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Preparation, Deformation and Fracture of Stoichiometric NiAl Single Crystals

Published online by Cambridge University Press:  15 February 2011

W. Löser ,
A. Köthe ,
G. Vaerst  and
A. Güth
W. Löser
Affiliation:
Institut für Festkörper und Werkstofforschung Dresden, Institut für Metallische Werkstoffe, P.O. Box 27 0016, D-01171 Dresden, F.R., Germany
A. Köthe
Affiliation:
Institut für Festkörper und Werkstofforschung Dresden, Institut für Metallische Werkstoffe, P.O. Box 27 0016, D-01171 Dresden, F.R., Germany
G. Vaerst
Affiliation:
Institut für Festkörper und Werkstofforschung Dresden, Institut für Metallische Werkstoffe, P.O. Box 27 0016, D-01171 Dresden, F.R., Germany
A. Güth
Affiliation:
Institut für Festkörper und Werkstofforschung Dresden, Institut für Metallische Werkstoffe, P.O. Box 27 0016, D-01171 Dresden, F.R., Germany
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Abstract

A modified Bridgman method involving vacuum treatment prior to the growth process was developed for preparation of high-accuracy stoichiometric NiAl crystals. Single crystals with stoichiometry deviations < 0.2 wt.% Ni characterized by residual resistance ratios R298K/R4.2K > 4 have been prepared. An improved gravimetric analysis ensured the best accuracy among the various wet chemical analysis methods tested and a total error less than 0.1 at.% for Ni determination in NiAl. The stoichiometric NiAl single crystals exhibit high compressive strain in <123> crystallographic axis of the order of 20 % in the as-grown state and 40 % after annealing 1 h at 1073 K. The critical resolved shear stress was reduced from 104 MPa to 45 MPa by annealing. In 3-point bend tests tensile strains to failure up to 10 % have been achieved. Microscopic oxide inclusions near the sample surface were identified as the cause of crack initiation in bent samples.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 460: Symposium Z – High-Temperature Ordered Intermetallic Alloys VII , 1996 , 407
Copyright
Copyright © Materials Research Society 1997

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References

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