Zig-zag twins and helical phase transformations

Yaniv Ganor, Traian DumitricǍ, Fan Feng, Richard D. James

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

We demonstrate the large bending deformation induced by an array of permanent magnets (applied field ∼0.02 T) designed to minimize poles in the bent state of the crystal. Planar cantilevers of NiMnGa (5M modulated martensite) ferromagnetic shape memory alloy deform into an arched shape according to theory, with a zig-zag microstructure that complies with the kinematic and magnetic compatibility between adjacent twin variants. A general theory of bent and twisted states is given, applicable to both twinning and austenite/martensite transformations. Some of these configurations achieve order-of-magnitude amplification of rotation and axial strain. We investigate also atomistic analogues of these bent and twisted configurations with perfect interfaces between phases. These mechanisms of large deformation, induced by small magnetic fields or temperature changes, have potential application to the development of new actuation technologies for micro-robotic systems.

Original languageEnglish (US)
Article number20150208
JournalPhilosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
Volume374
Issue number2066
DOIs
StatePublished - Apr 28 2016

Bibliographical note

Funding Information:
R.D.J. and F.F. were supported by AFOSR (FA9550-15-1-0207), ONR (N00014-14-0714), NSF/PIRE (OISE-0967140) and the MURI Program (FA9550-12-1-0458). T.D. was supported by the NSF (CMMI-1332228).

Publisher Copyright:
© 2016 The Author(s) Published by the Royal Society. All rights reserved.

Copyright:
Copyright 2017 Elsevier B.V., All rights reserved.

Keywords

  • Bending
  • Continuum mechanics
  • Ferromagnetic shape memory
  • Martensitic phase transformation
  • Nimnga

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