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Fracture Behaviour of Two-Phase γ-Titanium Aluminides

Published online by Cambridge University Press:  22 February 2011

Fritz Appel ,
Uwe Lorenz ,
Tao Zhang  and
Richard Wagner
Fritz Appel
Affiliation:
Institute for Materials Research, GKSS Research Center, Max-Planck-Str., D-21502 Geesthacht, Germany
Uwe Lorenz
Affiliation:
Institute for Materials Research, GKSS Research Center, Max-Planck-Str., D-21502 Geesthacht, Germany
Tao Zhang
Affiliation:
Institute for Materials Research, GKSS Research Center, Max-Planck-Str., D-21502 Geesthacht, Germany
Richard Wagner
Affiliation:
Institute for Materials Research, GKSS Research Center, Max-Planck-Str., D-21502 Geesthacht, Germany
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Abstract

Titanium aluminides with a lamellar microstructure consisting of the intermetallic phases ֱ2 (Ti3Al) and γ(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 (α2 + γ) 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.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 364: Symposium L – High-Temperature Ordered Intermetallic Alloys–VI , 1994 , 493
Copyright
Copyright © Materials Research Society 1995

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