Nanometer-scale crack initiation and propagation behavior of Fe{sub 3}Al-based intermetallic alloy
- Univ. of Calgary, Alberta (Canada). Dept. of Mechanical Engineering
- Univ. of Science and Technology-Beijing (China). Dept. of Materials Physics
The initiation and propagation of nanometer-scale cracks have been investigated in detail by in situ transmission electron microscope (TEM) observations for the intermetallic compound Fe{sub 3}Al under mode 1 loading. No dislocation was detected and no dislocation emission was found when cracks propagated directly from the thin edge of a double-jet hole where the thickness of the foil was below a critical thinness. Thinning took place in the thicker region of the foils because a great number of dislocations were emitted from the crack tip, and then an electron semitransparent region was formed in front of the crack tip. Following this process, a dislocation-free zone (DFZ) was formed. The maximum normal stress occurs in the zone. Nanometer-scale cracks initiated discontinuously ahead of the main crack tip in the highly stressed zone. The size of the smallest nanocrack observed was about 3 nm, and the tip radius of the nanocracks was less than 1 nm when the applied loading was low. The radius of the main crack tip was about 2.5 nm. The distances between discontinuous nanocracks and the main crack tip were about 5 to 60 nm, depending on the applied tensile loading. A relationship was found between the tensile loading and the nanocrack distance from the crack tip. The distance increases with the tensile loading, which is consistent with an ``elastic-plastic`` theoretical model.
- OSTI ID:
- 78412
- Journal Information:
- Metallurgical Transactions, A, Vol. 26, Issue 6; Other Information: PBD: Jun 1995
- Country of Publication:
- United States
- Language:
- English
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