Symposium FM
State-of-the-art Research and Applications of Shape Memory Alloys


FM-1:IL01  Multicaloric Heusler Compounds: Review and Prospects
O. Gutfleisch, K. Skokov, A. Taubel, L. Pfeuffer, F. Scheibel, TU Darmstadt, Materials Science, Functional Materials, Darmstadt, Germany; T. Gottschall, Helmholtzzentrum Dresden Rossendorf, HZDR, Germany

At TU Darmstadt we develop all p-metal and d-metal Heusler compounds for multifunctional applications with special emphasis on their elastocaloric, barocaloric, and magnetocaloric properties. Their multi-responsiveness to stimuli such as strain, pressure and magnetic field enable a variety of new design concepts for sensors, actuators and caloric cooling concepts. At the same time the compounds´ characteristic coupled magnetostructural transitions and related hysteresis phenomena can be tuned by electronic- and micro-structure as well as internal interfaces control on the one hand; and usefully exploited in e.g. a multi-stimuli cooling cycle on the other hand. Hence, the ideal active material should provide a conventional elastocaloric effect with a high mechanical fatigue resistance next to a large inverse magnetocaloric effect and tailored hysteresis. Recent work on NiMnCoIn and NiMnCoTi and related compounds is reviewed with particular emphasis on the disentanglement of the contributions of the magnetic, lattice and electronic subsystems to the magnetocaloric, magnetostrictive, resistive and thermal responses. Their mechanical properties and multi-response to high magnetic fields is also discussed in terms of application driven demands.

FM-1:IL03  A First-principles Perspective on the Interplay of Magnetism and Microstructure in Ni-Mn-based Heusler Alloys
M.E. Gruner, Faculty of Physics and Center for Nanointegration, CENIDE, University of Duisburg-Essen, Duisburg, Germany

Depending on composition and chemical order, Ni-Mn-based Heusler alloys exhibit interesting functional properties, which render them useful for magnetic shape memory applications or as magnetocaloric materials. This is linked to the presence of hierarchically twinned modulated structures in martensite, which can be interpreted as adaptive, self-organized arrangement of [110]-aligned nanotwins consisting of non-modulated tetragonal building blocks as was shown previously for the paradigmatic case of stoichiometric Ni-Mn-Ga [1]. A band-Jahn-Teller-type reconstruction of the Fermi surface which in particular softens the [110] transversal acoustic phonons leads to a downhill transformation path from cubic austenite to nanotwinned martensite. The twin interfaces are subject to competing repulsive and attractive interactions related to which we relate to the frustrated antiferromagnetic coupling between neighboring Mn atoms. Within this contribution, we explore on the basis of ab initio DFT calculations the signatures of the interdependence of magnetism, chemical order and nanotwinning in various Ni-Mn-based systems and their relevance for the functional properties. [1] M. E. Gruner, R. Niemann, P. Entel, R. Pentcheva, U. K. Rössler, K. Nielsch, S. Fähler, Sci. Rep. 8, 8489 (2018)

FM-1:IL05  Elasticity and Microstructures in Shape Memory Alloys: from Highly Mobile Interfaces to Kwinks
H. Seiner, Institute of Thermomechanics, Czech Academy of Sciences, Prague, Czech Republic

The talk will summarize the recent achievements in the field of application of a non-linear elasticity theory for interpreting the formation of martensitic microstructures observed in various shape memory alloys. We will show that, although the phenomena originate from the atomistic length-scales, the continuum-level description can capture several of their main features. As examples of this approach, the results for the following cases will be briefly presented: i) highly-mobile Type I and Type II macro-twin boundaries in Ni-Mn-Ga (including the non-conventional twinning), ii) branching of twin domains at the austenite-martensite interface in Cu-Al-Ni, iii) ultra-fine compound twinning in highly-textured oriented Ni-Ti wires, and iv) twinning-assisted kinking (i.e., kwinking) in plastically formed Ni-Ti. The fourth topic will be elaborated in more detail, explaining the concept of the kwinks, and how these interfaces arise from an interplay between twinning and highly anisotropic plastic slip in Ni-Ti.

FM-1:L06  Age Hardening Behavior of (Ni+Cu)-rich Ti-Ni-Cu Alloys
TAE-HYUN NAM, Ji-hyun Kim, Gyeongsang National University, Jinju, South Korea

In this study, microstructure, aging behavior and mechanical properties of a (Ni,Cu)-rich Ti-40Ni-12Cu (at%) shape memory alloy were investigated. Ti(Ni,Cu)2 phase remained after solution treatment at 1123 K, while it was almost dissolved into matrix after solution treatment at 1373 K. Aging at 723 K increased hardness of the 1373 K solution treated specimen, which was ascribed to the formation of the C11b-type precipitate that has tetragonality of 1.05 and coherent interface with matrix. The hardness reached the maximum at 2.5 h aging and then decreased with further prolonging aging time. Transformation temperatures of aged specimens were dependent on aging time, which were explained by composition effect, strain field around the precipitates and mean free path between precipitates. Aging at 873 K for 45 h of the 1373 K solution treated specimen induced the precipitation of stable Ti(Ni,Cu)2 phase with tetragonality of 2.55, thus the C11b-type precipitate was considered to be transient metastable precipitate. The specimen aged at 723 K for 2.5 h showed excellent superelasticity, which was ascribed to precipitation hardening due to metastable C11b-type precipitates.

FM-1:IL08  Transition Metals Doping of Ni-Mn-Ga and Comparison of Single Crystals Grown by Different Methods
O. Heczko, V. Kopecký, D. Musiienko, F. Nilsen, M. Rameš, P. Vertát, Š. Sukup, S. Heczko, L. Straka, FZU - Institute of Physics, Czech Academy of Sciences, Prague, Czech Republic; R. Colman, Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic

There are numerous attempts to increase Curie temperature TC and particularly martensitic transformation temperature TM of Ni-Mn-Ga exhibiting magnetically induced reorientation (MIR) by various doping. However, the results are somehow confusing, the alloys are often prepared hap-hazardously and poorly analysed and the systematic approach is missing. Here we report on the properties of systematically doped stoichiometric Ni2MnGa by same amount (5atom%) of ferromagnetic transition metals on all three possible positions, i.e. instead of Ni, Mn, Ga. We found that the largest increase of TC is for Co on Ni sites and the largest increase of TM for Co or Ni on Ga sites while doping of Fe on Ni sites totally suppressed the transformation. In addition, we compare the single crystals from different producers including our own grown in optical furnace from the point of view of magnetically induced reorientation (MIR) in order to evaluate various single crystal growth methods. We found significant variation of switching field, the energy needed for reorientation and temperature dependence of MIR in the crystals from different sources although the composition and structure of the martensite were quite the same. These differences can be ascribed to intrinsic defects and chemical gradient.

FM-1:IL09  Optimizing Novel Manufacturing Processes for Ni-Mn-Ga Magnetic Shape Memory Materials
E. Pagounis, ETO MAGNETIC GmbH, Stockach, Germany

Magnetic shape memory (MSM) are smart materials developed for advanced actuators, sensors, and energy harvesters. These materials are activated when inserted into a moderate magnetic field, and can generate large stroke and force at extremely short (ms) response time. Typical MSM materials are NiMnGa alloys in single crystalline form. It has been reported in several studies and publications that the performance of MSM materials in electromagnetic devices is highly dependent also on the production route employed. Each step is critical for the resulting magneto-mechanical (M-M) properties. In the present study the various production steps are described. The effect of process optimization on the M-M properties is presented, and some open questions are discussed. The results are supported by microstructural characterization (SEM-LOM microscopy, EBSD, XRF, etc.) and by measuring the most relevant M-M properties (field-induced strain, twinning stress, work output density, etc.). It has been found that by focused process modifications large improvements in the M-M properties and the fatigue life of MSM actuating elements can be achieved. Finally, the most important topics for further research towards the industrialization of MSM materials are proposed.

FM-1:IL10  NiMn Based Heusler Alloys for Magnetocaloric Applications: Direct and Inverse Magnetocaloric Effects, Large Scale Synthesis
S. Fabbrici, C. Bennati, F. Albertini, IMEM-CNR, Parma, Italy; F. Puglielli, V. Mussi, MUSP Laboratory, Piacenza, Italy; F. Cugini, N. Sarzi Amadè, M. Solzi, Department of Mathematical, Physical and Computer Sciences, University of Parma, Parma, Italy

Ni-Mn based Heusler alloys with metamagnetic martensitic transformation are among the most studied materials for future magnetocaloric applications thanks to the high adiabatic temperature changes related to their inverse magnetocaloric effect. These materials are rare earth free, easy to prepare and offer large tailoring possibilities. Remarkably, thanks to the strong discontinuities of the physical properties at the martensitic transformation (magnetization, volume), caloric effects can be obtained not only by applying magnetic fields but also by stress and pressure, enabling multicaloric applications. We will discuss their unique capability of showing both direct and inverse magnetocaloric effects, originating from their different magnetostructural and magnetic transitions that can be tailored with stoichiometry, and propose possible ways to exploit them in thermomagnetic cycles. Additionally, we will discuss a method for a reliable and large-scale production of these alloys with homogeneous composition and properties. The case of large scale preparation of polycrystalline Ni45.7 Co4.2Mn36.6In13.3 alloy and its magnetocaloric characterization will be presented.

FM-1:IL12  Coupled Transformation and Plasticity in NiTi Shape Memory Alloy
P. Sedlák, B. Benešová, M. Frost, H. Seiner, Institute of Thermo-mechanics, Czech Academy of Sciences, Prague, Czech Republic; L. Heller, P. Šittner, Institute of Physics, Czech Academy of Sciences, Prague, Czech Republic

Martensitic transformation in NiTi SMA proceeding at elevated temperatures and stresses starts to be coupled with mechanisms of plastic deformation in austenite and martensite. It is manifested by large irrecoverable strain generated during phase transformation, fast degradation of functional properties, change of thermo-mechanical coupling constant or unusual long transformation plateaus. In this contribution, we suggest a macroscopic thermodynamic description of these phenomena. Mutual interconnection of reversible transformation/reorientation processes and irreversible plastic deformation mechanisms motivated formulation of unique energetical and dissipation functions which can correctly describe material behavior and, at the same time, bring basic phenomenological understanding of this coupled mechanics. A comparison of experimental and simulated data will be presented, and it will be also discussed how the understanding and description of coupled transformation and plasticity can allow tailoring of strain heterogeneity on both micro and macro scale inside NiTi components.

FM-1:IL14  Symmetry Analysis of Martensitic Transition in Magneto-caloric Heusler Alloys
F. Orlandi1, A. Cakir2, R. Waite1, 3, P. Manuel1, D,D. Khalyavin1, M, Acet4, L. Righi5, 6, 1ISIS Facility, Rutherford Appleton Laboratory - STFC, Chilton, Didcot, UK; 2Mugla Stiki Kocman University, Department of Metallurgical and Materials Engineering, Mugla, Turkey; 3H.H. Wills Physics Laboratory, University of Bristol, Bristol, UK; 4Faculty of Physics and Center for Nanointegration (CENIDE), Universitat Duisburg-Essen, Duisburg, Germany; 5Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, Parma, Italy; 6IMEM-CNR, Parma, Italy

Martensitic transformations are strain driven transitions that determine the mechanical and physical properties in various materials. This is the case in Ni-Mn based Heusler alloys, where the martensite transition is pivotal for the magnetic shape memory and magneto-caloric properties. In this talk we will discuss the symmetry of the martensitic transformation in Ni-Mn based alloys. The analysis suggest that the transition is driven by two main distortions: the tetragonal strain and the incommensurate displacive modulation along the cubic [110] directions. These two order parameters are strongly coupled through a linear quadratic coupling in the free energy that determine the characteristics and behaviour of the transformation. These conclusions are based on neutron diffraction experiment conducted on Co doped Ni2MnGa alloys as well as on the strain induced transformation in single crystal of stoichiometric Ni2MnGa. The use of the superspace formalism to describe the crystal structure of the incommensurate modulated martensitic phases, joined with a group theoretical analysis and Landau theory highlights the close relationship between the lattice distortions at the core of the Ni2MnGa physical properties.

FM-1:L16  Ultrasonic-based Evaluation of NiTi Elasticity during Stress-induced Martensitic Transformation
T. GRABEC, K. Zoubkova, P. Stoklasova, P. Sedlak, H. Seiner, Institute of Thermomechanics of the CAS, Prague, Czech Republic

A polycrystalline NiTi sample was studied during pseudoplastic straining. Various ultrasonic methods were utilized to measure velocities of bulk and surface acoustic waves in several directions with respect to the mechanical loading. Using a numerical inverse procedure, a full elastic tensor of the transversely isotropic polycrystal during the stress-induced austenite→R-phase→martensite transformation was obtained. The evolution of the sample’s elasticity revealed an unexpectedly strong anisotropy of the R-phase already in the low-strain state, which was then retained in character throughout the transformation and even in the stress-free oriented martensite after unloading. The knowledge of the full elasticity allowed for a creation of a micromechanical model based on homogenization approaches, which led to the conclusion that the strong anisotropy was not caused predominantly by the anisotropy of the unit cell and the crystallographic texture but was rather related to twin boundaries both in the R-phase and martensite. This conclusion may provide an important link to explain the up-to-date discrepancy between the ab initio calculations and experimental results.

FM-1:L18  Shape Recovery Behaviour of NiTi-PMMA Composite
S. Samal, O. Kosjakova, D. Vokoun, P. Šittner, FZU-Institute of Physics of Czech Academy of Science, Prague, Czech Republic

NiTi is consider as shape memory material that remembers the shape and combining with polymer of PMMA for enabling one way shape memory effect. NiTi alloy of shape memory and superleastic sheet was used as substrate for coating of polymer on one side and both side surfaces. Composite were prepared by spin coating method with thickness in the ratio of 1: 3 with alloy : polymer ratio. The bending stiffness was calculated by using numerical, simulation and experimental methods. The effect of shape recovery from SMA to SE shows reverse in order.

FM-1:IL21  Multicaloric effects in Shape Memory Alloys
L. Manosa, Universitat de Barcelona, Barcelona, Catalonia, Spain

Giant magnetocaloric, barocaloric, elastocaloric and multicaloric effects have been reported for many Magnetic Shape Memory Alloys. These effects are associated with the sensitivity of the martensitic transition to magnetic and mechanical fields (uniaxial stress and hydrostatic pressure). While the single caloric response to the application of an external field has exhaustively been investigated there are very few reports on the multicaloric response of shape memory alloys. Here we will report on the advanced characterization of all relevant physical quantities that determine the multicaloric effect of prototype magnetic shape memory alloys. To that end, we have used purpose-designed experimental devices to determine the isothermal entropy and adibatic temperature changes resulting from the combined action of magnetic field and uniaxial stress. It will be shown that the multicaloric response of shape memory alloys by appropriate changes of uniaxial stress and magnetic field largely outperfoms the caloric response of the alloys when subjected to only a single stimulus.

FM-1:IL22  The Use of Magnetic Shape Memory Alloys in Multicaloric Refrigeration Cycles
T. Gottschall, E. Bykov, Y. Skourski, J. Wosnitza, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany; A. Gràcia-Condal, Ll. Mañosa, A. Planes, Universitat de Barcelona, Barcelona, Catalonia, Spain; B. Beckmann, A. Taubel, L. Pfeuffer, O. Gutfleisch, Technical University of Darmstadt, Darmstadt, Germany

With the world's increasingly affluent population demanding more comfortable living and working conditions, it is vital that we address the development of much more efficient cooling technologies as an urgent priority. An alternative approach is based on solid-state refrigeration by one of the caloric effects – electrocaloric, magnetocaloric, barocaloric or elastocaloric - where the material's temperature is forced to change under the application of an electrical, magnetic, or mechanical field [1]. However, there is also the possibility to combine these different effects in a beneficial way, in the so-called multicaloric cooling cycle. Magnetic Ni-Mn-based Heusler alloys are ideally suited for multicaloric applications due to their coupled magnetostructural transformation between martensite and austenite [2]. In this work, we discuss the current progress in the characterization of these materials for novel cooling technologies.
[1] T. Gottschall et al., Nat. Mater. 17, 929 (2018). [2] T. Gottschall et al., J. Appl. Phys. 127, 185107 (2020).

FM-1:L23  Magnetocaloric and Elastocaloric Properties of Polycrystalline Samples of NiMnGaCu Ferromagnetic Shape Memory Alloy: Effect of Improvement of Thermoelastic Martensitic Transformation
E. Villa1, C. Tomasi2, F. VILLA1, A. Nespoli1, F. Passaretti1, E. Bestetti1, R. Frigerio1, F. Albertini3, G. Lamura4, F. Canepa5, 1Consiglio Nazionale delle Ricerche – Istituto della Materia Condensata e di Tecnologie per l’Energia (CNR-ICMATE Sede di Lecco), Lecco, Italy; 2Consiglio Nazionale delle Ricerche – Istituto della Materia Condensata e di Tecnologie per l’Energia (CNR-ICMATE Sede di Genova), Genova, Italy; 3Consiglio Nazionale delle Ricerche – Istituto dei Materiali per l’Elettronica e il Magnetismo, Parma, Italy; 4CNR-SPIN, Genova, Italy; 5Dipartimento di Chimica e Chimica Industriale, Università di Genova, Genova, Italy

Among NiMnGa-based quaternary systems, NiMnGaCu exhibits an interesting giant magnetocaloric effect thanks to the temperature overlapping of magnetic transition and thermoelastic martensitic transformation (TMT), in particular for compositions with  6at% Cu content. In the present work in polycrystalline alloy samples with Ni50Mn18.5Cu6.5Ga25 at% chemical composition, we investigate the contribution of TMT to the total S change, which is the principal physical parameter involved in magnetocaloric effect. We present an extensive calorimetric and structural characterization to explore the correlation between microstructural properties induced by means of selected thermal treatments and magnetocaloric response. Moreover the elastocaloric properties were investigated, with the evaluation of S change in compression and flexural configuration. Our results give important hints on how the efficiency of the martensitic transition and its modulation in temperature has a final effect on the total performances of this alloys in possible magneto-machanical coupling for solid state refrigeration.

FM-2:IL01  Shell Ferromagnetism
M. Acet1, A. Cakir2, M. Farle1, 1Physics Faculty, Duisburg-Essen University, Duisburg, Germany; 2Department of Metallurgical and Materials Engineering, Muğla Sıtkı Koçman University, Muğla, Turkey

Shell-ferromagnetism involves the decomposition of a Ni-Mn based Heusler alloyed with 5 at% Al, Ga, In, Sn, or Sb. It decomposes into 2-5 nm cubic full Heusler precipitates surrounded by a tetragonal NiMn matrix when annealed at elevated temperatures under a magnetic field. At the precipitate/matrix interface, the moments align with strong pinning in the annealing-field direction so that these spins can only be fully rotated in fields exceeding 10 T, and they can withstand temperatures up to 500 K. Depending on the direction of the applied field, the anisotropy can be set continuously to any angle between 0° and 90°, both in bulk-plate and thin-film materials. Here, we discuss the growth mechanisms and the magnetic and structural properties of shell-ferromagnets.

FM-2:IL02  Microstructure Engineering of Magnetic Shape Memory Thin Films and Nanostructures
F. Casoli, M. Takhsha Ghahfarokhi, L. Nasi, S. Fabbrici, R. Cabassi, G. Trevisi, F. Albertini, IMEM - CNR, Parma, Italy; J.A. Arregi, M. Stano, M. Horky, J. Hajducek, V. Uhlir, CEITEC BUT, Brno, Czech Republic; A. Chirkova, F. Maccari, Functional Materials, TU Darmstadt, Darmstadt, Germany

Ferromagnetic shape memory Heuslers show multifunctional properties arising from a strong coupling between magnetic, thermal and mechanical degrees of freedom. Ni2MnGa is a model system within this class of compounds and shows a martensitic phase transformation from a cubic phase (austenite) to a lower symmetry phase (martensite) by decreasing temperature. We have grown Ni-Mn-Ga films with thickness up to 200 nm by RF sputtering on MgO(100) or Cr/MgO(100). The austenitic phase grows epitaxial at high temperature. In the martensitic phase, stable at room temperature, films show complex arrays of differently oriented twin microstructures, i.e., X and Y type, where the easy-magnetization directions are out-of-plane and in-plane, respectively. We will show how different external stimuli enable to engineer this microstructure, i.e., applying a stress to the sample during or after the growth, magnetic field cooling after the growth, reducing the growth temperature and then post-annealing the film. Finally, since for applications such as thermomagnetic actuation and energy harvesting the material needs to keep its properties down to micron and nanometre size, we will show the properties of different types of micro and nanostructures obtained from Ni-Mn-Ga films.

FM-2:IL03  Epitaxial NiTi Thin Films: Growth, Microstructure and Martensitic Phase Transition
K. Lünser1, 2, 3, S. Schwabe1, K. Nielsch1, 2, S. Fähler3, 1Leibniz IFW Dresden, Institute for Metallic Materials, Dresden, Germany; 2Institute of Materials Science, TU Dresden, Dresden, Germany; 3Helmholtz-Zentrum Dresden-Rossendorf, Institute of Ion Beam Physics and Materials Research, Dresden, Germany

Polycrystalline NiTi films are widely used for applications in microsystems due to their superelastic and shape memory properties. To customize the material for a specific purpose, a thorough understanding of the underlying martensitic microstructure formation is helpful. As the grain boundaries in polycrystalline films complicate the microstructure analysis, knowledge of the nucleation & growth of martensite and variant selection in NiTi thin films is still scarce. Here we use epitaxial NiTi films as a model system to examine the martensitic transformation and microstructure. Using DC magnetron sputter deposition, we grew epitaxial films with different orientations by varying the substrate material. By combining texture measurements and microscopy, we can examine the microstructure on several length scales and compare results with the phenomenological theory of martensite. Using in-situ measurements, we can additionally analyze the nucleation and growth processes and compare films with and without the R-phase as an intermediate stage. Our results are the starting point to understand the three dimensional shape of martensitic nuclei in NiTi, which results in a hierarchically twinned microstructure on different length scales.
This work is supported by DFG (FA 453/13).

FM-2:L04  Shape-memory Heusler Films Towards Nanoscale by Lithography Patterning
m. Takhsha, G. Trevisi, L. Nasi, F. Casoli, F. Albertini, IMEM-CNR, Parma, Emilia-Romagna, Italy; J.A. Arregi, M. Horký, V. Uhlír, CEITEC BUT, Brno University of Technology, Brno, South Moravian, Czech Republic

Shape-memory Heuslers are among the smart materials promising for e.g. magnetic-field induced actuation, sensing, energy harvesting, spintronics and solid-state refrigeration. The multi-functionality of these materials upon down-scaling brings further possibilities such as the suitability of integration into compact devices and the possibility of tuning material’s properties by adjusting the size. We have performed a systematic approach by fabricating arrays of submicron epitaxial Ni-Mn-Ga structures on (001) MgO. The structures include straight and radial stripes, squares and triangles. The material properties, i.e., martensitic phase transformation temperatures, sharpness of the transition, thermal hysteresis and the magnetic characteristics of the material are investigated and discussed as a function of the lateral size. With respect to the continuous epitaxial Ni-Mn-Ga films, a prominent broadening of the martensitic transformation (up to ~70 K) as well as shift of the martensitic transformation to higher temperatures (up to ~40 K) are highlighted as the major effects of the lateral size reduction in the nanofabricated structures. Notably, thermal hysteresis of the patterned structures shows a monotonic drop (up to ~29 %) by decreasing the lateral size in the nanoscale regime.

FM-2:L06  The Impact of the Interaction between Twin Microstructures and Magnetic Domain Patterns on the Magneto-mechanics of Magnetic Shape Memory Alloys
P. MüLLNER, M. Veligatla, Boise State University, Boise, ID, USA; A. Hobza, SpaceX  C.J. García-Cervera, University of California Santa Barbara & Basque Center for Applied Mathematics

Magneto-crystalline anisotropy couples magnetic and structural properties of magnetic shape memory (MSM) alloys on the atomistic scale. On the mesoscopic scale, magneto-crystalline anisotropy enables the magnetic-field-driven motion of twin boundaries, which causes magnetic-field-induced strain on the macroscopic length scale. Twin boundaries interact with magnetic domain boundaries and this interaction impacts the magneto-mechanical properties. For example, magneto-elastic defects form at the intersection of twin boundaries and magnetic domain boundaries. At high twin density, these defects cause hardening. In elongated samples, twin boundaries suppress the formation of magnetic domains parallel to the longest direction of the sample. Consequently, at a given fraction of each twin orientation, the torque exerted by a magnetic field on a magnetic shape memory alloy varies by up to a factor of 2 by changing the sequence of twins. Further, the interaction of magnetic domains and crystallographic twins reduces the rate of twinning and enhances the rate of electro-mechanical energy conversion. The design of MSM based devices must include the mesoscale interactions of magnetic domains and twin boundaries to optimize device performance.

FM-3:IL01  3D Reconstitution and Numerical Analysis of Thermo-mechanical Behavior of Porous and Cellular Shape Memory Alloys
T. BEN ZINEB1, R. Xu1, 2, S. Zhu3, C. Cissé4, R. Nishant3, C. Bouby1, A. Cherouat3, H. Zahrouni1, H. Hu2, W. Zaki4, 1Université de Lorraine, CNRS, Arts et Métiers Paris Tech, LEM3, Nancy, France; 2School of Civil Engineering, Wuhan University, Wuchang, Wuhan, China; 3University of Technology of Troyes, ICD/GAMMA3, Troyes, France; 4Khalifa University of Science and Technology, Abu Dhabi, UAE

The recent developments in additive manufacturing technology opened the possibility of considering cellular and porous shape memory alloys (SMAs) for more innovative applications. It makes possible to combine the adaptive properties of SMAs related to martensitic transformation and the lightening, dumping and functionally graded properties related porous and cellular materials. Therefore, the development of an adapted modeling of the thermomechanical response of cellular and porous SMAs at the material point, cellular and structure scales is emerging with interesting progress. In this communication, we present our recent contribution works in this topic. The constitutive thermomechanical models that we previously developed for NiTi and Iron-based SMAs were combined with analytical and numerical scale transition techniques and geometrical reconstitution numerical tools in order to predict the thermomechanical response of porous and cellular SMA structures using the finite element method. Examples of finite element analyses considering the effect of porosity, porous or cell size, shape and orientation are presented and discussed.

FM-3:L04  Thermomagnetic Thin Film Energy Harvester
J. Joseph, M. Kohl, Karlsruhe Institute of Technology (KIT), Institute of Microstructure Technology (IMT), Karlsruhe, Germany; M. Ohtsuka, Institute of Multidisciplinary Research for Advanced Matls, Tohoku University, Sendai, Japan; H. Miki, Institute of Fluid Science, Tohoku University, Sendai, Japan

Heusler alloys exhibit multiferroic phase transformations with abrupt changes in ferromagnetic ordering, which is highly attractive to perform energy conversion within small temperature differences. Here, we present the design, fabrication, and performance of a novel thermomagnetic energy harvester utilizing the ferromagnetic transition in a Ni-Mn-Ga thin-film device that has been optimized for a large abrupt change of magnetization within a narrow temperature range. A novel engineering approach is presented that relies on resonant self-actuation of the Ni-Mn-Ga film device in the field gradient of a heatable miniature permanent magnet. Thereby, thermal energy is converted to kinetic energy, which is transformed into electrical energy by electromagnetic induction using an integrated pick-up coil. This concept allows us to tailor the mechanical and thermal properties independently from each other and thus to match the mechanical and thermal duty cycles. For an energy harvester with a Ni-Mn-Ga film of 2 x 2 x 0.01 mm³ size and an overall footprint of 2 x 6.7 mm², we achieve a maximum power of 3.1µW. Upscaling the device with a film thickness of 40µm generates 5.3µW of power from an overall footprint of 2 x 5.5 mm², which compares well with state-of-the-art thermoelectric devices.

FM-3:L05  Investigation of the Damping Properties of Innovative NiTi Elements: Development of Proof of Concept and Demonstrators
F. Villa1, E. Bassani1, G. de Ceglia2, T. Claude Parkel3, F. Passaretti1, S. Viscuso4, E. Villa1, 1National Research Council - Institute of Condensed Matter Chemistry and Technologies for Energy (CNR ICMATE), Lecco, Italy; 2Technosprings Italia Srl, Besnate (VA), Italy; 3CSEM - Centre Suisse d’Electronique et de Microtechnique, Landquart (GR), Switzerland; 4TSS InnovationProjekte GmbH, Roveredo (GR), Switzerland

Since NiTi and NiTi-based shape memory alloys (SMAs) exhibit both pseudoelastic and intrinsic damping ability, they find application in several fields. Thanks to their functional properties, these materials could be integrated into dampers, junctions, connections or systems for the attenuation of vibrations including noise and more intense oscillations. The aim of this experimental study is the characterization of the damping behaviour of different NiTi semifinished products through dynamic thermomechanical analysis (DMTA) in order to obtain a preliminary indication for the integration of these innovative SMA elements in demonstrators. The investigated elements were a plain-woven mesh made of NiTi and steel thin wires, wave-shaped NiTi ribbons and NiTi single-turn wave springs; these products were studied in different configurations with different purposes and thermomechanical conditions which were investigated trough calorimetry and cyclic mechanical tests. Moreover, some demonstrators’ concepts, i.e. a cladding panel, two dampers and a shock absorber, were proposed and preliminary devices were realized and characterized. The perspectives and potential in the damping field of these NiTi semifinished products were investigated and discussed for the development of demonstrators.

FM-3:IL09  Development of Tube-based Structures to be Applied in Durable and Efficient Elastocaloric Cooling Device
S. Dall’Olio, A. Žerovnik, L. Porenta, Ž. Ahčin, J. Cerar, P. Kabirifar, J. Tušek, Faculty of Mechanical Engineering, University of Ljubljana, Ljubljana, Slovenia

Elastocaloric cooling technology, which utilizes the latent heat released/absorbed during the forward/reverse martensitic phase transformation in superelastic shape memory alloys (SMA), is being recognized as a promising alternative to the nowadays widely applied vapor-compression technology. Accordingly, different concepts of elastocaloric devices have been proposed and designed in recent years. The most promising overall cooling (heat-pumping) characteristics was obtained by active elastocaloric regenerator, which is a porous structure made of elastocaloric material thorough which a heat transfer fluid is pumped in a counter-flow direction. After a brief introduction and short overview of elastocaloric technology, the main challenges in designing durable and efficient compression-loaded elastocaloric regenerators will be discussed. Since superelastic Ni-Ti tubes seem to be the ideal candidates for elastocaloric regenerators loaded in compression, numerical and experimental analyses of buckling stability, fatigue behavior and heat transfer characteristics of tube bundles would be presented next. Finally, the first experimentally obtained cooling and heat-pumping characteristics of a novel tube-based elastocaloric regenerator in a new elastocaloric setup will be presented.


Cimtec 2022

Copyright © Techna Group S.r.l.
C.F.-P.I. 03368230409
Privacy Policy - Cookie Policy - Software Commercio Elettronico by Pianetaitalia.com