Accession Number:

ADA129811

Title:

Effect of Microstructure, Strength and Oxygen Content on Fatigue Crack Growth Rate of Ti-4.5Al-5.0Mo-1.5Cr (CORONA 5).

Descriptive Note:

Final rept.,

Corporate Author:

NAVAL RESEARCH LAB WASHINGTON DC

Personal Author(s):

Report Date:

1983-06-17

Pagination or Media Count:

40.0

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 dadN 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 AlphaBeta 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 AlphaBeta alloys such as Ti-6Al-4V, is rationalized in terms of crack path behavior.

Subject Categories:

  • Properties of Metals and Alloys
  • Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE