scholarly journals Direct, real time observation of fatigue crack growth using a field emission type SEM. Effects of grain orientation and grain boundary on fatigue crack growth.

1988 ◽  
Vol 37 (421) ◽  
pp. 1204-1208
Author(s):  
Masahiro JONO ◽  
Atsushi SUGETA ◽  
Shinji YAMADA
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Grain Boundary ◽  
Real Time ◽  
Crack Growth ◽  
Field Emission ◽  
Grain Orientation ◽  
Time Observation ◽  
Real Time Observation

Interfacial Composition Measurements in Complex Ni-Base Superalloys

1996 ◽  
Vol 458 ◽  
Author(s):  
E. L. Hall ◽  
J. Bentley
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Grain Boundary ◽  
Crack Growth ◽  
Time Dependent ◽  
Alloying Elements ◽  
Second Phase ◽  
Slow Cooling ◽  
X Ray ◽  
Boundary Composition

ABSTRACTIn this study, three different Ni-base superalloy / heat treatment combinations are studied in an attempt to assess the role of grain boundary morphology, composition, and phase distribution on mechanical properties, particularly time-dependent fatigue crack growth. The alloys chosen include one in which crack growth can be slowed by slow-cooling, and one in which crack growth is slow in the fast-cooled state. Both x-ray spectroscopy and energy-filtered imaging in the analytical electron microscope were used to measure grain boundary composition. The x-ray spectroscopy showed some enhancement of Cr, Mo, and W in the γ matrix at grain boundaries in the fast-cooled state, which was not present after slow cooling. Energy-filtered imaging showed no significant enhancement in alloying elements at interfaces in any of the samples studied. The results did show the tendency for the γ matrix to quickly equilibrate by second-phase precipitation, and a preference to avoid γ ‘- γ’ interfaces. The conclusions of this study are that time-dependent fatigue crack growth behavior in these alloys cannot be completely explained on the basis of grain boundary composition of major alloying elements.

scholarly journals Field Emission Phenomena and Applications. Real Time Observation of Individual Surface Adsorbate Dynamics.

Hyomen Kagaku ◽  
1996 ◽  
Vol 17 (12) ◽  
pp. 731-737
Author(s):  
Fumiya WATANABE ◽  
Gary M. MCCLELLAND ◽  
Harry HEINZELMANN
Keyword(s):  
Real Time ◽  
Field Emission ◽  
Time Observation ◽  
Real Time Observation

scholarly journals Influence of Grain Boundary on the Fatigue Crack Growth of 7050-T7451 Aluminum Alloy Based on Small Time Scale Method

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Weihan Wang ◽  
Weifang Zhang ◽  
Hongxun Wang ◽  
Xiaoliang Fang ◽  
Xiaobei Liang
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Grain Boundary ◽  
Crack Growth ◽  
Time Scale ◽  
Crack Tip ◽  
Fatigue Loading ◽  
Small Time ◽  
Scale Method

Based on the small time scale method, the influence of grain boundary on the fatigue crack growth of 7050-T7451 has been investigated. The interaction between fatigue crack and grain boundary was investigated by in situ SEM testing. Results showed that the fatigue crack growth will be retarded by grain boundary when the angle between fatigue crack and grain boundary is greater than 90 degrees. Mechanism analysis showed that the fatigue crack tip would not be able to open until the loading reached the 55% of maximum load, and the fatigue crack had been closed completely before the loading was not reduced to the minimum value, which led to the crack growth retardation. When the 7050-T7451 aluminum alloy suffered from fatigue loading with constant amplitude, a behavior of unstable fatigue crack growth could be observed often, and results indicated that the bridge linked mechanism led to the behavior. The grain boundary was prone to fracture during fatigue loading, and it became the best path for the fatigue crack growth. The fatigue crack tip would be connected with fractured grain boundary eventually, which led to the fast crack growth in different loading stage.

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