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TEM Characterization of Planar Defects in A Massively Transformed TiAl Alloy

Published online by Cambridge University Press:  15 February 2011

X. D. Zhang ,
J. M. K. Wiezorek ,
M. J. Kaufman ,
M. H. Loretto  and
H. L. Fraser
X. D. Zhang
Affiliation:
Department of materials Science and Engineering, The Ohio State University, 2041 College Road, Columbus, Ohio 43210
J. M. K. Wiezorek
Affiliation:
Department of materials Science and Engineering, The Ohio State University, 2041 College Road, Columbus, Ohio 43210
M. J. Kaufman
Affiliation:
Department of Materials Science and Engineering, University of Florida, Gainesville, FL
M. H. Loretto
Affiliation:
IRC in Materials, The University of Birmingham, B15 2TT, UK
H. L. Fraser
Affiliation:
Department of materials Science and Engineering, The Ohio State University, 2041 College Road, Columbus, Ohio 43210
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Abstract

The microstructure of a massively transformed Ti-49at.%Al alloy has been studied by conventional transmission electron microscopy (CTEM) and high resolution TEM (HREM). A high density of planar defects, namely complex anti-phase domain boundaries (CAPDB) and thermal micro-twins (TMT) have been observed. CTEM images and diffraction patterns showed that two anti-phase related γ-matrix domains were generally separated by a thin layer of a 90°-domain, for which the c-axis is rotated 90° over a common cube axis with respect to those of the γ-matrix domains. HREM confirmed the presence of two crystallographically different types of 90°-do-mains being associated with the CAPDB. Furthermore, interactions between the CAPDB and TMT have been observed. Local faceting of the generally wavy, non-crystallographic CAPDB parallel to the {111}-twinning planes occurred due to interaction with the TMT. The relaxation of the CAPDB onto {111} required diffusion which is proposed to be enhanced locally in the presence of the dislocations associated with the formation of TMT during the massive transformation.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 460: Symposium Z – High-Temperature Ordered Intermetallic Alloys VII , 1996 , 213
Copyright
Copyright © Materials Research Society 1997

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References

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