Magnetic Field-induced Martensitic Transformation Research Articles

Tuning martensitic transformation and magnetocaloric effect with Bi substitution in MnCo1-xBixGe alloys

In this work, the substitution of Bi for Co atoms in MnCo1-xBixGe (x = 0.01, 0.02, 0.04, 0.06, 0.08, 0.1) alloys was prepared. The crystal structure, magnetic properties, and magnetocaloric effect have been analyzed. By tuning the Bi-content in MnCoGe alloys, the reduction of martensitic transformation (MT) temperature and the presence of a first-order magnetostructural transition (MST) were observed. Magnetic field-induced MT indicates that the magnetic field is much harder to drive MT compared to the temperature. With the Bi-content for 0.01 ≤ x ≤ 0.06, orthorhombic-type phase and hexagonal-type phase coexist. Furthermore, we observed an increase in the fraction of the hexagonal-type phase and a corresponding decrease in the fraction of the orthorhombic-type phase. It is beneficial to the refrigeration capacity for the isothermal magnetization curves M(H) on magnetization and demagnetization procedures with small magnetic hysteresis loss. With a magnetic field of 5 T, magnetocaloric effect (MCE) can be observed involving magnetic entropy change (-ΔSM) of 26.42 J kg−1 K−1 for x = 0.06 and refrigeration capacity (RC) of 259.78 J kg−1 for x = 0.01. Thus, this material is considered a fabulous candidate for magnetic refrigeration cooling applications at room temperature.

Heat Treatment Effect on Thermal, Micro-Crystal Structure and Magnetic Behavior of Ni45Mn40Sn10Cu5 Heusler Shape Memory Alloy

Ni-Mn-Sn-based Heusler alloys are important materials that have potential applications as environmentally friendly smart materials with beneficial properties as well as being magnetic. Both the magnetic field-induced reverse martensitic transformation and the high operating temperature are crucial for the applications of Ni-Mn-Sn-based magnetic shape memory alloys. In this study, martensite transformation temperatures were determined by applying different heat treatments (700 °C, 900 °C, 1100 °C) to Ni45Mn40Sn10Cu5 sample produced by Arc Melter melting method. While reverse conversion was observed in T2 (no heat treatment) and 700°C heat treatment, no reverse conversion was observed at 900°C and 1100°C. When the X-ray diffractogram was examined, martensite phase and γ phase were determined. When the magnetic hysteresis of the samples was examined, it was observed that the magnetic saturation went towards zero with the increase in heat treatment and accordingly, there was a decrease in the magnetization effect.

Variation of Electrical Resistivity During Magnetic Field-Induced Martensitic Transformation in Vanadium added NiMnSnB alloys

In this study, the structural and electrical properties of Ni49-xVxMn37Sn12B2 (x = 0, 1, 2, and 3) ferromagnetic shape memory alloys were investigated. According to XRD analyzes at room temperature, the x=0 sample was in the martensite phase, the x=1 and 2 samples were in the mixture phase, and the x=3 sample was in the austenite phase. The resistivity analyses depend on temperature showed that all samples exhibited martensitic transformation and the phase transformation temperature decreased with V doping. Magnetoresistance (MR) values were calculated using ρ-T curves performed under 0 T and 1 T magnetic fields. The observed negative MR is consistent with Kataoka's s-d model. As-Af interval was determined and M-H measurements were made at constant temperatures determined in this interval. The results were attributed to the magnetic field-induced phase transformation (MFIPT). In order to examine the effects of MFIPT on the electrical resistivity, the resistivity depend on magnetic field was measured using the same thermal process. The overlapping of the curves in the high magnetic field revealed that the resistivity decreased due to the MFIPT as well as the MR.

Atomic occupation and role of Cr atoms in Cr-doped Ni43Co7Mn39Sn11 magnetic shape memory alloys

The atomic occupation, magnetic properties and the relationship between them of Ni43Co7Mn39-xCrxSn11(x = 0, 0.4, 0.6, 0.8, 1.0, 1.2 at%) alloys have been systematically investigated. To elucidate the occupancy of Cr atoms, extended X-ray absorption fine structure (EXAFS) is performed and Cr K-edge EXAFS analysis determines that Cr atoms occupy Y site of the Ni43Co7Mn38Cr1Sn11 sample. Ferromagnetic resonance shows the evolution of the microscopic magnetic properties of the magnetic atoms with the increase of Cr doping content, which further confirms the Y-site occupation of Cr atoms. The experimental results show that in the Ni43Co7Mn39Sn11 system, Cr doping replaces Mn at the Y site, breaking the symmetry of the crystal field of Mn atoms at the Z site, reducing the atomic displacement potential. The doping of Cr atoms significantly enhances the driving force of its magnetic field-induced martensitic transformation.

Dynamically tunable operating temperature range of Ni-Co-Mn-Sn magnetic shape memory alloys via pressure modulation

Ni-Mn-Sn ferromagnetic shape memory alloys (FSMAs) have recently attracted attention due to their magnetic field-induced reverse martensitic transformation. However, the low and narrow operating temperature range greatly hinders their application, which is challenging to be solved. Here, a novel concept is introduced and demonstrated to increase and dynamically tune the operating temperatures in Ni-Co-Mn-Sn FSMAs via pressure. This work presents a systematic study of the martensitic transformation and magnetic properties in Ni-Co-Mn-Sn FSMAs under the field of hydrostatic pressure by the first principle calculations. Applying pressure allows a dynamically tunable wide operating temperature range in Ni14Co2Mn13Sn3 alloy and Ni13Co3Mn13Sn3 alloy, which results from the improvement of the stability of the martensite. Notably, the operating temperatures of Ni14Co2Mn13Sn3 alloy can be improved from 198 K to a high temperature of 262 K within 3 GPa. The pressure has a weak effect on the martensitic transformation sequence of Ni14Co2Mn13Sn3 (PA-FA-4O-NM) and Ni14Co2Mn13Sn3 (PA-FA-NM). Meanwhile, the pressure can maintain a large magnetization difference (ΔM), which benefits the functional performance in FSMAs. Moreover, in terms of the magnetic properties and the martensitic transformation, the effects of pressure on them are discussed by electronic structure, respectively.

Recent Progress in Crystallographic Characterization, Magnetoresponsive and Elastocaloric Effects of Ni-Mn-In-Based Heusler Alloys—A Review

Ni-Mn-In-based magnetic shape memory alloys have promising applications in numerous state-of-the-art technologies, such as solid-state refrigeration and smart sensing, resulting from the magnetic field-induced inverse martensitic transformation. This paper aims at presenting a comprehensive review of the recent research progress of Ni-Mn-In-based alloys. First, the crystallographic characterization of these compounds that strongly affects functional behaviors, including the crystal structure of modulated martensite, the self-organization of martensite variants and the strain path during martensitic transformation, are reviewed. Second, the current research progress in functional behaviors, including magnetic shape memory, magnetocaloric and elastocaloric effects, are summarized. Finally, the main bottlenecks hindering the technical development and some possible solutions to overcome these difficulties are discussed. This review is expected to provide some useful insights for the design of novel advanced magnetic shape memory alloys.

Incubation Time of Occurrence of Magnetic Field-Induced Martensitic Transformation in an Fe–24.8Ni–3.7Mn (at%) Alloy

Incubation Time of Occurrence of Magnetic Field-Induced Martensitic Transformation in an Fe–24.8Ni–3.7Mn (at%) Alloy

Investigation on phase structure and magnetic properties of high-temperature Ni-Pt-Co-Mn-Sn magnetic shape memory alloys by first-principles calculations

Ni-Mn-Sn ferromagnetic shape memory alloys (FSMAs) as multi-functional materials have attracted great attention due to the magnetic field-induced reverse martensitic transformation (MFIRMT). However, it is still a challenge to achieve a high working temperature in this material. Here, we propose a Pt and Co co-doping method to realize the high working temperature of FSMAs materials. Butmostimportantly, the effect of Pt and Co doping cannot be added up simply because they have different influence trends on the working temperature in Ni-Mn-Sn alloys. To balance their influence is the critical step. We use the first principles to calculate and predict the effects of Pt and Co co-doping on the martensitic transformation temperature (TM), Curie temperature (TC), and the difference of magnetization (ΔM) in Ni16-x-yPtxCoyMn13Sn3 (x = 3, 4; y = 1, 2, 3). According to the prediction results, we reported that Ni11Pt3Co2Mn13Sn3 and Ni9Pt4Co3Mn13Sn3 show a large ΔM in the high-temperature environment (above 370 K). Particularly, the working temperature of Ni11Pt3Co2Mn13Sn3 reaches the highest temperature (~440 K) in Ni-Mn-Sn alloys. Hence, Ni11Pt3Co2Mn13Sn3 is expected to become a new type of high-temperature FSMAs. This Pt and Co co-doping method in Ni-Mn-Sn alloys provides an ideal strategy to discover new high-performance FSMAs.

Observation of inverse magnetocaloric effect in magnetic-field-induced austenite phase of Heusler alloys Ni50−xCoxMn31.5Ga18.5 (x=9 and 9.7)

Magnetocaloric effect (MCE), magnetization, specific heat, and magnetostriction measurements were performed in both pulsed and steady high magnetic fields to investigate the magnetocaloric properties of Heusler alloys Ni50-xCoxMn31.5Ga18.5 (x = 9 and 9.7). From direct MCE measurements for Ni41Co9Mn31.5Ga18.5 up to 56 T, a steep temperature drop was observed for magnetic-field-induced martensitic transformation (MFIMT), designated as inverse MCE. Remarkably, this inverse MCE is apparent not only with MFIMT, but also in the magnetic-field-induced austenite phase. Specific heat measurements under steady high magnetic fields revealed that the magnetic field variation of the electronic entropy plays a dominant role in the unconventional magnetocaloric properties of these materials. First-principles based calculations performed for Ni41Co9Mn31.5Ga18.5 and Ni45Co5Mn36.7In13.3 revealed that the magnetic-field-induced austenite phase of Ni41Co9Mn31.5Ga18.5 is more unstable than that of Ni45Co5Mn36.7In13.3 and that it is sensitive to slight tetragonal distortion. We conclude that the inverse MCE in the magnetic-field-induced austenite phase is realized by marked change in the electronic entropy through tetragonal distortion induced by the externally applied magnetic field.

Martensitic transformation and structural states in Ni44.0Mn43.5Sn12.5-xAlx (x = 1, 2, 3 at.%) magnetic shape memory alloys prepared by vacuum hot pressing

Heusler-type Ni–Mn–Sn magnetic shape memory alloys (MSMAs) that exhibit a significant magnetocaloric effect due to magnetic field-induced martensitic transformation (MT) represent promising applications within the field of solid-state cooling. However, their MT and physical properties strongly depend on the intricacies of the fabrication technology employed. In the current study, we demonstrated the advantages of the use of powder metallurgy in the preparation of MSMAs. Powders were vacuum hot pressed to fabricate Ni44.0Mn43.5Sn12.5-xAlx (x = 1, 2, 3 at.%) MSMAs. The way in which the Al influenced the martensitic transformation (MT) behavior, the structural characteristics, and the thermomechanical properties of the MSMAs was investigated. The findings revealed that the MT temperature increases significantly in response to Al doping, by approximately 20 K/1 at.%Al. Striking nanostructural states were revealed in the austenite phase, giving rise to the unusual stress-strain behavior of the alloys studied.

Ni-Co-Mn-Sn quaternary alloys: Magnetic hysteresis loss reduction and ductility enhancement by iron alloying

Abstract The influence of Fe-alloying on the structural transition temperatures, microstructure, and mechanical and magnetocaloric properties of polycrystalline Ni41Co9−xFexMn40Sn10 (at. %) (x = 0–3) alloys has been studied. The substitution of Fe for Co introduced the so-called γ phase when the Fe content exceeds 1 at. %. The transformation temperatures decreased almost linearly with increasing Fe content without alteration of the transformation sequence. The compressive strength and maximum compressive strain increased to 1270 MPa and 21.3 % for Fe content of 3 at. %. In addition, the fracture type changed gradually from typical intergranular cracking to transgranular cracking with increasing Fe content. Magnetic field-induced reverse martensitic transformation was modified by increasing the Fe alloying, leading to the reduction of magnetic hysteresis loss (∼ 82.5 % drop after addition of 3 at. % Fe) but at the expense of a significant reduction in the maximum magnetic entropy change value.

Thermal, magnetic field- and stress-induced transformation in Heusler-type Co-Cr-Al-Si shape memory alloys

The phase diagram, including the martensitic and magnetic transformations, was determined by thermoanalysis and thermomagnetization measurements in the CoxCr79-xAl10.5Si10.5 section of the Co-based Heusler shape memory alloy. Magnetization measurements under pulsed magnetic fields were conducted and magnetic field-induced reverse martensitic transformation was clearly observed at room temperature. A superelastic behavior was obtained in the Co55.7Cr23.3Al10.5Si10.5 alloy in the temperature range of 198 to 423 K. The critical stress for martensitic transformation was found to show a negative temperature dependence at temperatures lower than approximately 310 K due to the magnetic effect despite the normal temperature dependence at higher temperatures.

Microstructure, Martensitic Transformation, and Inverse Magnetocaloric Effect in Ni48Mn39.5Sn12.5−xAlx Metamagnetic Shape Memory Alloys

The effect of Al substitution on microstructure, martensitic transformation and magnetocaloric properties in Ni48Mn39.5Sn12.5−xAlx (x = 0, 1, 2, 3) alloys is reported. At room temperature, depending on Al concentration, the alloys have typical Heusler L21 austenite structure and/or orthorhombic martensite structure with Pmma space group. A secondary Ni-Mn-Al phase also appears already for low Al concentrations (x ≥ 1). On cooling, irrespective of Al substitution, all the samples show ferromagnetic type ordering below 303 K in the austenite phase. The martensitic transition temperature varies with Al content. All the alloys undergo magnetic field-induced reverse martensitic transformation giving rise to an inverse magnetocaloric effect. The largest magnetic entropy change (8.5 J·kg−1·K−1) is observed near 280 K for the Ni48Mn39.5Sn12.5 alloy.

Stress- and Magnetic Field-Induced Martensitic Transformation at Cryogenic Temperatures in Fe–Mn–Al–Ni Shape Memory Alloys

Stress-induced and magnetic-field-induced martensitic transformation behaviors at low temperatures were investigated for Fe–Mn–Al–Ni alloys. The magnetic-field-induced reverse martensitic transformation was directly observed by in situ optical microscopy. Magnetization measurements under pulsed magnetic fields up to 50 T were carried out at temperatures between 4.2 and 125 K on a single-crystal sample; full magnetic-field-induced reverse martensitic transformation was confirmed at all tested temperatures. Compression tests from 10 to 100 K were conducted on a single-crystal sample; full shape recovery was obtained at all tested temperatures. It was found that the temperature dependence of both the critical stress and critical magnetic field is small and that the transformation hysteresis is less sensitive to temperature even at cryogenic temperatures. The temperature dependence of entropy change during martensitic transformation up to 100 K was then derived using the Clausius–Clapeyron relation with critical stresses and magnetic fields.

Site preference, electronic structure and possible martensitic transformation in Heusler alloys Ni2CoZ (Z = Al, Ga, In, Si, Ge, Sn, Sb)

The site preference, electronic structure, magnetic properties and martensitic transformation in Heusler alloys Ni2CoZ (Z = Al, Ga, In, Si, Ge, Sn, Sb) have been investigated by first-principles calculations. Different from literature, it is found that these Ni2CoZ alloys tend to form XA structure (Hg2CuTi-type), except for Ni2CoIn, in which L21 (Cu2MnAl-type) structure is preferable. Theoretical calculation reveals that the tetragonal martensitic phase has a lower total energy compared with the cubic austenitic phase, therefore, a structural transition from cubic to tetragonal is likely to happen in these Ni2CoZ alloys. The largest energy difference is observed in Ni2CoIn. It is interesting that Ni2CoSi is paramagnetic in austenitic state, while is ferromagnetic in martensitic state. This leads to a large change in the total moment, which is meaningful for the realization of magnetic field-induced martensitic transformation in this alloy.

Large reversible magnetostrain in polycrystalline Ni50Mn33In17−xGax

The structure and strain behavior associated with martensitic transformation for polycrystalline Ni50Mn33In17−xGax (x = 4, 5, 7, 8) have been investigated. All samples show a bcc Heusler structure at room temperature. A large positive transformation strain parallel the solidification direction and negative strain perpendicular to this direction are observed upon martensitic transformation. The same value of reversible magnetostrain in a magnetic field of 70 kOe is found due to the magnetic field-induced reverse martensitic transformation. The largest value of −0.28% and 0.49% along this two directions were observed for x = 4 sample, which is much larger than that in Co-doped NiMnIn polycrystalline. The strain value shows a little decrease with increasing Ga content. Texture and anisotropy effect on the strain are discussed.

Observation of magnetic-field-induced transformation in MnCo0.78Fe0.22Ge alloys with colossal strain output and large magnetocaloric effect

The thermal, structural and magnetic properties were studied for the hexagonal MnCo0.78Fe0.22Ge alloys, which undergoes a first-order phase transformation from paramagnetic hexagonal phase into ferromagnetic orthorhombic martensite on cooling. Owing to the magnetostructural coupling, large magnetocaloric effect (∆SM=−10.97Jkg−1K−1) was obtained at 254K. In-situ synchrotron high-energy X-ray diffraction experiments were conducted to reveal the detailed change in crystallographic structure of phases and the effect of applied magnetic field on phase transformation behaviors. An anomalously huge strain of 11.89% and volume expansion of 4.35% in unit-cell were obtained between martensite and parent phase across the transformation. Furthermore, the magnetic field-induced martensitic transformation was directly evidenced at 250K, which eventually demonstrates the possibility to achieve magnetic-field-induced strain and large magnetocaloric effect simultaneously.

Thermal and magnetic field-induced martensitic transformation in Ni50Mn25−xGa25Cux (0 ⩽ x ⩽ 7) melt-spun ribbons

We have studied the phase transformation behavior of melt-spun ribbons with x = 0, 1, 2, …, 7 (at%). It is shown that Cu substitution simultaneously increases and decreases the martensitic transformation temperature TM and the magnetic transition temperature of austenite , respectively. In Ni50Mn18Ga25Cu7 ribbons, the magnetic and structural transformations are coupled. The field-induced martensitic transformation from a paramagnetic austenite with lower magnetization to a ferromagnetic martensite with higher magnetization has been studied. The critical field μoHcr above which the magnetic field can induce the martensitic transition is well defined and decreases linearly with the decrease of the temperature at a reduction rate of 1 T K−1. Under a magnetic field of 5 T, the starting temperature of martensitic transformation (Ms) increases by ~9 K. Such a magnetic field-induced transformation is irreversible and temperature dependent, giving rise to the maximum magnetic entropy change of 17.8 J kg−1 K−1 and hysteresis losses of 43.6 J kg−1 under the magnetic field change of 5 T, respectively.

Magnetic Field-Induced Reverse Martensitic Transformation and Thermal Transformation Arrest Phenomenon of Ni41Co9Mn39Sb11 Alloy

In order to investigate behavior of magnetic field-induced reverse martensitic transformation for Ni-Co-Mn-Sb, magnetization experiments up to a static magnetic field of 18 T and a pulsed magnetic field of 40 T were carried out. In the thermomagnetization curves for Ni41Co9Mn39Sb11 alloy, the equilibrium transformation temperature T0 was observed to decrease with increasing applied magnetic field, μ0H, at a rate of dT0/dμ0H = 4.6 K/T. The estimated value of entropy change evaluated from the Clausius-Clapeyron relation was about 14.1 J/(K·kg), which was in good agreement with the value obtained by differential scanning calorimetric measurements. For the isothermal magnetization curves, metamagnetic behavior associated with the magnetic field-induced martensitic transformation was observed. The equilibrium magnetic field, μ0H0 = (μ0HAf + μ0HMs)/2, of the martensitic transformation tended to be saturated at lower temperature; that is, transformation arrest phenomenon was confirmed for the Ni-Co-Mn-Sb system, analogous with the Ni(Co)-Mn-Z (Z = In, Sn, Ga, Al) alloys. Temperature dependence of the magnetic field hysteresis, μ0Hhys = μ0HAf − μ0HMs, was analyzed based on the model for the plastic deformation introduced by the dislocations. The behavior can be explained by the model and the difference of the sweeping rate of the applied magnetic field was well reflected by the experimental results.

Magnetic field-induced martensitic phase transformation in magnetic shape memory alloys: Modeling and experiments

In this work, a continuum based model of the magnetic field induced phase transformation (FIPT) for magnetic shape memory alloys (MSMA) is developed. Hysteretic material behaviors are considered through the introduction of internal state variables. A Gibbs free energy is proposed using group invariant theory and the coupled constitutive equations are derived in a thermodynamically consistent way. An experimental procedure of FIPT in NiMnCoIn MSMA single crystals, which can operate under high blocking stress, is described. The model is then reduced to a 1-D form and the material parameter identification from the experimental results is discussed. Model predictions of magneto-thermo-mechanical loading conditions are presented and compared to experiments.