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- MakaleAçık Erişim2025Scopus SJRQ2Effects of multiple element doping in NiTi based SMAs: Variation of phase transition and structural properties with Cu and Ag doping
Tatar, Cengiz; Mohammed, Safar Saeed; Kanca, M Sait; Qadir, Rezhaw Abdalla; Kök, Mediha
In this study, Ni41−2xTi49Cu7+xAg3+x (x = 0, 1, 2, 3) shape memory quaternary alloys were synthesized by arc melting, and their thermal, structural and mechanical properties were extensively investigated. Systemically, investigations have been carried out on the phase transformation behavior, thermodynamic properties, microstructure and oxidation resistance of the alloys with increasing Cu and Ag content. Differential Scanning Calorimetry (DSC) showed the shape memory effects of all alloys at low temperature. The transformation temperatures increased with increasing Cu and Ag concentrations. Thermodynamic analysis showed that Gibbs free energy trends and entropy were attributed to increased thermal stability at higher doping levels. XRD analysis confirmed the presence of martensitic (β19, β19′) and intermetallic Ti2(NiCu) phases, and grain refinement was found in higher doped samples. Microhardness measurements showed more homogeneous and stabilized microstructures at increasing doping, while SEM imaging showed that the hardness increased significantly. Thermogravimetric analysis showed that Cu and Ag slightly compromised the oxidation resistance due to the destabilization of the passive oxide layers. These results suggest that varying the Cu and Ag content in NiTi-based alloys is an effective method for improving mechanical strength and thermomechanical performance in advanced engineering applications.
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İncele - MakaleAçık Erişim2024Scopus SJRQ2Zr and V-doped effect on Martensitic transformations and magnetic properties of NiMnIn shape memory alloy
Taşgın, Yahya; Kanca, M. Sait; Kök, Mediha; Öner, Ecem Özen; Güler, Ömer
In this study, the elements vanadium (V) and zirconium (Zr) were doped separately as a fourth element to the ternary NiMnIn Heusler magnetic shape memory alloy and the alloys were produced as ingots by arc-melting method. The shape memory properties, microstructures, magnetic and microstructural changes of these new alloys were investigated in detail. The vanadium (V) and zirconium (Zr) elements doped into the alloy caused a decrease in the transformation temperature values of the alloy, but did not cause a significant change in its magnetic properties. The master sample, which has low hysteresis, undergoes a phase transition from the martensite phase to the austenite phase due to an increase in the nucleation of austenite phases at the twinning boundaries. Here, the vanadium and zirconium doping of the alloy caused an increase in the strength and ductility values of the alloy and this caused the formation of the second phase. Due to the increase of this phase formation in the alloy, it can be said that there is a slight decrease in the shape retention of the alloy.
AtıfScopus3WoS3OpenAlex3İncele - MakaleAçık Erişim2023Scopus SJRQ3Impact of electron concentration on the transformation temperature and important physical properties of NiMnSnFe ferromagnetic shape memory alloys
Malkoç, Türkan; Kanca, Muhammed Sait; Işık, Erdem; Kök, Mediha
This study aimed to explore the influence of electron concentration on the NiMnSn alloy, which is a crucial ferromagnetic shape memory alloy (FSMA). The alloy was doped with various amounts of iron element to assess its effect. According to DSC measurement, iron doping has resulted in a general decrease in the transformation temperature value of NiMnSn alloy, as well as a decrease in the transformation enthalpy value. The orthorhombic martensite phase of NiMnSn alloy was replaced by L21 austenite crystal structure in X-ray measurements. Martensite, austenite, and precipitate phases were observed in SEM images. Iron doping significantly increased the magnetic saturation value of NiMnSn alloy, according to magnetic measurements, and thermomagnetic measurements revealed similar results. Graphical Abstract: [Figure not available: see fulltext.]
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