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

Tuesday 5:30 PM
July 11, 2017
Room: Crystal Ballroom A
Location: Hyatt Regency Chicago

P2-6: Effect of Co Content on Martensitic Transformation and Mechanical Properties of Ni-Mn-Fe-Ga Ferromagnetic Shape Memory Alloys: Haibo Wang1; Yan Feng2; Ailian Liu3; 11139, City Road, Jiaojiang District, Taizhou University; 2Statekey Laboratory of Solidification Processing, Northwestern Polytechnical University; 3College of Materials Science and Engineering, Heilongjiang University of Science and Technology
     Ni-Mn-Fe-Ga alloy is a kind of ferromagnetic shape memory alloy (FSMA), which exhibits not only magnetic field controlled shape memory effect but also improved ductility. However, the martensitic transformation temperatures decrease when the toughness increase with the Fe content increasing. Considering the application properties of Ni-Mn-Fe-Ga alloy, it is very meaningful to increase the martensitic transformation temperatures and mechanical properties extremely. In this paper, the effect of Co addition on martensitic transformation and mechanical property of Ni-Mn-Fe-Ga FSMA is studied. The experimental results show that the martensitic transformation temperatures firstly increase and then keep unchanged with increasing Co content. Compressed fracture strength and strain increase significantly with Co content increasing. When Co content is up to 6 at. %, the fracture strength and strain are 2098 MPa and 38.3%, respectively. Keywords: Ni-Mn-Fe-Ga-Co, Shape Memory Alloy, Martensitic Transformation, Mechanical Properties

P2-7: Effect of Defects on the Martensitic Transformation and the Magnetic Properties of Ni-Mn-Sn Metamagnetic Shape Memory Alloys: Vicente Sánchez-Alarcos1; Iraultza Unzueta2; Vicente Recarte1; José Ignacio Pérez-Landazábal3; José Angel García2; Fernando Plazaola4; Javier López-García5; José Alberto Rodríguez-Velamazán6; 1Physics Department - INAMAT, Public University of Navarra; 2BC Materials; 3Physics Department, Public University of Navarra; 4Departamento de Electricidad y Electrónica, Universidad del País Vasco; 5Physics Department, Public University of Navarra - Institute Laue Langevin; 6Institut Laue Langevin
    Due to the dependence of the exchange interactions on the Mn-Mn distance, the variation of atomic order is the most usual way to properly tune both the magnetic properties and the martensitic transformation temperature in Ni-Mn-based magnetic shape memory alloys. In Ni-Mn-Sn alloys, in turn, the extraordinary high stability of the L21 structure precludes the variation of atomic order by means of conventional thermal treatments. As an alternative, the effect of microstructure on magnetostructural properties of Ni-Mn-Sn alloys has been explored. DSC, magnetization, neutron diffraction and Mössbauer spectroscopy measurements performed on mechanically-deformed and thermally-treated alloys confirm that long-range atomic order is also unaffected by deformation. Nevertheless, a local but significant effect of mechanically-induced defects on the magnetism, and therefore on the MT, is found. The origin of such effect is discussed in terms of the influence of dislocations on local magnetism via the density of antiphase boundaries.

P2-8: Entropy Change during bcc/fcc Martensitic Transformation in Fe-Mn-Al-Ni Shape Memory Alloy: Ji Xia1; Xiao Xu1; Toshihiro Omori1; Ryosuke Kainuma1; 1Tohoku University
    Recently, it has been reported in a new iron-based Fe-Mn-Al-Ni SMA that superelasticity can be obtained by using the martensitic transformation between the ferromagnetic α (BCC) parent and antiferromagnetic martensite γ (FCC) phases[1]. The temperature dependence of the critical stress in this alloy is extremely small due to the small entropy change (△S=SM-SP), which is determined as -0.43 J mol-1 K-1 by the Clausius-Clapeyron relation [1]. Till now, no direct measurements of △S have ever been made. In this study, the results of the specific heat measurements (2-473 K) for the parent and deformation-induced martensite phases of Fe-Mn-Al-Ni SMA are presented. The entropy change is found to be roughly in agreement with the previous report [1] at about 250 K, while the △S is also found to be affected by the magnetic transitions.[1] T. Omori, K. Ando, M. Okano, X. Xu, Y. Tanaka et al. Science 333 (2011) 68-71.

P2-9: Influence of Magnetomechanical Cycling on Properties and Microstructure of Ni-Mn-Ga Magnetic Shape Memory Materials: Markus Laufenberg1; Thomas Schiepp1; Leonardo Riccardi1; Ralf Haist1; Emmanouel Pagounis1; Maciej Szczerba2; Robert Chulist2; 1ETO MAGNETIC GmbH; 2Institute of Metallurgy and Materials Science, Polish Academy of Sciences
     Magnetic Shape Memory (MSM) materials are promising candidates for high stroke, fast frequency response actuators. The magneto-mechanical properties and its stability over high cycle numbers of MSM materials are crucial for the design of actuators and applications. However, a systematic and statistically relevant study of the dependence of these properties on cycle numbers is missing to date.In the present paper we present measurement results of magneto-mechanical properties of Ni-Mn-Ga MSM materials before and after magneto-mechanical cycling. The influence of the cycle number on the shape of the hysteretic field-stress-strain characteristics is analyzed in detail. The findings are correlated with the evolution of the microstructure which is studied by means of electron backscattering diffraction (EBSD) and X-ray diffraction (XRD). The consequences of these results for the design of MSM actuators are discussed.

P2-10: Comparison of highly mobile twin boundaries in Cu–Ni–Al and Ni–Mn–Ga shape memory single crystals: Marek Vronka1; Miroslav Karlik2; Yanling Ge3; Oleg Heczko1; 1Institute of Physics of the Czech Academy of Sciences; 2Czech Technical University in Prague; 3Aalto University
    We compared twinning systems in Cu–Ni–Al and Ni–Mn–Ga single crystals from macroscale down to atomic scale. Using newly developed formalism we studied the twinning stress or mobility and microstructure of the equivalent twin boundaries. In Cu–Ni–Al, compound twinning exhibits the twinning stress of 1 to 2 MPa and Type II twinning stress is approximately 20 MPa, which is much higher than twinning stress for Type II in Ni–Mn–Ga (0.1 to 0.3 MPa). No temperature dependence was found for twinning stress of Type II in both alloys. Transmission electron microscopy revealed that in contrast to Ni–Mn–Ga, there was no internal twinning in Cu–Ni–Al, only stacking faults. The highest density of stacking faults was observed in the presence of Type I twin boundaries. The extremely low twinning stress may be associated with the deep hierarchy of twinning in Ni–Mn–Ga.

P2-11: Jerky Magnetic and Acoustic Noises Induced by External Magnetic Field in Martensitic Single Crystalline Ni2MnGa: Lajos Daróczi1; Eszter Piros1; László Tóth1; Dezső Beke1; 1University of Debrecen
    Allowing free expansion of monovariant Ni2MnGa single crystal (produced by uniaxial compression), first unipolar magnetic noise was detected during magnetization along hard direction, which was followed by bipolar, well-correlated magnetic and acoustic signals accompanied with the superplastic shape change. In the following cycles (along the easy magnetization direction) low intensity unipolar magnetic noise was observed. The first cycle could be reproduced only after longitudinal compression of the sample. Constraining the longitudinal elongation, subsequent unipolar and bipolar magnetic signals were detected in reproducible manner. The bipolar magnetic and acoustic signals during detwinning are due to changes of magnetization during twin boundary motions, while the unipolar and bipolar magnetic signals were attributed to domain wall motions and domain rotations, respectively. The evaluated power exponents of energy and amplitude distributions of noises are in good agreement with our former results, obtained either during shape change as well as during magnetization along both directions.

P2-12: Magnetic Microstructure of Ni-Mn based Metamagnetic Shape Memory Alloys: Pawel Czaja1; Wojciech Maziarz1; 1Institute of Metallurgy and Materials Science
     Metamagnetic shape memory alloys undergoing magnetic field induced reverse martensitic phase transformation have received considerable attention since they are capable of the magnetic field induced strain circa 5o times larger than earlier Ni-Mn-Ga alloys. In addition they also show other highly interesting phenomena such as inverse magnetocaloric effect and exchange bias, what makes them exciting new materials. The coupling between magnetism and structure underpins this unique behaviour and it is found that magnetic properties of such alloys in particular of the low temperature martensite phase are very complex. This contribution reports on magnetic domain structures in Ni-Mn-(Co, Cu, Sn) based alloys, which are studied in bulk specimens by Magneto Optical Kerr Microscopy and Magnetic Force Microscopy techniques.Financial support from PBS/A5/36/2013 project is acknowledged.

P2-13: Microstructural Studies of Ni-Mn based Heusler Melt Spun Ribbons: Wojciech Maziarz1; Robert Chulist1; Anna Wójcik1; Maciej Szczerba1; Paweł Czaja1; Jan Dutkiewicz1; Eduard Cesari1; 1Institute of Metallurgy and Materials Science, Polish Academy of Sciences
    Ni-Mn based Heusler metamagnetic shape memory alloys undergo magnetic field induced reverse martensitic transformation showing an inverse magnetocaloric effect. Due to the high degree of chemical homogeneity obtained in melt spun ribbons the rapid solidification process of has received considerable attention. This contribution is focused on detailed microstructure investigations performed by scanning (SEM) and transmission (TEM) electron microscopy of ribbons with martensite or austenite structure and two phase austenite/martensite structure. SEM EBSD measurements performed for wheel and free side of ribbons as well their cross-sections revealed the microstructure, texture and chemical composition at the micro scale. TEM observation performed on thin foils prepared by double jet electro-polishing allowed to identify chemical micro-segregations, local changes of structure and types of martensite confirmed also by high resolution electron microscopy (HREM). Applying these two electron microscopy techniques allowed to describe real microstructure of metamagnetic shape memory ribbons going from micro to atomic scale.

P2-15: Observation of Martensitic Transformation in Ni-Mn-Ga: Vít Kopecký1; Petr Veřtát1; Ladislav Straka1; Oleg Heczko1; 1Institute of Physics of the Czech Academy of Sciences, Czech Republic
    Magnetic shape memory (MSM) effect includes several effects and the most promising one is called magnetically induced reorientation (MIR) which provides large strain (up to 12 %) in mild magnetic field. Although the MIR effect is not directly connected to phase transition, existence of diffusionless martensitic transition is crucial. Martensitic transition connects high-symmetry cubic phase (called austenite) and lower-symmetry martensitic phase, however, lattices of phases are not directly compatible at habit plane. That produces shear stress which is lowered by twinning of the martensite. Twinned martensite and also the habit plane can be observed by optical microscopy. We used Nomarski contrast to distinguish between twin variants of martensite and we present micrographs and video clips of habit plane propagating through sample and martensite variants twinned and branched towards the habit plane. Additionally, we calculated compatibility of interfaces using lattice parameters derived from X-ray diffraction.

P2-16: Peculiar Behaviour of the Magnetic Transition in Martensite of Ni-Mn-Ga: Sergiy Konoplyuk1; Volodymyr Kokorin2; Andrej Dalinger3; Hans Jurgen Maier3; 1Institute of Magnetism; 2Institute of magnetism; 3Institut für Werkstoffkunde (Materials Science), Leibnitz Universität Hannover
    A hysteretic magnetic transition from para- to ferromagnetic phase was found to occur in the martensitic phase of Ni51.9Mn27Ga21.1. Simultaneous measurements of magnetic susceptibility and electric resistivity revealed that two successive transformations, martensitic and magnetic ones, take place rather than single coupled one. Calorimetric study confirmed absence of the transformation latent heat during the hysteretic magnetic transition. The hysteresis phenomenon is suggested to be associated with variation of the lattice constants below martensitic transformation temperatures.

P2-17: Phase Transitions in Heusler Ni(Co)-Mn(Cr,C)-(In,Sn): Insight from First Principles: Vasiliy Buchelnikov1; Vladimir Sokolovskiy1; Mikhail Zagrebin1; Olga Miroshkina1; 1Chelyabinsk State University
     It is well known that the addition of fourth an fifths elements into Heusler Ni-Mn-(In,Sn) alloys strongly affect the Curie and martensitic transformation temperatures. A series of Ni(Co)-Mn(Cr,C)-(In,Sn) Heusler alloys have been theoretically investigated by the help of density functional theory and Monte Carlo simulations to obtain Curie and martensitic transition temperatures. By using ab-initio calculations it was found the most energetically favorable magnetic and structural states for both austenite and martensite phases in Heusler Ni(Co)-Mn(Cr,C)-(In,Sn) alloys. It was shown that the large magnetocaloric effects must be observed in Ni16Mn10Сr2In4, Ni14Co2Mn11Сr1In4, Ni14Co2Mn11С1In4, and Ni14Co2Mn11Сr1Sn4 Heusler alloys.As a result, in such compounds a large magnetization drop and giant inverse magnetocaloric effect can be expected of ≈ 10 K in a 2 T field across the magnetostructural phase transition.

P2-18: Probing the Possibility of Coexistence of Martensite Transition and Half-metallicity in Ni and Co-based Full-Heusler Alloys: An Ab initio Calculation: Tufan Roy1; Dhanshree Pandey2; Aparna Chakrabarti2; 1 Raja Ramanna Centre for Advanced Technology, Indore-452013, India; 2Raja Ramanna Centre for Advanced Technology, Indore-452013, India
    Using first-principles calculations, we have studied the mechanical, electronic, and magnetic properties of some Heusler alloys, namely, Ni2BC and Co2BC (B = Sc, Ti, V, Cr, and Mn as well as Y, Zr, Nb, Mo, and Tc; C = Ga and Sn). From energetic point of view, we have studied the possibility of finding electronically stable alloys having a tetragonal phase lower in energy compared to the respective cubic phase. For some alloys, the tetragonal phase has indeed been found to have lower energy compared to the cubic phase. Further, we find that the values of tetragonal shear constant show a consistent trend: a high positive value for materials, not prone to tetragonal transition and low or negative value for the others. We predict that Co2MoGa is likely to possess shape memory alloy property and half-metallic-like nature - two mutually exclusive properties as is generally observed in the literature.

P2-19: Ternary Diagrams of Magnetic and Structural Properties of Ni-Mn-Ga in the Austenite and Martensite Structures: Vladimir Sokolovskiy1; Mikhail Zagrebin1; Vasiliy Buchelnikov1; Iulia Sokolovskaya1; Alexey Zayak2; 1Chelyabinsk State University; 2Bowling Green State University
    At present, among ferromagnetic shape memory alloys, Ni-Mn-Ga are the most studied by means of theoretical and experimental approaches. Such interest is related to the unique properties exhibited by the stoichiometric Ni2MnGa. In this work we present a systematic investigation of magnetic and structural properties of a broad range of Ni-Mn-Ga alloys by means of DFT calculations, which are carried out for austenite and martensite. Equilibrium lattice parameters, tetragonalities c/a, magnetic moments, and formation energies of a wide range of Ni-Mn-Ga alloys have been mapped on compositional ternary diagrams that give a bigger picture of the variety of physical properties of these alloys. Obtained magnetic exchange parameters have been used for Monte-Carlo simulations of the Curie point as a function of compositions. It has been seen that calculated data has are in a very good agreement with experimental one for Ni2MnGa, and allow us to predict properties of non-stoichiometric compounds.

P2-20: Theoretical Investigations of the Structural, Magnetic and Electronic Properties of Ni-Mn-Cr-(Ga,Ge) Heusler Alloys: Mikhail Zagrebin1; Vladimir Sokolovskiy1; Elizaveta Smolyakova1; Vasiliy Buchelnikov1; 1Chelyabinsk State University
    It is well known that the addition of fourth element into Ni-Mn-(Ga,Ge) can strongly affect the Curie and martensitic transformation temperatures. A series of Ni2Mn1-xCrx(Ga,Ge) (0 ≤ x ≤ 1) Heusler alloys have been theoretically investigated by DFT as well as Monte Carlo simulations to obtain Curie temperatures. By using ab initio calculations it was found that the most energetically favorable magnetic state for both austenite and martensite phases in Ni2Mn1-xCrx(Ga,Ge) is a ferromagnetic state. Besides, an increase in energy difference between austenite and martensite with increasing Cr content was observed. With respect to the exchange coupling constants, it was shown that Ni-Mn(Cr) pairs show the strongest ferromagnetic exchange interaction between nearest neighbor atoms. It was demonstrated that the most part of total spin up and spin down density of states is caused by Ni atoms. Estimated Curie temperatures for Ni-Mn-Cr-Ga alloys are in a good agreement with experimental data.

P2-21: {110} Nanotwinning Near Reverse Martensitic Transformation in Ni50.0Mn28.7Ga21.3 Magnetic Shape Memory Alloy: Ladislav Straka1; Jan Drahokoupil1; Petr Veřtát1; Jaromír Kopeček1; Oleg Heczko1; 1Institute of Physics, Prague
     X-ray diffraction indicated the structure of Ni50.0Mn28.7Ga21.3 single crystal being five-layered modulated martensite (10M) with a=0.5974 nm, b=0.5949 nm, c=0.5589 nm at room temperature, and sudden change to a=b=0.5949 nm, c=0.5616 nm near reverse martensitic transformation at TA≈327 K. The latter five-layered martensite structure with a=b, marked as 10M', remained stable upon cooling until about the martensite transformation temperature TMTA-10 K, where it transformed back to 10M with ab. The range of phase stability combined with the theoretical calculation of diffraction pattern and SEM observations indicate that the 10M' is in reality a {110} nanotwinned original 10M phase with the twin width of order 10 nm. The role of this nanotwinning for martensitic transformation is discussed.

P2-22: Magneto-structural Properties of Si-doped Ni–Co–Mn–Sn Heusler Ribbons: Anna Wojcik1; Wojciech Maziarz1; Maciej Szczerba1; Maciej Kowalczyk2; Eduard Cesari3; Jan Dutkiewicz1; 1Institute of Metallurgy and Materials Science, Polish Academy of Sciences; 2Faculty of Materials Science and Engineering, Warsaw University of Technology; 3Departament de Física, Universitat de les Illes Balears
    The inverse magnetocaloric effect in Ni–Co–Mn–Sn based Heusler alloys is related to the martensitic transformation which is accompanied by large magnetization change. The addition of the fifth element (Si) as well as fabrication method (melt-spinning) give an opportunity to tune the martensitic transformation temperature, while enhancing the magnetocaloric properties. Four alloys with the nominal composition Ni44Co6Mn36Sn11-xSix (x=0-3 at.%) were fabricated by means of melt spinning technique. The structure and microstructure have been investigated by XRD, SEM and TEM methods. Ribbons possess single martensite structure indexing as 12M independently on the Si content. The phase transition temperatures and magnetocaloric effect were determined using DSC and PPMS techniques. Temperatures of martensitic transformation show complex behavior. The value of magnetocaloric effect is increased for ribbons containing 1 and 2 at.% of Si. The results have been obtained within the frame of project PBS/A5/36/2013.

P2-23: Three-variant Magnetic Shape Memory Alloys: Heidi Feigenbaum1; Constantin Ciocanel1; Jeffery Eberle1; 1Northern Arizona University
    The unique properties of magnetic shape memory alloys (MSMAs) are due to the fact that martensitic phase of the material is comprised of tetragonal unit cells. The vast majority of MSMAs used to date have been trained to accommodate only two martensitic variants, i.e. two configurations of the unit cells. In this work, a three-variant MSMA is studied. The three-variant MSMA can be strained due to stress and/or magnetic field in any of the three rectangular directions. In particular, the three-variant MSMA is characterized experimentally under three-dimensional load conditions, which include lateral stress, axial stress, and magnetic field. The model by LaMaster et al. (2014) is modified and used to predict the experimental results. The predictions capture some of the general trends seen experimentally, but do not accurately reproduce the data. Possible reasons for the mismatch between experimental data and model predictions are discussed.