.

Microstructure and stability of a cast Ni-base superalloy containing low level of Cr and high level of W

ZHENG Liang, GU Chen-qing, ZENG Qiang, HOU Shu-e

2004, 24(1): 17-21.

[Abstract](1436) [PDF 266KB](271)

Abstract:
The microstructure and stability of a conventional cast equiaxed nickel base superalloy, Ni-1.5Cr-10Co-16W-2Mo-6Al-1Ti-1Nb-0.1C-0.02B-0.1Zr, which possesses a high temperature strength corresponding to that of the first generation single crystal superalloy, were described in this paper. Microstructures of as-cast and 850℃/3000h, 950℃/1000h and 1100℃/50h～500h thermal exposure specimens were investigated by optical metallography, quantitive metallography, SEM and EDS. Results show that the size of specimen directly affects the volume fraction and sizes of phases in microstructure. The eutectic γ' in heavy section of specimen appears to be lower volume fraction and larger size. Section size has no significant effects on the volume fraction of MC carbides, but the increase of MC size will accompany with the enlargement of the section size. This superalloy exhibits a surprisingly good microstructural stability, due to no harmful TCP phase precipitates after long term thermal exposure in the 850℃ to 1100℃ range. Furthermore, in this temperature range, the carbide reactions are the slow decomposition of MC and precipitation of M6C carbides along the grain boundary, interdendrite zone and periphery of eutectic γ'. In addition, after 1100℃/500h thermal exposure there are still about 50vol.% MC carbides which reserved from original as-cast microstructure.

Effect of ultimate heat treatment on the tribological properties of carbon-carbon composites

YU Shu, LI Xi-bin, LIU Gen-shan, PU Ji-qiang, PU Bao-jian, XIONG Xiang

2004, 24(1): 22-27.

[Abstract](1468) [PDF 330KB](307)

Abstract:
After different temperatures of ultimate heat treatment(HTT), the microstructure, graphitization degree, heat transfer coefficient and the tribological properties of the carbon-carbon composite are studied. The results show that with the increase of the HTT's temperature, the pyrocarbon of rough lamina's optical activity is increased while the smooth lamina's microstructures have not any change analyzed under polarized light; the pyrolytic carbon's interlayer distance is decreased when the crystal size and graphitization degree are increased; the heat transfer coefficient in either parallel or perpendicular directions of the fiber is increased. At the same time, with the increase of the HTT's temperature, a thin and dense film on the friction surface is formed which leads to a reduction of friction coefficient wear loss. The results also show that the HTT's temperature of 1800℃ is too low to make any influence on the carbon-carbon composites and the most wear loss is due to oxidation of composites.

Influence of Li on the early stage clustering behavior of Al-Zn-Mg-Cu-Li series alloy

WEI Fang, BAI Pu-cun, ZHOU Tie-tao, LIU Pei-ying, ZHANG Yong-gang, CHEN chang-qi

2004, 24(1): 28-31.

[Abstract](1524) [PDF 722KB](368)

Abstract:
Lennard-Jones(L-J)type potential is used to determine the pair interaction values between atoms and vacancies based on the rapid hardening phenomena at early aging stage of Al-Zn-Mg-Cu-Li alloy.It is found that Mg/vacancies clusters are formed in addition to Zn/vacancies,Cu/vacancies and Zn/Mg complex clusters in Al-Zn-Mg-Cu alloy.At higher addition of Li, there are Li/vacancies clusters in Al-Zn-Mg-Cu-Li alloy,but less Zn/Mg clusters.

Some problems on preparation process of the La_0.8Sr_0.2MnO₃ material by gelcasting

LI Guo-jun, LIU Xiao-guang, CHEN Da-ming

2004, 24(1): 32-35.

[Abstract](1328) [PDF 200KB](195)

Abstract:
In preparation process of the La0.8Sr0.2MnO3 materials by gelcasting technology, some problems on removing of air bubble, heating gelation, gelling process and characteristic of green bodies were discussed. Analytical results shows that the green bodies with uniform microstructure can be obtained by vacuum eliminating air bubble and heating gelation.

Influence of SiC_P content and inhibitor on the corrosion behavior of SiC_P/Al metal matrix composites

LU Feng, TANG Zhi-hui, ZHANG Xiao-yun, ZHONG Qun-peng, CAO Chun-xiao

2004, 24(1): 36-40.

[Abstract](1492) [PDF 728KB](254)

Abstract:
The corrosion behavior of ZL101A aluminum alloy and silicon carbide particulate/aluminum(SiCP/Al) metal matrix composites was studied in a medium of aqueous sodium chloride(NaCl) solution,where the SiCP/Al composites contained 5vol%, 10vol%, 15vol% and 20vol% SiCP. Corresponding ZL101A base aluminum alloy was subjected to identical test conditions to study the influence of SiCP on corrosion characteristics. By means of immersion test at room temperature, sodium molybdate(Na2MoO4) and sodium silicate(Na2SiO3) were used as inhibitors. Weight loss and scanning electron microscopy(SEM) were used to evaluate the corrosion rate and surface microstructure of the SiCP/Al metal matrix composites. The results show that average corrosion rate do not vary greatly in relation to the amount of SiCP reinforcement, even some degree of decrease. Normal pit initiation and propagation were altered by the presence of the SiCP reinforcement. Pits on the SiCP/Al composites were significantly more numerous, shallow, and wide spread than on the ZL101A matrix materials.It was found that more effective to prevent the pit initiation on the surface of the SiCP/Al composites with Na2MoO4, Na2SiO3.No obvious effectiveness was observed when containing of the SiCP reinforcement with 15vol% and 20vol% in the SiCP/Al composites.

Rrsearch on mathematical model of carbon steel and low alloy steel in atmosphere

WANG Jing-ru, ZHANG Zheng, ZHONG Qun-peng

2004, 24(1): 41-46.

[Abstract](1488) [PDF 912KB](321)

Abstract:
Research on long-term corrosion mechanism of carbon steel and low alloy steel, with the fick diffusion law, the mathematical model of atmospheric corrosion of carbon steel and low alloy steel is presented. The model is proved by using corrosion data of carbon steel and low alloy steel exposed 1,2,4,8 and 16 years in natural environment, and putting forward the complex model of three stages of corrosion of carbon steel and low alloy steel, and forecasting the corrosion law of three stages respectively. The first stage exhibits the linear function; the second stage exhibits the parabola function, the result of regression indicates that parabola function is more accurate than power function; the third stage exhibits the linear function as well.

Study of the effect of materials of rubber fuel tank on aluminum alloy corrosion

LI Bin, TAO Chun-hu, LI Di, LU Feng, MA Yi-jun, ZHU Yi

2004, 24(1): 47-52.

[Abstract](1346) [PDF 813KB](348)

Abstract:
The contact corrosion between 7A04-T6 alloy(clad), 7A04-T6 alloy, 7B04-T6 alloy(clad), 7B04-T6 alloy and materials of rubber fuel tank was studied. The result shows that rubber anti-aging coatings have very important effect on aluminum alloy corrosion.The corrosion order of four rubber anti-aging coatings was decided. The chemical composition of rubber anti-aging coatings was analyzed by EDS. Chloride ion concentration and pH of anti-aging coatings immersed solution were studied. The experiment results show that main components of rubber anti-aging coatings which caused aluminum alloy corrosion were chloride ion and metal oxide.

Liquid infiltration joining of C/SiC and Nb

TONG Qiao-ying, CHENG Lai-fei, ZHANG Li-tong

2004, 24(1): 53-56.

[Abstract](1370) [PDF 182KB](255)

Abstract:
Liquid infiltration joining of C/SiC composite with various woven style and Nb was studied. The join procedure was carried out at the temperature of 1300℃ with the holding time of 45min in vacuum. The pressure applied was 20 MPa. Ni-base interlinker was employed as the interlayer. Results showed joints of laminated C/SiC composite and Nb had been disjoined during the joints were cooled from the joining temperature to room temperature. However favorable joints of 3D C/SiC composite and Nb could be gained.

Effect of friction welding, heat treatment technology on the microstructure and property for drill rod S135

MAO Xin-fu, FU Li, SHANG Gao-feng, ZHAO Ren-cun, SHI Bi

2004, 24(1): 57-62.

[Abstract](1453) [PDF 873KB](296)

Abstract:
Analysis of the friction welding and heat treatment parameters of compatible steel 36CrNiMo4A,as well as strength and ductility for the drill rod S135 are presented, and the reason of lower ductility of joint welded by original friction welding and heat treatment parameters is described.It was found that microstructure and ductility could be improved by the optimization friction welding and heat treatment parameters for the drill rod S135. The microstructure and property of the drill rod S135 reached and/or exceeded that of the NKK drill rod S135.

2004 Vol. 24, No. 1