航空材料学报

MICROSTRUCTURE EVOLUTION MECHANISM DURING THE SPRAY DEPOSITION OF IC6 SUPERALLOY

Mi Guofa, Li Zhou, Liang Zhikai, Zhao Xianguo, Tian Shifan

1997, 17(1): 1-8.

[Abstract](1478) [PDF 774KB](319)

Abstract:
By analyzing the microstructure along the longitudinal section of deposited preform, it is observed that there are evidently different microstructures among the periphery part, near top/bottom surface and the central part of the pre form. Annealing of the specimen taken from the periphery part and near top/bottom surface of the deposited pre form, revealed that fine dendrite fragments merge and coarse to lead to form near spheric grains. According to the experiment, its growth obeys the following function as: D2-D02=6.37×1020e(-70036.1/T)·τ and the activated energy of boundary migration is equal to 582KJ/mol. The formation of non-dendrite spheric grain structure is finally completed in the process of high temperature annealing and relies on two mechanisms: (1) the homogenization of dendrites which did not experience severe de formation during spray atomization codeposition; (2) growth and coarsing of the deformed and fractured dendrite.

EFFECT OF ALLOY COMPOSITION ADJUSTMENT ON THE SOLIDIFICATION BEHAVIOUR OF SUPERALLOY DZ125

Hou Shu’e, Zheng Yunrong, Chen Rongzhang

1997, 17(1): 9-16.

[Abstract](1494) [PDF 681KB](259)

Abstract:
Solidification sequence of primary phases was determined,and the percent of solid and liquid of two alloys at different temperature in the range of solidus and liquidus was measured for superalloy DZ125. The results indicated that alloy of high W,Al,low Mo,Ti could narrow down the range of solidus and liquidus obviously,consequently would cause beneficial effect on castability of the alloy. The Ti element exhibits certain effect on the size,number,patten of (γ+γ’) eutectic.

QUANTITATIVE PHASE ANALYSIS OF INCONEL 718 ALLOY

Liu Wenchang, Yao Mei, Chen Zonglin, Jiang Zhaoqun, Wang Shaogang, Li Weihong

1997, 17(1): 17-22.

[Abstract](1582) [PDF 359KB](182)

Abstract:
The relationship between the lattice constant of γ phase and the content of a phase,γ" and γ’ phases in Inconel 718 is presented. The amount of δ,γ"andγ’ phases were determined by the combination of X-ray differaction techniques and the relationship between the lattice constant of γ phase and the content of δphase, γ" and γ’ phases.

ANALYSIS OF THE HIGH-TEMPERATURE FRACTURE OF Ni-BASED SINGLE CRYSTAL SUPERALLOY DD100

Zhou Candong, Dong Xianping, Yu Jinxing, Zhang Yuanhu, Sun Chuanqi, Liu Zeyao, Li Qijuan, Wu Changxin

1997, 17(1): 23-30.

[Abstract](1562) [PDF 749KB](230)

Abstract:
The microstructure and fracture of Ni-based single crystal DD100 and the factors of influencing the ductility of the alloy have been investigated. With an addition of Hf in DD100 alloy,no obvious porosities were found and the amount of γ/γ’ eutectic was increased. Sub-boundaries,porosities and γ/γ’ eutectics appear in the tensile specimens without containing Hf. It was found that the effect of sub-boundary on the properties was greater than the others.

INVESTIGATION OF GRAIN BOUNDARY SEGREGATION AND HYDROGEN-INDUCED FRACTURE MECHANISM IN HIGH STRENGTH ALUMINUM ALLOY

Song Renguo, Zhang Baojin, Zeng Meiguang

1997, 17(1): 31-38.

[Abstract](1675) [PDF 458KB](363)

Abstract:
The model of grain boundary segregation and intergranular fracture for a trinary alloy was proposed in this paper. The effects of Mg, H grain boundary segregation on intergranular fracture work in high strength aluminum alloy were investigated by using the model combined with quasichemical theory. The results indicated that both Mg and H segregation result in a decreas of the intergranular fracture energy and hydrogen embrittles grain boundary more intense than magnesium does,which is consistent with the experimental results of stress corrosion for 7075 aluminum alloy.

MECHANISM OF CRACK INITIATION AND CRACK PROPAGATION OF 16Co14Ni10Cr2Mo STEEL UNDER IMPACT LOADING

Wen Wu, Wan Xiaoru

1997, 17(1): 39-43.

[Abstract](1476) [PDF 411KB](168)

Abstract:
Fracture mechanism of 16Co14Ni10Cr2Mo steel under the condition of impact load is investigated in this paper. It is found that, with blunting to verticles while crack initiating, crack propagating in 16Co14Ni10Cr2Mo steel is an alternative process through coalescence of microvoids, including primary voids and secondary voids located on high-energy interfaces.

THE FATIGUE AND FRACTURE BEHAVIOURS OF POWDER METALLURGY SUPERALLOY AT HIGH TEMPERATURE

Xie Jizhou, Shen Zhumin, Hou Jingyong

1997, 17(1): 44-51.

[Abstract](1469) [PDF 449KB](150)

Abstract:
The low cycle fatigue, fatigue crack growth rate and fracture thoughness of powder metallurgy superalloys Rene’ 95 and II741 have been studied at high temperature. The rcsults show that the low cycle fatigue property of alloy Rene’ 95 is higher than that of alloy GH4169. In view of the combination of strength and ductility, it appears not as good as compared with forging alloy. The fatigue crack growth rates da/dN and fracture thoughness Kic of these alloys are basically the same.

THE STUDY OF IMPROVEMENT HEAT TREATMENT OF SUPERALLOY DZ-22

She Li, Wang Luobao, Chen Rongzhang

1997, 17(1): 52-57.

[Abstract](1348) [PDF 535KB](181)

Abstract:
The effect of two heat treatment on the microstructure and mechanical properties of superalloy DZ-22 was studied in this paper. Experimental results showed that the Ni5Hf-phase may be eliminated by means of pretreatment at 1180℃ for 2h. The incipient melting of DZ-22 superalloy may be effectively controlled. With increasing solution temperature,more and finer γ’ phases were reprecipitated during cooling and aging. The tensile strength at 25℃, 760℃, 980℃ and 760℃, 980℃, 1040℃ srtess-repture life of this alloy increased significantly.

A HOT-MELT EPOXY RESIN SYSTEM ADAPTED FOR TAPE WINDING

Shen Chao, Liu Dongxun

1997, 17(1): 58-62.

[Abstract](1411) [PDF 311KB](275)

Abstract:
A dicyandiamide low viscosity epoxy resin system accelerated by substituted urea was investigated. It is adapted for tape winding and can be fairly cured at 125℃ with contact pressure.

1997 Vol. 17, No. 1