Strain-induced dimensionality crossover and associated pseudoelasticity in the premartensitic phase of Ni2MnGa

Nie, Zhihua; Ren, Yang; Wang, Y. D.; Liu, D. M.; Brown, Dennis E.; Wang, G.; Zuo, Liang

doi:10.1063/1.3506508

Cited by 12 publications

(10 citation statements)

References 21 publications

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“…Macroscopically the premartensite phase of Ni 2 MnGa keeps an overall cubic symmetry of the parent L21 phase; however, high resolution electron microscopy showed that the premartensite contains a very fine mixture of variously oriented spontaneous strain states on the scale of nanometers (). This makes the character of Ni–Mn–Ga premartensite superficially similar to the strain‐glass phases reported for the NiTi alloy .…”

Section: Introductionmentioning

confidence: 99%

“…The observed cubic structure suggests that the tweed domains are smaller than coherent length of the X‐ray structural method. Despite of the overall cubic symmetry, high resolution synchrotron X‐ray diffraction () shows that the premartensite phase/tweed exhibits the modulation or shuffling with approximate wave vector [1/3, 1/3, 0]. There is a discussion whether this modulation is commensurate () or incommensurate (), but it does not change the overall picture that the premartensite can be considered as consisting of fine (approximate) 6 M modulated phase with all possible modulation directions randomly distributed, or, equivalently, as adaptive phase with (

2 \overset{1}{true}

) 2 shuffling period .…”

Section: Introductionmentioning

confidence: 99%

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Elasticity and magnetism of Ni₂ MnGa premartensitic tweed

Seiner

Kopecký

Landa

et al. 2014

Physica Status Solidi (b)

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Magnetic, magneto‐elastic and elastic measurements were used to characterize the thermal evolution of the premartensite phase of Ni2 MnGa. The premartensitic transition is shown to correspond to a sharp maximum of magnetostriction and a pronounced minimum of the (110) 〈1true1‾0〉 shear stiffness (the c′ elastic coefficient); no additional softening of the c′ coefficient prior to the martensitic transformation was observed. In contrast, a significant softening of the (100) 〈010〉 stiffness (the c44 elastic coefficient) was observed in the vicinity of the martensitic transition, while this coefficient is fully unaffected by the premartensitic transition. A simple two‐dimensional model of the tweed is presented to explain this mutual independence between the c′ and c44 shears and the effect of tweed formation on both of them.

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Section: Introductionmentioning

confidence: 99%

2 \overset{1}{true}

) 2 shuffling period .…”

Section: Introductionmentioning

confidence: 99%

Elasticity and magnetism of Ni₂ MnGa premartensitic tweed

Seiner

Kopecký

Landa

et al. 2014

Physica Status Solidi (b)

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“…31,32 As the total free energy altered by different phonon vibration modes is not so large, a low elastic modulus can be predicted via the domain-switch mechanism. 20 The transition in phonon softening modes caused by the uniaxial stress field is accomplished by a small atomic displacement, which is analogous to the stress-induced structural transition between the two low-crystal-symmetry domains; thus, a giant low-or non-hysteretic stress-fieldinduced response in the Ni 2 MnGa precursor martensite may be maintained.…”

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confidence: 99%

“…19 This peculiar superelasticity in premartensite has been related to reversible redistribution of the precursor modulations from three-dimension to two-dimension under the applied uniaxial stress. 20 However, the physical mechanism on the change in modulation dimensionality is still unknown. It can hardly be explained simply by the reorientation of nanotwinned tetragonal martensitic variants, as the detwinning process should be normally irreversible and produces plastic deformation in alloys.…”

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confidence: 99%

“…20 The premartensitic and martensitic transition temperatures of this system were detected to be 230 K and 175 K by using a superconducting quantum interference device (SQUID). High energy synchrotron in-situ x-ray diffraction experiments were performed at Advanced Photon Source, Argonne National Laboratory, to monitor the structural evolutions of the Ni 2 MnGa crystal as a function of temperature, uniaxial stress, and hydrostatic pressure.…”

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confidence: 99%

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Strain-induced dimensionality crossover of precursor modulations in Ni2MnGa

Nie

Wang

Shang

et al. 2015

Applied Physics Letters

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Precursor modulations often occur in functional materials like magnetic shape memory alloys, ferroelectrics, and superconductors. In this letter, we have revealed the underlying mechanism of the precursor modulations in ferromagnetic shape memory alloys Ni2MnGa by combining synchrotron-based x-ray diffraction experiments and first-principles phonon calculations. We discovered the precursor modulations along [011] direction can be eliminated with [001] uniaxial loading, while the precursor modulations or premartensite can be totally suppressed by hydrostatic pressure condition. The TA2 phonon anomaly is sensitive to stress induced lattice strain, and the entire TA2 branch is stabilized along the directions where precursor modulations are eliminated by external stress. Our discovery bridges precursor modulations and phonon anomalies, and sheds light on the microscopic mechanism of the two-step superelasticity in precursor martensite.

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