B2 ⇒ B19′ ⇒ B2T Martensitic Transformation as a Mechanism of Plastic Deformation of NiTi

  • P. ŠittnerEmail author
  • L. Heller
  • P. Sedlák
  • Y. Chen
  • O. Tyc
  • O. Molnárová
  • L. Kadeřávek
  • H. Seiner


Deformation of superelastic NiTi wire with tailored microstructure was investigated in tensile loading–unloading tests up to the end of the stress plateau in wide temperature range from room temperature up to 200 °C. Lattice defects left in the microstructure of deformed wires were investigated by transmission electron microscopy. Tensile deformation is localized up to the highest test temperatures, even if practically no martensite phase exists in the wire at the end of the stress plateau. In tensile tests at elevated temperatures around 100 °C, at which the upper plateau stress approaches the yield stress for plastic deformation of martensite, upper plateau strains become unusually long, transformation strains become unrecoverable and deformation bands containing {114} austenite twins appear in the microstructure of deformed wires. These observations were rationalized by assuming activity of B2 ⇒ B19′ ⇒ B2T martensitic transformation into the austenite twins representing a new mechanism of plastic deformation of NiTi, additional to the dislocation slip in austenite and/or martensite. It is claimed that this transformation becomes activated in any thermomechanical load in which the oriented B19′ martensite is exposed to high stress at high temperatures, as e.g., during shape setting or actuator cycling at high applied stress.


Materials Stress-induced martensitic transformation Superelasticity Twinning 



Ms. Y. Chen acknowledges the support of her Ph.D. work from Nanjing University of Aeronautics and Astronautics, China as well as from the Functional Materials Department, Institute of Physics of the ASCR, Prague, Czech Republic. Support of the research from Czech Science Foundation (CSF) projects 18-03834S (P. Šittner), 17-00393 J (L. Heller) is acknowledged. MEYS of the Czech Republic is acknowledged for the support of infrastructure projects FUNBIO-SAFMAT (LM2015088), LNSM (LM2015087), SOLID 21 (CZ.02.1.01/0.0/0.0/16_019/0000760) and European Spallation Source—participation of the Czech Republic – OP (CZ.02.1.01/0.0/0.0/16_013/0001794). National Natural Science Foundation of China (No. 11872207) is acknowledged.


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© ASM International 2019

Authors and Affiliations

  • P. Šittner
    • 1
    • 3
    Email author
  • L. Heller
    • 1
    • 3
  • P. Sedlák
    • 1
    • 5
  • Y. Chen
    • 2
  • O. Tyc
    • 3
    • 4
  • O. Molnárová
    • 3
  • L. Kadeřávek
    • 3
    • 4
  • H. Seiner
    • 5
  1. 1.Nuclear Physics Institute of the CASHusinec, ŘežCzech Republic
  2. 2.State Key Laboratory of Mechanics and Control of Mechanical StructuresNanjing University of Aeronautics and AstronauticsNanjingChina
  3. 3.Institute of Physics of the CASPragueCzech Republic
  4. 4.Faculty of Nuclear Sciences and Physical EngineeringCTU PraguePrague 2Czech Republic
  5. 5.Institute of Thermomechanics of the CASPragueCzech Republic

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