On the stress-induced formation of R-phase in ultra-fine-grained Ni-Rich NiTi shape memory alloys
- 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 thePhase 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.…
Autor*innen: | Jürgen Olbricht, A. Yawny, J.L. Pelegrina, A. Dlouhy, G. Eggeler |
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Dokumenttyp: | Zeitschriftenartikel |
Veröffentlichungsform: | Verlagsliteratur |
Sprache: | Englisch |
Titel des übergeordneten Werkes (Englisch): | Metallurgical and materials transactions A |
Jahr der Erstveröffentlichung: | 2011 |
Verlag: | The Minerals, Metals and Materials Society |
Verlagsort: | Warrendale |
Jahrgang/Band: | 42A |
Ausgabe/Heft: | 9 |
Erste Seite: | 2556 |
Letzte Seite: | 2574 |
Freie Schlagwörter: | NiTi; Phase transformation; Pseudoelasticity; R-phase; Shape memory |
DOI: | 10.1007/s11661-011-0679-y |
ISSN: | 1073-5623 |
ISSN: | 1543-1940 |
Verfügbarkeit des Dokuments: | Datei im Netzwerk der BAM verfügbar ("Closed Access") |
Datum der Freischaltung: | 19.02.2016 |
Referierte Publikation: | Ja |
Datum der Eintragung als referierte Publikation: | 08.12.2011 |