Fracture behavior of two-phase {gamma}-titanium aluminides
- GKSS Research Center, Geesthacht (Germany). Inst. for Materials Research
Titanium aluminides with a lamellar microstructure consisting of the intermetallic phases {alpha}{sub 2} (Ti{sub 3}Al) and {gamma}(TiAl) suffer from brittleness at ambient temperatures but exhibit at the same time a relatively high fracture toughness. This discrepancy indicates particular processes stabilizing crack propagation in the lamellar microstructure. In this context, the toughening mechanisms were investigated in ({alpha}{sub 2} + {gamma}) TiAl alloys which contained different volume fractions of lamellar colonies. The fracture toughness for crack propagation parallel or across the lamellar interfaces was estimated by using chevron-notched bending bars. Electron microscope studies were performed to characterize the related processes of crack tip plasticity. Special emphasis was paid to the crystallography of crack propagation and to the interaction of crack tips with lamellar interfaces. Accordingly, the lamellar morphology derives some of its toughness from interface-related processes which stabilize crack propagation by deflecting the crack tip and providing the necessary dislocation sources for crack tip shielding in the process zone ahead of the crack tip.
- OSTI ID:
- 78365
- Report Number(s):
- CONF-941144--; ISBN 1-55899-265-0
- Country of Publication:
- United States
- Language:
- English
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