航空材料学报

Effects of residual stress on the delay of fatigue crack initiation in the mixed-mode stress field for aluminum alloys

CHEN Ying-feng, LI Ying-yan, NIU Li-sha, SHI Hui-ji

2003, 23(4): 1-4.

[Abstract](1432) [PDF 292KB](206)

Abstract:
Behavior of fatigue crack initiation from the hole edge of a circular ring specimen containing an internal notch was investigated experimentally and calculatedly for two aluminum alloys. Effects of an expanded hole that forms residual stress and deformation at the hole edge on the delay of fatigue crack initiation were studied. An obvious increase in the delay of crack initiation was obtained in the case of mode Ⅰ stress field due to the compressive residual stresses produced by the hole expansion process. However in the case of the mixed mode Ⅰ+Ⅱ the delay was less obvious because of the existence of shearing stress.

Thermal stability and high temperature properties of TC6 titanium alloy at conventionally annealed state

ZHU Zhi-shou, WANG Qing-ru, SHA Ai-xue

2003, 23(4): 5-9.

[Abstract](1457) [PDF 378KB](310)

Abstract:
Conventional annealing is a simple and feasible processing for most α+β titanium alloys. The thermal stability and other high temperature properties of TC6 titanium alloy at conventionally annealed state have been studied and compared with those at duplex-annealed and isothermally annealed states. The results show that, both of TC6 taitanium alloy bars and forgings at conventionally annealing state have excellent microstructure and mechanical property stability after exposure at 300℃ over 5000h. The tensile, creep and rupture properties at different temperatures after conventional annealing are equivalent to those after duplex-annealing and isothermal annealing. The properties of bars and forging products of TC6 titanium alloy can meet the demands of aircraft structure parts under 300℃ application condition.

Wide-gap brazing between K403 and DZ4 superalloys

LI Xiao-hong, ZHONG Qun-peng, CAO Chun-xiao

2003, 23(4): 10-15.

[Abstract](1412) [PDF 410KB](285)

Abstract:
The wide-gap brazing between K403 and DZ4 superalloys was investigated by using two tungsten-containing filler metals( N171 and N300) and Rene'95 superalloy powder. The results show that the wide-gap brazing between K403 and DZ4 could be realized by filling the joint gap with Rene'95 powder of proper particle size in advance. Post-brazing diffusion treatment at high temperature for a long time could obviously improve the joint microstructures, and prevented remelting of the wide-gap joints during the solution treatment. However, in order to prevent that the superalloy powder was excessively dissolved by the filler metal, the joints should be diffusion treated first at a lower temperature, and then at high temperature. The joints brazed with N300 filler metal and Rene'95 powder possessed good mechanical properties at high temperature. After being diffusion treated, the joint tensile strength at 900℃ reached 92% of that of casting K403 base metal, and stress-rupture life time under 980℃/126MPa was 135h. After being solution treated, the joint tensile strength at 900℃ surpassed that of casting K403 base metal (i. e. 677MPa), and stress-rupture life time was also raised slightly.

Investigation on mechanical properties of fine grain cast by mould agitation

TANG Xin, YU Bao-zheng, LIU Fa-xin, HAN Mei, GAI Qi-dong

2003, 23(4): 16-20.

[Abstract](1412) [PDF 266KB](225)

Abstract:
The mechanical properties of fine grain cast and conventional cast integral turbine wheel were evaluated. The results show that fine grain cast technology improve markedly the mechanical properties of integral turbine wheel including the room and high temperature tensile properties, the rupture-stress properties of mid-temprature. At the same time,the low cycle fatigue(LCF) properties were improved considerably.The LCF life of fine grain cast turbine disk was two times longer than conventional casting at 650℃.

Effect of aging on microstructure and mechanical properties of 0Cr15Ni5Cu2Ti steel

ZHONG Ping, XIA Min-yun, WANG Jun-li, HUANG Wan-sheng, YANG Gen-lin, WANG Li

2003, 23(4): 21-25.

[Abstract](1565) [PDF 255KB](307)

Abstract:
The effect of aging on microstructure and mechanical properties of martensitic precipitation hardening stainless steel 0Cr15Ni5Cu2Ti were examined. The impact toughness of aging at 455～460℃ was lowest. The maximum ultimate tensile strength and hardness were reached after aging at 460℃ due to the precipitation of coherent phase of fine copper-rich particles.Aging at higher temperatures resulted in loss of strength and hardness and these were attributed to the result of precipitate coarsening.

Ground-based investigations of atomic oxygen erosion behaviors of Kapton and ZnO-siloxane coatings on Kapton

ZHANG Lei, YAN Chuan-wei, SUN Gang, TONG Jing-yu, LI Jin-hong, CAO Chu-nan

2003, 23(4): 26-30.

[Abstract](1462) [PDF 234KB](270)

Abstract:
The erosion behaviors of Kapton and ZnO-siloxane coatings on Kapton have been studied during exposure in AO environment in ground-based simulation facility. The variation of chemical and physical properties of samples surface after exposed to AO fluxes were investigated by LAMBDA-9 spectrophotometer,X-ray photoelectron spectroscopy(XPS), fourier transform infrared spectroscopy(FTIR) and scanning electron microscopy(SEM). The results indicate that Kapton undergoes dramatically chemical degradation,including mass loss and change of surface morphologies;ZnO-siloxane coatings have excellent properties for anti-AO effects. The erosion product have SiO2 left surface, thus, providing protection from further attack by the energetic oxygen atoms.

Study on the electron beam curing composites reinforced by AS4 carbon fiber

BAO Jian-wen, LI Ye, CHEN Xiang-bao, SUN Xiao-dan

2003, 23(4): 31-34.

[Abstract](1485) [PDF 178KB](208)

Abstract:
The properties of epoxy resin matrix EB99-1 and its composites reinforced by AS4 carbon fiber were investigated. EB99-1 resin possesses excellent processing property, good mechanical property, low cure shrinkage, low moisture content, and good heat resistance. The result show, AS4/EB99-1 composites can be used at 91℃ on the hygrothermal condition. The comprehensive mechanical properties of AS4/EB99-1 composites are more excellent than thermal curing T300/4211 composites.

Preliminary application of the advanced PBO fiber wound composite

WANG Bin, JIN Zhi-hao, QIU Zhe-ming, LIU Ai-hua

2003, 23(4): 35-39.

[Abstract](1513) [PDF 220KB](477)

Abstract:
The unidirectional composites and the Φ150mm pressure vessels were fabricated with poly(p-phenylene benzobisoxazole) (PBO) fiber as well as Kevlar-49 and F-12 fiber by filament winding.The mechanical properties of the composites and the vessels were investigated.The results show that the performance of Φ150mm PBO/epoxy vessel is the best.The maximum vessel performance factor (PV/W) with PBO fiber is 60km and the ratio of delivered fiber strength is 90%. Although hoop deformation of PBO/epoxy vessel cylindrical section is bigger than that of F-12 fiber wound vessel, PBO fiber is well suited for special vessel application.

Effect of cold plasma graft treatment on the interfacial properties of carbon fiber braided/epoxy composites

LIU Xin-yu, QIN Wei, WANG Fu-ping

2003, 23(4): 40-43.

[Abstract](1490) [PDF 176KB](461)

Abstract:
The cold plasma graft technology is used for treating the surface of carbon fiber braided. It creates active function groups on the fiber surface. The effects of cold plasma graft treatment on the interlaminar shear strength of carbon fiber braided/epoxy composite are examined. Results show that cold plasma treatment improves the surface polarity of carbon fiber and therefore improves interfacial properties of composites.

Study of the mutual damage of polycarbonte both in fatigue and creep

SONG Zhi-min, HUANG Wan-xia, NI Hai-ying, LIU Min-zhi, XIANG Hai

2003, 23(4): 44-47.

[Abstract](1433) [PDF 214KB](243)

Abstract:
The mutual damage of polycarbonte both in fatigue and creep were studied. The results show that the mutual damage of polycarbonte existed both in fatigue and creep. The fracture life appeared less than any one of pure fatigue or creep. The fracture mechanism is that fatigue cycle load causes molecular chains or chain segments to be elongated and shortened cyclically;and then the molecular chains or chain segments which movements were resisted in single directional external force are loosened and activated.Therefore it encourages creep movement and fracture. The degree of mutual damages both in fatigue and creep is closely related to temperature. The degree of mutual damages at lower temperature is greater than that at higher temperature.The fracture life is shorter at higher temperature because the individual damage of pure fatigue or creep increases.

Toughening of epoxy resin by modification with acrylate liquid rubber containing pendant epoxy groups

KONG Jie, NING Rong-chang, TANG Yu-sheng, BAI Zhen-quan

2003, 23(4): 48-51.

[Abstract](1566) [PDF 197KB](370)

Abstract:
Toughening of epoxy resin by modification with acrylate liquid rubber containing pendant epoxy groups was investigated. The additions of 5phr of liquid rubber lead to 63% and 350% increase in impact strength and fracture toughness GIC) respectively. At the mean time, tensile strength, tensile modulus, flexural strength and glass transition temperatures of modified resin were less than that of the parent epoxy resin. The SEM analysis of the fracture surfaces indicated that the modified epoxy system exhibited two-phase morphology with rubber sphericity particles dispersing in matrixes.

Superplasticity of Ti-15-3 titanium alloy

LI Cai-ju, GU Jia-lin, LIU Qing

2003, 23(4): 52-58.

[Abstract](1538) [PDF 487KB](557)

Abstract:
Ti-15-3 (Ti-15V-3Cr-3Sn-3Al) alloy, which is developed as a metastable β titanium, is one of the best candidates for aerospace industry applications. The properties and applications of Ti-15-3 alloy have been reviewed briefly, and the progress in the study of superplasticity of solute treated, hot rolled and cold rolled Ti-15-3 alloy is summarized and evaluated. Further research work and some prospects on superplasticity of Ti-15-3 alloy are proposed in the light of the research results and the existing questions.

Recent development on surface decoration of carbon nanotubes

CAO Mao-sheng, QIU Cheng-jun, ZHU Jing

2003, 23(4): 59-62.

[Abstract](1424) [PDF 174KB](639)

Abstract:
Theories and experimental methods on surface decoration of carbon nanotubes are reviewed.New approaches and research development towards surface decoration of carbon nanotubes are introduced. Finally,an brief technique survey on this field are also given.

2003 Vol. 23, No. 4