航空材料学报

Modeling and prediction of solidification behavior of low-expansion superalloy welds

GUO Shao-qing, LI Xiao-hong, YUAN Hong, MAO Wei, YAN Ming-gao

2004, 24(6): 1-6.

[Abstract](1452) [PDF 256KB](264)

Abstract:
In order to predict the tendency of low-expansion superalloys on weld solidification cracking, the modified M-F model was used to simulate solute redistribution in weld solidification. Basic procedures were developed and the solidification reaction sequence, type and amount of eutectic product were calculated for superalloys with different compositions. It is shown that the primary solidification is followed by eutectic-type L→(γ+NbC) reaction and L→(γ+Laves) reaction sequentially for weld metals of GH903 and GH907, hence the terminal eutectic constituent is made up of γ/NbC and γ/Laves. While for GH909 weld only reaction L→(γ+Laves) occurs after primary solidification and more terminal γ/Laves eutectic forms than the other two alloys. Thus the tendency of GH909 to weld solidification cracking is higher than that of GH903 and GH907. Varying carbon content of GH909 can change its solidification path, but the effectiveness of improving weldability only by increasing carbon content is limited.

Statistical analysis of crack growth character for 30CrMnSiNi2A and GC4(40CrMnSiMoVA) steel

XU Ren-ping, LI Shu-lan

2004, 24(6): 7-10.

[Abstract](1498) [PDF 588KB](302)

Abstract:
Based on the research of mechanical performance, crack growth rates and crack growth life for 30CrMnSiNi2A and GC4 steel were analyzed statistically on the same crack length condition. By analysis and comparison, two conclusions were obtained: (i) crack growth rate of 30CrMnSiNi2A steel was smaller than that of GC4 steel; (ii) crack growth life of 30CrMnSiNi2A steel was longer than that of GC4 steel. Because the variance of the fatigue life of 30CrMnSiNi2A steel was much larger than that of GC4, the 99.9% reliability safe life of 30CrMnSiNi2A steel was nearly similar to that of GC4 steel, even though its reliability safe life was still longer than that of GC4 steel.

Microstructure and mechanical properties of 40Cr steel nano-crystallized surface after high energy peening

ZHANG Jun-bao, LIU Zhi-wen, SONG Hong-wei, WU Jie, SHI Bi, XIONG Tian-ying

2004, 24(6): 11-15.

[Abstract](1439) [PDF 686KB](389)

Abstract:
Nano-crystallization surface on 40Cr steel was obtained by ultrasonic high energy peening treatment. SEM, TEM and nano-indention techniques were used to analyse microstructure and mechanical properties. Experimental results show that nano-crystallization surface is a mixture composed by homogeneous dispersing nano-sized ferrite grains and nano-sized cementite grains. Transition region under nano-crystallization surface is composed by nano-sized cementite grains and micro sized ferrite grains. Average diameter of grains on nano-crystallization surface is about 3nm, and gradually increases asdepth increased from surface. Hardness of nano-crystallization surface is high up to 8GPa, which is more than 3 times of the matrix, and drops sharply as depth increased from surface. Modulus of nano-crystallization surface, 252GPa, is much close to that of the matrix.

Superplastic diffusion bonding of Ni based alloy/γ-TiAl based alloy

LI Zi-fu, WU Guo-qing, HUANG Zheng, RUAN Zhong-jian

2004, 24(6): 16-19,24.

[Abstract](1591) [PDF 994KB](181)

Abstract:
The intended bonding alloys of Ni based alloy and γ-TiAl based alloy were treated by laser surface modification, which provided a good structure condition for turning the bonding of dissimilar alloys to the bonding of similar alloys. Microstructures of laser cladding coating on the substrate of Ni based alloy and superplastic diffusion bonding of Ni based alloy with γ-TiAl based alloy at different bonding temperatures were discussed. The results showed that laser surface modification improved shear strength of the bond,and sound bond could be achieved at 900℃ with a pressure of 60MPa for1h.

Artificial neural network prediction for the amount of TCP phase of Re-containing nickel base single crystal superalloys

LI Jun-wei, PENG Zhi-fang

2004, 24(6): 20-24.

[Abstract](1498) [PDF 240KB](210)

Abstract:
Based on an advanced neural network method and a large number of data from Re-containing nickel base single crystal superalloys with a considerable amount of TCP phase, an artificial neural network model was constructed to predict the amount of the TCP phase for Re-containing nickel base single crystal superalloys. The results show that the amount of the TCP phase can be more accurately predicted by the present neural network method than the reported conventional regression method for the Re-containing nickel base single crystal superalloys. Therefore, it can be used as an assessment tool for the determination of the amount of the TCP phase in designing Re-containing nickel base single crystal superalloys. The sequence of influence of alloying elements on the TCP phase amount present in the superalloys investigated is analyzed combined with the use of statistical orthogonal tests and neural network prediction.

Effect of cooling rate in cast solidification on microstructures of in-situ (TiW)C/Fe composites

ZHOU Xiao-ming, REN Ying-lei, JIANG Wen-hui, WANG Wu-xiang, YAN Ming-gao

2004, 24(6): 25-28.

[Abstract](1423) [PDF 474KB](181)

Abstract:
The effect of cooling rate in cast solidification on the microstructures of 10vol% (TiW)C/Fe composites was investigated. The results show that in the 10vol% (TiW)C/Fe composites, as the only second phase, (TiW)C has two kinds of morphologies, homogeneously distributed in iron matrix, and most of them are spherulic with few rod-like. Within the spherulic (TiW)C phase, there is an inhomogeneous distribution of titanium and tungsten. Its core is rich in titanium, while the periphery is rich in tungsten. When the cooling rate is fast, the amount of second phases is less than that in slow cooling rate, and the net eutectic is separated out along the interfaces, meanwhile, the rod-like is disappeared, which is favorable for the increasing of wear resistance. When the cooling rate is slow, the size of second phases becomes smaller, and a quantity of eutectic is found, which is harmful to mechanical properties. Thus, an moderate increase in cooling rate favors to attain ideal microstructures.

The damping capacity of fiber reinforced AZ91 magnesium matrix composites

GU Jin-hai, ZHANG Xiao-nong, GU Ming-yuan

2004, 24(6): 29-33.

[Abstract](1459) [PDF 714KB](303)

Abstract:
In fiber reinforced magnesium matrix composites, a special interfacial layer was obtained by coating a pyrocarbon on the surface of fibers, and then, the damping capacity of the composites was studied. The results show that, the carbon coating on the fibers may improve the overall damping of composite when temperature is lower than about 170℃, the relevant damping mechanisms are ascribed to dislocation damping, interface damping and the intrinsic damping of the constituents; while at temperature above 170℃, the damping of the composite without the coating exceeds that with the coating owing to the contribution of interface damping and grain boundary damping.

Improvement of oxidation resistance of C_f/SiC composites by polysiloxane seal treatment

SUO Xiang-bo, CHEN Zhao-hui, WANG Song, MA Qing-song

2004, 24(6): 34-37,46.

[Abstract](1447) [PDF 922KB](218)

Abstract:
The Cf/SiC composites fabricated by polycarbosilane pyrolysis were sealed by low viscosity polysiloxane infiltration under vacuum followed by curing under gas pressure, and the oxidation resistance of the Cf/SiC composites before and after seal treatment was investigated. It was found that the sealed Cf/SiC composites showed improved oxidation resistance at 1500℃ for a short period of time. After soaked at 1500℃ for 10min under static air, the sealed Cf/SiC composites retained 95% of original flexural strength and 99.1% of original mass while the untreated Cf/SiC composites retained only 67% and 91.9%, respectively. The improved oxidation resistance of the sealed Cf/SiC composites was attributed to (1) O2 was consumed during the pyrolysis of polysiloxane and (2) the pores were healed by viscous SiO2 derived from the pyrolysis, preventing O2 from diffusing into the composites.

Interfacial studies on CF/PPEK and CF/PPES composites

LIU Wen-bo, WANG Rong-guo, JIA Jin, ZHANg Hong-tao, XIE Huai-qin

2004, 24(6): 38-41.

[Abstract](1533) [PDF 639KB](426)

Abstract:
The interfacial state and structure of carbon fiber/poly phthalazinone ether ketone(CF/PPEK) and carbon fiber/poly phthalazinone ether sulfone(CF/PPES) composites were studied by X-ray photoelectron spectroscopy(XPS)and scan electron microscope(SEM). It was revealed that there were new functional groups were found on the interface of fiber and polymer, which induced strong physical and chemical interaction on the interface of CF/PPEK and CF/PPES.

Structure and token of alumina by gel-casting

TONG Jian-feng, CHEN Da-ming, LI Bao-wei, LIU Xiao-guang

2004, 24(6): 42-46.

[Abstract](1448) [PDF 812KB](354)

Abstract:
The density,strength,cavity proportion and microstructure of the ceramic flans by gel-casting were studied. The research showed that the solid loading,content of monomer and ratio of monomer and crossing linker were the main effect factors on the density. As the solid loading increased, the bend strength of flan decreased,meanwhile, the cavity proportion in flan decreased from 110nm to 90nm.The bend strength of ceramic flans by gel-casting was preferable to those by injecting and tape-casting.

The study of structure and performance of ceramic coating on aluminum alloy by plasma microarc oxidation

TENG Min, HE Xiao-dong, LI Yao

2004, 24(6): 47-49.

[Abstract](1403) [PDF 496KB](232)

Abstract:
The surface morphology and phase component of ceramic coating on LY12 aluminum alloy were analyzed using SEM and XRD. The nano-hardness and elastic modulus of the ceramic coating were determined using Nano Indenter XP system. The result showed that ceramic coating was composed of the two-layer structure with surface loose zone and compact zone and ceramic coating mainly contained α-Al2O3,γ-Al2O3 phase. The curves of nano-hardness and elastic modulus across the ceramic coating were similar from the interior to the surface of the coating, where nano-hardness and elastic modulus gradually reduced.

A new series of hydrophobic agents and corrosion resistance of the hydrophobic films

ZHU Li-qun, LI Wei-ping, WU Jun

2004, 24(6): 50-55.

[Abstract](1482) [PDF 996KB](459)

Abstract:
The synthetic technology of a new series of hydrophobic agents (named as BH-102 and BH-103) was studied. And the hydrophobicity and corrosion resistance of the BH hydrophobic films were researched. The results show that the surfaces of electroless nickel coating and phosphorizing film on steel treated with BH hydrophobic agents have good hydrophobicity with hydrophobic angle exceeding 105°.The corrosion resistance of the phosphorizing film on steel can be significantly enhanced by BH hydrophobic films. And BH-103 hydrophobic film with two corrosion inhibitors offers even better corrosion resistance than BH-102 with a single corrosion inhibitor.

Investigation on the computational method of vibration response of dry friction system with cubic nonlinearity for metal rubber

LI Yu-yan, HUANG Xie-qing, MAO Wen-xiong

2004, 24(6): 56-60.

[Abstract](1271) [PDF 1277KB](372)

Abstract:
The vibration response of dry friction system with cubic nonlinearity for metal rubber was investigated under harmonic excitation by the harmonic balancing technique(HB) and the technique which links Fourier series with harmonic balancing technique(FHB). Some conclusions were given. If cubic nonlinear factor was bigger, the results of HB and FHB were near. Two computational methods could be both applied. However, if cubic nonlinear factor was smaller, the differences of two computational methods were great, FHB method was more accurate in theory, therefore FHB method should be applied. The experiment on the dynamic response of the damper for metal rubber was studied. It was shown that natural frequency and transmissibility amplitude for the damper had both nonlinear characteristics.

2004 Vol. 24, No. 6