Thermally induced martensitic transformation and structural properties in Ni-Ta high-temperature shape memory alloys
Firat University, Department of Physics, 23119, Elazig, Turkey
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Accepted: 16 November 2018
Published online: 9 January 2019
The morphological, structural and martensitic phase transformation properties of the binary Ni-Ta high-temperature shape memory alloys depending on the composition via SEM-EDX, XRD and DSC observations have been investigated. It was found that the different Ta contents did not change the high-temperature shape memory behaviors of alloy samples with completed martensitic transformation above 220° C, but had a dramatic effect on the reverse transformation temperatures () and transformation hysteresis () of alloy samples. As the Ta content of the alloy samples decreased, the temperatures shifted to high-temperatures ( ° C, and the values arose to temperatures above 100° C. However, different Ta contents did not cause considerable changes on the morphological and structural properties of the alloy samples. While a very rare dispersed NiTa2 precipitate phase was observed in the microstructure of the alloy samples with Ta contents above 25 at.%, Ni-rich areas were rarely detected in the microstructure of the alloy sample with Ta content below 25 at.%. In addition, no crack formation was observed in the microstructures of the alloy samples.
© Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature, 2019