Crack Growth Processes at Elevated Temperatures in Advanced Materials
Abstract
Research in this program during the past 3 years has fracture studies on intermetallic alloys. Most of the work was focused on alloys based on the intermetallic compounds Ti3Al and TiAl, but some work to characterize alloys based on Nb3Al was also accomplished. The mechanisms controlling fatigue and fracture toughness of these new materials have been determined and compared to similar knowledge for other alloys. For a TiAl alloy with lamellar microstructure, fatigue cracks grew 10 times slower at 800 degrees C in vacuum, and the threshold for the crack growth was higher than for 25 degrees C in air. Growth was intermittent and crack tip opening alternated between blunt and sharp, just as found for other alloys. Crack growth was influenced by the direction of the lamellae relative to the loading axis, especially at low stresses. For crack growth perpendicular to the lamella direction, crack advance was linked to the width of the lamellae. Fatigue crack closure was about the same as for other alloys. Because of the similarity of crack growth behavior between this and other titanium alloys, a crack tip geometric model previously used for other materials was applied.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 1992
- Accession Number
- ADA249023
Entities
People
- David L. Davidson
- James Lankford
- Kwai S. Chan
Organizations
- Southwest Research Institute