T. Imai
,
L. Geng
,
J. F. Mao and I. Tochigi 1) National Industrial Research Institute of Nagoya
,
1-1 Hirate-cho
,
Kita-ku
,
Nagoya
,
462-8510
,
Japan 2) School of Materials Science & Engineering
,
Harbin Institute of Technology
,
Harbin 15001
,
China 3) Kanagawa High-Technology Foundation
,
Kanagawa Science Park
,
3-2-1
,
Sakado
,
Takatsu-ku
,
Kawasaki
,
Kanagawa 213
,
Japan
金属学报(英文版)
β-Si3N4 whisker reinforced aluminum composites was fabricated by squeeze casting before extrusion and an effect of content of Mg on the High Strain Rate Superplastic- ity (HSRS) were investigated, The optimum temperature of the composites at which maximum total elongation is obtained decreases according to magnesium content and the β-Si_3N_4w/Al-3Mg exhibits the total elongation of about 200% at the strain rate of 10~(-1) s~(-1) and at 853-858 K, although the β-Si_3N_4w/Al-0Mg composite shows about 100% elongation at the strain rate of about 1×10~(-1) s~(-1) at 903-913 K. Optimum strain rate of the composites fabricated by squeeze casting was about 1×10~(-1) s~(-1) but TEM observation indicates that the β-Si_3N_4w/Al-Mg has a fine grain of about 2- 3μm and that the whisker might no react with Mg at the interfaces, although the β-Si_3N_4 whisker react with aluminum matrix.
关键词:
high strain rate superplasticity
,
null
,
null
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
,
null
,
null
,
null
TAN YiDalian University of Technology
,
Dalian
,
ChinaSHINODA THitachi Research Laboratory
,
Hitachi Ltd. 391-12 Hitachi
,
JapanMISHIMA YTokyo Institute of Technology
,
Nagatuta. Midori-Ku
,
Yokohama 227
,
JapanSUZUKI TDepartment of Metallurgical Engineering
,
Tokyo Institute of Technology. Ookayama
,
Meguro-Ku
,
Tokyo 152
,
Japan
金属学报(英文版)
The effects of boron addition on defect hardening at room temperature and on high temperature creep properties are investigated in the B2 NiAl intermetallic compound. It is found that boron addition is effective on increasing the room temperature hardeness on the Ni-rich side but it has no effect on the A1-rich side of stoichiometry. These observations are attributed to interstitial dissolution of boron in Ni-rich NiAl and to a lack of solubility and also due to an enrichment at grain boundaries on the A1-rich side. The similar effect is found in high temperature creep resistance of NiAl by boron addition. The high temperature creep resistance increases on the Ni-rich side but it does not affect the A1-rich side of off-stoiciometry.
关键词:
LIU Shicheng
,
Dalian Railway Insitute
,
Dalian
,
ChinaHamaguchi Yoshikazu
,
Kuwano Hisashi
,
Muroran Institute of Technology
,
Muroran
,
Japan
金属学报(英文版)
The stable ranges concerning the composition and temperature have been experimentally de- termined for the intermetallic compounds in system Fe-Cr-Mo at high-temperatures. The isothermal section of the Fe-Cr-Mo ternary phase diagram at 1250℃ and the formation re- actions for the intermetallic compounds, which are different in part from those shown in the literature, have been proposed.
关键词:
Fe-Cr-Mo system
,
null
,
null
,
null
,
null
M.Morinaga and H. Yukawa Department of Materials Science and Engineering
,
Graduate School of Engineering
,
Nagoya University
,
Furo-cho
,
Chikusa-ku
,
Nagoya 464-8603
,
Japan
金属学报(英文版)
The electronic structures are calculated by the DV-Xa molecular orbital method employing small model clusters in order to clarify the roles of the hydride forming elements, A, (e.g., La, Zr Ti, Mg) and non-forming elements, B, (e.g., Ni, Mn, Fe) in hydrogen storage alloys. It is confirmed from this calculation that hydrogen interacts more strongly with hydride non-forming elements, B, than hydride forming elements, A, in agreement with our previous calculations. However,the B-H interaction is enhanced only when some A element exists in the neighborhood. Otherwise, such a B-H interaction never operates in the alloy. In this sense,the coexistence of A and B elements are essential in the constitution of hydrogen storage alloys. Also, it is shown that the A/B compositional ratio of hydrogen storage alloys is understood in terms of a simple parameter, 2Bo(A - B) / /Bo(A - A)+ Bo(B-B)], where the Bo(A-B), Bo(A-A) and the Bo(B-B) are the bond strengths between atoms given in the parentheses.
关键词:
electronic structure
,
null
,
null
,
null
,
null
,
null
,
null
