航空材料学报

A STUDY OF THE MECHANICAL PROPERTIES OF POLYCRYSTALLINE AND SINGLE CRYSTAL OF NiAl-BASED INTERMETALLIC ALLOYS

Chen Jian, Zheng Qi, Tang Yajun, Hu Zhuangqi

1996, 16(3): 1-10.

[Abstract](1523) [PDF 1004KB](284)

Abstract:
In this paper,the room temperature tensile properties of polycrystalline and single crystal of Ni50Al30Fe20 intermetallic alloy,and also room temperature and high temperature compressive properties of polycrystalline and single crystal of Ni50Al30Fe20 and Ni50Al40Ti10 intermetallic alloy,as well as the effect of Ni coating on the properties of Ni50Al40Ti10 were investigated.It was found that 1% plastic elongation at room temperature can be obtained in the[100]oriented "hard crystal"of Ni50Al30Fe20.Its fracture surface is consisted by {110} cleavage planes.The river patterns on the cleavage planes need to nucleate again after it passes the Υfilmbetween the dendrites during its propagation.Polycrystalline Ni50Al30Fe20 exhibits brittle fracture under tension.When compressed at room temperature,kinking occurs in the[100]oriented"hard crystal"of Ni50Al30Fe20 whereas swaging occurs in polycrystalline sample of Ni50Al30Fe20.However,brittle fracture occurs for both polycrystalline and single crystal of Ni50Al40Ti10.After the surface of Ni50Al40Ti10 is coated by 10μm thick Ni,its fracture strength is improved.When Ni50Al30Fe20 is tested around the brittle-ductile transition(BDT)temperature,it exhibits"yield point"phenomenon.The BDT temperature of Ni50Al40Ti10 is higher than that of Ni50Al30Fe20.When Ni50Al40Ti10 is tested by compression,it exhibits brit tle fracture below BDT temperature.A small amount of plastic deformation can be obtained only at BDT temperature or higher temperature.The[100]oriented single crystal is even more brittle than the polycrystalline sample.

STUDY ON SHAPE MEMORY EFFECT DEGRADATION BEHAVIOUR AND ITS MECHANISM OF NiTi SHAPE MEMORY ALLOY

Ma Yingli, Hu Guangli

1996, 16(3): 11-18.

[Abstract](1523) [PDF 811KB](189)

Abstract:
Shape memory effect degradation behaviour of near equiatomic NiTi shape memory alloy was examined under two different techniques.The microstructure of NiTi shape memory alloy and the mechanism of its shape memory effect degradation were studied by means of TEM.

HREM IMAGE PROCESSING OF GRAIN BOUNDARY PHASES IN INCOLOY 907

Wang Rongming, Li Chunzhi, Yan Minggao

1996, 16(3): 19-24.

[Abstract](1458) [PDF 897KB](180)

Abstract:
The microstructures of various kinds of grain boundary phases in low expansion superalloy Incoloy 907 have been investigated by high resolution electron microscopy(HREM)and high resolution image processing.High resolution images of the grain boundaries phases have been clearly obtained after image processing.Theεphase is closely bounded with the matrix and the interfaces are clean and smooth.No segregation has been found at the interfaces.The orthorhombic phase and the triclinic phase are well bounded with the matrix and some phases of nanometers size can be found occasionally at the interfaces.

INFLUENCE OF STRENGTHENING EFFECTS AND ENVIRONMENT EFFECTS ON FATIGUE PROPERTIES OF 300M ULTRA-HIGH STRENGTH STEEL

Ding Chuanfu

1996, 16(3): 25-32.

[Abstract](1487) [PDF 788KB](217)

Abstract:
In this paper,the fatigue properties of rolled and non-rolled screw-thread specimens in 300M ultrahigh strength steel in air and 3.5% NaCl water solution were investigated.The relationship of environmental effects and strengthening effects is revealed.It has been found experimentally that an intersection is existed between two S-N curves in saltwater and air at f=10Hz Strengthening effects are acted mainly above the stress levels of the intersection.Environmental effects are acted mainly below the stress levels of the intersection.

RECRYSTALLIZATION BEHAVIOR OF COLD ROLLED INCONEL 718 ALLOY

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

1996, 16(3): 33-38.

[Abstract](1473) [PDF 570KB](193)

Abstract:
The recrystallization behavior and the variation in hardness of cold rolled Inconel 718 alloy have been investigated in the temperature range of 810～910℃ as a function of cold rolling reduction and annealing time.It is shown that the austenite can be fully recrystallized at 910℃.As the cold rolling reduction increases,the 90% recrystallization time and the recrystallized grain size decrease.The variation in hardness depends on the recovery and recrystallization of austenite and the precipitation of δ,γ",γ'phases.At 910℃,hardness initially decreases sharply,and then increases.Hardness at the extreme point increases with cold rolling reduction increasing.At 860℃,hardness initially decreases due to the recovery and recrystallization of austenite for the more than 25% cold rolled samples,and then increases due to the precipitation of γ",γ'phases.After 30 minutes hardness decreases up to 2 hours and then increases slightly or remaIns constant.

EFFECT OF FINE GRAIN CASTING PROCESS ON TENSILE PROPERTIES OF K418 ALLOY

Yuan Wenming, Tang Xin, Liu Faxin, Cheng Rongzhang

1996, 16(3): 39-44.

[Abstract](1503) [PDF 692KB](124)

Abstract:
The tensile properti.es of K418 cast alloys by fine grain casting process and coventionally cast process have been determined at different temperatures.The results showed that the yield strength and ultimate tensile strength were obviously improved by fine grain casting process,and the relationship between the tensile strength from room temperature to 600℃ and the average diameters of the grain size of the alloy are consistent with the Hall-Petch formula.

HOMOGENEOUS DISPERSION OF SiC IN Ti-6Al-4V BY MECHANICAL ALLOYING

Li Zongxia

1996, 16(3): 45-49.

[Abstract](1487) [PDF 525KB](197)

Abstract:
Advantages and disadvantages of metal-matrix composites reinforced by continual fibers and ceramic particles are discussed in this paper.Mechanical alloying process was employed to prepare the SiC dispersed Ti-6Al-4V composite powder.Variation of particle morphology,particle size and crystal structureduring mechanical alloying are studied by XRD and SEM.

STUDIES ON THE DISSOLUTION CHARACTERISTICS OF STAINLESS STEEL BASE METAL IN THE LIQUID NICKELBASED AMORPHOUS AND CRYSTALLINE BRAZING FILLER METALS DURING VACUUM BRAZING PROCESS

Zhang Xinping, Shi Yaowu, Ren Yaowen

1996, 16(3): 50-56.

[Abstract](1450) [PDF 437KB](289)

Abstract:
Based on the model of quantitatively calculating the dissolution thickness of the base metal in liquid brazing filler metals,the dissolution characteristics of stainless steel base metal(1Cr18Ni9Ti)in the liquid Nickel-based(Ni82Cr7.5Si4.5B3Fe3)amorphous and crystalline brazing filler metals during the vacuum brazing process was investigated.The influences of the brazing temperature and the brazing holding time as well as the brazing clearance on dissolution thickness of base metal during vacuum high temperature brazing have also been considered in detail.The results indicate that the brazing temperature has a more evident effect on dissolution thickness of base metal than the brazing holding time,and the wider for brazing clearance the larger for dissolution thickness of base metal,and the quantitative formula of estimating the dissolution thickness of base metal can be used to optimize the brazing parameters.

INVESTIGATION ON THERMOLOGY PROPERTIES AND THERMAL SHOCK RESISTANCE OF SiO₂-Si₃N₄ ANTENNA WINDOW MATERIAL

Yao Junjie, Li Baoshun, Huang Xiaoxian, Guo Jingkun

1996, 16(3): 57-62.

[Abstract](1452) [PDF 467KB](195)

Abstract:
Thermology properties and thermal shock resistance of the SiO2-Si3N4 composites were investigated in this paper.It is found that thermal expansion coefficient,thermal diffusivity and thermal conductivity of the composites increase when the Si3N4 content increases;in the same Si3N4 content,they all increase when temperature increase;the composites retain the excellent thermal shock resistance of the SiO2 matrix material.

1996 Vol. 16, No. 3