In this study, some thermal, mechanical, and magnetic properties of Co86Al14 and Co82Al14Cr4 (at.%) alloys have been investigated. The alloys were produced by arc melting method, and their thermal properties such as phase transformation temperature, enthalpy, and entropy were measured using differential scanning calorimetry (DSC). In addition, TG/DTA device has been utilized for determining Curie temperature for each sample. Furthermore, to specify crystal structure and microstructure of specimens, XRD and optical microscope techniques were used. In addition, Vickers hardness test as a mechanical property has been accomplished to compare the effect of Cr addition to CoAl-based shape memory alloy. Finally, at room temperature, physical property measurement system has been used to reveal magnetization of SMAs. The transformation temperatures obtained from DSC measurement at a heating rate of 20 °C min−1 for Co86Al14 (at.%) alloy were As = 235.3 °C, Af = 293.4 °C, Ms = 105.1 °C, and Mf = 56.9 °C, while the same measurements for Co82Al14Cr4 (at.%) alloy gave As = 295.1 °C, Af = 333.4 °C, Ms = 166.5 °C, and Mf = 136.6 °C, which showed a significant increase due to the incorporation of (4 at.%) of Cr. In contrast, the quantitative values of each enthalpy and entropy were diminished. Moreover, magnetization saturation values for the CoAl and CoAlCr shape memory alloys were determined by H–M measurements to be 127.23 and 107.06 emu g−1, respectively, and their Curie temperature (TC) were 716.71 and 686.22 °C, respectively. What is more, Vickers hardness values for the CoAl and CoAlCr alloys were measured to be 203.40 and 239.22 HV, respectively. Thus, the microhardness value increased remarkably for adding (4 at.%) of chromium to CoAl-based SMA.
Ferromagnetic shape memory alloy (FSMA) Curie temperature Austenite phase
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This work has been supported by Firat University Research-Project Unit (Project No: FF:13.05). This study has been produced from Turkan Malkoc's Ph.D.
Mohdjani J, Leary M, Subic A, Gibson AM. A review of shape memory alloy research, applications and opportunities. Mater Des. 2014;56:1078–113.CrossRefGoogle Scholar
Xuan HC, Wang DH, Zhang CL, Han ZD, Gu XB, Du YW. Boron’s effect on martensitic transformation and magnetocaloric effect in Ni43Mn46Sn11Bx alloys. Appl Phys Lett. 2008;92:102503.Google Scholar
Chernenko VA, Besseghini S. Ferromagnetic shape memory alloys: scientific and applied aspects. Sens Actuat. 2008;142:542–8.CrossRefGoogle Scholar
Kulkova SE, Eremeev SV, Kulkov SS. Electronic structure and magnetic properties of Co- and Mn- based Heusler alloys and thin film. Solid State Commun. 2004;1:793–7.CrossRefGoogle Scholar
Pirge G, Hacioglu A, Ermis M, Altintas S. Determination of composition of NiMnGa magnetic shape memory alloys using hybrid evolutionary algorithms. Comput Mater Sci. 2009;45:189–93.CrossRefGoogle Scholar
Dhaka RS, D’Souza SW, Marinaj M, Chakrabarti A, Schlagel DL, Lograsso TA, Barmam SR. Photoemission study of the (100) surface of NiMnGa and Mn2NiGa ferromagnetic shape memory alloys. Surf Sci. 2009;25:1999–2004.CrossRefGoogle Scholar
Murakami Y, Shinko D, Oikawa K, Kainuma R, Ishida K. Magnetic domain structure in Co–Ni–Al shape memory alloys studied by lorentz microscopy and electron holography. Acta Mater. 2002;50:2173–84.CrossRefGoogle Scholar
Umetsu RY, Ito W, Ito K, Koyama K, Fujita A, Oikawa K, Kanomata T, Kainuma R, Ishidab K. Anomaly in entropy change between parents and martensite phases in the Ni50Mn34In16 Heusler alloys. Scr Mater. 2009;52:25–8.CrossRefGoogle Scholar
Han ZD, Wang DH, Zhang CL, Xuan HC, Zhang JR, Gu BX, Du YW. Effect of lattice contraction on martensitic tranformation and magnetocaloric effect in Ge doped Ni–Mn–Sn alloys. Mater Sci Eng. 2009;157:40–3.CrossRefGoogle Scholar
Malkoc T (2014) Production of CoAl based ferromagnetic shape memory alloys and investigation of their physical properties. Ph.D. Thesis, Firat University Institute, Turkey.Google Scholar
Zhang PN, Liu J. Microstructure and mechanical properties in Co–Ni–Ga–Al shape memory alloys with two-phase structure. J Alloys Compd. 2008;462:225–8.CrossRefGoogle Scholar
Dagdelen F, Malkoc T, Kok M, Ercan E. Comparison of the transformation temperature, microstructure and magnetic properties of Co–Ni–Al and Co–Ni–Al–Cr shape memory alloys. Eur Phys J Plus. 2016;1(131):196.CrossRefGoogle Scholar
Salzbrenner RJ, Cohen M. On the thermodynamics of thermoelastic martensitic transformations. Acta Metall. 1978;27:739–48.CrossRefGoogle Scholar
Kok M, Aydogdu A. Effect of composition on the thermal behavior of NiMnGa alloys. J Therm Anal Calorim. 2013;113:859–63.CrossRefGoogle Scholar
Ando K, Omori T, Sato J, Sutou Y, Oikawa K, Kainuma R, Ishida K. Effect of alloying elements on FCC/HCP martensitic transformation and shape memory properties in Co–Al alloys. Mater Trans. 2006;47:2381–6.CrossRefGoogle Scholar
Omori T, Sutou Y, Oikawa K, Kainuma R, Ishida K. Shape memory effect in the ferromagnetic Co-14at%Al alloy. Scr Mater. 2005;52:565–9.CrossRefGoogle Scholar
Chen F, Tian B, Tong Y, Zheng Y. Transformation behavior and shape memory effect of a CoAl alloy. Int J Mod Phys B. 2009;52:1931–6.CrossRefGoogle Scholar
Omori T, Sutou Y, Oikawa K, Kainuma R, Ishida K. Shape memory and magnetic properties Co–Al ferromagnetic shape memory alloys. Mater Sci Eng. 2006;57:1045–9.CrossRefGoogle Scholar
Cullity BD, Graham CD. Introduction to magnetic materials. New York: Wiley; 2009.Google Scholar
Niitsu K, Omori T, Nagasako M, Oikawa K, Kainuma R, Ishida K. Phase transformations in the B2 phase of Co-rich Co–Al binary alloys. J Alloys Compd. 2011;509:2697–702.CrossRefGoogle Scholar