Magnetic Shape Memory - Polymer Hybrids

2016 ◽  
Vol 879 ◽  
pp. 133-138 ◽  
Author(s):  
Ilkka Aaltio ◽  
Frans Nilsén ◽  
Joonas Lehtonen ◽  
Yan Ling Ge ◽  
Steven Spoljaric ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Shape Memory ◽  
Single Crystals ◽  
Magnetic Particles ◽  
Shape Change ◽  
Shape Memory Polymer ◽  
Raw Material ◽  
Magnetic Shape Memory ◽  
Polymer Hybrids ◽  
The Magnetic Field

Martensitic Ni-Mn-Ga based alloys are known for the Magnetic Shape Memory (MSM) effect, which upon application of an external magnetic field can generate a strain up to 12 % depending on the microstructure of the martensite. The MSM effect occurs by rearrangement of the martensite variants, which is most advantageous in single crystals. Single crystals are, however, rather tedious to produce and there has been attempts to achieve MSM effect in polycrystals. However, in polycrystals the magnetic field induced shape change remains low as compared to single crystals. As an alternative to the former, hybrid MSM materials offer several advantages. When compared to single crystals, hybrids have extended freedom of shaping, lower raw material price, relatively large MSM strain and easier manufacturability. Embedding MSM particles into a suitable polymer matrix results in actuation function or good vibration damping performance. In the present study we report on the mechanical, structural and magnetic properties of MSM polymer hybrids, which are prepared by mixing gas-atomized Ni-Mn-Ga MSM powder into epoxy matrix and aligning the magnetic particles in a magnetic field.

Effects of Surface Pinning, Locking and Adaption of Twins on the Performance of Magnetic Shape-Memory Alloys

2011 ◽  
Vol 684 ◽  
pp. 177-201 ◽  
Author(s):  
Markus Chmielus ◽  
Peter Müllner
Keyword(s):  
Magnetic Field ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Surface Damage ◽  
Magnetic Shape Memory ◽  
Magnetic Shape Memory Alloys ◽  
Fatigue Lifetime ◽  
Twin Density ◽  
External Constraints ◽  
The Magnetic Field

We study the effect of surface modifications and constraints on the mechanical properties of Ni-Mn- Ga single crystals, which are imposed by (i) structural modifications near the surface, (ii) mounting to a solid surface, and (iii) guiding the stroke. Spark eroded samples were electropolished and characterized before and after each polishing treatment. Surface damage was then produced with spark erosion and abrasive wearing. Surface damage stabilizes and pins a dense twin-microstructure and prevents twins from coarsening. The density of twins increases with increasing degree of surface deformation. Twinning stress and hardening rate during mechanical loading increase with increasing surface damage and twin density. In contrast, when a damaged surface layer is removed, twinning stresses, hardening rate, and twin density decrease. Constraining the sample by mounting and guiding reduces the magnetic-field-induced strain by locking twins at the constrained surfaces. . For single-domain crystals and for hard magnetic shape-memory alloys, external constraints strongly reduce the magnetic-field-induced strain and the fatigue lifetime is short. In contrast, for selfaccommodated martensite and for soft magnetic shape-memory alloys, the twin-microstructure adapts well to external constraints and the fatigue lifetime is long. The performance of devices with MSMA transducers requires managing stress distributions through design and control of surface properties, microstructure, and constraints.

Recent Developments of Magnetic SMA

2008 ◽  
Vol 59 ◽  
pp. 1-10 ◽  
Author(s):  
Outi Söderberg ◽  
Ilkka Aaltio ◽  
Yan Ling Ge ◽  
Xu Wen Liu ◽  
Simo Pekka Hannula
Keyword(s):  
Magnetic Field ◽  
Phase Transformation ◽  
Shape Memory ◽  
Dimensional Change ◽  
Magnetic Shape Memory ◽  
Dimensional Changes ◽  
Different Types ◽  
Recent Developments ◽  
Giant Magnetocaloric Effect ◽  
The Magnetic Field

In the shape memory alloys (SMAs) the thermal triggering induces reversible dimensional change by the phase transformation – these materials may also be ferrior ferromagnetic, however, here only the ferromagnetic SMAs are discussed. In certain SMAs the austenitemartensite phase transformation is influenced by the magnetic field as either austenite or martensite is promoted by the field and this is exploited for the dimensional changes. However, in the magnetic shape memory (MSM) alloys no phase transformation occurs as the remarkable dimensional changes take place by the twin variant changes in the martensitic phase activated by the external magnetic field at constant temperature. In addition to the phase transformation or magnetic shape memory effect, the applied magnetic field may also result in the conventional magnetostriction (MS), enhance the superelasticity (magneticfieldassisted superelasticity MFAS) or induce the giant magnetocaloric effect (GMCE). Certain alloys such as NiMnGa may even be multifunctional showing more than one of these effects. The present paper gives an overview of the different types of the magnetically activated SMA alloys, their properties as well as their potentials for applications in the frameworks of the recent studies.

Hysteresis effects in the magnetic-field-induced reverse martensitic transition in magnetic shape-memory alloys

2010 ◽  
Vol 108 (4) ◽  
pp. 043914 ◽  
Author(s):  
Thorsten Krenke ◽  
Seda Aksoy ◽  
Eyüp Duman ◽  
Mehmet Acet ◽  
Xavier Moya ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Martensitic Transition ◽  
Magnetic Shape Memory ◽  
Magnetic Shape Memory Alloys ◽  
The Magnetic Field

Shape Memory Alloys: A Summary of Recent Achievements

2008 ◽  
Vol 583 ◽  
pp. 21-41 ◽  
Author(s):  
Peter Entel ◽  
Vasiliy D. Buchelnikov ◽  
Markus E. Gruner ◽  
Alfred Hucht ◽  
Vladimir V. Khovailo ◽  
...  
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Shape Memory ◽  
Shape Change ◽  
Heusler Alloys ◽  
Systematic Change ◽  
Magnetic Shape Memory ◽  
Electronic Density ◽  
Modulated Phases ◽  
Modulated Structures

The Ni-Mn-Ga shape memory alloy displays the largest shape change of all known magnetic Heusler alloys with a strain of the order of 10% in an external magnetic field of less than one Tesla. In addition, the alloys exhibit a sequence of intermediate martensites with the modulated structures usually appearing at c/a < 1 while the low-temperature non- modulated tetragonal structures have c/a > 1. Typically, in the Ni-based alloys, the martensitic transformation is accompanied by a systematic change of the electronic structure in the vicinity of the Fermi energy, where a peak in the electronic density of states from the non-bonding Ni states is shifted from the occupied region to the unoccupied energy range, which is associated with a reconstruction of the Fermi surface, and, in most cases, by pronounced phonon anomalies. The latter appear in high-temperature cubic austenite, premartensite but also in the modulated phases. In addition, the modulated phases have highly mobile twin boundaries which can be rearranged by an external magnetic field due to the high magnetic anisotropy, which builds up in the martensitic phases and which is the origin of the magnetic shape memory effect. This overall scenario is confirmed by first-principles calculations.

scholarly journals Recent Developments in Ni-Mn-Ga Foam Research

2009 ◽  
Vol 635 ◽  
pp. 119-124 ◽  
Author(s):  
Peter Müllner ◽  
Xue Xi Zhang ◽  
Yuttanant Boonyongmaneerat ◽  
Cassie Witherspoon ◽  
Markus Chmielus ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Grain Boundaries ◽  
Single Crystals ◽  
Cyclic Strain ◽  
Martensite Phase ◽  
Magnetic Shape Memory ◽  
Magnetic Shape Memory Alloys ◽  
Major Barrier

Grain boundaries hinder twin boundary motion in magnetic shape-memory alloys and suppress magnetic-field-induced deformation in randomly textured polycrystalline material. The quest for high-quality single crystals and the associated costs are a major barrier for the commercialization of magnetic shape-memory alloys. Adding porosity to polycrystalline magnetic-shape memory alloys presents solutions for (i) the elimination of grain boundaries via the separation of neighboring grains by pores, and (ii) the reduction of production cost via replacing the directional solidification crystal growth process by conventional casting. Ni-Mn-Ga foams were produced with varying pore architecture and pore fractions. Thermo-magnetic training procedures were applied to improve magnetic-field-induced strain. The cyclic strain was measured in-situ while the sample was heated and cooled through the martensitic transformation. The magnetic field-induced strain amounts to several percent in the martensite phase, decreases continuously during the transformation upon heating, and vanishes in the austenite phase. Upon cooling, cyclic strain appears below the martensite start temperature and reaches a value larger than the initial strain in the martensite phase, thereby confirming a training effect. For Ni-Mn-Ga single crystals, external constraints imposed by gripping the crystal limit lifetime and/or magnetic-field-induced deformation. These constraints are relaxed for foams.

scholarly journals Coexisting Multiple Martensites in Ni57−XMn21+XGa22 Ferromagnetic Shape Memory Alloys: Crystal Structure and Phase Transition

Metals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1534
Author(s):  
Lian Huang ◽  
Daoyong Cong ◽  
Mingguang Wang ◽  
Yandong Wang
Keyword(s):  
Magnetic Field ◽  
Crystal Structure ◽  
Phase Transition ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Alloy System ◽  
Magnetic Shape Memory ◽  
Ferromagnetic Shape Memory Alloys ◽  
Ferromagnetic Shape Memory ◽  
The Magnetic Field

A comprehensive study of the crystal structure and phase transition as a function of temperature and composition in Ni57−xMn21+xGa22 (x = 0, 2, 4, 5.5, 7, 8) (at. %) magnetic shape memory alloys was performed by a temperature-dependent synchrotron X-ray diffraction technique and transmission electron microscopy. A phase diagram of this Ni57−xMn21+xGa22 alloy system was constructed. The transition between coexisting multiple martensites with monoclinic and tetragonal structures during cooling was observed in the Ni51.5Mn26.5Ga22 (x = 5.5) alloy, and it was found that 5M + 7M multiple martensites coexist from 300 K to 160 K and that 5M + 7M + NM multiple martensites coexist between 150 K and 100 K. The magnetic-field-induced transformation from 7M martensite to NM martensite at 140 K where 5M + 7M + NM multiple martensites coexist before applying the magnetic field was observed by in situ neutron diffraction experiments. The present study is instructive for understanding the phase transition between coexisting multiple martensites under external fields and may shed light on the design of novel functional properties based on such phase transitions.

Magnetic Field Activation of Thermoresponsive Shape-Memory Polymer with Embedded Micron Sized Ni Powder

2010 ◽  
Vol 123-125 ◽  
pp. 995-998 ◽  
Author(s):  
Da Wei Zhang ◽  
Yan Ju Liu ◽  
Jin Song Leng
Keyword(s):  
Magnetic Field ◽  
Shape Memory ◽  
Coupling Agent ◽  
Silane Coupling Agent ◽  
Nickel Powder ◽  
Shape Memory Polymer ◽  
Initial Shape ◽  
Silane Coupling ◽  
Shape Memory Composite ◽  
The Magnetic Field

The shape memory polymer (SMP) materials are able to change these shape in response to external stimulus such as stress, temperature, solvent, PH, magnetic, electricity or light. The above-mentioned methods are only to recover initial shape of the deformed SMP, could not give the SMP predeformation. In this paper, magnetic field gives the shape memory polymer composite (SMPC) pre-deformation was studied, through on and off of magnetic field the two-way activation of SMPC was achieved. Shape memory effect of shape memory composite in magnetic field was studied. The SMPC was filled by nickel powder, and the nickel powder was treated by silane coupling agent. The Tg of shape memory composite was measured by dynamic mechanical analyzer. The surface element of treated nickel powder was analysized with XPS. The results indicated that the shape of composite filled by untreated nickel powder did not change in the magnetic field, while the composite filled by treated nickel powder was drawn in the magnetic field. The tensile stretch was decrease with the increase of nickel powder content in the shape memory composite. The addition of silane coupling agent onto nickel powder surface was helpful for the dispersion of nickel in polymer.

Experimental Study on the Magnetic Properties of MSMA and the Function of MSMA Actuator of Reticulated Shell Structure

2013 ◽  
Vol 846-847 ◽  
pp. 539-542
Author(s):  
Jin Sheng He ◽  
Tao Yang ◽  
She Liang Wang ◽  
Guang Yuan Weng
Keyword(s):  
Magnetic Field ◽  
Shape Memory ◽  
Shell Structure ◽  
Coupling Effect ◽  
Memory Function ◽  
Magnetic Shape Memory ◽  
Magnetic Shape Memory Alloy ◽  
Reticulated Shell Structure ◽  
Strain Model ◽  
The Magnetic Field

With shape memory function of new smart material, the magnetic control properties of magnetic shape memory alloy could be used to fabricate intelligent actuators for vibration control of reticulated shell structure. The major performance parameters of the microstructure of the materials has been considered in the functional relationship between the magnetic field and strain model of traditional magnetic shape memory alloys (MSMA). But the magnetic field of MSMA do not considered, induced strain and pre-pressure, ambient temperature and other factors, which is a mutual restraint relationship and coupling. Selected Ni53Mn25Ga22, in this paper, as the material for the research on deformation under the action of temperature, magnetic field, pressure coupling effect, and according to the test data designed a MSMA actuator drive.

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