W. H. Tian
,
S.L. Hu and M. Nemoto(Department of Materials Physics
,
University of Science and Technology Beijing
,
Beijing 100083
,
China)(Department of Materials Forming
,
University of Science and Technology Beijing
,
Beijing 100083
,
China)(Department of Materials Science and Engineering
,
Faculty of Engineering
,
Kyushu University
,
Fukuoka 812
,
Japan)
金属学报(英文版)
The Co3 Ti phase hardens appreciably by the fine precipitation of disordered fcc Co-rich phase upon aging after quenching from solution annealing temperature. Transmission electron microscope (TEM)observations revealed that the precipitates are platelet in shape, lying nearly parallel to the {100} planes of the L12-ordered matrix, and perfectly coherent with the matrix lattice at the beginning of aging. The high temperature strength increases appreciably with the fine precipitation of disondered Co-rich phase over the whole temperature range investigated. TEM observations of the deformed alloys after underaging revealed that saperdislocations are pinned by precipitates indicating an attractive interaction between dislocations and precipitates.
关键词:
Co_3 Ti
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W.H. Tian
,
S.L. Hu and M. Nemoto(1) Department of Materials Physics
,
University of Science and Technology Beijing
,
Beijing 100083
,
China 2) Department of Materials Forming
,
University of Science and Technology Beijing
,
Beijing 100083
,
China 3) Department of Materials Science and Engineering
,
Faculty of Engineering
,
Kyushu University
,
Fukuoka 812
,
Japan)Manuscript received in revised form 12 October 1998
金属学报(英文版)
The effect of Cr addition on the microstructures and mechanical properties of NiAl inermetallic alloys containing 4 to 8 mol% Cr has been characterized. It is shown that Cr is not only an efficient soild solution strengthener in NiAl, it is also an efficient precipitation Strengthener by fine dispersion of α-Cr particles. Transmission electron microscope observations have revealed that fine spherical particles of α-Cr appeared homogeneously in the NiAl matrix by aging at temperatures around 1073K after solution annealing at 1563K. The aging behavior was investigated by microhardness measurements and the temperature dependence of the yield stress of NiAl containing α-Cr particles was investigated by compression tests over the tempemture range from 298 to 1173K. NiAl alloys happened appreciably by the precipitation of α-Cr particles.Dislocations bypass the particles during deformation and typical Orowan loops were observed surrounding the α-Cr particles after deformation. Although the dispersion Of α-Cr particles increases the yield strength of NiAl at intermediate temperutre, the strength decreases appreciably at higher temperatures.
关键词:
NiAl
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S.C Liu(Research Institute for Fracture Technology Faculty of Engineering
,
Tohoku University
,
Sendai
,
Japan
,
on leave from Dalian Railway Institute
,
Dalian 116028
,
China)II-Hyun Kown
,
T Hashida and H Takahashi(Research Institute for nacture Technology
,
Faculty of Engineering
,
Tohoku Univeristy
,
Sendai
,
Japan)
金属学报(英文版)
In order to evaluate the tendency of mechanical properties degrudation due to weld-ing and other processing in materials used for supporting coils in super conducting rnaguets utilized in thermonuclear jusion reactore, a small punch (SP) test was used.This test, which was originally developed to study irradiation damage using miniatursized specimens was performed at 77 and 4 K for solution treated and sensitized JN1 austenitic stainless steel, a candidate cryogenic structural material. The area under the load-deflection curve up to the maximum applied load in SP test was defined as the SP enerpy, to characterize the resistance to fracture. Although solution treated material exhibited ductile fracture mode with high SP enerpy, embrittlement behavior due to sensitization at 650-800°for 1-5 h was shown clearlg by SP test with brittle intergranular fracture and decreased SP enerpy. Comparison of the results obtained by SP test with those by fracture toughness test showed the usefulness of SP test for evaluation of sensitization induced embrittlement at cryogenic temperature. The re-sults obtained in this study can be very usefol in predicting the degradation due to welding and other processing in cryogenic materials.
关键词:
small punch test
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Y.Umakoshi
,
T. Nakano and H .Y. Yasuda (Department of Materials Science and Engineering
,
Faculty of Engineering
,
Osaka University
,
2-1
,
Yamada-Oka
,
Suita
,
Osaka 565 Japan)
金属学报(英文版)
Plastic behaviour of TiAl polysynthetically twinned (PST) crystals is reviewed to show our knowledge and understanding for receiving a good combination of strength and ductility of two phase TiAl alloys under monotonic and cyclic loading conditions. Anisotropy and mechanism of strength, ductility, toughness. cyclic hardening and fatigue life are described focusing on the effect of lamellar structure.
关键词:
:Fatigue. Deformation
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W.H. Tian and M. Nemoto2(Department of Materials Physics
,
University of Science and Technology Beijing
,
Beijing 100083
,
China)(Department of Materials Science and Engineering
,
Faculty of Engineering
,
Kyushu University
,
812
,
Fukuoka
,
Japan)
金属学报(英文版)
Precipitation of Ni2Al in supersaturated NiAl containing Ta and corresponding hardening have been investigated by hardness measurements and by transmission electron microscope observations. Selected area electron diffraction, high resolution electron microscopy and energy dispersive X-ray spectrometer analysis have shown that the Ni2Al with a hexagonal structure precipitates coherently in the B2-NiAl matrix. Ni2Al is an ordered phase with a. unit cell parameter, aNi2All=aNiAl and CNi2Al= aNiAl. The orientation relationship between the Ni2Al precipitate and the B2-NiAl matrix is (0001)Ni2Al (111)NiAl and [1120]Ni2Al[110]NiAl. NiAlhardens appreciably by the precipitation of Ni2Al phase.
关键词:
intermetallic compound
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