Effect of Microstructure, Strength and Oxygen Content on Fatigue Crack Growth Rate of Ti-4.5Al-5.0Mo-1.5Cr (CORONA 5).
Abstract
Fatigue crack growth rate behavior in CORONA 5, an alloy developed for applications requiring high fracture toughness, has been examined for eight material conditions. These conditions were designed to give differences in microstructure, strength level, and oxygen content, in such a manner that the separate effects of these variables could be defined. For all eight conditions, fatigue crack growth rates (da/dN) are virtually indistinquishable over the full all spectrum of stress-intensity range (Delta K) examined. Concomitantly, it is noted that over the sizeable solution annealing range studied, the primary alpha-phase morphology was substantially invariant. A change in microfractographic appearance occurs at delta KT, as extensive secondary cracking along Alpha/Beta interfaces is observed at all hypertransitional levels of Delta K, but not for Delta K < Delta KT. for each material condition, the mean length of primary Alpha platelets is approximately the same as the cyclic plasic zone size at Delta KT. Accordingly, locations of Delta KT (and their similarity for the different material conditions) are rationalized in conformance with a cyclic plastic zone model of fatigue crack growth. Finally, the difference in behavior of CORONA 5, as compared to conventional Alpha/Beta alloys such as Ti-6Al-4V, is rationalized in terms of crack path behavior.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 17, 1983
- Accession Number
- ADA129811
Entities
People
- D. Eylon
- F. H. Froes
- George R. Yoder
Organizations
- United States Naval Research Laboratory