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Crystallography and Phase Transitions in the Ta-Ru and Nb-Ru Shape Memory Alloys

Published online by Cambridge University Press:  02 July 2020

R. W. Fonda  and
R. A. Vandermeer
R. W. Fonda
Affiliation:
Naval Research Laboratory, Code 6324, Washington, DC, 20375
R. A. Vandermeer
Affiliation:
Naval Research Laboratory, Code 6324, Washington, DC, 20375
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Extract

A new class of shape memory alloys, based on near-equiatomic compositions of Ta-Ru and Nb-Ru, was recently discovered at the Naval Research Laboratory. These alloys exhibit transformation temperatures ranging up to 1400 °C for Ta-Ru and 1100 °C for Nb-Ru, making them the highest transition temperature shape memory alloys yet discovered. Other shape memory alloys typically have transition temperatures within a couple hundred degrees of room temperature. These two alloy systems are quite similar in their transformation behavior. Near the equiatomic composition, the high temperature β phase of both systems has a B2-ordered cubic crystal structure. During cooling, the cubic lattice of β undergoes a slight tetragonal distortion to form the β' phase. Continued cooling of the tetragonal β'(within specific composition ranges) causes a transformation to β'', which is reported to have an orthorhombic crystal structure. The effect of alloy composition on the temperatures, hysteresis, and strains of these transformations was determined by dilatometry.

Type
Phase Transformations in Metals and Alloys
Information
Microscopy and Microanalysis , Volume 3 , Issue S2: Proceedings: Microscopy & Microanalysis '97, Microscopy Society of America 55th Annual Meeting, Microbeam Analysis Society 31st Annual Meeting, Histochemical Society 48th Annual Meeting, Cleveland, Ohio, August 10-14, 1997 , August 1997 , pp. 711 - 712
Copyright
Copyright © Microscopy Society of America 1997

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References

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