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High Temperature Deformation of Single Crystals of NiAl

Published online by Cambridge University Press:  01 January 1992

Keith R. Forbes ,
Uwe Glatzel ,
R. Darolia  and
William D. Nix
Keith R. Forbes
Affiliation:
Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305.
Uwe Glatzel
Affiliation:
Institut fur Metallforschung, BH18, Technische Universität Berlin, 1000 Berlin 12, FRG.
R. Darolia
Affiliation:
Engineering Materials Technology Laboratories, GE Aircraft Engines, 1 Newman Way, Cincinnati, OH 45215.
William D. Nix
Affiliation:
Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305.
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Abstract

The high temperature deformation properties of single crystals of stoichiometric NiAl have been studied in tension creep and in constant strain rate compression at temperatures between 850 and 1200°C. Samples were tested in a “soft”, [223], orientation and the “hard”, [001], orientation. The samples exhibit a strong orientation dependence of the strength and show other revealing deformation characteristics. The activation energy for steady state flow in both hard and soft orientations is near that for lattice self diffusion. Soft oriented crystals reach steady state rapidly and develop little dislocation substructure. Deformation of these soft oriented crystals occurs by the glide of b=<001> dislocations.

The creep curves of hard oriented crystals show pronounced sigmoidal creep, suggesting that the dislocations move in a sluggish manner, multiply in the early stages of creep and, ultimately, lead to strain hardening. Hard oriented crystals also develop extensive dislocation substructure during creep. This dislocation substructure is composed of b=<100> dislocations, which have no resolved shear stress for glide. Evidence for {101}<101> glide in hard oriented crystals is presented and a model is developed by which the decomposition of gliding b=<101> dislocations can produce the observed b=<100> dislocation networks. The increased creep resistance of hard oriented crystals compared to soft oriented crystals is described in terms of the differences in dislocation mobility and substructure formation for deformation in these directions.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 288: Symposium L – High-Temperature Ordered Intermetallic Alloys V , 1992 , 45
Copyright
Copyright © Materials Research Society 1995

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