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Comparison of the Creep Properties of Cast and Powder Metallurgy-Extruded Binary NiAl

Published online by Cambridge University Press:  15 February 2011

S. V. Raj ,
Anita Garg  and
Thomas R. Bieter
S. V. Raj
Affiliation:
NASA Lewis Research Center, MS 24–1,21000 Brookpark Road, Cleveland, OH 44135.
Anita Garg
Affiliation:
AYT Corp., NASA Lewis Research Center, MS 77–5, 21000 Brookpark Road, Cleveland, OH 44135.
Thomas R. Bieter
Affiliation:
Department of Materials Science and Mechanics, Michigan State University, East Lansing, Ml 48824–1226.
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Abstract

A comparison of published creep data on binary NiAl showed that there is a discrepancy in the reported magnitudes of the stress exponents, n, which usually vary between about 4.5 and 6.5. In general, a close examination of the data suggested that n ≈ 4.5 for cast materials arid 6.5 for powder-metallurgy extruded NiAl. Constant load compression creep tests were conducted on a cast and extruded binary NiAl between 800 and 1200 K over a wide range of initial applied stresses varying between 4.0 and 200 MPa. The microstructures were characterized by transmission electron microscopy. The observed variations in the creep behavior of the extruded cast and powder-metallurgy NiAl appeared to be due to a grain size effect. Despite similarities in the values of n, no significant substructure was observed in most of the grains in the cast and extruded specimens at 1100 and 1200 K in contrast to the PM-extruded alloy, which revealed a wide range of substructural features in the power-law creep region. However, extensive subgrain formation and dislocations were widely observed at lower temperatures and higher stresses in the cast and extruded material.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 460: Symposium Z – High-Temperature Ordered Intermetallic Alloys VII , 1996 , 473
Copyright
Copyright © Materials Research Society 1997

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References

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