Martensite Finish Temperature Research Articles

Physical mechanisms for dependence of temperature-induced phase transition and shape memory effect on grain size in nanocrystalline NiTi shape memory alloys

Physical mechanisms for dependence of temperature-induced phase transition and shape memory effect (SME) on grain size (GS) of nanocrystalline NiTi shape memory alloys (SMAs) were revealed by combining experiment and molecular dynamics simulation. Influences of GS on phase transition temperature and stress level during tension loading below martensite transition finish temperature Mf are interpreted by core-shell theory that energy of shell (grain boundary (GB)) is higher than that of core (grain interior), so shell becomes an obstacle to deformation of the core and the obstacle increases with reducing GS because the fraction of GB increases with decreasing GS. Due to the constraint of shell, martensite transition during cooling is so incomplete that stress-induced martensite occurs in nanocrystalline NiTi SMAs deformed below Mf. After unloading, some stress-induced martensite phases are retained due to the lack of driving force for reverse martensite transition at low temperature. This is why SME occurs in the alloy with GS below 10 nm when no temperature-induced phase transition happens. Under the same tension strain, inelastic strain after unloading increases with increasing GS. The increase of GS causes the increase of SME strain, and the residual strain after heating the deformed nanocrystalline NiTi SMAs stems from the plastic deformation of martensite and austenite in grain interior during tension.

Uncovering the isothermal transformation dynamics and elemental diffusion behavior of reversed austenite in PH13-8Mo steel

The isothermal transformation kinetics and microstructural evolution of the reversed austenite significantly influence the properties of PH13-8Mo steel. However, the microscopic phase transformation behavior related to elemental diffusion during isothermal processes for PH13-8Mo steel needs further examination. Herein, we systematically investigate the isothermal transformation and elemental diffusion behavior of reversed austenite in PH13-8Mo steel. Phase transformation kinetic measurements unravel that the complete elimination of residual austenite can be achieved. Only hierarchical martensitic microstructure without austenite is detected after the solution-cooling treatment at 927 °C with a cooling rate of 10 °C/s, determining the critical martensite transformation start and finish temperature to be 176.6 °C, 11.6 °C. The isothermal kinetics of reverted austenite satisfy the Johnson-Mehl-Avrami relationship. The fraction of reversed austenite increases from 0.14 % at 510 °C to 8.73 % at 593 °C. Lath martensite boundaries with large kernel average misorientation values promote elemental diffusion at the interface. Further, the underlying behavior of elemental diffusion is elucidated during the isothermal aging process. The interfacial model indicates the growing width of the reversed austenite up to 100 nm and the compositional gradient formed by the elemental diffusion during aging for 0–5 h at 593 °C. The interdiffusion coefficient calculations interpret the diffusion direction of alloying element Ni from martensite to reversed austenite; Cr and Mo may form alloying carbides at the austenite-martensite interface; Al possesses the fastest diffusivity in martensite and austenite phases. The present work unveils the phase transformation kinetics of PH13-8Mo steel, achieving quantitative regulation for maraging stainless steel.

MICROSTRUCTURE EVOLUTION AND PHASE TRANSFORMATIONS IN MICROALLOYED ARMOX 500T STEEL DURING A DILATATION PROCESS

With this work we successfully developed two modified Armox 500T alloys using microalloying with different amounts of niobium (Nb) and boron (B) to obtain a finer grain size, which in return enhances the remnant properties. Furthermore, different heat-treatment cycles were designed and performed using a quenching dilatometer to study the combined effect of thermal cycling and microalloying with Nb and B on the microstructure and transformation temperatures including the start and finish temperature of the austenite transformation (Ac1, Ac3) and the martensite start and finish temperature (Ms, Mf) of the investigated alloys. Dilatometry results show that increasing the content of Nb from 0.07 w/% to 0.13 w/% and B from 0.0035 to 0.0046 w/% increases the temperature range between Ac1 and Ac3 by 55 °C, indicating a broader range for changing heat-treatment temperatures. In addition, the Ms temperature is reduced by 13 °C due to austenite refinement caused by the microalloying of Nb and B. The effect of the annealing temperature at a constant heating rate showed a significant impact on the austenite grain size and hardness. Furthermore, the kinetics of phase transformations were theoretically studied using Thermo-Calc, and the numerical predictions were confirmed experimentally with dilatometry results. Metallography investigations using a scanning electron microscope (SEM) and an optical microscope (OM) were conducted to evaluate the microstructure evolution of the developed alloys. Hardness tests were performed to evaluate the effect of the grain refinement of martensite lathes caused by microalloying with Nb, B, and heat-treatment thermal cycling. It is found that the hardness of the modified Armox alloys in this research was improved by 14 % in comparison with the conventional Armox 500T.

An interpretable boosting-based predictive model for transformation temperatures of shape memory alloys

In this study, we demonstrate how the incorporation of appropriate feature engineering together with the selection of a Machine Learning (ML) algorithm that best suits the available dataset, leads to the development of a predictive model for transformation temperatures that can be applied to a wide range of shape memory alloys. We develop a gradient boosting ML surrogate model capable of predicting Martensite Start, Martensite Finish, Austenite Start, and Austenite Finish transformation temperatures with an average accuracy of more than 95% by explicitly taking care of potential distribution changes when modeling different alloy systems. We included heat treatment, rolling, extrusion processing parameters, and alloy system categorical features in the model input features to achieve more accurate and realistic results. In addition, using Shapley values, which are calculated based on the average marginal contribution of features to all possible coalitions, this study was able to gain insights into the governing features and their effect on predicted transformation temperatures, providing a unique opportunity to examine the critical parameters and features in martensite transformation temperatures.

Molecular dynamics simulation of phase transformation and wear behavior of Ni35Al30Co35 high temperature shape memory alloy

Ni–Al–Co alloys as one of the ferromagnetic high-temperature shape memory alloys (HTSMA) are attractive in aerospace and defense applications, due to their high phase transition temperature range (400–700K), high recoverable strain and good machinability. However, the underlying physics for the phase transformation behavior of β single-phase and β+γ two-phase Ni–Al–Co ternary alloys remain unclear. In this work, molecular dynamics simulation of phase transition, pseudoelasticity (PE) and wear behavior of Ni35Al30Co35 alloy were analyzed using the EAM potential. It shows that Ni35Al30Co35 alloy has a high martensite start temperature of 825K and an austenite start temperature of 631K, respectively. After five thermal cycles, martensite and austenite start and finish temperatures are stable around 500K and 700K. The initial structure of Ni35Al30Co35 alloy at 1000K is identified as BCC (β phase) and FCC (γ phase) structure, transforming to L10 structure through martensitic transformation. Furthermore, PE of Ni35Al30Co35 alloy exhibits about a 9.1% recoverable strain under <001> oriented uniaxial tension tests and about a 6.6% recoverable strain under <001> oriented uniaxial compression tests at a temperature of 1200K, showing the potential used in extreme environment. Moreover, spherical indenters with a radius of 15 Å were used to investigate the wear behavior of Ni35Al30Co35 alloy under different temperature. It was found that the PE effect affects the frictional behavior during nano-scratching. Combining the effect of high temperature softening and phase transition PE, the wear rate increases nearly by 5.3% when the temperature rises from 300K to 1000K. Furthermore, the friction force curve obtained is consistent with the friction force curve obtained by simulation at 300K.

Dynamic Cyclic Fatigue and Differential Scanning Calorimetry Analysis of R-Motion

The aim of this study was to assess the dynamic cyclic fatigue resistance of an R-Motion file at simulated body temperature and document corresponding phase transformations compared to OneCurve and HyFlex EDM (HFEDM). R-Motion (25/.06), OneCurve (25/.06), and HFEDM (25/.06) files were selected and divided into 3 groups (n=9) according to the file type. Dynamic cyclic fatigue testing was done with a custom-made artificial stainless-steel canal that had a 90° angle of curvature and a 5-mm radius of curvature. Files were operated continuously at body temperature until fracture in the artificial canal. The time to fracture was calculated. Statistical analysis was performed, and significance was set at 5%. Phase transformation temperatures for 2 instruments of each group were analysed by differential scanning calorimetry (DSC) analysis. The highest mean time to fracture value was measured in the HFEDM group (277.84 ± 2.51), followed by the R-Motion group (115.09 ± 0.01), whilst the lowest value was found in the OneCurve group (44.28 ± 3.63). Post hoc pairwise comparisons were all statistically significant (P < .001). DSC heating curves show austinite start temperatures to be 33.94 °C and 43.32 °C and austinite finish temperatures to be 35.09 °C and 50 °C for R-Motion and HFEDM, respectively. DSC cooling curves show martensite start temperatures to be 27.54 °C and 44.52 °C and martensite finish temperatures to be 29.13 °C and 37.68 °C for R-Motion and HFEDM, respectively. DSC curves of OneCurve failed to demonstrate transformation temperatures within the tested heat range. Crystalline arrangement of Ni and Ti atoms within the NiTi alloys greatly affects the dynamic cyclic fatigue resistance of the file.

The Influence of Cooling Rate between Ms and Mf on the Mechanical Properties of Low Alloy 42SiCr Steel Treated by the Q-P Process

A series of experiments was conducted by quenching and partitioning (Q-P) heat-treated alloys to investigate the effect of cooling intensity on the mechanical properties of low alloy steel 42SiCr. By applying a conventional heat treatment, reasonable high strength can be achieved; however, the alloys become more brittle. To obtain an optimal balance, advanced heat treatment methods like the Q-P process can be used. It consists of quenching to temperatures between martensite start and martensite finish temperatures and holding, which leads to the stabilization of untransformed austenite by carbon partitioning. The martensitic microstructure is then formed with a small volume fraction of retained austenite embedded on a microscopic scale. The material’s deformability can be significantly improved by using such heat treatment processes. Moreover, to improve advanced high strength properties (AHSS), an additional Q-P process can be applied, which leads to erasing the influence of cold forming as well as enhancement of the mechanical properties. Several combinations of the Q-P process with/without partitioning were performed with various cooling rates for both heat treatment methods. Ultimate Tensile Strength (UTS), Ductility and Hardness (HV10), as well as the microstructure of the alloys, are compared to evaluate the cooling intensity effects. The cooling rate is found not to be a significant factor influencing mechanical properties, which is a crucial point for practical material heat treatment.

Structural changes of TiPt high-temperature shape memory alloys induced by high pressure torsion

The microstructure of a TiPt high temperature shape memory alloy induced by high pressure torsion (HPT) was studied using synchrotron radiation experiments and transmission electron microscopy. Upon the severe plastic deformation, the parent B19 martensite is strongly refined and highly strained. While neither strong chemical disorder nor amorphization are encountered, the occurrence of crystal reflections is observed that can be indexed in terms of the L10 phase and long range ordered stacking structures. The occurrence of the L10 phase might be triggered by the high hydrostatic stress as well as shear stress superimposed during the HPT. The austenite and martensite start and finish temperatures of TiPt are not affected by the HPT since upon heating, recrystallization occurs prior to the onset of the reverse martensite to austenite transformation.

Design and preparation of nickel-titanium implant for lumbar vertebra

The growing number of spine diseases and surgeries has resulted in advancements in equipment and implants. On the other hand, given the uniqueness of the anatomy of the spine, particularly in terms of mechanical characteristics, selecting the type of implant is critical. In addition to high biocompatibility and superelasticity, the implant utilized in the spine needs properties like strength, fatigue resistance, and elastic modulus close to the bone, which is found in nitinol. NiTi alloy lumbar-like samples were prepared by sintering and mechanical braiding method. The mechanical properties study revealed that the elastic modulus of the sample was 3.5 GPa, and the compressive strength at 6 % strain was 200 MPa. NiTi alloy is thermoelastic, making it a good candidate for placement in bone tissue. The biocompatibility and non-toxicity of the bone cells, with cell viability of over 4 × 104 cells within 48 h, indicate that the produced implant has suitable cellular biocompatibility. Besides, the differential scanning calorimetric test shows that the austenite start and finish temperatures are 26 and 51 °C, respectively, and martensite start and finish temperatures are − 2 and − 33 °C, respectively. These values are consistent with the body temperature of 37 °C. The corrosion test also indicates that the implant has a good corrosion resistance of about 0.3 ohm cm2. Developing this kind of implant is intended to make treating spinal problems easier.

Degradation of recovery properties after heat treatment in hot-forged NiTiFe alloy

NiTiFe is a kind of low-temperature shape memory alloy (SMA) with great application potential in aerospace, such as pipe joints. Heat treatment can effectively regulate the microstructure and recovery properties (recovery strain and recovery stress) of SMAs. In this study, the microstructure, recovery properties, and transformation temperatures of hot-forged Ni47Ti50Fe3 shape memory alloy (SMA) before and after heat treatment (HT) with different HT temperatures (550–950 ℃) were analyzed. The results show that when the HT temperature is above 650 ℃, the density of high- and low-angle grain boundaries was reduced. The recovery properties of the hot-forged NiTiFe alloy deteriorate with increasing HT temperature. The initial hot-forged samples showed the best recovery strain of 8.32% and recovery stress of 449 MPa, which were reduced to 5.99% and 299 MPa, respectively, after 950 ℃ HT. The R↔B2 phase transformation temperature changes little with the increasing HT temperature. But the reverse martensitic phase transformation finish temperature increased from − 75 ℃ to − 50 ℃ after tensile deformation at − 180 ℃. The EBSD and HRTEM analyses of the microstructure after the free and constrained recovery tests were carried out. The {114}B2 and {112}B2 twins remained after the free recovery process, and more of those twins remained after the constrained recovery process. Although the recrystallization and grain growth can reduce the defects density which are the obstacles to the form of detwinning martensite, it also makes the deformation twins prone to form during the tensile and constrained recovery process, thus leading to poor recovery properties.

Mechanical and Metallurgical Evaluation of 3 Different Nickel-Titanium Rotary Instruments: An In Vitro and In Laboratory Study.

An in-depth evaluation of the mechanical and metallurgical properties of NiTi instruments is fundamental to assess their performance and to compare recently introduced instrument with widespread ones. According to this, since there are no data on this topic, the aim of the study was to mechanically and metallurgically evaluate an instrument recently introduced into the market (ZenFlex (ZF)), by comparing it with two well-known instruments with similar characteristics: Vortex Blue (VB) and EdgeSequel Sapphire (EES). According to this, 195 instruments were selected: 65 ZF, 65 VB and 65 EES. Each group was divided in subgroups according to the mechanical tests (i.e., cyclic fatigue resistance, torsional resistance and bending ability; (n = 20)) and the metallurgical test (differential scanning calorimetry (n = 5)). A scanning electron microscopy was performed to verify the causes of fracture after mechanical tests (cyclic fatigue and torsional tests). According to results, VB showed the highest flexibility and cyclic fatigue resistance in comparison to the other instruments, with a statistically significant difference (p < 0.05). Regarding torsional resistance, EES showed the lowest value of torque at fracture, with a statistically significant difference, whilst the comparison between ZF and VB showed no statistically significant difference (p > 0.05). DSC analysis pointed out that VB had the highest austenite start and finish temperatures, followed by ESS and then ZF. ESS sample showed the highest martensite start and finish temperatures followed by VB and ZF. Considering the results, it can be concluded that VB showed the best mechanical performance during static tests in comparison to ESS and ZF. This is fundamentally due to the interaction of parameters such as instrument design and heat-treatments that are able to enhance its mechanical performance.

Evolution of Transformation Strain During Partial Transformation Cycling of an NiTi Shape Memory Alloy

This paper deals with how the magnitude of transformation strain changes on partial transformation cycling of an NiTi shape memory alloy. A near-equiatomic NiTi shape memory alloy was allowed to undergo partial thermal cycling keeping the stress constant at 100 MPa for various upper cycle temperatures (between austenite start and austenite finish), using a custom-built thermomechanical cycling test setup. The displacement and the temperature of the sample during cycling were measured using a LASER extensometer and an optical pyrometer, respectively. The test results show that the recovery strain and thermal hysteresis width decrease with increasing number of cycles during partial cycling. In addition, martensite start and martensite finish temperatures increase during the initial cycles, whereas austenite start and austenite finish temperatures decrease during the initial cycles, followed by their saturation.

The Influence of the Soaking Temperature Rotary Forging and Solution Heat Treatment on the Structural and Mechanical Behavior in Ni-Rich NiTi Alloy.

The structural and thermophysical characteristics of an Ni-rich NiTi alloy rod produced on a laboratory scale was studied. The soak temperature of the solution heat-treatment steps above 850 °C taking advantage of the precipitate dissolution to provide a matrix homogenization, but it takes many hours (24 to 48) when used without thermomechanical steps. Therefore, the suitable reheating to apply between the forging process steps is very important, because the product’s structural characteristics are dependent on the thermomechanical processing history, and the time required to expose the material to high temperatures during the processing is reduced. The structural characteristics were investigated after solution heat treatment at 900 °C and 950 °C for 120 min, and these heat treatments were compared with as-forged sample structural characteristics (one hot deformation step after 800 °C for a 30 min reheat stage). The phase-transformation temperatures were analyzed through differential scanning calorimetry (DSC), and the structural characterization was performed through synchrotron radiation-based X-ray diffraction (SR-XRD) at room temperature. It was observed that the solution heat treatment at 950 °C/120 min presents a lower martensitic reversion finish temperature (Af); the matrix was fully austenitic; and it had a hardness of about 226 HV. Thus, this condition is the most suitable for the reheating stages between the hot forging-process steps to be applied to this alloy to produce materials that can display a superelasticity effect, for applications such as crack sensors or orthodontic archwires.

Effect of Quenching and Partitioning Heat Treatment on the Fatigue Behavior of 42SiCr Steel

The manufacturing of advanced high-strength steels with enhanced ductility is a persistent aim of research. The ability of a material to absorb high loads while showing a high deformation behavior is a major task for many industrial fields like the mobility sector. Therefore, the material properties of advanced high-strength steels are one of the most important impact factors on the resulting cyclic fatigue behavior. To adjust advanced material properties, resulting in high tensile strengths as well as an enhanced ductility, the heat treatment process of quenching and partitioning (QP) was developed. The quenching takes place in a field between martensite start and martensite finish temperature and the subsequent partitioning is executed at slightly elevated temperatures. Regarding the sparsely investigated field of fatigue research on quenched and partitioned steels, the present work investigates the influence of a QP heat treatment on the resulting microstructure by light and scanning electron microscopy as well as on the mechanical properties such as tensile strength and resistance against fatigue regarding two different heat treatment conditions (QP1, QP2) in comparison to the cold-rolled base material of 42SiCr steel. Therefore, the microscopic analysis proved the presence of a characteristic quenched and partitioned microstructure consisting of a martensitic matrix and partial areas of retained austenite, whereas carbides were also present. Differences in the amount of retained austenite could be observed by using X-ray diffraction (XRD) for the different QP routes, which influence the mechanical properties resulting in higher tensile strength of about 2000 MPa for QP1 compared to about 1600 MPa for QP2. Furthermore, the transition for the fatigue limit was approximated by using stepwise load increase tests (LIT) and afterwards verified by constant amplitude tests (CAT) in accordance with the staircase method, whereas the QP1 condition reached the highest fatigue strength of 900 MPa. Subsequent light and scanning electron microscopy of selected fractured surfaces and runouts showed a different behavior regarding the size of the fatigue fracture area and also differences in the microstructure of these runouts.

Thermomechanical training and structural tests for adaptive SMA bumps with two-way shape memory effect

In this paper, shape memory alloy (SMA) bumps with two-way shape memory effect (TWSME) are trained by simple but effective training approaches, which provides a new idea for the actuations of the shock control bump (SCB) on airfoil. Two different configurations of bump structures (2D and 3D SMA bumps) are designed and fabricated. The bumps are required to exhibit TWSME so that it can change its shape by heating and cooling between two stable states at austenitic phase and martensitic phase, respectively. To obtain the TWSME, the material is trained in the range of martensitic finish temperature and austenitic finish temperature whilst a displacement boundary condition is imposed. A set of fixtures, which can be assembled to the universal testing machine (UTM), are designed to achieve the clamped boundary condition during thermal cycles of the training process. After training, SMA bumps with the TWSME, that bulge at low-temperature and become flat at high, are obtained. Structural tests and deformation control are then carried out afterwards to show the deformation performance of the trained SMA bumps.

EFFECT OF HEAT INPUT AND POST WELD HEAT TREATMENT ON THE PHASE TRANSFORMATION TEMPERATURE OF TIG-WELDED NiTinol SHEETS

NiTinol Shape Memory Alloys (SMA) are becoming one of the ideal choices for biomedical industries due to their unique properties such as Shape Memory Effect (SME), Super Elasticity (SE) and Biocompatibility. In the process of making complicated biomedical implants, welding processes play a vital role. In this work, an attempt was made to study the effect of heat input and Post Weld Heat Treatment (PWHT) on the TIG-welded NiTinol SMA. TIG welding was carried out on 1-mm thick NiTinol sheets. With increase in heat input, there was a significant variation in Phase Transformation Temperature (PTT) of welded samples. The variation in PTT is attributed to the formation of intermetallic phases such as Ti2Ni, Ni3Ti and NiTiO3 and coarse grain formation. Electron Back Scattered Diffraction (EBSD) analysis on the weld revealed that the average grain size of parent material was increased from 9.92851[Formula: see text][Formula: see text]m to 48.292345[Formula: see text][Formula: see text]m after the welding process. The PWHT was carried out on the best weld characteristic sample. PWHT did not produce significant effect on PTT. Austenite start and finish temperature slightly decreased after PWHT, whereas slight drift towards the positive side was noticed in martensite start and finish temperature.

Architected material analogs for shape memory alloys

Architected material analogs for shape memory alloys

Experimental and numerical analyses of quenching performance of hot stamping blanks by two-phase refrigerant cooling using R1234yf

This study aims to investigate the quenching performance of hot stamping blanks by two-phase refrigerant and conventional single-phase cooling. A low-global-warming potential refrigerant, R1234yf, is used as the working fluid for the two-phase refrigerant cooling. The quenching performance of the water and R1234yf cooling methods is evaluated experimentally and via simulations using a three-dimensional transient thermo-fluid model. The R1234yf cooling method presents a higher cooling capacity and energy efficiency than the water cooling method owing to the effective evaporative heat transfer characteristics of the former. Under the same mass flow rate conditions, the blank hardness and its standard deviation achieved by the R1234yf cooling method are 7.3–31.5 HV higher and 13.1–54.3% lower than those by the water cooling method, respectively. Furthermore, the R1234yf cooling method decreases the hotspot area in the internal lower die and realizes a more uniform temperature distribution compared to water cooling. In addition, the daily production by the R1234yf cooling method is 9.5 − 15.3% higher than that by the water cooling method owing to the shorter approach time to the martensite finish temperature in the former. Accordingly, owing to its higher blank quality and productivity, the R1234yf cooling method has a superior quenching performance than water cooling during the hot stamping process.

Influence of Ausforming Treatment on Super Elasticity of Cu-Zn-Al Shape Memory Alloy for Seismic Energy Dissipaters

In order to develop the application of the more cost-effective copper-based shape memory alloys (SMAs), rather than nickel–titanium as earthquake energy dissipaters, the influence of ausforming-induced plastic deformation on phase transformations, microstructure, super elasticity and mechanical properties of the shape memory alloy Cu-26Zn-4Al was examined. These specific SMA properties were targeted by applying appropriate parameters of the thermomechanical (the so-called ausforming) process: beta-phase homogenization at 800 °C for 20 min, one-step hot rolling at 800 °C and water quenching. The results showed significant microstructural changes, increased mechanical resistance and change in the phase transformation behavior. The SMA treated by ausforming retained the reversible austenitic–martensitic transformation ability, with the appearance of the super-elastic effect up to 6% of strain recovery. Although some strengthening occurred after hot rolling (an increase in true yield strength of 125 MPa was detected), all phase transformation temperatures were decreased. The smallest decrease was detected for the austenite finish temperature (32.8 °C) and the largest for the martensite finish temperature (42.0 °C), allowing both the expansion and the lowering of the temperature range of super elasticity, which is favorable for construction applications. It is concluded that it is possible to achieve an optimal combination of adequate strength and improved transformation behavior of Cu-Zn-Al alloy by applying the ausforming treatment.

Low-temperature hall effect and martensitic transition temperatures in magnetocaloric Ni50Mn35Sb15−xGex (x = 0, 1, 3) alloys

The field dependence of Hall resistivity ρH and magnetization M of the magnetocaloric Ni50Mn35Sb15−xGex (x = 0, 1, 3) alloys were measured at T = 4.2 K and in magnetic fields of up to 70 kOe. The martensitic transitions temperatures, i.e., the martensite start temperature MS, martensite finish temperature MF, austenite start AS and austenite finish AF temperatures, were obtained from the magnetization temperature dependence that measured from 4.2 to 350 K in a field of 1 kOe. It was observed that the martensitic transitions temperatures correlate strongly both with the valence electron concentration e/a and with the electronic transport characteristics, which are the coefficients of normal R0 and anomalous RS Hall effect and the concentration of charge carriers n. Apparently, similar correlations should be observed in other magnetocaloric compounds that could be used to study martensitic transitions.