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Deformation of Polysynthetically Twinned TiAl Single Crystals with Near-Hard Orientations

Published online by Cambridge University Press:  10 February 2011

Min-Chul Kim ,
M. Nomura ,
V. Vitek  and
D. P. Pope
Min-Chul Kim
Affiliation:
Now with Korea Atomic Energy Research Institute, Yusung, Taejon, KOREA
M. Nomura
Affiliation:
Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104, USA
V. Vitek
Affiliation:
Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104, USA
D. P. Pope
Affiliation:
Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104, USA
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Abstract

Compression tests were performed on specially-oriented PST TiAl crystals to which strain gages were attached in order to precisely measure the three axial strains in the samples during deformation. It was found that all samples deform by plane strain except when the compression axis is nearly perpendicular to the lamellar planes. This measurement technique was used to determine the orientations in which the various slip systems are operative in PST samples, and this, in turn was employed to explain the shape of the flow stress vs. orientation curve. An important component of this explanation is the fact that slip of ordinary dislocations and twinning are closely coupled in this material, implying that the twinning must occur relatively slowly-at about the same rate that ordinary dislocations move. Atomistic calculations have shown that a slow twinning process is to be expected in this material at low temperatures, perhaps even by a thermally activated process.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 552: Symposium KK – High-Temperature Ordered Intermetallic Alloys VIII , 1998 , KK3.1.1
Copyright
Copyright © Materials Research Society 1999

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References

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