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Microstructural Effects On Fatigue-Crack Growth Behavior In γ-TiAl/β-TiNb Intermetallic Composites

Published online by Cambridge University Press:  15 February 2011

K. T. Venkateswara Rao  and
R. O. Ritchie
K. T. Venkateswara Rao
Affiliation:
Department of Materials Science and Mineral Engineering, University of California at Berkeley Berkeley, CA 94720
R. O. Ritchie
Affiliation:
Department of Materials Science and Mineral Engineering, University of California at Berkeley Berkeley, CA 94720
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Abstract

Cyclic crack-propagation behavior is examined in a series of γ-TiAl intermetallic alloys reinforced with pancake-shaped, ductile β-TiNb particles as a function of microstructure and specimen orientation. In contrast to results under monotonic loading, TiNb reinforcements are found to be far less effective in impeding crack extension under cyclic loading due to their susceptibility to premature fatigue failure, and consequently to the diminished role of shielding from crack-bridging mechanisms. Modest improvements in fatigue-crack growth resistance are observed in TiAl/TiNb composites compared to monolithic γ-TiAl, provided the particle faces are oriented perpendicular to the crack plane; however, properties are compromised in orientations where the particle edges are stacked normal to the crack plane. Microstructural effects on cyclic crack growth are less prominent in the composites, with crack-growth rates exhibiting a strong dependence on the applied ΔK level; measured exponents for the da/dN-ΔK relationship range between 10 and 20, and are found to decrease with increasing ductile phase content, yet are independent of particle thickness.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 273: Symposium Q – Intermetallic Matrix Composites II , 1992 , 127
Copyright
Copyright © Materials Research Society 1992

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References

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