The influence of lamellar structure on crack propagation in two-phase TiAl alloys

Conference · Sat Dec 30 23:00:00 EST 1995

OSTI ID:225164

Chen, M; Lin, D ^[1]

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1. Shanghai Jiao Tong Univ. (China). Dept. of Materials Science and Engineering

In situ TEM technique was employed to investigate the influence of the lamellar structure on crack propagation in two-phase alloys. It was found that the way of crack propagation in lamellar structure depends strongly on the angle between crack growth and lamellar lath direction. Only if crack growth is roughly parallel to lamellar interface, microcracks nucleate at interfaces ahead of the main crack and the crack propagates by ligament break. Therefore, shear ligament toughening plays an important role under this condition. When crack growth is perpendicular to lamellae or between perpendicular and parallel, the crack propagation is inhibited by lamellar interfaces and the crack tips are blunted by lamellar interface separating or sliding. The crack propagates by tearing lamellae and accompanies a larger strain area around the crack tips. However, microcracks rarely occur under this condition. Microcracks are always nucleated in {alpha}{sub 2} lamellae. Two kinds of mechanisms of microcrack nucleation vary with the angle between crack growth and lamellar lath direction. As crack growth is parallel to the lamellae, the stress field ahead of crack tip may play a dominant role. As crack growth is perpendicular to lamellae, local stress concentration caused by interaction between deformation process and {alpha}{sub 2}/{gamma} interface and external stress induce {alpha}{sub 2} lamellae fracture and microcrack formation.

• OSTI ID: 225164
• Report Number(s): CONF-950201--; ISBN 0-87339-304-X
• Country of Publication: United States
• Language: English

Related Subjects

33 ADVANCED PROPULSION SYSTEMS
36 MATERIALS SCIENCE
AEROSPACE INDUSTRY
ALUMINIUM ALLOYS
ANNEALING
AUTOMOBILES
CASTING
CHROMIUM ALLOYS
CRACK PROPAGATION
CRYSTAL GROWTH
FORGING
INTERFACES
INTERMETALLIC COMPOUNDS
LAMELLAE
MATERIALS
MICROSTRUCTURE
NUCLEATION
ORIENTATION
TITANIUM ALLOYS
TRANSMISSION ELECTRON MICROSCOPY
TWINNING
VANADIUM ALLOYS