Traveling Surface Undulation on a Ni-Mn-Ga Single Crystal Element

Andrew Armstrong, Bibek Karki, Aaron Smith, Peter Müllner

Research output: Contribution to journalArticlepeer-review

4 Scopus citations

Abstract

Active materials couple a stimulus (electrical, magnetic, and thermal) with a mechanical response. Typical materials such as piezoelectrics strain as bulk materials to the stimuli. Here we consider an undulation created by heterogeneous deformation within a magnetic shape memory alloy (MSM) transducer. We study the mechanical response of an MSM element vs two surface treatments: a polished state with minimal surface stresses, and a micropeened state with compressive surface stress. The polished element had a sharp-featured, faceted trough shape. The micropeened element had a smooth trough shape and an additional crest. The undulation was created by a rotating localized magnetic field, which caused heterogeneous variation of the twin-microstructure. For the polished and micropeened elements, the twin-microstructures were coarse and fine, respectively. For the polished element, the undulation moved by the nucleation of a few twin boundaries, which traveled along the entire element. For the micropeened sample, the twin boundaries moved back and forth over a short distance, thereby creating a dense twin lamellar, which formed the trough. The motion of the lamellar approximated the single thick twin while allowing additional degrees of freedom due to increased mobile interface density and different initial conditions of domain volume fraction. The dense twin microstructure also smoothed the magnetic flux pattern. The undulation amplitude was about 40 μm for the sample in both treatments.

Original languageAmerican English
Article number085001
JournalSmart Materials and Structures
Volume30
Issue number8
DOIs
StatePublished - Aug 2021

Keywords

  • Inhomogeneous magnetic field
  • Laser profilometry
  • Magnetic shape memory alloy
  • Msm pump
  • Ni-mn-ga
  • Shotpeening
  • Surface treatment

EGS Disciplines

  • Materials Science and Engineering

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