Inter-martensite strain evolution in NiMnGa single crystals

R. F. Hamilton, H. Sehitoglu, K. Aslantas, C. Efstathiou, H. J. Maier

Research output: Contribution to journalArticlepeer-review


Stress-induced martensitic transformations are clarified in classes of NiMnGa alloys which undergo the stress-free, thermal-induced inter-martensite transformation austenite (A) ⇌ pre-martensite (PM) ⇌ martensite. This study implements a comprehensive experimental approach, including analysis of the strain-temperature and stress-strain response, which discloses stress-induced inter-martensite transitions. The evolution of the transitions is elucidated using in situ digital image correlation (DIC) measurements of meso-scale strain fields. Under stress, this body of work unequivocally demonstrates that the transformation path becomes A ⇌ PM ⇌ I ⇌ 10M. The I-phase is an intermediate stress-induced martensite with a modulation period between three and five-layers. Owing to the intermediate transition, the thermal hysteresis in the strain-temperature response is tiny (<10 °C) compared with the hysteresis (32 °C) for A ⇌ 10M. The differential hysteresis levels are rationalized based on a thermo-mechanical formulation. Meso-scale DIC measurements quantify inter-martensite strain levels, which are indistinguishable from macro-scale stress-strain and strain-temperature responses.

Original languageEnglish (US)
Pages (from-to)2231-2236
Number of pages6
JournalActa Materialia
Issue number10
StatePublished - Jun 2008


  • Compression test
  • Digital image correlation
  • Metastable phases
  • Strain vs. temperature
  • Thermal hysteresis

ASJC Scopus subject areas

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


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