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Does A Threshold Stress For Creep Exist in Hfc-Dispersed Nial?

Published online by Cambridge University Press:  26 February 2011

J. Daniel Whittenberger ,
Ranjan Ray  and
Sunil C. Jha
J. Daniel Whittenberger
Affiliation:
NASA Lewis Research Center, Cleveland, OH 44135
Ranjan Ray
Affiliation:
Marko Materials, Inc. N. Billerica, MA 01862
Sunil C. Jha
Affiliation:
Texas Instruments, Attleboro, MA, 02703
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Abstract

Recently it was proposed [S.C. Jha, et al., Mater. Sci. & Eng. A119 (1989) 103 & J.D. Whittenberger, et al., J. Mat. Sci. 25, (1990) 2771] on the basis of constant velocity testing at 1300 K that dispersion strengthened NiAl composites containing about 4 wt pct HfC possess threshold stresses for creep. Further 1300 K compression testing has been conducted on NiAl+4HfC,and diametrically opposite behavior has been found: for constant load creep tests normal power law behavior was observed (strain rate proportional to the stress raised to the power n); however additional constant velocity testing still indicates that the flow stress is essentially independent of strain rate below 10−6 s−1. Examination of NiAl+4.3HfC specimens after being deformed under constant velocity conditions revealed that the original hot extruded small grain structure could be converted to large, elongated grains during testing. Such a transformation appears to be responsible for the apparent threshold stress behavior in HfC dispersed NiAl.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 213: Symposium Q – High-Temperature Ordered Intermetallic Alloys IV , 1990 , 581
Copyright
Copyright © Materials Research Society 1991

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References

REFERENCES

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