High strength NiTiHf shape memory alloys with tailorable properties

S. M. Saghaian, H. E. Karaca, H. Tobe, A. S. Turabi, S. Saedi, S. E. Saghaian, Y. I. Chumlyakov, R. D. Noebe

Research output: Contribution to journalArticlepeer-review

79 Scopus citations


Microstructure of NiTiHf shape memory alloys can be engineered to have high strength and operate at high stress levels for a large temperature window. Nanoprecipitation is well-known method to improve the strength of materials but it can be employed to NiTiHf alloys to substantially alter their phase transformation characteristics (martensite morphology, transformation strain, hysteresis and stress). The martensitic transformation of Ni-rich Ni51.2Ti28.8Hf20 was severely suppressed in the solution treated condition (900 °C-3h/water quench) and after aging at low temperatures, while the transformation temperatures were greater than 100 °C after 650 °C-3h aging. Generation of nanosize precipitates (∼20 nm in size) after 3 h aging at 450 °C and 550 °C improved the strength of the material, resulting in a near perfect dimensional stability during isobaric thermal cycling at stress levels of greater than 1500 MPa, with work output of 20–30 J cm−3. Superelastic behavior with 4% recoverable strain was demonstrated at low temperatures (−20 to 40 °C) after aging at 450 °C-3h and at elevated temperatures (120–160 °C) after aging at 550 °C-3h, with stresses reaching 2 GPa without the onset of plastic deformation. A clear relationship between thermal treatments, microstructure, mechanical and shape memory properties will be shown.

Original languageEnglish
Pages (from-to)211-220
Number of pages10
JournalActa Materialia
StatePublished - Aug 1 2017

Bibliographical note

Publisher Copyright:
© 2017 Acta Materialia Inc.


  • High strength
  • Martensitic transformation
  • Ni-rich NiTiHf
  • Shape memory alloys

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys


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