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Short-Range to Long-Range Ordering Reactions in a Ni-25Mo-8Cr Alloy

Published online by Cambridge University Press:  26 February 2011

Mukul Kumar  and
Vijay K. Vasudevan
Mukul Kumar
Affiliation:
Department of Materials Science and Engineering, University of Cincinnati, Cincinnati, OH 45221
Vijay K. Vasudevan
Affiliation:
Department of Materials Science and Engineering, University of Cincinnati, Cincinnati, OH 45221
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Abstract

The transformation from short-range↔long-range order in Haynes® Alloy 242, a nominal Ni-25Mo-8Cr (in wt.%) alloy, during both continuous heating and cooling and isothermal holding at temperatures between 550 and 750°C is reported using dilatometry and microhardness measurements, and optical and transmission electron microscopy The long-range to short-range order transformation temperature was observed to increase with an increase in the degree of prior order. Aging below the transformation temperature led to considerable hardening; this hardening was associated with the formation of a very high volume fraction of Ni2Mo domains/precipitates. On aging at 700°C and below, the hardness initially increases and then levels off, with no evidence of overaging for times to 2000 hours. The role of both short- and long-range order on the transformation temperature, thermal expansion and hardening behavior and the mechanisms of transformation from short-range to long-range order were established and will be discussed.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 213: Symposium Q – High-Temperature Ordered Intermetallic Alloys IV , 1990 , 187
Copyright
Copyright © Materials Research Society 1991

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References

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