The effects of boron addition on the magnetic and mechanical properties of NiMnSn shape memory alloys

J Therm Anal Calorim DOI 10.1007/s10973-016-5576-6 The effects of boron addition on the magnetic and mechanical properties of NiMnSn shape memory alloys Y. Aydogdu1 • A. S. Turabi2 • A. Aydogdu1 • M. Kok3 • Z. D. Yakinci4 H. E. Karaca2 • Received: 29 January 2016 / Accepted: 14 May 2016  Akadémiai Kiadó, Budapest, Hungary 2016 Abstract The effects of boron addition on the microstructure, magnetic, mechanical, and shape memory properties of Ni50Mn40-xSn10Bx (at.%) (x = 1, 2, 3, 4, 6, 8) polycrystalline alloys were systematically investigated. It was revealed that transformation temperatures, magnetic behavior, mechanical, and shape memory properties can be tailored by B content. Transformation temperatures were decreased while saturation magnetization was increased with the addition of boron. In addition to magnetic behavior, ferromagnetic austenite transforms to weakly magnetic martensite, and then, martensite becomes ferromagnetic during cooling. The low amount of B addition (up to 4 %) to NiMnSn creates the second phase which provides higher strength and ductility. However, the high volume fraction of the second phase reduces the shape recovery because the phase transformation does not occur in the second phase. Brittleness takes place when the B amount is more than 6 % in NiMnSnB alloys. The amount of boron content in the NiMnSnB alloys plays a significant role to modify the magnetic, mechanical, and shape memory properties. & Y. Aydogdu y.aydogdu@gazi.edu.tr 1 Department of Physics, Faculty of Science, Gazi University, Ankara, Turkey 2 Department of Mechanical Engineering, University of Kentucky, Lexington, KY 40506, USA 3 Department of Physics, Faculty of Science, Firat University, Elazig, Turkey 4 Vocational School of Health Service, Inonu University, Malatya, Turkey Keywords Shape memory effect
Boron addition
Saturation magnetization
Phase transformation
Thermal characterization
Composition alteration Introduction Heusler NiMn-based magnetic shape memory alloys (MSMAs) have been widely studied since they exhibit the magnetic shape memory effect [1–3], magnetocaloric effect [4–6], magnetoresistance [7, 8], magnetothermal conductivity [9], and the elastocaloric effect [10] in addition to the conventional shape memory effect [11–13]. In general, the origin of these particular properties is the firstorder magneto-structural transformation from ferromagnetic austenite phase to weakly magnetic martensite phase where a large magnetization difference is determined [2]. The magnetization difference is the main source of driving force for the magnetic field-induced martensitic phase transformation [14]. NiMnSn alloys have attracted great attention since they do not contain expensive elements like Ga or In and show MSMA behavior. Thus, they are a potential candidate for large-scale applications where they can be used as magnetic actuators, high-efficiency sensors, and environmentfriendly magnetic refrigerators. However, practical applications of NiMn-based MSMAs are limited due to their brittleness which limits their use in the polycrystalline form. In order to overcome the brittleness problem in polycrystalline form, alloying with quaternary elements such as Fe [15–17], Co [18, 19], Cu [20, 21] is employed. Ma et al. [21] reported that hot workability and ductility of NiMnGa alloys can be altered due to the formation of second phases by Cu addition. Although it was shown that transformation temperatures and magnetic behavior of 123 Y. Aydogdu et al. (a) Heat flow endo up/mW mg–1 Ni50Mn40–xSn10Bx (at.%) (x = 0, 1, 2, 3, 4, 6) B6 B4 B3 0.5 B2 Heating B1 Cooling B0 –80 –40 0 40 80 120 160 200 240 280 Temperature/°C (b) 240 Ni50Mn40–xSn10Bx (at.%) (x = 0, 1, 2, 3, 4, 6) Temperature/°C 200 Ms 160 120 80 40 0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 B Content/% Fig. 1 a DSC response of NiMnSnB alloys and b Ms of NiMnSnB alloys as a function of B content NiMnSn can be modified by Fe or Co addition [22, 23], the effects of alloying on their mechanical properties such as strength and ductility were not investigated in detail. Alloying with boron has been widely used for grain refinement of shape memory alloys to improve ductility [24–26]. Previous studies on B-doped NiMn-based shape memory alloys revealed that transformation temperatures and saturation magnetization can be tailored by changing the amount of B content in the alloy [27–29]. In NiMnSbB alloys, B doping decreases the Curie temperature, saturation magnetization and the transformation temperatures [30]. In (Ni53.5Mn26Ga20.5)1-xBx (x = 0.5 and 1) alloys, B addition decreases the transformation temperatures and increases the saturation magnetization [31]. Improved ductility and strength were observed in NiMnGaB alloys [29]. The effect of boron doping on transformation temperatures and magnetocaloric effect in Ni43Mn46Sn11Bx alloys was reported where transformation temperatures and the Curie temperature of austenite were increased with B addition [32]. The effects of Sn content substituted for Mn on mechanical and shape memory properties of Ni50Mn40-xSn10?x (at.%) (x = 0, 1, 2, 3) alloys were investigated in our previous study [33]. It was revealed that Ni50Mn40Sn10 exhibits high transformation temperatures of about 100 C, good shape memory effect and perfect superelasticity at 190 C. Thus, Ni50Mn40Sn10 alloy is selected to study the effects of B addition on mechanical and shape memory properties. First-order magnetic phase transformation near room temperature is desired for magnetic refrigeration application where NiMn-based Heusler alloys can be employed [34, 35]. Thus, NiMnSn alloys are promising for practical applications due to tunable transformation temperatures with composition altering. It should be noted that composition altering modifies the valence electron concentration (e/a) due to the atomic radius difference between substituted elements and the e/a ratio plays a crucial role in tailoring transformation temperatures [36–38]. Substitution of Mn with B in NiMnSnB alloys gives us the ability to alter e/a ratio drastically. It should also be noted that there is a lack of systematic study of the literature about the effects of alloying NiMn-based alloys with high B content ([1 %). In this study, the effects of B addition on the magnetic behavior, mechanical and shape memory properties were investigated in Ni50Mn40-xSn10Bx (at.%) (x = 1, 2, 3, 4, 6, 8). Boron is chosen as the quaternary element because it does not carry a magnetic moment, has Table 1 Characteristic temperatures and enthalpy obtained from DSC responses, e/a ratios and Vickers hardness of Ni50Mn40-xSn10Bx alloys Sample Composition Ms/C Mp/C Mf/C As/C Ap/C Af/C DHavg/J g-1 e/a Hardness (HV) B0 Ni50Mn40Sn10 216.9 195.6 181.9 195.5 209.9 227.6 29.5 8.2 451 B1 Ni50Mn39Sn10B 167 158.2 146.9 169.3 178 181.8 29 8.16 420 B2 B3 Ni50Mn38Sn10B2 Ni50Mn37Sn10B3 126.9 104.1 107.4 92.3 72.4 82 103.6 100.3 124.6 114.2 141.5 122.2 21.5 18.5 8.12 8.08 350 346 B4 Ni50Mn36Sn10B4 91.1 76.7 68.2 82.9 94.5 105.8 17.3 8.04 375 B6 Ni50Mn34Sn10B6 0.9 -16.3 -26.5 -5.7 7.4 21 6.8 7.96 587 B8 Ni50Mn32Sn10B8 – – – – – – – 7.88 492 123 The effects of boron addition on the magnetic and mechanical properties of NiMnSn shape memory… Fig. 2 SEM images of a B0, b B1, c B2, d B4, e B6 and f B8 to show the effect of B addition on microstructure in Ni50Mn40-xSn10Bx (at.%) alloys a smaller atomic radius compared with the other elements of NiMnSn and could improve ductility and strength. Experimental procedure Ni50Mn40-xSn10Bx (at.%) (x = 1, 2, 3, 4, 6, 8) polycrystalline alloys were fabricated by the vacuum arc melting method in a water-cooled Cu crucible by using high-purity elements of Ni (99.9 %); Mn (99.99 %); Sn (99.9 %); and B (99.999 %). The ingots were melted four times to ensure homogenization, and then, they were annealed at 800 C for 72 h. The microstructure of the alloys was analyzed by a LEO–EVO 40 scanning electron microscope (SEM). In order to reveal the microstructure of the alloys, specimens were polished and etched with a solution of 20 mL HCl, 5 g FeCl3–H2O and 96 mL methanol. Transformation temperatures were determined by PerkinElmer differential scanning calorimetry (DSC) with 10 C min-1 heating– cooling rate in a nitrogen atmosphere with flow rate of 20 mL min-1. Magnetization properties were measured by physical property measurement system (PPMS) (Quantum Design 7). The mechanical experiments were conducted on 3 9 3 9 6 mm3 compression samples by using a MTS Landmark servo hydraulic test frame. Thermal cycling experiments were performed with the rates of 5 and 10 C min-1 for cooling and heating, respectively. The strain was measured by a MTS high-temperature extensometer with a gage length of 12 mm. IGOR Pro 6 Technical graphing and data analysis software was used to plot and analyze the experimental results. The alloys will be named according to their boron content as B0, B1, B2, B3, B4, B6 and B8 throughout the text. Results and discussion DSC curves of the NiMnSnB alloys (up to 6 %) are shown in Fig. 1a. It is clear that all the alloys up to 6 % B content show reversible phase transformation. Based on the DSC 123 Y. Aydogdu et al. (a) 10 Ni50Mn40–xSn10Bx (at.%) (x = 0, 1, 2, 3, 4) Magnetization/emu g–1 9 B0 B1 B2 B3 B4 8 7 6 5 4 3 2 1 0 40 80 120 160 200 240 280 240 280 Temperature/°C (b) 40 Magnetization/emu g–1 35 Ni50Mn40–xSn10Bx (at.%) (x = 6, 8) 30 B6 B8 25 20 15 10 5 0 0 40 80 120 160 200 Temperature/°C Fig. 3 Magnetization response of a Ni50Mn40-xSn10Bx (at.%) (x = 0, 1, 2, 3, 4), b Ni50Mn40-xSn10Bx (at.%) (x = 6, 8) alloys under 5 T results, martensite start (Ms) and finish (Mf), austenite start (As) and finish (Af) temperatures, and transformation enthalpy (DH) are determined and shown in Table 1. Also, e/a and hardness values were included in Table 1. It should be noted that since B (with three valence electrons) is substituted with Mn (with seven valence electrons), e/ a ratio decreased with B content. Figure 1b shows that Ms drastically decreases with increasing B content or decreasing e/a ratio. For instance, 6 % B addition decreased Ms from 216.9 to 0.9 C, as shown in Table 1. Phase transformation was not observed for B8 when it was cooled down to -60 C. Although the decrease in the transformation temperatures can be attributed to the decrease of e/a ratio, which highly influences the transformation temperatures in Heusler alloys [36], it should be noted that second phase formation changes the composition of the matrix which alters the e/a ratio. Moreover, the covalent radius of boron element (0.80 Å) is much smaller than Mn (1.17 Å) [39] which could result in modified atomic interactions and lattice parameters that could also 123 decrease the TTs [40–42]. Room temperature hardness tests show that hardness of Ni50Mn40-xSn10Bx decreases with B while they are martensite. It is worth mentioning that B6 and B8 alloys were in the parent phase where the other alloys were in the martensite phase at room temperature. The transformation temperatures of B0 and B1 alloys are above 100 C which qualifies them as high-temperature MSMAs. Moreover, the transformation temperatures can be altered in the range of 200 C by simply replacing the Mn with B. It should be also noted that enthalpy (DH) was decreased with increasing B content due second phase formation. Since the second phase does not undergo a phase transformation, the volume fraction of the alloy that transforms decreases, resulting in lower enthalpy. Effects of B addition in Ni50Mn40-xSn10Bx (at.%) alloys on the microstructure were revealed by SEM, as shown in Fig. 2a-f. It is clear that B addition results in the formation of second phases, mainly along the grain boundaries up to 4 % B addition. The volume fraction of the second phase gradually increases, and they disperse in the matrix at high B content ([6 %), as shown in Fig. 2e, 2f. Formation of second phases significantly affects shape memory properties of NiMnSnB alloys since they do not undergo martensitic transformation and alter the composition of the matrix. Energy dispersive spectroscopy (EDS) compositional analysis was performed on the second phase. While the exact composition of the second phase could not be determined, since boron could not be detected by EDS, it was found that the second phase has high Ni and very low Sn content. It should be noted as the matrix becomes Nipoor and Sn-rich, the e/a ratio might decrease further since Ni has ten valence electrons while Sn has four valence electrons. As mentioned before, transformation temperatures decrease with a decrease in e/a. Magnetization vs temperature responses of NiMnSnB alloys were determined where the alloys were heated from 30 C to 275 C and then cooled down back to 40 C under the constant magnetic field of 5T, as shown in Fig. 3. For the alloys that are martensite at room temperature (Fig. 3a), magnetization drastically increases upon heating due to the back transformation from weakly magnetic martensite to ferromagnetic parent phase. With further heating, the magnetization of austenite decreases as the temperature approaches to the Curie temperature. Transformation temperatures determined from the magnetization curves are in agreement with DSC results where they decreased with increasing B content. Moreover, B addition slightly increased the magnetization difference between transforming phases. As shown in Fig. 3b, phase transformation was not observed in B6 and B8 alloys since they are already in austenite at 30 C. It should also be noted B0 shows two-stage transformation which was also observed in DSC tests. The effects of boron addition on the magnetic and mechanical properties of NiMnSn shape memory… (a) 80 (b) 60 60 B0 at –100 °C B1 B2 B3 B4 B6 B8 40 20 0 Magnetization/emu g–1 Magnetization/emu g–1 Ni50Mn40–xSn10Bx (at.%) (x = 0, 1, 2, 3, 4, 6, 8) Ni50Mn40–xSn10Bx (at.%) (x = 0, 1, 2, 3, 4, 6, 8) –20 –40 –60 –80 B0 B1 B2 B3 B4 B6 B8 40 20 0 at 30 °C –20 –40 –60 –10 –8 –6 –4 –2 0 2 4 6 8 10 –10 –8 –6 –4 Magnetic field/T (c) 0 2 4 6 8 10 10 Ni50Mn40–xSn10Bx (at.%) (x = 0, 1, 2, 3, 4, 6, 8) 8 Magnetization/emu g–1 –2 Magnetic field/T B0 B1 B2 B3 B4 B6 B8 6 4 2 0 at 250 °C –2 –4 –6 –8 –10 –8 –6 –4 –2 0 2 4 6 8 Magnetic field/T Fig. 4 Magnetization behavior of Ni50Mn40-xSn10Bx (at.%) alloys at a 100 C, b 30 C, c 250 C (b) 100 MPa 0.5 300 MPa 200 MPa 100 MPa Cooling Heating 0.5 Cooling Heating 400 MPa Compressive strain/% 200 MPa Ni50Mn34Sn10B6 Ni50Mn37Sn10B3 Ni50Mn40Sn10 Cooling Heating 0.5 Compressive strain/% 300 MPa (c) Compressive strain/% (a) 200 MPa 100 MPa 5 MPa 5 MPa 5 MPa 120 140 160 180 200 220 240 Temperature/°C 60 80 100 120 140 160 180 Temperature/°C –60 –40 –20 0 20 40 Temperature/°C Fig. 5 Thermal cycling responses of Ni50Mn40-xSn10Bx (at.%) (x = 0, 3, 6) alloys under selected stress levels Magnetization responses of Ni50Mn40-xSn10Bx (at.%) alloys at -100, 30 and 250 C are shown in Fig. 4. As shown in Fig. 4a, all the alloys are ferromagnetic at -100 C where the magnetization was drastically increased and saturated with a magnetic field. All the alloys except B8 are martensite at -100 C. Saturation magnetization increased only slightly with B content up to 4 % and then increased substantially with the further increase in B content in the NiMnSnB alloy. The saturation magnetization of B0, B4 and B8 was obtained as 12.8, 19.4 and 56.8 emu g-1 at -100 C, respectively. At 30 C, shown in Fig. 4b, B6 and B8 alloys exhibit ferromagnetic 123 Y. Aydogdu et al. 123 B6 and B8 were found to be very brittle. However, it should be noted that the strength was improved substantially for B8. The failure stress values were 388, 668 and 877 MPa for B0, B4 and B8, respectively. B1 exhibits the highest deformation up 5.7 % where it was 3.8 % for B0. Microstructural, mechanical and shape memory properties of NiMnSn shape memory alloys are highly sensitive to the addition of boron. Boron could occupy interstitial sites when it is added in low amounts, but boron addition at higher quantities promotes the formation of the second phase. Substituting the Mn with B in Ni50Mn40-xSn10Bx (at.%) (x = 1, 2, 3, 4, 6, 8) alloys raises the volume fraction of second phase formation and decreases the transformation temperatures. Although the second phase formation increased the strength, it also made the alloy more brittle. The amount of shape recovery was smaller with a high volume of untransformed second phase particles. Moreover, ductility was remarkably increased with Recoverable strain/% 2.5 1.0 Ni50Mn40Sn10 Ni50Mn37Sn10B3 Ni50Mn34Sn10B6 2.0 0.8 1.5 0.6 1.0 0.4 0.5 0.2 0.0 Irrecoverable strain/% 0.0 0 50 100 150 200 250 300 350 400 450 Compressive stress/MPa Fig. 6 Recoverable and irrecoverable strain as a function of compressive stress for Ni50Mn40-xSn10Bx (at.%) (x = 0, 3, 6) alloys 1000 900 Compressive stress/MPa behavior with high saturation magnetization of 41.8 and 33.2 emu g-1, respectively, since they are austenite. Other NiMnSnB alloys with less than 6 % B show linear behavior since they tested above the Curie temperature of martensite. The magnetization responses of all the alloys were increased linearly with the magnetic field at 250 C, above their Curie temperature of austenite, as shown in Fig. 4c. From Fig. 4, we can conclude that the alloys transform from ferromagnetic austenite to nonmagnetic martensite upon phase transformation during cooling. Martensite becomes ferromagnetic with further cooling. Figure 5 shows the thermal cycling results of B0, B3 and B6 alloys under constant compressive stress from 5 to 400 MPa. The samples were heated up to above their Af, loaded to a selected stress level and then thermally cycled to observe the shape memory effect. Applied stress was increased until the irrecoverable strain of 0.15 % or more was observed. The maximum applied stress was 300, 400 and 200 MPa for B0, B3 and B6 alloys, respectively. The transformation temperatures of all the alloys were increased with stress. For B0, Ms was 177.4 C under 5 MPa and increased to 203.8 C under 300 MPa. Transformation temperatures were decreased with increasing B content which is in good agreement with DSC results. Ms temperatures of B0, B3 and B6 alloys were obtained as 177.4, 114 and -8 C, respectively, under 5 MPa. Figure 6 shows the recoverable and irrecoverable strains, extracted from thermal cycling results shown in Fig. 5 as a function of applied stress for Ni50Mn40-xSn10Bx (at.%) (x = 0, 3, 6) alloys. The volume fraction of selected martensite variants increases. Thus, the recoverable strain increases and then saturates with stress. At high stress levels, plastic deformation takes place and results in irrecoverable strain. For B0, the maximum recoverable strain was found to be 2.1 % under 300 MPa which also resulted in an irrecoverable strain of 0.2 %. For B3, the maximum recoverable strain was determined as 1.38 % where the irrecoverable strain was 0.15 % under 400 MPa. The maximum recoverable strain of B6 was only 0.70 % where the irrecoverable strain was 0.12 % under 200 MPa. Thus, under 300 MPa, B3 has lower irrecoverable strain than B0 due to increased strength. However, recoverable strain decreases with increasing B content due to the increased volume fraction of the second phase which does not undergo phase transformation. In order to obtain the strength and ductility behavior of Ni50Mn40-xSn10Bx (at.%) alloys, the alloys were loaded at room temperature until failure in compression, as shown in Fig. 7. It should be noted that, according to the DSC results, B6 and B8 alloys are austenite while others are martensite initially. The addition of 1 % boron increased both the strength and the ductility. Further increase in boron increased the strength, but decreased the ductility. Ni50Mn40–xSn10Bx (at.%) (x = 0, 1, 2, 4, 6, 8) X B8 800 700 B4 X X B2 600 500 B1 400 X B6 X X B0 300 200 100 0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 Compressive strain/% Fig. 7 Mechanical response of Ni50Mn40-xSn10Bx (at.%) alloys at room temperature The effects of boron addition on the magnetic and mechanical properties of NiMnSn shape memory… 1 % of B addition where brittleness obviously appeared with B addition above 6 %. Conclusions The effects of B addition on the shape memory properties of Ni50Mn40-xSn10Bx (at.%) alloys were investigated by thermal, magnetization and mechanical experiments in this study. Transformation temperatures were decreased with increasing B content which can be attributed to decreased e/a ratio and formation of second phases. The volume fraction of the second phase increased with B content. Upon cooling, ferromagnetic austenite transforms to weakly magnetic martensite, and then, martensite becomes ferromagnetic. B addition increases the strength initially, but the alloy became brittle with a high amount of B addition. Ni50Mn39Sn10B1 alloy was deformed until 5.7 % at room temperature where maximum deformation was 3.8 % for Ni50Mn40Sn10. Maximum failure stress was 338 MPa for Ni50Mn40Sn10 alloy and increased to 877 MPa for Ni50Mn32Sn10B8. Moreover, B addition decreases the shape recovery due to the increased volume fraction of second phase formation. The maximum recoverable strain was 2.1 % for Ni50Mn40Sn10 decreased to 0.70 % in Ni50Mn34Sn10B6. Acknowledgements This work is supported by TUBITAK under Project No: 113F234 and National Science Foundation (NSF) CMMI award #0954541. References 1. Kainuma R, Imano Y, Ito W, Sutou Y, Morito H, Okamoto S, et al. Magnetic-field-induced shape recovery by reverse phase transformation. Nature. 2006;439(7079):957–60. 2. Sutou Y, Imano Y, Koeda N, Omori T, Kainuma R, Ishida K, et al. Magnetic and martensitic transformations of NiMnX (X = In, Sn, Sb) ferromagnetic shape memory alloys. Appl Phys Lett. 2004;85(19):4358–60. 3. Karaca HE, Karaman I, Basaran B, Lagoudas DC, Chumlyakov YI, Maier HJ. One-way shape memory effect due to stress-assisted magnetic field-induced phase transformation in Ni2MnGa magnetic shape memory alloys. Scripta Mater. 2006;55(9):803–6. doi:10.1016/j.scriptamat.2006.07.025. 4. Planes A, Mañosa L, Acet M. Magnetocaloric effect and its relation to shape-memory properties in ferromagnetic Heusler alloys. J Phys Condens Matter. 2009;21(23):233201. 5. Pasquale M, Sasso C, Giudici L, Lograsso T, Schlagel D. Fielddriven structural phase transition and sign-switching magnetocaloric effect in Ni–Mn–Sn. Appl Phys Lett. 2007;91(13):131904. 6. Krenke T, Duman E, Acet M, Wassermann EF, Moya X, Mañosa L, et al. Inverse magnetocaloric effect in ferromagnetic Ni–Mn– Sn alloys. Nat Mater. 2005;4(6):450–4. 7. Koyama K, Okada H, Watanabe K, Kanomata T, Kainuma R, Ito W, et al. Observation of large magnetoresistance of magnetic Heusler alloy Ni50Mn36Sn14 in high magnetic fields. Appl Phys Lett. 2006;89(18):182510. 8. Pathak AK, Dubenko I, Karaca HE, Stadler S, Ali N. Large inverse magnetic entropy changes and magnetoresistance in the vicinity of a field-induced martensitic transformation in Ni50 - xCoxMn32 - yFeyGa18. Appl Phys Lett. 2010;97(6): 062505. doi:10.1063/1.3467460. 9. Zhang B, Zhang X, Yu S, Chen J, Cao Z, Wu G. Giant magnetothermal conductivity in the Ni–Mn–In ferromagnetic shape memory alloys. Appl Phys Lett. 2007;91(1):012510. 10. Castillo-Villa PO, Mañosa L, Planes A, Soto-Parra DE, SanchezLlamazares J, Flores-Zuniga H, et al. Elastocaloric and magnetocaloric effects in Ni–Mn–Sn (Cu) shape-memory alloy. J Appl Phys. 2013;113(5):053506. 11. Turabi AS, Karaca HE, Tobe H, Basaran B, Aydogdu Y, Chumlyakov YI. Shape memory effect and superelasticity of NiMnCoIn metamagnetic shape memory alloys under high magnetic field. Scripta Mater. 2016;111:110–3. doi:10.1016/j. scriptamat.2015.08.027. 12. Karaca HE, Karaman I, Basaran B, Chumlyakov YI, Maier HJ. Magnetic field and stress induced martensite reorientation in NiMnGa ferromagnetic shape memory alloy single crystals. Acta Mater. 2006;54(1):233–45. doi:10.1016/j.actamat.2005.09.004. 13. Karaca HE, Karaman I, Brewer A, Basaran B, Chumlyakov YI, Maier HJ. Shape memory and pseudoelasticity response of NiMnCoIn magnetic shape memory alloy single crystals. Scripta Mater. 2008;58(10):815–8. doi:10.1016/j.scriptamat.2007.12.029. 14. Karaca HE, Karaman I, Basaran B, Ren Y, Chumlyakov YI, Maier HJ. Magnetic field-induced phase transformation in NiMnCoIn magnetic shape-memory alloys—A new actuation mechanism with large work output. Adv Funct Mater. 2009;19(7):983–98. doi:10.1002/adfm.200801322. 15. Chen F, Wang H, Zheng Y, Cai W, Zhao L. Effect of Fe addition on transformation temperatures and hardness of NiMnGa magnetic shape memory alloys. J Mater Sci. 2005;40(1):219–21. 16. Wu Z, Liu Z, Yang H, Liu Y, Wu G, Woodward RC. Metallurgical origin of the effect of Fe doping on the martensitic and magnetic transformation behaviours of Ni 50 Mn 40-x Sn 10 Fe x magnetic shape memory alloys. Intermetallics. 2011;19(4): 445–52. 17. Ma Y, Xu L, Li Y, Jiang C, Xu H, Lee Y-K. Martensitic transformation, ductility, and shape-memory effect of polycrystalline Ni56Mn25–xFexGa19 alloys. Zeitschrift für Metallkunde. 2005; 96(8):843–46. 18. Karaca H, Turabi A, Basaran B, Pathak A, Dubenko I, Ali N et al. Compressive response of polycrystalline NiCoMnGa high-temperature meta-magnetic shape memory alloys. J. Mater Eng Perform. 2013;22(10):3111–4. 19. Ma Y, Yang S, Liu Y, Liu X. The ductility and shape-memory properties of Ni–Mn–Co–Ga high-temperature shape-memory alloys. Acta Mater. 2009;57(11):3232–41. 20. Wang J, Jiang C. A single-phase wide-hysteresis shape memory alloy Ni 50 Mn 25 Ga 17 Cu 8. Scripta Mater. 2010;62(5): 298–300. 21. Ma Y, Yang S, Jin W, Liu X. Ni 56 Mn 25-x Cu 9 Ga 19 (x = 0, 1, 2, 4, 8) high-temperature shape-memory alloys. J Alloy Compd. 2009;471(1):570–4. 22. Cong D, Roth S, Pötschke M, Hürrich C, Schultz L. Phase diagram and composition optimization for magnetic shape memory effect in Ni–Co–Mn–Sn alloys. Appl Phys Lett. 2010;97:021908. 23. Bachaga T, Daly R, Suñol J, Saurina J, Escoda L, Legarreta L, et al. Effects of Co additions on the martensitic transformation and magnetic properties of Ni–Mn–Sn shape memory alloys. J Supercond Novel Magn. 2015;28(10):3087–92. 24. Suzuki Y, Xu Y, Morito S, Otsuka K, Mitose K. Effects of boron addition on microstructure and mechanical properties of Ti–Td– Ni high-temperature shape memory alloys. Mater Lett. 1998; 36(1):85–94. 123 Y. Aydogdu et al. 25. Yang WS, Mikkola D. Ductilization of Ti–Ni–Pd shape memory alloys with boron additions. Scr Metall Mater. 1993;28(2):161–5. 26. Kök M, Yakinci Z, Aydogdu A, Aydogdu Y. Thermal and magnetic properties of Ni51Mn28. 5Ga19. 5B magnetic-shapememory alloy. J Therm Anal Calorim. 2014;115(1):555–9. 27. Gautam BR, Dubenko I, Pathak AK, Stadler S, Ali N. The structural and magnetic properties of Ni2 Mn1-xBxGa Heusler alloys. J Magn Magn Mater. 2009;321(1):29–33. 28. Gautam BR, Dubenko I, Pathak AK, Stadler S, Ali N. Effect of isoelectronic substitution on magnetic properties of Ni(2)Mn(GaB) Heusler alloys. J Phys-Condens Matter. 2008;20(46):5. doi:10.1088/0953-8984/20/46/465209. 29. Aydogdu Y, Turabi AS, Kok M, Aydogdu A, Tobe H, Karaca HE. Effects of the substitution of gallium with boron on the physical and mechanical properties of Ni–Mn–Ga shape memory alloys. Appl Phys A. 2014;117(4):2073–8. 30. Luo H, Meng F, Jiang Q, Liu H, Liu E, Wu G, et al. Effect of boron on the martensitic transformation and magnetic properties of Ni 50 Mn 36.5 Sb 13.5 - xBx alloys. Scripta Mater. 2010; 63(6):569–72. 31. Ramudu M, Satish Kumar A, Seshubai V. Influence of boron addition on the microstructure, structural and magnetic properties of Ni 53.5 Mn 26.0 Ga 20.5 alloy. Intermetallics. 2012;28:51–7. 32. Xuan H, Wang D, Zhang C, Han Z, Gu B, Du Y. Boron’s effect on martensitic transformation and magnetocaloric effect in Ni43Mn46Sn11Bx alloys. Appl Phys Lett. 2008;92(10):2503. 33. Aydogdu Y, Turabi AS, Kok M, Aydogdu A, Yakinci ZD, Aksan MA et al. The effect of Sn content on mechanical, magnetization and shape memory behavior in NiMnSn alloys. J Alloys Compd. 2016;683:339–45. 123 34. Zimm C, Jastrab A, Sternberg A, Pecharsky V, Gschneidner Jr K, Osborne M et al. Description and performance of a near-room temperature magnetic refrigerator. Adv Cryog Eng. 1998: 1759–66. 35. Khovaylo V, Skokov K, Gutfleisch O, Miki H, Kainuma R, Kanomata T. Reversibility and irreversibility of magnetocaloric effect in a metamagnetic shape memory alloy under cyclic action of a magnetic field. Appl Phys Lett. 2010;97(5):052503. 36. Chernenko V. Compositional instability of b-phase in Ni–Mn–Ga alloys. Scripta Mater. 1999;40(5):523–7. 37. Marcos J, Mañosa L, Planes A, Casanova F, Batlle X, Labarta A. Multiscale origin of the magnetocaloric effect in Ni–Mn–Ga shape-memory alloys. Phys Rev B. 2003;68(9):094401. 38. Bachaga T, Daly R, Escoda L, Sunol J, Khitouni M. Influence of chemical composition on martensitic transformation of MnNiIn shape memory alloys. J Therm Anal Calorim. 2015;122(1): 167–73. 39. Pauling L. Atomic radii and interatomic distances in metals. J Am Chem Soc. 1947;69(3):542–53. 40. Glavatskyy I, Glavatska N, Dobrinsky A, Hoffmann J-U, Söderberg O, Hannula S-P. Crystal structure and high-temperature magnetoplasticity in the new Ni–Mn–Ga–Cu magnetic shape memory alloys. Scripta Mater. 2007;56(7):565–8. 41. Zheng H, Xia M, Liu J, Huang Y, Li J. Martensitic transformation of (Ni 55.3 Fe 17.6 Ga 27.1) 100 - x Co x magnetic shape memory alloys. Acta Mater. 2005;53(19):5125–9. 42. Glavatskyy I, Glavatska N, Söderberg O, Hannula S-P, Hoffmann J-U. Transformation temperatures and magnetoplasticity of Ni– Mn–Ga alloyed with Si, In, Co or Fe. Scripta Mater. 2006; 54(11):1891–5.