Effect of the precipitates on the thermodynamics of the martensitic transformations in Ti-rich Ni-Ti-Co thin films
| Autor: | L.M. Isola, Jorge Alberto Malarria, M.F. Giordana, B.F. Malvasio |
|---|---|
| Rok vydání: | 2020 |
| Předmět: |
Materials science
Annealing (metallurgy) Mechanical Engineering Metals and Alloys Elastic energy Thermodynamics 02 engineering and technology Shape-memory alloy 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences 0104 chemical sciences Amorphous solid Condensed Matter::Materials Science Differential scanning calorimetry Thermoelastic damping Mechanics of Materials Electrical resistivity and conductivity Martensite Materials Chemistry 0210 nano-technology |
| Zdroj: | Journal of Alloys and Compounds. 818:152904 |
| ISSN: | 0925-8388 |
| DOI: | 10.1016/j.jallcom.2019.152904 |
| Popis: | The wide-spread multiple transformation in T i -rich N i - T i shape memory alloys produced by T i 2 N i nano-precipitates was investigated. For this purpose, a series of amorphous T i - N i - C o thin films with the same composition were subjected to different annealing treatments. The characteristic temperatures and heat of the transformations were measured by four-point probe resistivity and differential scanning calorimetry. A critical review of the thermodynamics of thermally-induced thermoelastic martensitic transformations is presented. The values of the frictional work and the stored elastic energy associated with the thermoelastic transformations were assessed from the transformation temperatures, and related with the transformation heats measured in the samples annealed at different temperatures. It was observed that the stored elastic energy decreases as the annealing temperature rises due to a change in the distribution of the T i 2 N i precipitates, in concordance with an increase of the transformation heat measured by the calorimeter. Nevertheless, the values of the frictional work were independent of the annealing temperature. The influence of the dissipation of the stored elastic energy on the transformation temperatures and thermal hysteresis is discussed. Finally, a better understanding of the wide-spread multiple transformation, as an effect of the local stresses introduced by T i 2 N i nano-precipitates in the matrix, is proposed. |
| Databáze: | OpenAIRE |
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