Inverse Martensitic Transformation Research Articles

Actuation response of typical biased shape memory alloy wire under variable electric heating rates: Experimental investigation and modeling

Electric heating is commonly used to induce the inverse martensitic transformation in shape memory alloy (SMA) wire actuators. Different actuation responses can be achieved when adjusting the heating currents. In this study, typical biased NiTi SMA wire actuators were tested under the heating currents of 1.5 A, 3 A, 4 A, and 5 A. It was found that SMA wire actuators under three typical biases (dead weight, linear spring, dead weight & linear spring) behaved differently as the heating current increased. Moreover, under dead weight bias and mixed bias, high heating currents tended to cause dynamic responses during actuation. The maximum inertia load induced by dynamic responses was 2.65 times as much as the static load. In contrast, the actuation response under linear spring bias was relatively steady. A model based on the SMA constitutive equation and the dynamic equation was also established, which was capable of simulating the dynamic actuation responses of SMA wire actuators under high electric heating rates.

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.

Giant reversible magnetoresistance effect in a Ni46Co3Mn35Cu2In14 polycrystalline alloy

In this work, the reversible magnetoresistance properties in a Ni46Co3Mn35Cu2In14 polycrystalline alloy were studied. By using Co substitution for Ni to improve the magnetic properties and Cu substitution for Mn to reduce the transformation hysteresis, large magnetic field dependence of the transformation temperature up to 6.8 K T−1 and low transformation hysteresis of 11.5 K were achieved. Such optimized magnetostructural transformation parameters allowed the complete and reversible magnetic field induced inverse martensitic transformation to be realized under the field of 5 T, giving rise to a giant reversible magnetoresistance of −73.5%.

Achieving a broad refrigeration temperature region through the combination of successive caloric effects in a multiferroic Ni50Mn35In15 alloy

Solid-state refrigeration based on the caloric effects has been conceived to be a high-efficient and environmental-friendly alternative to replace the vapor-compression refrigeration technique. The implementation of solid-state refrigeration requires that the refrigerants should possess not only remarkable caloric effect but also wide working temperature region. In this work, we demonstrate that various caloric effects can be achieved successively in a multiferroic Ni50Mn35In15 meta-magnetic shape memory alloy prepared by directional solidification, including inverse magnetocaloric effect around inverse martensitic transformation, conventional magnetocaloric effect around Curie transition and elastocaloric effect above Curie transition. Among them, the elastocaloric effect is particular striking, where a giant adiabatic temperature variation up to –19.7 K is achieved on removing a moderate stress of 350 MPa due to the elimination of negative magnetic contribution, with the specific adiabatic temperature change of 56 K GPa–1. Furthermore, through the combination of these successive caloric effects, a broad refrigeration temperature region covering the temperature range from 270 K to 380 K can be achieved. It is demonstrated that the combination of various caloric effects could be a promising way to extend the working temperature range of solid state refrigeration.

Experimental Research on Inhibition of temperature to inverse martensitic phase transformation of NiTi Shape Memory Alloy

The effects of temperature changes, load cycles, and amplitude changes on the mechanical properties of NiTi shape memory alloys such as the attenuation of energy dissipation capacity, equivalent damping ratio, and residual strain were studied experimentally. Experimental results show that: under different temperature and amplitude, the shape memory alloy achieves stable performance after 10 cycles, and the attenuation of energy dissipation capacity mainly occurs in the first 6 cycles; as the temperature decreases or the number of cycles increases, equivalent damping ratio tends to decrease; When the temperature decreases near the completion temperature of austenite transformation, the residual strain is significantly affected. Even if the strain amplitude is small, residual deformation accumulation will occur, inhibiting the occurrence of reverse martensite transformation, and it is not good for the super-elasticity of SMA.

Giant Strain Control of Antiferromagnetic Moment in Metallic FeMn by Tuning Exchange Spring Structure

AbstractManipulation of the antiferromagnetic moment in antiferromagnets (AFMs) is a crucial issue for developing AFM‐based spintronic devices. Lattice strain is an effective strategy to modulate the antiferromagnetic moment and is traditionally based on a direct crystalline tailoring of AFMs. A novel method for strain tuning the antiferromagnetic moment by controlling the exchange spring in the AFM, which is applicable to other conventional AFM materials, is reported. Specifically, a TiNi(Nb) shape memory alloy (SMA) is used as the substrate of Ta/NiFe/FeMn multilayers. By thermally driven inverse martensitic phase transformation in the SMA, a significant strain of 1.3% is transferred into the film, which toggles a noticeable magnetic moment rotation of NiFe by nearly 90° in the film plane, resulting in a consequent twirling of the Néel vector of FeMn due to interfacial exchange interaction. In turn, the antiferromagnetic moment of FeMn is tailorable by tuning the exchange spring. Simultaneously, the exchange bias field is tuned significantly with a maximal variation of 350% due to the twist of the antiferromagnetic moment, which facilitates strain‐assisted magnetization reversal for developing a logic memory device. These findings provide an alternative strategy to advance the development of an AFM‐based memorizer by temperature‐driven strain engineering.

Large magnetic entropy change and magnetostrain in a directionally solidified Ni45.7Co4.2Mn37.3Sb12.8 alloy

Heusler-type Ni-(Co)-Mn-X (X = In, Sn, Sb) meta-magnetic alloys can exhibit various magneto-functional behaviors due to the strong coupling between the magnetic and structural orders. Here, we demonstrate large magnetocaloric effect and magnetic shape memory effect in a directionally solidified Ni45.7Co4.2Mn37.3Sb12.8 alloy with 〈5 5 3〉A preferred orientation. It is shown that large magnetic entropy change up to 27.4 J kg−1 K−1 can be achieved under the field change of 5 T. Moreover, a large magnetic field-induced strain of 0.42% was also obtained with no-prestrain through inverse martensitic transformation induced by applying a magnetic field of 7 T. The present magnetostain is much higher than those in polycrystalline Ni-(Co)-Mn-Sb based alloys reported previously. Such enhanced magneto-functional behavior could be attributed to the highly textured microstructure and enlarged lattice distortion through Co addition.

Tuning the Reversible Magnetocaloric Effect in Ni–Mn–In‐Based Alloys through Co and Cu Co‐Doping

AbstractThe reversibility of the giant magnetocaloric effect (MCE) through the magnetic field–induced magnetostructural transformation in Ni–Mn–In‐based alloys is a key issue towards the potential magnetic refrigeration applications. In this work, Co and Cu are simultaneously doped to tune the reversible magnetocaloric properties associated with the magnetostructural transformation. Owing to the integration of large magnetization difference ΔM, suitable transformation entropy ΔStr, and narrow thermal hysteresis ΔThys in a Ni46Co3Mn35Cu2In14 alloy, the reversible field–induced inverse martensitic transformation is realized in a wide temperature range of 30 K under the field of 5T, yielding a maximum reversible magnetic entropy change ΔSMmax of 16.4 J kg−1 K−1. Moreover, under a low field change of 1.5T, a large reversible adiabatic temperature variation ΔTad of 2.5 K is also obtained, representing the highest value so far under the low field change of 1.5T in Ni–Mn‐based alloys. It is demonstrated that multi‐component alloying by combining the effects of appropriate substitutional elements is an effective way to develop high‐performance magnetocaloric materials.

Atomistic investigation of pseudoelasticity in zirconia nanopillars

Molecular dynamics simulations are performed to investigate the underlying atomistic mechanism of the pseudoelastic behavior of zirconia nanopillar. For the [0 0 1]-oriented zirconia nanopillar subjected to uniaxial compressive loading, the strain up to 13.1% can be recovered through inverse martensitic transformation, while larger strain leads to the loss of pseudoelasticity. The irreversible deformation arises owing to the crack propagation, which results from the shear deformation along the phase interfaces. The energy and stress analysis reveals that the responsible mechanism for the pseudoelasticity is the high surface-stress-induced internal stresses at the nanometer scale. The size effect on the martensitic transformation and pseudoelasticity is also elucidated. The simulation results facilitate our understanding of the pseudoelasticity in zirconia nanopillar at the atomic scale.

Martensitic transformation and magnetic properties in Mn49−xCuxNi41Sn10(x = 0–2)

The crystal structure, phase transition, metamagnetic behavior and magnetic entropy change (ΔSM) of the Mn49−xCuxNi41Sn10(x = 0–2) alloys were systematically studied. The results of experiment about crystal structure confirm that Mn49−xCuxNi41Sn10 alloys have a highly ordered cubic L21 Heusler structure. With Cu element improving, all samples have a martensitic transformation and inverse martensitic transformation by analyzing the result of magnetic measurement. The saturation magnetization of samples decreases gradually, the martensitic transformation temperature (TM) of as-annealed samples increases to a high-temperature area, and the Curie temperature (TC) of samples moves to a low-temperature area with the content of Cu element increasing from x = 0 to x = 2. The positive values of magnetic entropy change (ΔSM) of all alloys were investigated near the martensitic transformation. When the applied magnetic field is 3 T, a worthwhile value of ΔSM can reach up to 32.0 J·kg−1·K−1 in Mn47Cu2Ni41Sn10 alloy.

Magnetic and martensitic transformations in Ni48Co2Mn35In15 melt-spun ribbons

As-solidified Ni48Co2Mn35In15 ribbons were prepared through the melt-spinning method, and their structural, magnetic, magnetocaloric properties, and martensitic transformations were investigated. The inverse martensitic transformation temperature (TA=325 K) for the melt spun ribbons shifted by 55 K to higher temperature relative to that of the bulk material (TA = 270 K). The working temperature range of the magnetic entropy change (ΔSM) in Ni48Co2Mn35In15 ribbons has been significantly expanded relative to that of bulk. The roles of the magnetostructural transitions on the magneto-responsive properties of the ribbons are discussed.

Correlation between crystallographic and microstructural features and low hysteresis behavior in Ni50.0Mn35.25In14.75 melt-spun ribbons

In this work, crystallographic, microstructural and magnetocaloric investigations were performed on textured Ni50Mn35.25In14.75 melt-spun ribbons with low thermal (6 K) and magnetic-field induced hysteresis (−0.73 J kg−1 at 2 T) and moderate maximum magnetic entropy change ΔSMmax (11 J kg−1 K−1 at 5 T) at room temperature (302 K). The austenite in the ribbons crystallizes into a L21 structure, whereas martensite has a monoclinic incommensurate 6 M modulated structure as determined with the superspace theory. By means of electron backscatter diffraction technique, the morphological and crystallographic features of microstructure were systematically characterized. Ribbons possess a fine microstructure with an average grain size (initial austenite phase) of around 10 μm, whereas the 6 M martensite has a self-accommodated microstructure with 4 kinds of twin-related martensite variants. During inverse martensitic transformation, the austenite prefers to nucleate at the grain boundaries of initial austenite. By means of cofactor conditions and crystallographic orientation analyses, the good geometrical compatibility between austenite and martensite was confirmed. Based on the crystal structure and microstructure information obtained, the reason of the low thermal hysteresis was discussed.

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.

Large magnetoresistance in a directionally solidified Ni44.5Co5.1Mn37.1In13.3 magnetic shape memory alloy

Polycrystalline Ni44.5Co5.1Mn37.1In13.3 alloy with coarse columnar-shaped grains and 〈001〉A preferred orientation was prepared by directional solidification. Due to the strong magnetostructural coupling, inverse martensitic transformation can be induced by the magnetic field, resulting in large negative magnetoresistance up to −58% under the field of 3 T. Such significant field controlled functional behaviors should be attributed to the coarse grains and strong preferred orientation in the directionally solidified alloy.

Inverse Martensitic α → γ Transformation in Nanostructured Maraging Steels

The critical temperature (A s) of the start of heating-induced α → γ phase transformation has been determined in two nanostructured maraging steels. It is established that, irrespective of the method of nanostructure formation and dimensions of structure constituents within the range studied, the A s value of the inverse martensitic transformation decreases so as to fall in the interval of aging temperatures. Special features of the development of α → γ phase transformation in the hardened matrix are determined. Factors favoring the decrease in A s are analyzed and the results of investigations are generalized.

Microstructural Feature and Magnetocaloric Effect of Mn50Ni40.5In9.5 Melt-Spun Ribbons

The microstructure and magnetocaloric properties of the melt-spun and annealed Mn50Ni40.5In9.5 ribbons were studied. It is shown that the post-annealing results in a considerable increase of the grain size for the initial austenite, where the columnar-shaped austenite grains almost run through the whole ribbon. Both the melt-spun and annealed ribbons consist of the mixture of austenite and martensite at room temperature, where a 8-layered modulated (8M) martensite structure was identified through selected area electron diffraction (SAED). Further High-angle Annular Dark-field (HAADF) characterizations reveal that the modulation period of 8M martensite is not homogeneous in one martensite plate. Due to strong magneto-structural coupling, the inverse martensitic transformation from a weak magnetic martensite to a strong magnetic austenite can be induced by the magnetic field, resulting in the inverse magnetocaloric effect around room temperature. For a field change of 5 T, the magnetic entropy change ΔSM of 3.7 J·kg−1·K−1 and 6.1 J·kg−1·K−1, and the effective refrigerant capacity RCeff of 52.91 J·kg−1 and 99.08 J·kg−1 were obtained for melt-spun and annealed ribbons, respectively. The improvement of the magnetocaloric properties after annealing should be attributed to the enhanced atomic ordering and magnetization difference between two phases, as well as the reduced hysteresis loss. In addition, both the melt-spun and annealed ribbons can work at a relatively wide temperature range, i.e., δTFWHM = 34 K for melt-spun ribbons and δTFWHM = 28 K for annealed ribbons.

Martensite transformations in the surface layer at grinding of parts of hardened steels

The mechanism of direct and inverse martensitic transformation in the surface layer of a ground part of hardened steel under the influence of the grinding temperature was investigated. It is shown that the reverse martensitic transformation is carried out during grinding according to the martensite-perlite-austenite scheme. The possibility of high-speed tempering of martensite to perlite is shown, under the action of a contact grinding temperature, which, with a further increase in temperature, turns into austenite, forming an extremely harmful defect in the working surface –quenching burn. In the present work, it is shown that the quenching burn in the form of austenite is happened by the M–P–A diffusion mechanism. This made it possible to obtain graphical and analytical dependencies, using which it is possible to calculate the Ac1 temperature points of the formation of austenite for virtually any steel grade depending on the content of carbon and alloying elements. The latter circumstance makes it possible to create such grinding conditions (the type of abrasive, the characteristics of the wheel, the use of coolant, treatment regime), at which the austenite formation temperature is not attained and the quenching does not happen. Thus, as a result of the studies, it is possible to determine safe grinding temperatures for steels of different chemical compositions and treatment regimens that do not cause an increase in the grinding temperature above a certain level.

Influence of Cu Doping on Martensitic and Magnetic Transitions in Ni-Mn-Sn Alloys

In this work, the fourth element Cu was introduced to substitute Ni in polycrystalline Ni-Mn-Sn alloys. It was shown that Cu doping did not change the crystal structure of the martensite in Ni50-xCuxMn39Sn11 (x=0, 1, ......,7) alloys, but resulted in the decrease of martensitic transformation temperatures. Due to the higher atomic radius of Cu with respect to that of Ni, the lattice volume of martensite unit cell increases with the gradual substitution of Ni by Cu. For the alloys with the Cu content of 0-4%, the martensitic transformation is from weak magnetic (paramagnetic) austenite to weak magnetic (paramagnetic) martensite. When the Cu content is higher than 4%, the paramagnetic to ferromagnetic transition of austenite was introduced. The temperature interval between magnetic transition and structural transformation was enlarged with the increase of Cu content. Due to the relatively smaller magnetization difference between austenite and martensite, the field induced inverse martensitic transformation behavior is not significant in the present Cu-doped alloys.

Inspection of Adiabatic Shear Bands in High Manganese TRIP Steels

Adiabatic shear bands (ASBs) develop generally during high strain rates. This paper investigates the transformation induced plasticity (TRIP) effect during ASBs formation at high strain rates in high manganese TRIP steels containing initial austenite and ferrite by EBSD technique. Results show that TRIP effect takes place mainly before the formation of ASBs. After ASBs formation, TRIP effect is strongly restricted by the size effect, the increase of stacking fault energy (SFE) and even inverse martensitic transformation due to the rise of temperature. The TRIP effect before ASBs formation contributes to the resistance of adiabatic shear failure. Dynamic recrystallization driven by subgrains rotation occurs within ASBs, and ultrafine grains often show strong shear textures with twin relationship owing to slip mechanism.

EELS study of the inverse martensitic transformation of 2H and 18R Cu–Al–Zn alloys

Abstract Changes in 3d states occupancy associated with the inverse martensitic transformation in two samples of Cu–Al–Zn alloys with 2H and 18R martensitic structures were investigated by electron energy loss spectroscopy (EELS). The Cu L2,3 white-lines intensities, which reflect the unoccupied density of states in 3d bands, were measured in situ, during the phase transformation in both the martensite and austenite phases. We find that the white-lines intensity decreases during the inverse transformation, when going from martensite to austenite. Even though the initial 3d occupation numbers in 2H and 18R martensitic structures are different, after the transformation, the 3d occupation numbers in the now austenitic structure have decreased in both samples, indicating that some electrons left Cu 3d bands during phase transformation. Interestingly enough, the occupation numbers in the final phases, which have the same structure, reach the same value, indicating that changes in EELS spectra are a consequence of structural changes.