MSMnet: Magnetomechanics of Magnetic Shape Memory Alloys: Session 4
Program Organizers: Peter Müllner, Boise State University

Thursday 8:00 AM
July 13, 2017
Room: Wrigley
Location: Hyatt Regency Chicago

Session Chair: Hanus Seiner, Institute of Thermomechanics, Czech Academy of Sciences

8:00 AM  
On the Orientation of the Magnetic Field for Maximization of the Voltage Output with Magnetic Shape Memory Alloys: Constantin Ciocanel1; Heidi Feigenbaum1; Roger Guiel1; 1Northern Arizona University
    The power harvesting capability of NiMnGa has been studied by several groups, including the authors, primarily with the material exposed to mutually perpendicular magnetic field and compressive stress and with a coil surrounding the material along the direction of the compressive stress. However, our theoretical model (LaMaster et al. 2014) of the material's magneto-mechanical response suggests that applying the magnetic field normal to the compressive stress is not the most favorable orientation of the field for power harvesting; higher power output may be achieved when the bias field has components both parallel and perpendicular to the applied compressive stress. To check model’s predictions, and find the orientation of the applied magnetic field that maximizes voltage output, experiments have been carried out on a MSMA exposed to bi-axially applied magnetic fields whose resultant magnitude was approximately constant but the orientation varied between 0 and 45 degrees relative to the coil direction.

8:40 AM  
Structure and Properties of Ni-Mn-Ga 14M Martensite used in Magnetic Actuators: Emmanouel Pagounis1; Markus Laufenberg1; Maciej J. Szczerba2; Robert Chulist2; 1ETO MAGNETIC GmbH; 2IMMS, Polish Academy of Sciences
    Magnetic Shape Memory (MSM) alloys are promising candidates for high stroke, fast frequency response actuators. The magnetomechanical properties of these materials depend to a large extend on their martensitic structure. To date, only alloys with 10M structures are finding applications as actuators or sensor components. However, the 14M martensite can generate a considerably larger magnetic field-induced strain of about 11%, and can, thus, contribute in reducing the size of MSM actuators. In this paper we present new measurement results of magnetic and mechanical properties of the 14M martensite. Temperature dependent magnetization measurements reveal details of intermartensitic transformation sequences. Crystallographic features of the 10M to 14M intermartensitic transformation are analyzed by means of synchrotron and conventional x-ray diffraction techniques. Using these methods new insights into the intermartensitic transformation is shown. Moreover, the structure-property relations are revealed and mechanical properties prior to and after the transformation (e.g. twinning stress) are emphasized.

9:00 AM  
Magnetic Torque in Single Crystal Ni-Mn-Ga: Anthony Hobza1; Peter Müllner1; 1Boise State University
    Magnetic shape memory elements with large aspect ratio tend to bend in a magnetic field. In this study, a single crystal specimen of Ni-Mn-Ga was constrained with respect to bending and subjected to an external magnetic field. We measured the torque required to rotate the specimen as a function of the sample orientation in relation to the magnetic field. The largest torque was obtained for a single domain sample with the easy axis of magnetization parallel to the longest axis of the sample. With increasing strain, the torque decreased. For a fully expanded sample with the easy axis perpendicular to the sample length, the maximum torque was reduced by a factor of 5.88. In this case, shape anisotropy counter-acted magnetocrystalline anisotropy and reduced the torque. We will discuss implications of the magnetic torque on the performance of magnetic shape memory elements and on actuator design.

9:20 AM  
Submicroliter Fluid Management for Micro-bioreactors using a Magnetic Shape Memory Micropump: Aaron Smith1; Daniel Fologea2; Peter Müllner2; 1Shaw Mountain Technology; 2Boise State University
    The precise management of nanoliter volumes of liquid presents a major roadblock in the development and research of highly stable droplet lipid bilayers which can be used as micro-bioreactors or as artificial membrane systems for the study of cellular transporters. We created and manipulated a droplet lipid bilayer and delivered sub-microliter volumes of the electrically controlled nano-valve lysenin into the droplet using a micropump made from the magnetic shape memory (MSM) alloy Ni-Mn-Ga. Manipulation of the droplet volume allowed direct control of the membrane surface area thus varying the density of the channels inserted into the membrane. Analysis of these results verified the functionality of channel transporters reconstituted in the membrane. This research validates the MSM micropump as a high precision fluid delivery system which can be used in the fields of medical and life science research which brings MSM technology closer to successful commercialization.

9:40 AM  
Giant Field Induced Reversible Strain Through Phase Transformation in NiMnGa and NiMnCoIn Alloys: Ali Turabi1; Haluk Karaca2; Soheil Saedi2; Ethan Vance2; Guher Toker2; Emmanouel Pagounis3; Yury Chumlyakov4; 1Izmir University of Economics; 2University of Kentucky; 3ETO MAGNETIC GmbH; 4Tomsk State University
     Magnetic shape memory alloys have received considerable attention as a multifunctional material due to their ability to demonstrate large magnetic field induced strain (MFIS) through variant reorientation or phase transformation. Although, large MFIS can be observed by variant reorientation, low actuation stress (<10MPa) is inevitable due to limited driving force by magnetocrystalline anisotropy energy. In order to obtain large actuation stress and strain, field induced phase transformation phenomena in single crystalline of NiMnGa and NiMnCoIn alloys was investigated with magneto-thermo-mechanical experiments in this study. NiMnCoIn alloys exhibited fully reversible MFIS about 5 % and magnetostress above 100 MPa which is very promising for actuator applications. In addition, 2 % of reversible MFIS and 26 MPa of magnetostress were determined in NiMnGa alloys. Experimental results of superelasticity at selected temperatures and field, and thermal cycling under selected stresses and field provided the data to create magnetic field dependent stress-temperature phase diagram.

10:00 AM Break