Structure and Phase Stability of NiMnGa Ferromagnetic Shape Memory Alloys by Experimental and Ab Initio Techniques

This paper summarizes some of our recent results on crystal structure, microstructure, orientation relationship between martensitic variants and crystallographic features of martensitic transformation in Ni-Mn-Ga FSMAs. It was shown that Ni53Mn25Ga22 has a tetragonal I4/mmm martensitic structure at room temperature. The neighboring martensitic variants in Ni53Mn25Ga22 have a compound twinning relationship with the twinning elements K1={112}, K2={11-2}, η1=<11-1>, η2=<111>, P={1-10} and s=0.379. The ratio of the relative amounts of twins within the same initial austenite grain is ~1.70. The main orientation relationship between austenite and martensite is Kurdjumov-Sachs (K-S) relationship. Based on the crystallographic phenomenological theory, the calculated habit plane is {0.690 -0.102 0.716}A (5.95° from {101}A), and the magnitude, direction and shear angle of the macroscopic transformation shear are 0.121, <-0.709 0.105 0.698>A (6.04° from <-101>A) and 6.88°, respectively.

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DETERMINATION OF CRYSTAL STRUCTURE AND CRYSTALLOGRAPHIC CHARACTERISTICS IN Ni-Mn-Ga FERROMAGNETIC SHAPE MEMORY ALLOYS

International Journal of Modern Physics B ◽

10.1142/s0217979209061603 ◽

2009 ◽

Vol 23 (06n07) ◽

pp. 1771-1776

Author(s):

D. Y. CONG ◽

Y. D. ZHANG ◽

C. ESLING ◽

Y. D. WANG ◽

X. ZHAO ◽

...

Keyword(s):

Crystal Structure ◽

Shape Memory Alloys ◽

Shape Memory ◽

High Performance ◽

Room Temperature ◽

Martensitic Structure ◽

Magnetic Shape Memory ◽

Ferromagnetic Shape Memory Alloys ◽

Electron Backscattered Diffraction ◽

Ferromagnetic Shape Memory

Ni - Mn - Ga ferromagnetic shape memory alloys (FSMAs) have received great attention during the past decade due to their giant magnetic shape memory effect and fast dynamic response. The crystal structure and crystallographic features of two Ni - Mn - Ga alloys were precisely determined in this study. Neutron diffraction measurements show that Ni 48 Mn 30 Ga 22 has a Heusler austenitic structure at room temperature; its crystal structure changes into a seven-layered martensitic structure when cooled to 243K. Ni 53 Mn 25 Ga 22 has an I4/mmm martensitic structure at room temperature. Electron backscattered diffraction (EBSD) analyses reveal that there are only two martensitic variants with a misorientation of ~82° around <110> axis in each initial austenite grain in Ni 53 Mn 25 Ga 22. The investigation on crystal structure and crystallographic features will shed light on the development of high-performance FSMAs with optimal properties.

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Neutron diffraction study on crystal structure and phase transformation in Ni-Mn-Ga ferromagnetic shape memory alloys

Powder Diffraction ◽

10.1154/1.2790932 ◽

2007 ◽

Vol 22 (4) ◽

pp. 307-311 ◽

Cited By ~ 3

Author(s):

D. Y. Cong ◽

Y. D. Wang ◽

J. Z. Xu ◽

L. Zuo ◽

P. Zetterström ◽

...

Keyword(s):

Crystal Structure ◽

Phase Transformation ◽

Neutron Diffraction ◽

Shape Memory Alloys ◽

Shape Memory ◽

Neutron Diffraction Study ◽

Martensitic Structure ◽

Ferromagnetic Shape Memory Alloys ◽

Structure Changes ◽

Ferromagnetic Shape Memory

Crystal structure and phase transformation behaviors in two Ni-Mn-Ga ferromagnetic shape memory alloys (FSMAs) with compositions of Ni48Mn30Ga22 and Ni53Mn25Ga22 (at. %) as a function of temperature were investigated by in situ neutron diffraction experiments. Neutron diffraction technique proves to be highly efficient in characterizing structural transformation in Ni-Mn-Ga FSMAs, which consist of nearby elements in the periodic table. Our neutron results show that Ni48Mn30Ga22 has a cubic, L21 Heusler structure from 373 to 293 K. Its crystal structure changes into a seven-layered orthorhombic martensitic structure when cooled to 243 K, and no further transformation is observed upon cooling to 19 K. Neutron diffraction results also show that Ni53Mn25Ga22 has a tetragonal I4/mmm martensitic structure from 20 to 403 K. A pre-transformation around room temperature is observed from an abrupt jump in unit-cell volume of Ni53Mn25Ga22, which corresponds with an endothermic peak detected in a heated DSC curve.

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Structural Characterization of Co70-xNixGa30 Ferromagnetic Shape Memory Alloys

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.52.103 ◽

2008 ◽

Vol 52 ◽

pp. 103-108 ◽

Cited By ~ 3

Author(s):

Sidananda Sarma ◽

A. Srinivasan

Keyword(s):

Magnetic Susceptibility ◽

Shape Memory ◽

Room Temperature ◽

Structural Parameters ◽

Ac Magnetic Susceptibility ◽

X Ray Diffraction ◽

Ferromagnetic Shape Memory Alloys ◽

Two Phase ◽

X Ray ◽

Ferromagnetic Shape Memory

Polycrystalline ingots of Co70–xNixGa30 (20 ≤ x ≤ 26) ferromagnetic shape memory alloy (FSMA) were prepared by arc melting elemental powders followed by homogenization at 1230 °C for 24 hrs and quenching in liquid nitrogen. Room temperature X-Ray diffraction (XRD) patterns of as-quenched samples exhibited single-phase tetragonal structure for alloy compositions with x = 21 to 26, and a two-phase structure (cubic A2-phase along with weak tetragonal phase) for the alloy with x = 20. Rietveld refinement was performed on the X-ray diffraction patterns to obtain the refined structural parameters. Differential Scanning Calorimeter (DSC) curves recorded from 30 °C to 250 °C revealed martensite-austenite and austenite-martensite transformations in all alloys except the alloy with composition x = 20. Low temperature ac magnetic susceptibility measurements confirmed the existence of martensitic transformations in the alloy with x = 20. The structural transformation temperatures show a linear variation with e/a ratio. All the alloys were ferromagnetic at room temperature. Curie temperature was determined using a high temperature ac magnetic susceptibility measurement set-up.

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Magneto-Mechanical Behaviour of Textured Polycrystals of NiMnGa Ferromagnetic Shape Memory Alloys

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.52.29 ◽

2008 ◽

Vol 52 ◽

pp. 29-34 ◽

Cited By ~ 6

Author(s):

Stefan Roth ◽

Uwe Gaitzsch ◽

Martin Pötschke ◽

Ludwig Schultz

Keyword(s):

Magnetic Field ◽

Heat Treatment ◽

Shape Memory ◽

Directional Solidification ◽

Mechanical Behaviour ◽

Martensitic Structure ◽

Ferromagnetic Shape Memory Alloys ◽

Induced Stress ◽

Ferromagnetic Shape Memory ◽

Induced Changes

Textured polycrystalline NiMnGa alloys were prepared by directional solidification. Alloys were chosen to have either the 7M or the 5M modulated martensitic structure after proper heat treatment. Mechanical training allowed to reduce the twin boundary pinning stress to below the magnetically induced stress. Thus, magnetic field induced changes in the mechanical behaviour could be demonstrated. The conditions of preparation and mechanical training will be discussed together with their influence on structure, microstructure, and the magneto-mechanical behaviour.

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Effect of Mn Concentration on Magneto-mechnaical Properties in Directionally Solidified Ferromagnetic Shape Memory Ni-Mn-Ga Alloys

Defence Science Journal ◽

10.14429/dsj.66.10214 ◽

2016 ◽

Vol 66 (4) ◽

pp. 391

Author(s):

R.K Singh ◽

M. Manivel Raja ◽

P. Ghosal ◽

R.P. Mathur

Keyword(s):

Magnetic Field ◽

Crystal Structure ◽

Mechanical Properties ◽

Phase Transformation ◽

Chemical Composition ◽

Room Temperature ◽

Martensite Phase ◽

Directionally Solidified ◽

Ferromagnetic Shape Memory ◽

Mn Concentration

Heusler type alloys Ni50Mn25+xGa25-x (x=2,3,4 and 5) based on near stoichiometric Ni2MnGa compositions were directionally solidified using modified Bridgman method. The alloys thus prepared were characterized for their chemical composition, crystal structure, microstructure, phase transformation, magnetic and magneto-mechanical properties. The directionally solidified Ni50Mn30Ga20 alloy rod exhibited maximum magnetocrystalline value of 95 kJm-3 and lowest detwinning stresses for martensite phase of about 5MPa. The reversible room temperature magnetic field induced strain of 0.2% under external magnetic field of 0.6T and 0.05kN bias load was obtained for the directionally solidified Ni50Mn30Ga20 alloy.

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Development of Co-Ni-Ga Ferromagnetic Shape Memory Alloys with Enhanced Properties

Materials Science Forum ◽

10.4028/www.scientific.net/msf.587-588.650 ◽

2008 ◽

Vol 587-588 ◽

pp. 650-653

Author(s):

Sidananda Sarma ◽

A. Srinivasan

Keyword(s):

Room Temperature ◽

Composition Dependence ◽

Martensite Phase ◽

Ferromagnetic Shape Memory Alloys ◽

Atom Ratio ◽

Structural Characterisation ◽

Β Phase ◽

Arc Melting ◽

Ferromagnetic Shape Memory ◽

Ice Water

Polycrystalline ingots of Co70-xNixGa30 (22 ≤ x ≤ 25) alloys were prepared by a sequence of arc melting high purity Co, Ni and Ga in argon atmosphere, followed by homogenization at 1150°C under a pressure of 10-3 Pa, and quenching in ice water. Structural characterisation of the quenched alloys was carried out to verify the presence of the martensite phase at room temperature. The martensite start (Ms), martensite finish (Mf), austenite start (As) and austenite finish (Af) temperatures for the alloys were determined using a differential scanning calorimeter. The ferromagnetic to paramagnetic phase transition temperature (TC) of the alloys was determined using an indigenously developed ac susceptometer. All the alloys are FSMAs with Ms, Af and TC above room temperature. The composition dependence of the properties of these alloys could be understood on the basis of the e/a (electrons to atom) ratio and the Co/Ni ratio. Presence of γ-phase precipitates along with the β-phase in these alloys enhances the ductility as well as influences the physical properties of these alloys.

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

Metals ◽

10.3390/met11101534 ◽

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.

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Neutron Diffraction Studies of Magnetic Shape Memory Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.684.73 ◽

2011 ◽

Vol 684 ◽

pp. 73-84 ◽

Cited By ~ 4

Author(s):

José M. Barandiarán ◽

Jon Gutiérrez ◽

Patricia Lázpita ◽

J. Feuchtwanger

Keyword(s):

Crystal Structure ◽

Neutron Diffraction ◽

Shape Memory Alloys ◽

Shape Memory ◽

Site Occupancy ◽

Magnetic Shape Memory ◽

Ferromagnetic Shape Memory Alloys ◽

Magnetic Shape Memory Alloys ◽

Moment Distribution ◽

Ferromagnetic Shape Memory

The characteristics of neutron diffraction applied to the study of Ferromagnetic Shape Memory Alloys are revised. Main studies refer to crystal structure, preferential site occupancy, variant reorientation and magnetic moment distribution in the alloys

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Tunable Martensitic Transformation and Magnetic Properties of Sm-Doped NiMnSn Ferromagnetic Shape Memory Alloys

Crystals ◽

10.3390/cryst11091115 ◽

2021 ◽

Vol 11 (9) ◽

pp. 1115

Author(s):

Najam ul Hassan ◽

Mohsan Jelani ◽

Ishfaq Ahmad Shah ◽

Khalil Ur Rehman ◽

Abdul Qayyum Khan ◽

...

Keyword(s):

Magnetic Properties ◽

Martensitic Transformation ◽

Shape Memory Alloys ◽

Shape Memory ◽

Transformation Temperature ◽

Room Temperature ◽

Field Variation ◽

Martensitic Transformation Temperature ◽

Ferromagnetic Shape Memory Alloys ◽

Ferromagnetic Shape Memory

NiMnSn ferromagnetic shape memory alloys exhibit martensitic transformation at low temperatures, restricting their applications. Therefore, this is a key factor in improving the martensitic transformation temperature, which is effectively carried out by proper element doping. In this research, we investigated the martensitic transformation and magnetic properties of Ni43Mn46-x SmxSn11 (x = 0, 1, 2, 3) alloys on the basis of structural and magnetic measurements. X-ray diffraction showed that the crystal structure transforms from the cubic L21 to the orthorhombic martensite and gamma (γ) phases. The reverse martensitic and martensitic transformations were indicated by exothermic and endothermic peaks in differential scanning calorimetry. The martensitic transformation temperature increased considerably with Sm doping and exceeded room temperature for Sm = 3 at. %. The Ni43Mn45SmSn11 alloy exhibited magnetostructural transformation, leading to a large magnetocaloric effect near room temperature. The existence of thermal hysteresis and the metamagnetic behavior of Ni43Mn45SmSn11 confirm the first-order magnetostructural transition. The magnetic entropy change reached 20 J·kg−1·K−1 at 266 K, and the refrigeration capacity reached ~162 J·Kg−1, for Ni43Mn45SmSn11 under a magnetic field variation of 0–5 T.

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