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On the Stress-Induced Formation of R-Phase in Ultra-Fine-Grained Ni-Rich NiTi Shape Memory Alloys
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SYSNO ASEP 0376005 Document Type J - Journal Article R&D Document Type Journal Article Subsidiary J Článek ve WOS Title On the Stress-Induced Formation of R-Phase in Ultra-Fine-Grained Ni-Rich NiTi Shape Memory Alloys Author(s) Olbricht, J. (DE)
Yawny, A. (AR)
Pelegrina, J.L. (AR)
Dlouhý, Antonín (UFM-A) RID, ORCIDSource Title Metallurgical and Materials Transactions A. - : Springer - ISSN 1073-5623
42A, č. 9 (2011), s. 2556-2574Number of pages 19 s. Language eng - English Country US - United States Keywords martensitic transformations ; rietveld method ; single-crystals Subject RIV JG - Metallurgy R&D Projects GA106/09/1913 GA ČR - Czech Science Foundation (CSF) CEZ AV0Z20410507 - UFM-A (2005-2011) UT WOS 000292936900006 DOI 10.1007/s11661-011-0679-y Annotation Phase transformations in binary ultra-fine-grained (UFG) pseudoelastic NiTi wires were studied in a wide temperature range using mechanical loading/unloading experiments, resistance measurements, differential scanning calorimetry (DSC), thermal infrared imaging, and transmission electron microscopy (TEM). The formation of R-phase can be detected in the mechanical experiments. It is shown that the stress-strain response of the R-phase can be isolated from the overall stress-strain data. The R-phase always forms prior to B19´ when good pseudoelastic properties are observed. The stress-induced B2 to R-phase transition occurs in a homogeneous manner, contrary to the localized character of the B2/R to B19´ transformations. The temperature dependence of the critical stress values for the formation of the martensitic phases shows a Clausius Clapeyron type of behavior with constants close to 6 MPa/K (B19´) and 18 MPa/K (R-phase). A stress-temperature map is suggested that summarizes the experimentally observed sequences of elementary transformation/deformation processes. Workplace Institute of Physics of Materials Contact Yvonna Šrámková, sramkova@ipm.cz, Tel.: 532 290 485 Year of Publishing 2012
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