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Identification of Cleavage Planes in an Al3Ti-Base Alloy by Electron Channeling in the SEM

Published online by Cambridge University Press:  26 February 2011

E. P. George ,
W. D. Porter  and
D. C. Joy
E. P. George
Affiliation:
Metals and Ceramics Division, Oak Ridge National Laboratory, P. O. Box 2008, Oak Ridge, TN 37831-6093
W. D. Porter
Affiliation:
Metals and Ceramics Division, Oak Ridge National Laboratory, P. O. Box 2008, Oak Ridge, TN 37831-6093
D. C. Joy
Affiliation:
Metals and Ceramics Division, Oak Ridge National Laboratory, P. O. Box 2008, Oak Ridge, TN 37831-6093
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Abstract

Selected area electron channeling patterns were used to identify the cleavage planes in a polycrystalline Al3Ti-base alloy having the L12 structure. In order to do this unambiguously in the scanning electron microscope (SEM), one needs to know that the cleavage facet from which any given channeling pattern is obtained is indeed normal to the electron beam. We accomplished this by utilizing a recently-developed technique in which an optical microscope with a short depth of focus is inserted in the SEM column and used to measure the elevations of several points on the cleavage facets. By appropriately tilting and rotating the sample, and using the optical microscope to measure elevations, it was possible to orient the facets normal to the beam. The cleavage planes in a cast and extruded alloy having an equiaxed grain structure were compared with those in a directionally-solidified (DS) alloy of the same composition. Of the eight cleavage facets examined in the DS material, six were of the {110} type and two were of the {111} type. Of the six facets examined in the cast and extruded material, two each were of the {110} and {111} types, and one each were of the {100} and {013} types. Although it cannot be said that all possible cleavage planes have been identified in this alloy, the availability of several low-strength cleavage planes apparently exacerbates its brittleness.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 133: Symposium H – High-Temperature Ordered Intermetallic Alloys III , 1988 , 311
Copyright
Copyright © Materials Research Society 1989

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References

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