Neutron diffraction study of shape memory effect of Ni2MnGa-type alloys

Kazuko Inoue, Yasuo Yamaguchi, Yukio Noda, Kenji Ohoyama, Hiroyuki Kimura, Kazuyuki Enami

Research output: Contribution to journalConference articlepeer-review

5 Citations (Scopus)

Abstract

We synthesized the off-stoichiometric Heusler-type alloys, Ni2.18Mn0.82Ga and Ni2.19Mn0.81Ga, which have a thermo-elastic martensitic transformation temperature coincident with a Curie temperature, 340K and 350K, respectively. The single crystal of this alloy shows a shape memory effect. From the Rietveld analysis of powder neutron diffraction experiments, we found that the martensitic phase of the alloys consists of two crystal structures. One is an orthorhombic structure and the other is a tetragonal structure, both of them are distorted from a cubic Heusler structure. Each structure is constructed from a shuffling of the each other structure. The shape memory effect of a single crystal occurred when the mass fractions of martensitic phase and the mother phase become fifty-fifty. By the neutron diffraction of a single crystal, we were able to determine the direction of the crystal growth and to observe the structure change accompanied to the martensitic transformation. From the powder neutron diffraction under the magnetic field, we confirmed that the external magnetic field causes the transformation from paramagnetic mother phase to ferromagnetic martensitic phase. To control the shape memory effect by external magnetic field becomes realistic.

Original languageEnglish
Pages (from-to)2261-2266
Number of pages6
JournalMaterials Science Forum
Volume426-432
Issue number3
Publication statusPublished - 2003 Jan 1
EventThermec 2003 Processing and Manufacturing of Advanced Materials - Madrid, Spain
Duration: 2003 Jul 72003 Jul 11

Keywords

  • Controlling the shape memory effect by external magnetic field
  • Heusler-type NIMnGa alloys
  • Martensltic transformation
  • Neutron Diffraction
  • Shape memory effect

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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