Inter-martensitic transitions in Ni-Fe-Ga single crystals

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

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Abstract

The strain-temperature response of Ni-Fe-Ga single crystals underscores the role of the inter-martensitic transformation in creating intersecting heating and cooling segments; the separation of these segments occurs due to irreversibilities at high stresses and at high temperatures. An ultra-narrow tensile (1 °C) and compressive (<10 °C) thermal hysteresis are observed for the A ⇌ 10M ⇌ 14M case, accompanied by a small stress hysteresis (<30 MPa) in compressive and tensile stress-strain responses. The hysteresis levels increase and the intersecting segments disappear at high stresses and at high temperatures. This paper reports the use of a thermo-mechanical formulation to rationalize the role of inter-martensitic transformations. Plotting the transformation stress as a function of temperature indicates that inter-martensitic transformations enable a very wide pseudoelastic temperature range, as high as 425 °C. The measured Clausius-Clapeyron curve slope in compression (2.75 MPa °C-1) is eight times the tensile slope (0.36 MPa °C-1); the higher slope is attributed to the predominance of A ⇌ L10 at high temperatures.

Original languageEnglish (US)
Pages (from-to)4867-4876
Number of pages10
JournalActa Materialia
Volume55
Issue number14
DOIs
Publication statusPublished - Aug 1 2007

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All Science Journal Classification (ASJC) codes

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

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