Crack-growth processes at elevated temperatures in advanced materials. Annual report, 1 Jan 91-1 Jan 92

Technical Report · Sat Feb 01 00:00:00 EST 1992

OSTI ID:5286408

Davidson, D L; Chan, K S; Lankford, J

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.

• Research Organization: Southwest Research Inst., San Antonio, TX (United States)
• OSTI ID: 5286408
• Report Number(s): AD-A-249023/3/XAB; SWRI-06-2699/3; CNN: F49620-89-C-0032
• Resource Relation: Other Information: Original contains color plates: All DTIC and NTIS reproductions will be in black and white
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
CRACK PROPAGATION
NIOBIUM ALLOYS
TITANIUM ALLOYS
AIR
ALLOYS
CRACKS
FATIGUE
FRACTURE PROPERTIES
INTERMETALLIC COMPOUNDS
MECHANICAL PROPERTIES
MICROSTRUCTURE
RESEARCH PROGRAMS
STRESSES
TITANIUM
WIDTH
CRYSTAL STRUCTURE
DIMENSIONS
ELEMENTS
FLUIDS
GASES
METALS
TRANSITION ELEMENTS
360103* - Metals & Alloys- Mechanical Properties