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The Disordering Phase Transformation in (Ni70Fe30)3(V98-xAlxTi2) Alloys with 0 < × < 80*

Published online by Cambridge University Press:  21 February 2011

A. Dasgupta  and
J. A. Horton
A. Dasgupta
Affiliation:
Metals and Ceramics Division, Oak Ridge National Laboratory, P.O. Box X, Oak Ridge, TN 37831
J. A. Horton
Affiliation:
Metals and Ceramics Division, Oak Ridge National Laboratory, P.O. Box X, Oak Ridge, TN 37831
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Abstract

The sequence of disordering transformation processes in the A3B type alloy series (Ni70Fe30)3(V98-xAlxTi2), currently under development for high-temperature structural applications, was studied by differential scanning calorimetry (DSC), x-ray diffraction, optical microscopy, and transmission electron microscopy (TEM). Results of DSC show that in all alloys there are two endothermic stages of phase transformation from the ordered to the disordered state. With increasing x, the disordering transition temperature, Tc, reaches a maximum ∼1000°C at x ≈ 50, and then decreases. Interrupted heating, followed by water quenching, was used to characterize the crystal structure and the microstructure of the intermediate phases. For the x + 20 alloy, TEM observations showed ordered regions of DO22 phase in a matrix of disordered fcc (Al) phase at intermediate temperatures. The ordered domains transformed morphologically into cuboid like regions at higher temperatures. From a combined study by all the techniques, we conclude that in alloys with x between 0 and 20, the sequence of phase transformations upon heating is: DO22 → DO22 + Al → Al, whereas in alloys with x > 40, the major sequence is Ll2 + B2 → Ll2 + Al → Al.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 39: Symposium G – High-Temperature Ordered Intermetallic Alloys I , 1984 , 117
Copyright
Copyright © Materials Research Society 1985

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Footnotes

*

Research sponsored by the Office of Energy Systems Research, Division of Energy Conservation and Utilization Technologies (ECUT), U.S. Department of Energy Under Contract DE-ACO5-840R21400 with the Martin Marietta Energy Systems, Inc.

References

REFERENCES

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