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Creep Mechanisms of Fully-Lamellar TiAl Based Upon Interface Sliding

Published online by Cambridge University Press:  10 February 2011

L. M. Hsiung  and
T. G. Nieh
L. M. Hsiung
Affiliation:
Materials Science and Technology Division, Lawrence Livermore National Laboratory, L-369, P.O. Box 808, Livermore, CA 94551-9900, U.S.A.
T. G. Nieh
Affiliation:
Materials Science and Technology Division, Lawrence Livermore National Laboratory, L-369, P.O. Box 808, Livermore, CA 94551-9900, U.S.A.
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Abstract

Deformation mechanisms of fully lamellar TiAl with a refined microstructure (γ lamellae: 100 ∼ 300 nm thick, α2 lamellae: 10 ∼50 nm thick) crept at 760°C have been investigated. As a result of a fine structure, the motion and multiplication of lattice dislocations within both γ and α2 lamellae are limited at low creep stresses (< 400 MPa). Therefore, the glide and climb of lattice dislocations are insignificant to creep deformation. The cooperative motion of interfacial dislocations on γ/α2 and -γ/γ interfaces (i.e. interface sliding) is proposed to be the dominant deformation mechanism at low stresses. Lattice dislocations impinged on lamellar interfaces are found to be the major obstacles impeding the motion of interfacial dislocations. The number of impinged lattice dislocations increases as the applied stress increases and, subsequently, causes the pileup of interfacial dislocations along the interfaces. Accordingly, deformation twinning activated by the pileup of interfacial dislocations is proposed to be the dominant deformation mechanism at high stresses (> 400 MPa).

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 552: Symposium KK – High-Temperature Ordered Intermetallic Alloys VIII , 1998 , KK1.3.1
Copyright
Copyright © Materials Research Society 1999

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References

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