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Role of Interface Boundaries in the Deformation Behavior of TiAl Polysynthetically Twinned Crystal: In situ Transmission Electron Microscopy Deformation Study

Published online by Cambridge University Press:  01 July 2005

Sung G. Pyo  and
Nack J. Kim
Sung G. Pyo
Affiliation:
Logic Process Development, R&D Center, MagnaChip, Cheongju 361-725, Korea
Nack J. Kim*
Affiliation:
Center for Advanced Aerospace Materials, Pohang University of Science and Technology, Pohang 790-784, Korea
*
a)Address all correspondence to this author. e-mail: njkim@postech.ac.kr
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Abstract

To understand the role of boundaries in the deformation behavior of TiAl, in situ straining experiments in transmission electron microscopy have been performed on thin foils of polysynthetically twinned (PST) crystal of Ti–49.3 at.% Al. The deformation behavior of PST TiAl is anisotropic, depending on the angle between the lamellar boundaries and the straining axes. For L-orientation, deformation twins and ordinary dislocations transmit across the true-twin (TT) boundaries but are reflected at the pseudo-twin (PT) and rotational order-fault (RO) boundaries. For transverse (T) orientation, deformation twins are transmitted across all TT, PT, and RO boundaries. For I-orientation, shear deformation occurs parallel to the lamellar boundaries. There is a transmission of deformation across the interphase (IP) boundary in longitudinal orientation, but deformation is blocked and reflected at the IP boundary in T-orientation. The role of the various types of boundaries in localized deformation behavior was evaluated by considering Schmid factors and geometric compatibility factors.

Keywords

Intermetallic alloysMechanical propertiesTransmission electron microscopy (TEM)
Type
Articles
Information
Journal of Materials Research , Volume 20 , Issue 7 , July 2005 , pp. 1888 - 1901
Copyright
Copyright © Materials Research Society 2005

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