Fundamental aspects of fatigue and fracture in a TiAl sheet alloy
- Southwest Research Inst., San Antonio, TX (United States)
- McDonnell Douglas Corp., St. Louis, MO (United States)
The fatigue mechanisms in a TiAl sheet alloy, heat treated to the lamellar and equiaxed microstructures, were studied to determine the effects of microstructure on the initiation of microcracks and their subsequent growth into large cracks. The nucleation and growth history of individual microcracks were followed. For comparison, fatigue crack growth and fracture toughness were also characterized using specimens containing a machined notch with a fatigue precrack. The results indicated that microcracks initiated at grain/colony boundaries and at slip bands. Most microcracks were arrested after nucleation, but a few grew at stress intensity ranges below the large crack threshold. The populations of nonpropagating and propagating cracks varied with life fractions. Ligaments in the wake of a fatigue crack were more severely strained than the crack-tip region of the main crack, and, as a result, they were more prone to fatigue failure. The destruction of the crack-wake ligaments is expected to result in lower fracture resistance in materials under cyclic loading than those under monotonic loading.
- Sponsoring Organization:
- Department of the Air Force, Washington, DC (United States)
- OSTI ID:
- 605811
- Journal Information:
- Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science, Journal Name: Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science Journal Issue: 1 Vol. 29; ISSN 1073-5623; ISSN MMTAEB
- Country of Publication:
- United States
- Language:
- English
Similar Records
Fracture and fatigue of cast gamma TiAl based aluminides
Fatigue-crack growth behavior in a dual-phase ({gamma}+{alpha}{sub 2}) TiAl intermetallic alloy at elevated temperatures