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Measurement of Twinning Elements in PST TiAl Single Crystal

Published online by Cambridge University Press:  15 February 2011

Lei Lu  and
David P. Pope
Lei Lu
Affiliation:
Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104
David P. Pope
Affiliation:
Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104
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Abstract

Twinning is the major deformation mode at room temperature in TiAl polysynthetically twinned (PST) crystals (lamellar structure, TiAl is the major phase and Ti3Al is the minor phase). We present here the results of Atomic Force Microscope (AFM) observations of deformation twinning displacements measured on the free surfaces of PST single crystals. AFM is used in this experiment because of its very high resolution for topological measurements and its ability to measure surface displacements from very small twins.

Measurements were made on samples with different compression axes and surface orientations. When a twin intersects a free surface, a definite displacement is produced which is easily related to the twinning elements. The majority of the surface offsets observed correspond to those for ordinary twinning, within a very small deviation. Thus it is concluded that these are ordinary twins. The widths of the twinning bands are around 300nm, smaller than the widths of the TiAl lamellae. Slip bands are also observed. They are characterized by a much more irregular geometry than the twinning bands. At some places where twins intersect a domain boundary slip bands are produced in the adjacent domain.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 460: Symposium Z – High-Temperature Ordered Intermetallic Alloys VII , 1996 , 249
Copyright
Copyright © Materials Research Society 1997

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References

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