J. C. Feng
,
M. Naka
,
J. C. Schuster(School of Materials Science and Engineering
,
Harbin Institute of Technology
,
Harbin
,
150001
,
China
,
Joining and Welding Research Institute
,
Osaka University
,
Mihogaoka 11 - 1
,
Ibaraki
,
Osaka 567
,
Japan
,
Institute of Physical Chemistry
,
University of Vienna
,
Austria )
金属学报(英文版)
Bonding of SiC to SiC using Ni and Ni - 25at%Cr foils was performed at high temperature.Interface structures and reaction phases were investigated by EPMA analyses and XRD diffraction method, re- spectively. At a bonding temperature of 1273K Ni reacts with SiC and forms various Ni silicides con- taining graphite baside SiC. Ni3Si without graphite was formed at Ni side.The interface structure of SiC/Ni joint was SiC/Ni2Si + C/Ni31 Si12 + G/Ni3 Si/Ni. At the interface between SiC and Ni- 25at%Cr alloy the Ni silicide was only Ni2Si at the same bonding temperature,and further(Cr, Ni)7 (Si, C)3 carbide was formed between Ni silicide + graphite zone and Ni - 25at%Cr alloy.The interface structure of SiC/Ni - 25at%Cr alloy was SiC/Ni2Si + C/(Cr, Ni)7 (Si, C)3+Ni(ss. Cr, Si)/Ni - 25at%Cr.
关键词:
interfacial structure
,
null
,
null
,
null
D.L. Chen
,
B. Weiss and R.Stickler(Institute for Physical Chemistry-Materials Science
,
University of Vienna
,
Waehringer Strasse 42
,
A-1090 Vienna
,
Austria Zhongguang WANG)(State Key Lab. for Fatigue and Fracture of Materials
,
Institute of Metal Research
材料科学技术（英文）
The state-of the-art of fatigue crack closure effect, involving the mechanisms, measurements,models, evaluation methods, innuencing factors and existing problems is briefly reviewed. Attention is concentrated on a new consideration of closure effect and a re-definition of the effective d riving force for the propagation of a fatigue crack. A theoretical basis fOr measuring the closure effect is established. The proposed closure concept takes into account the role of the lower portion of loading cycle below the opening load. The conventionaI closure concept is proven to be correct only for some extreme cases which are practically non-existent fOr engineering materials. A miniature strain gauge tech nique is developed to measure the crack closure. Stressratio-change tests at threshold level clearly indicate the shortcomings of the conventional closure concept, and the validity of the newly-proposed closure concept. The application of the proposed concept can give rise to a new method for the determination of the effective fatigue threshold of materials. If the fatigue threshold is measured at a sufficiently negative stress ratio (R
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