Effect of porosity on the magneto-mechanical behavior of polycrystalline magnetic shape-memory Ni-Mn-Ga foams

C. Witherspoon, P. Zheng, M. Chmielus, D. C. Dunand, P. Müllner*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

17 Scopus citations

Abstract

Porosity in polycrystalline Ni-Mn-Ga alloys reduces internal constraints imposed by grain boundaries which suppress magnetic-field-induced strain in non-porous, polycrystalline magnetic shape-memory alloys. We present here a systematic study of the porosity effect on the magneto-mechanical properties of polycrystalline Ni-Mn-Ga foams. Starting from replicated foams created by casting with ceramic space holders, their porosities were increased by successive acid dissolution steps after which the magnetic-field-induced strain was measured, for each porosity level, after thermo-magneto-mechanical training. Consistently, the magnetic-field-induced strain increased with increasing porosity, in the extreme case by one order of magnitude for a small porosity increase of 1.3%, demonstrating that removal of constraints by porosity is responsible for the high magnetic-field-induced strain in polycrystalline Ni-Mn-Ga foams.

Original languageEnglish (US)
Pages (from-to)64-71
Number of pages8
JournalActa Materialia
Volume92
DOIs
StatePublished - Jun 15 2015

Keywords

  • Foam architecture
  • Heusler alloys
  • Martensitic phase transformation
  • Ni<inf>2</inf>MnGa
  • Thermal cycling

ASJC Scopus subject areas

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

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