Cyclic deformation, dislocation structure, and internal fatigue crack generation in a Ti-Fe-O alloy at liquid nitrogen temperature
Abstract
To clarify the internal fatigue crack generation in a Ti-Fe-O (near α-type) alloy, microstructures, internal fatigue crack initiation sites, and dislocation structures in samples fractured during high-cycle fatigue tests at liquid nitrogen temperature were studied. The alloy contained two kinds of elongated α-phase microstructures, i.e., recovered α grains and recrystallized α grains. Untested samples contained mobile dislocations in recovered α grains, but in recrystallized α grains, any dislocations were observed. Internal crack initiation sites were formed transgranularly and were related to the recrystallized α grain region, judging from their morphology, size, and chemistry. Dislocations in recovered α grains were rearranged after cyclic loading in either planar arrays or subgrain structures due to dislocation annihilation. Few dislocations were seen in recrystallized α grains. We discuss the relationship between localized strain incompatibility due to coplanar arrays in recovered α, grains and transgranular cracking in recrystallized α grains, and propose a model for fatigue crack generation.
- Publication:
-
Metallurgical and Materials Transactions A
- Pub Date:
- November 2000
- DOI:
- 10.1007/BF02830339
- Bibcode:
- 2000MMTA...31.2793Y
- Keywords:
-
- Fatigue;
- Material Transaction;
- Fatigue Crack;
- Crack Initiation;
- Slip Plane