Martensitic phase transformations in nanocrystalline NiTi studied by TEM

Thomas Waitz; Vil U. Kazykhanov; Hans-Peter Karnthaler

doi:10.1016/j.actamat.2003.08.036

Martensitic phase transformations in nanocrystalline NiTi studied by TEM

Thomas Waitz, Vil U. Kazykhanov, Hans-Peter Karnthaler

Publications: Contribution to journal › Article › Peer Reviewed

Abstract

By high pressure torsion (HPT) deformation almost complete amorphization is obtained in bulk Ni-50.3at.%Ti containing B19? martensite. During low temperature annealing tiny crystallites retained after the HPT deformation are acting as nuclei and trigger the nanocrystallization of B2 austenite. It is shown that the density of the nuclei is a function of the HPT strain and determines together with the annealing temperature the grain size of the nanocrystals ranging from 5 to 350 nm. Upon cooling the nanostructures transform to B19? partially since the grain boundaries hinder the autocatalytic formation of martensite. The large transformation strains of B19? are reduced by very fine (001) compound twins. With decreasing grain size an increasing energy barrier arises and the martensitic transformation is completely suppressed in grains smaller than 60 nm. The R-phase transformation causing only small transformation strains is observed in grains between 15 and 60 nm. Whereas in grains below 15 nm B2 remains indicating that no transformation occurs at all. Œ 2003 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Original language	English
Pages (from-to)	137-147
Number of pages	11
Journal	Acta Materialia
Volume	52
Issue number	1
DOIs	https://doi.org/10.1016/j.actamat.2003.08.036
Publication status	Published - 2004

Austrian Fields of Science 2012

1030 Physics, Astronomy

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10.1016/j.actamat.2003.08.036

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title = "Martensitic phase transformations in nanocrystalline NiTi studied by TEM",

abstract = "By high pressure torsion (HPT) deformation almost complete amorphization is obtained in bulk Ni-50.3at.%Ti containing B19? martensite. During low temperature annealing tiny crystallites retained after the HPT deformation are acting as nuclei and trigger the nanocrystallization of B2 austenite. It is shown that the density of the nuclei is a function of the HPT strain and determines together with the annealing temperature the grain size of the nanocrystals ranging from 5 to 350 nm. Upon cooling the nanostructures transform to B19? partially since the grain boundaries hinder the autocatalytic formation of martensite. The large transformation strains of B19? are reduced by very fine (001) compound twins. With decreasing grain size an increasing energy barrier arises and the martensitic transformation is completely suppressed in grains smaller than 60 nm. The R-phase transformation causing only small transformation strains is observed in grains between 15 and 60 nm. Whereas in grains below 15 nm B2 remains indicating that no transformation occurs at all. {\OE} 2003 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.",

author = "Thomas Waitz and Kazykhanov, {Vil U.} and Hans-Peter Karnthaler",

note = "Zeitschrift: Acta Materialia DOI: 10.1016/j.actamat.2003.08.036 Affiliations: Institute of Materials Physics, University of Vienna, Boltzmanngasse 5, A-1090 Vienna, Austria; Institute of Advanced Materials, Ufa Stt. Aviat. Technical University, 12 K. Marksa Street, 450000 Ufa, Russian Federation Adressen: Waitz, T.; Institute of Materials Physics; University of Vienna; Boltzmanngasse 5 A-1090 Vienna, Austria; email: [email protected] Import aus Scopus: 2-s2.0-0344874707 04.12.2007: Datenanforderung 2001 (Import Sachbearbeiter)",

year = "2004",

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volume = "52",

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T1 - Martensitic phase transformations in nanocrystalline NiTi studied by TEM

AU - Waitz, Thomas

AU - Kazykhanov, Vil U.

AU - Karnthaler, Hans-Peter

N1 - Zeitschrift: Acta Materialia DOI: 10.1016/j.actamat.2003.08.036 Affiliations: Institute of Materials Physics, University of Vienna, Boltzmanngasse 5, A-1090 Vienna, Austria; Institute of Advanced Materials, Ufa Stt. Aviat. Technical University, 12 K. Marksa Street, 450000 Ufa, Russian Federation Adressen: Waitz, T.; Institute of Materials Physics; University of Vienna; Boltzmanngasse 5 A-1090 Vienna, Austria; email: [email protected] Import aus Scopus: 2-s2.0-0344874707 04.12.2007: Datenanforderung 2001 (Import Sachbearbeiter)

PY - 2004

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N2 - By high pressure torsion (HPT) deformation almost complete amorphization is obtained in bulk Ni-50.3at.%Ti containing B19? martensite. During low temperature annealing tiny crystallites retained after the HPT deformation are acting as nuclei and trigger the nanocrystallization of B2 austenite. It is shown that the density of the nuclei is a function of the HPT strain and determines together with the annealing temperature the grain size of the nanocrystals ranging from 5 to 350 nm. Upon cooling the nanostructures transform to B19? partially since the grain boundaries hinder the autocatalytic formation of martensite. The large transformation strains of B19? are reduced by very fine (001) compound twins. With decreasing grain size an increasing energy barrier arises and the martensitic transformation is completely suppressed in grains smaller than 60 nm. The R-phase transformation causing only small transformation strains is observed in grains between 15 and 60 nm. Whereas in grains below 15 nm B2 remains indicating that no transformation occurs at all. Œ 2003 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

AB - By high pressure torsion (HPT) deformation almost complete amorphization is obtained in bulk Ni-50.3at.%Ti containing B19? martensite. During low temperature annealing tiny crystallites retained after the HPT deformation are acting as nuclei and trigger the nanocrystallization of B2 austenite. It is shown that the density of the nuclei is a function of the HPT strain and determines together with the annealing temperature the grain size of the nanocrystals ranging from 5 to 350 nm. Upon cooling the nanostructures transform to B19? partially since the grain boundaries hinder the autocatalytic formation of martensite. The large transformation strains of B19? are reduced by very fine (001) compound twins. With decreasing grain size an increasing energy barrier arises and the martensitic transformation is completely suppressed in grains smaller than 60 nm. The R-phase transformation causing only small transformation strains is observed in grains between 15 and 60 nm. Whereas in grains below 15 nm B2 remains indicating that no transformation occurs at all. Œ 2003 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

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DO - 10.1016/j.actamat.2003.08.036

M3 - Article

SN - 1359-6454

VL - 52

SP - 137

EP - 147

JO - Acta Materialia

JF - Acta Materialia

IS - 1

ER -

Martensitic phase transformations in nanocrystalline NiTi studied by TEM

Abstract

Austrian Fields of Science 2012

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