Direct observation of fast-moving twin boundaries in magnetic shape memory alloy Ni–Mn–Ga 5 M martensite

Saren, Andrey; Nicholls, Tim W; Tellinen, J.; Ullakko, K.

doi:10.1016/j.scriptamat.2016.04.004

Cited by 25 publications

(12 citation statements)

References 15 publications

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“…At the same time, some interesting insights can be identified regarding the ranges of the measured values. The two highest velocity data points (about 13 m/s and 14 m/s) are in general agreement with the high values reported by the Ullakko's group [13][14][15]. About 20 other data points have velocities in the range of 0-3 m/s, which is in agreement with our previous results [6,7].…”

Section: Discussionsupporting

confidence: 92%

“…Pulsed magnetic field experiments were also reported by Smith et al [12] and by Saren et al [13][14][15]. There, a 10M Ni-Mn-Ga single crystal sample with length of few mm was subjected to ls scale pulsed magnetic field actuation, and the resulting motion of a single twin boundary that propagated throughout the crystal's length was followed using laser vibrometry and high-speed photography.…”

Section: Introductionmentioning

confidence: 77%

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Variability of Twin Boundary Velocities in 10M Ni–Mn–Ga Measured Under $$\upmu{\text{s}}$$-Scale Force Pulses

Mizrahi

Shilo

Faran

2020

Shap. Mem. Superelasticity

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Twin boundary motion is the basic mechanism responsible for fast actuation of magnetic shape memory (MSM) alloys. Previous studies implied on a wide diversity of twin boundary velocities measured under similar conditions. Here, a data set of more than 400 velocity values is measured under conditions that are relevant for MSM applications and represents the dynamic behavior of 73 twin boundaries. Velocities are measured using an electromechanical setup that applies a controllable ls-scale force pulse and combines force measurements with high-speed imaging. The latter allows extracting velocities of individual twin boundaries, which are then correlated to the macroscopic stress in the sample. The appearance of type I twins is more prevalent than type II, resulting a much larger data set for type I twins. Statistical analysis of velocity points of type I twins reveals an increasing trend of the velocity with the macroscopic stress, as well as useful information on the probability distribution of velocity data. Velocities of type II twins exhibit large variability over a relatively narrow stress range. This can reason the large differences in maximal velocities reported previously for this twin type. The obtained statistical data can improve the design and modeling of MSM actuators.Keywords Magnetic shape memory Á Ni-Mn-Ga Á Twin boundary velocity Á Force pulse Á High-speed imaging This article is an invited submission to Shape Memory and Superelasticity selected from presentations at the International Conference onFerromagnetic Shape Memory Alloys (ICFSMA) held June 2-7, 2019 in Prague, Czech Republic, and has been expanded from the original presentation.

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Section: Discussionsupporting

confidence: 92%

Section: Introductionmentioning

confidence: 77%

Variability of Twin Boundary Velocities in 10M Ni–Mn–Ga Measured Under $$\upmu{\text{s}}$$-Scale Force Pulses

Mizrahi

Shilo

Faran

2020

Shap. Mem. Superelasticity

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“…This is mainly due to their large magnetic field-induced strains (MFIS) and fast response times [1][2][3]. For example, the Ni2MnGa-based alloys, with their high recovery strain values (over 10% for a single crystal [4]) and fast response time (less than a millisecond [5]), have found their applications as industrial FSMAs. However, this is not the case for their use in high-frequency actuators and sensors, which is due to their low martensitic transition temperature and high cost of single crystal preparation [6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Microstructure and Magnetic Field-Induced Strain of a Ni-Mn-Ga-Co-Gd High-Entropy Alloy

Bao

et al. 2021

Materials

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The effect of a high-entropy design on martensitic transformation and magnetic field-induced strain has been investigated in the present study for Ni-Mn-Ga-Co-Gd ferromagnetic shape-memory alloys. The purpose was to increase the martensitic transition temperature, as well as the magnetic field-induced strain, of these materials. The results show that there is a co-existence of β, γ, and martensite phases in the microstructure of the alloy samples. Additionally, the martensitic transformation temperature shows a markedly increasing trend for these high-entropy samples, with the largest value being approximately 500 °C. The morphology of the martensite exhibits typical twin characteristics of type L10. Moreover, the magnetic field-induced strain shows an increasing trend, which is caused by the driving force of the twin martensite re-arrangement strengthening.

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“…The maximum magnetic-field-induced strain depends on the martensite structure and lattice parameters and varies between 6 and 12 % [2][3][4][5] . With a few microseconds response time [6], these materials have great potential as actuators. Numerous research groups have studied the material properties of Ni-Mn-Ga single crystals and its response to variable magnetic fields to improve the performance of MSM actuators [7][8][9][10][11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%

“…The switching behavior of the material dictates the response of the actuator. Recently, Saren et al [6] and Smith et al [18] reported twin boundary velocities of 39 and 82 m/s implying actuation speeds of 2.4 and 4.8 m/s. Pagounis et al summarized some recent progress on MSM actuators [19].…”

Section: Introductionmentioning

confidence: 99%

Sensitivity of twin boundary movement to sample orientation and magnetic field direction in Ni-Mn-Ga

et al. 2020

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When applying a magnetic field parallel or perpendicular to the long edge of a parallelepiped Ni-Mn-Ga stick, twin boundaries move instantaneously or gradullay through the sample. We evaluate the sample shape dependence on twin boundary motion with a micromagnetics computational study of magnetic domain structures and their energies. Due to the sample shape, the demagnetization factor varies with the direction of external magnetic field. When the external magnetic field is applied perpendicular to the long edge of the sample, i.e. in the direction in which the demagnetizing field is highest, the magnetic energy intermittently increases when the strength 2 of the applied magnetic field is low. This energy gain hinders the twin boundary motion and results in a gradual switching, i.e. a gradual magnetization reversal as the applied magnetic field is increased. The formation of 180⁰ magnetic domains offsets this effect partially. In contrast, when the applied magnetic field is parallel to the long edge of the sample, i.e. in the direction in which the demagnetizing field is lowest, the energy decreases with each subsequent magnetization domain reversal and the twin boundary moves instantaneously with ongoing switching. The actuation mode with the field parallel to the long sample edge lends itself for on-off actuators whereas the actuation mode with the field perpendicular to the long sample edge lends itself to gradual positioning devices.

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Direct observation of fast-moving twin boundaries in magnetic shape memory alloy Ni–Mn–Ga 5 M martensite

Cited by 25 publications

References 15 publications

Variability of Twin Boundary Velocities in 10M Ni–Mn–Ga Measured Under $$\upmu{\text{s}}$$-Scale Force Pulses

Variability of Twin Boundary Velocities in 10M Ni–Mn–Ga Measured Under $$\upmu{\text{s}}$$-Scale Force Pulses

Microstructure and Magnetic Field-Induced Strain of a Ni-Mn-Ga-Co-Gd High-Entropy Alloy

Sensitivity of twin boundary movement to sample orientation and magnetic field direction in Ni-Mn-Ga

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