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  Structural superplasticity in a fine-grained eutectic intermetallic NiAl-Cr alloy

Frommeyer, G., Kowalski, W., & Rablbauer, R. (2007). Structural superplasticity in a fine-grained eutectic intermetallic NiAl-Cr alloy. Metallurgical and Materials Transactions A, 37A, 3511-3517.

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Item Permalink: http://hdl.handle.net/11858/00-001M-0000-0019-5590-3 Version Permalink: http://hdl.handle.net/11858/00-001M-0000-0019-5592-0
Genre: Journal Article

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 Creators:
Frommeyer, G.1, Author              
Kowalski, W., Author
Rablbauer, R.2, Author              
Affiliations:
1Materials Technology, Max-Planck-Institut für Eisenforschung GmbH, Max Planck Society, ou_1863367              
2Innovative Steel Research, Materials Technology, Max-Planck-Institut für Eisenforschung GmbH, Max Planck Society, ou_1863369              

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 Abstract: A rapidly solidified and thermomechanically processed fine-grained eutectic NiAl-Cr alloy of the composition Ni33Al33Cr34 (at %) exhibits structural superplasticity in the temperature regime from 900 °C to 1000 °C at strain rates ranging from 10-5 to 10-3 s-1. The material consists of a B2-ordered intermetallic NiAl(Cr) solid solution matrix containing a fine dispersion of bcc chromium. A high strain-rate-sensitivity exponent of m = 0.55 was achieved in strain-rate-change tests at strain rates of about 10-4 s-1. Maximum uniform elongations up to 350 % engineering strain were recorded in superplastic strain to failure tests. Activation energy analysis of superplastic flow was performed in order to establish the diffusion-controlled dislocation accommodation process of grain boundary sliding. An activation energy of Qc = 288 ± 15 kJ/mole was determined. This value is comparable with the activation energy of 290 kJ/mole for lattice diffusion of nickel and for 63Ni tracer self-diffusion in B2-ordered NiAl. The principal deformation mechanism of superplastic flow in this material is grain-boundary sliding accommodated by dislocation climb controlled by lattice diffusion, which is typical for class II solid-solution alloys. Failure in superplastically strained tensile samples of the fine-grained eutectic alloy occurred by cavitation formations along NiAl || Cr interfaces.

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Language(s): eng - English
 Dates: 2007
 Publication Status: Published in print
 Pages: -
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 Rev. Method: Peer
 Identifiers: eDoc: 334359
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Title: Metallurgical and Materials Transactions A
  Alternative Title : Metall. Mater. Trans. A
Source Genre: Journal
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Pages: - Volume / Issue: 37A Sequence Number: - Start / End Page: 3511 - 3517 Identifier: -