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.

In-Situ Study of Temperature- and Magnetic-Field-Induced Incomplete Martensitic Transformation in Fe-Mn-Ga

Significant interest in the stoichiometric and off-stoichiometric Fe2MnGa alloys is based on their complex phase transition behavior and potential application. In this study, temperature- and magnetic-field-induced phase transformations in the Fe41.5Mn28Ga30.5 magnetic shape memory alloy were investigated by in situ synchrotron high-energy X-ray diffraction and in situ neutron diffraction techniques. It was found that incomplete phase transformation and phase coexistence behavior are always observed while applying and removing fields in Fe41.5Mn28Ga30.5. Typically, even at 4 K and under 0 T, or increasing the magnetic field to 11 T at 250 K, it can be directly detected that the martensite and austenite are in competition, making the phase transition incomplete. TEM observations at 300 K and 150 K indicate that the anti-phase boundaries and B2 precipitates may lead to field-induced incomplete phase transformation behavior collectively. The present study may enrich the understanding of field-induced martensitic transformation in the Fe-Mn-Ga magnetic shape memory alloys.

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.

Dissipation losses limiting first-order phase transition materials in cryogenic caloric cooling: A case study on all-d-metal Ni(-Co)-Mn-Ti Heusler alloys

Ni-Mn-based Heusler alloys, in particular all-d-metal Ni(-Co)-Mn-Ti, are highly promising materials for energy-efficient solid-state refrigeration as large multicaloric effects can be achieved across their magnetostructural martensitic transformation. However, no comprehensive study on the crucially important transition entropy change Δst exists so far for Ni(-Co)-Mn-Ti. Here, we present a systematic study analyzing the composition and temperature dependence of Δst. Our results reveal a substantial structural entropy change contribution of approximately 65 J(kgK)-1, which is compensated at lower temperatures by an increasingly negative entropy change associated with the magnetic subsystem. This leads to compensation temperatures Tcomp of 75 K and 300 K in Ni35Co15Mn50-yTiy and Ni33Co17Mn50-yTiy, respectively, below which the martensitic transformations are arrested. In addition, we simultaneously measured the responses of the magnetic, structural and electronic subsystems to the temperature- and field-induced martensitic transformation near Tcomp, showing an abnormal increase of hysteresis and consequently dissipation energy at cryogenic temperatures. Simultaneous measurements of magnetization and adiabatic temperature change ΔTad in pulsed magnetic fields reveal a change in sign of ΔTad and a substantial positive and irreversible ΔTad up to 15 K at 15 K as a consequence of increased dissipation losses and decreased heat capacity. Most importantly, this phenomenon is universal, it applies to any first-order material with non-negligible hysteresis and any stimulus, effectively limiting the utilization of their caloric effects for gas liquefaction at cryogenic temperatures.

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.

The Critical Behaviour and Magnetism of MnCoGe0.97Al0.03 Compounds

The critical behaviour associated with the field-induced martensitic transformation heavily relies on the vacancy and transition of the magnetic phase in MnCoGe based-compounds. Due to this revelation, an intensive investigation was brought forth to study the substitution of Ge (atomic radius = 1.23 Å) by Al (atomic radius = 1.43 Å) in MnCoGe0.97Al0.03 alloy compound. The room-temperature X-ray diffraction indicated that the reflections were identified with the orthorhombic structure (TiNiSi-type, space group Pnma) and minor hexagonal structure (Ni2In-type, space group P63/mmc). The substitution of Al in the supersession of Ge transmuted the crystal structure from TiNiSi-type to Ni2In-type structure. The MnCoGe0.97Al0.03 compound’s magnetism was driven by interactions that are long in range, as indicated by the study of the critical behaviour in the proximity of TC. The magnetic measurement and neutron diffraction revealed that the structural transition took place with the decrease in temperature. The results from neutron diffraction signify that the transformation of the magnetic field-induced martensitic has a crucial function in producing the immense effect of magnetocaloric systems such as these. This outcome serves a critical function for investigations in the future.

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.

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.

Nanoscale magnetic phase competition throughout the Ni50−xCoxMn40Sn10 phase diagram: Insights from small-angle neutron scattering

The $\mathrm{N}{\mathrm{i}}_{2}\mathrm{MnSn}$-derived $\mathrm{N}{\mathrm{i}}_{50\ensuremath{-}x}\mathrm{C}{\mathrm{o}}_{x}\mathrm{M}{\mathrm{n}}_{25+y}\mathrm{S}{\mathrm{n}}_{25\ensuremath{-}y}$ alloys are premier examples of a class of off-stoichiometric Heusler alloys recently discovered to exhibit attractive magnetic properties in tandem with extraordinarily reversible martensitic phase transformations. Multiferroicity, magnetic phase competition and separation, field-induced martensitic transformations, magnetic shape memory behavior, and sizable magneto-, elasto-, and barocaloric effects result, generating substantial interest and application potential. In this work we expand on a prior small-angle neutron scattering (SANS) study at a single composition $(\mathrm{N}{\mathrm{i}}_{44}\mathrm{C}{\mathrm{o}}_{6}\mathrm{M}{\mathrm{n}}_{40}\mathrm{S}{\mathrm{n}}_{10})$ by exploring all three main regions of the recently established $\mathrm{N}{\mathrm{i}}_{50\ensuremath{-}x}\mathrm{C}{\mathrm{o}}_{x}\mathrm{M}{\mathrm{n}}_{40}\mathrm{S}{\mathrm{n}}_{10}$ phase diagram, i.e., at the representative $y=15$ composition. Wide temperature and scattering wave-vector range $(20\ensuremath{-}500\phantom{\rule{0.16em}{0ex}}\mathrm{K},0.004\ensuremath{-}0.2\phantom{\rule{0.16em}{0ex}}{\AA{}}^{\ensuremath{-}1})$ SANS data on $x=2$, 6, and 14 polycrystals provide a detailed picture of the evolution in magnetic order and inhomogeneity. Consistent with recent studies with a variety of techniques, phase separation into short-range coexisting ferromagnetic and antiferromagnetic regions is deduced below the martensitic transformation at $x=2$ and 6, with average ferromagnetic cluster spacing of \ensuremath{\sim}13 nm. Remarkably, at $x=14$, where the martensitic transformation is suppressed and ferromagnetic austenite is stabilized to low temperatures, nanoscopic magnetic inhomogeneity nevertheless persists. Distinct ferromagnetic clusters (\ensuremath{\sim}36-nm average spacing) in a ferromagnetic matrix are observed at intermediate temperatures, homogenizing into a uniform long-range ordered ferromagnet only at low temperatures. This unusual ferromagnet cluster/ferromagnet matrix inhomogeneity, as well as $x$-dependent subtleties of the superparamagnetic freezing of ferromagnetic clusters, are discussed in light of $^{55}\mathrm{Mn}$ nuclear magnetic resonance data, and the recent observation of annealing-induced core/shell nanoprecipitates. The origins of nanoscale magnetic inhomogeneity are discussed in terms of statistical variations in local composition and structure, tendency to chemical phase separation, and other forms of disorder.

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.

Microstructure, magnetic and magnetocaloric properties in magnetic-field-induced martensitic transformation Mn1−xCo1+xGe alloy ribbons

The sharp field-induced metamagnetic martensitic transformation plays a pivotal role in magnetoresponsive effects for ferromagnetic shape memory alloys (FSMAs). Homogeneous polycrystalline Mn1−xCo1+xGe alloy ribbons are prepared by using the arc-melting and melt-spinning technique in this work. The microstructure, crystalline structure, magnetic and magnetocaloric properties are studied in these ribbons. The substitution of Co for Mn reduces the structural transformation temperature, which leads to the realization of coincident magnetostructural transformation. Strikingly, a magnetic-field-induced martensitic transformation is observed in these ribbons. Therefore, large magnetocaloric effect, including maximum magnetic entropy change (ΔSM,max) value of ∼28 and 25 Jkg−1K−1 and effective refrigeration capacity (RCeff) of ∼168 and 181 Jkg−1 are obtained for x=0.035 and 0.09 samples, respectively, under the field change of μ0ΔH=0–7T. Furthermore, the average hysteresis loss of these ribbons reduces largely in contrast to their bulk counterparts. These results would provide the new experimental data for magnetic refrigerant materials and pave the way for the further investigation of other FSMAs.

Magnetic and Structural Properties of MnCoGe with Minimal Fe and Sn Substitution

The magnetic and structural properties of MnCo0.92Fe0.08Ge1−xSnx (x = 0.02, 0.05, and 0.1) were investigated. A first-order magnetic transition was observed, which was accompanied by the martensitic transformation from a hexagonal Ni2In-type to an orthorhombic TiNiSi-type structure in the vicinity of 320 K for x = 0.02 and 170 K for x = 0.05 with thermal hysteresis of approximately 20 K. The magnetization of MnCo0.92Fe0.08Ge0.95Sn0.05 was estimated to be 102 Am2 kg−1 in 5 T at 10 K. High field magnetization curves up to 55 T for MnCo0.92Fe0.08Ge0.95Sn0.05 indicated the field-induced martensitic transformation. Mössbauer spectroscopy experiments revealed that Fe atoms occupied 79%–85% in the Co-site and 21%–15% in the Mn-site.

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.

Phase transition and magnetocaloric properties of Mn50Ni42-x Co x Sn8 (0 ≤ x ≤ 10) melt-spun ribbons.

The characteristics of magnetostructural coupling play a crucial role in the magnetic field-driven behaviour of magnetofunctional alloys. The availability of magnetostructural coupling over a broad temperature range is of great significance for scientific and technological purposes. This work demonstrates that strong magnetostrucural coupling can be achieved over a wide temperature range (222 to 355 K) in Co-doped high Mn-content Mn50Ni42-x Co x Sn8 (0 ≤ x ≤ 10) melt-spun ribbons. It is shown that, over a wide composition range with Co content from 3 to 9 at.%, the paramagnetic austenite first transforms into ferromagnetic austenite at TC on cooling, then the ferromagnetic austenite further transforms into a weakly magnetic martensite at TM. Such strong magnetostructural coupling enables the ribbons to exhibit field-induced inverse martensitic transformation behaviour and a large magnetocaloric effect. Under a field change of 5 T, a maximum magnetic entropy change ΔSM of 18.6 J kg-1 K-1 and an effective refrigerant capacity RCeff of up to 178 J kg-1 can be achieved, which are comparable with or even superior to those of Ni-rich Ni-Mn-based polycrystalline bulk alloys. The combination of high performance and low cost makes Mn-Ni-Co-Sn ribbons of great interest as potential candidates for magnetic refrigeration.

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.