ICAMS / Interdisciplinary Centre for Advanced Materials Simulation

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On the Oxidation behavior and Its Influence on the martensitic transformation of Ti-Ta high temperature shape memory alloys

D. Langenkämper, A. Paulsen, C. Somsen, J. Frenzel, G. Eggeler.

Shape Memory and Superelasticity, 5, 63-72, (2019)

Abstract
In the present work, the influence of oxidation on the martensitic transformation in Ti–Ta high-temperature shape memory alloys is investigated. Thermogravimetric analysis in combination with microstructural investigations by scanning electron microscopy and transmission electron microscopy were performed after oxidation at 850 °C and at temperatures in the application regime of 450 °C and 330 °C for 100 h, respectively. At 850 °C, internal oxidation results in the formation of a mixed layered scale of TiO2 and β-Ta2O5, associated with decomposition into Ta-rich bcc β-phase and Ti-rich hexagonal α-phase in the alloy. This leads to a suppression of the martensitic phase transformation. In addition, energy dispersive X-ray analysis suggests an oxygen stabilization of the α-phase. At 450 °C, a slow decomposition into Ta-rich β-phase and Ti-rich α-phase is observed. After oxidation at 330 °C, the austenitic matrix shows strong precipitation of the ω-phase that suppresses the martensitic transformation on cooling.


Keyword(s): HTSMA; Ti–Ta; oxidation; TEM; martensite; austenite
Cite as: https://link.springer.com/article/10.1007%2Fs40830-018-00206-1
DOI: 10.1007/s40830-018-00206-1
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