Abstract
The magnetic properties of the new Fe41Ni28Co17Al11.5(Ti+Nb)2.5 (at. %) shape memory alloy system were studied in this work. The magnetic properties were characterized by thermo-magnetization and a vibrating sample magnetometer (VSM). In iron-based shape memory alloys, aging heat treatment is crucial for obtaining the properties of superelasticity and shape memory. In this study, we focus on the magnetization, martensitic transformation temperatures, and microstructure of this alloy during the aging process at 600 °C. From the X-ray diffraction (XRD) results, the new peak γ’ is presented during the aging process. The intensity of this new peak (γ’) increases with the aging time, while the intensity of the FCC (111) austenite peak decreases with aging time. Transmission electron microscope (TEM) results show that the size of the precipitate increases with increasing the aging times from 24 to 72 h. Thermo-magnetization results show that: (1) phase transformation is observed when the aging time is at least 24 h, (2) the transformation temperature increases with the aging time, (3) transformation temperatures tend to increase while the magnetic field increases from 0.05 to 7 Tesla, and (4) the magnetization saturates after aging time reaches 24 h. Vibrating sample magnetometer (VSM) results show that thermal process was found to significantly affect the magnetic properties of this alloy, especially on saturated magnetic magnetization and magnetic moment reversal behavior.
Highlights
Shape memory alloys (SMAs) are functional materials, and they possess two recoverable properties: the shape memory effect and superelasticity
No β-NiAl precipitate peaks were observed from the X-ray diffraction (XRD) pattern because the grain size was large and the formation of high- and low-angle grain boundaries was random, resulting in a limited number of β phases
The martensitic transformation was not observed in the solution-treated sample
Summary
Shape memory alloys (SMAs) are functional materials, and they possess two recoverable properties: the shape memory effect and superelasticity. Nickel–Titanium (NiTi) SMAs nowadays are commercial SMAs and are used in different areas of industry, such as aerospace, automotives, and robotics, due to their high recoverable strain around 7% [1,2,3]. NiTi SMAs have a high cost in terms of material and difficulty to manufacture, which limits the application of these alloys [4]. In contrast to NiTi alloys, iron-based SMAs have a low material cost and good workability. FeNiCoAlXB (X: Ta, Nb, Ti) polycrystals [5,6,7,8] and single crystals [9,10,11,12] show at least 5% superelastic strain. The martensitic transformation (MT) of the FeNiCoAlXB (X: Ta, Nb, Ti) alloy system is face-centered cubic (fcc) (austenite) to body-centered tetragonal (bct) (martensite)
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