Karaduman, Oktay

Rare earth compounds, including lanthanide hydroxides, have been greatly interested for their promising uses, such as in optoelectronics or photonics, due to their unique electronic and optical transitions properties based on their 4f electron shells. In this work, for the first time new transparent flower-like lanthanum(III)hydroxide (La(OH)3) with borate (LaB3O6) composite nanosheets having a semiconducting band gap suitable for optoelectronics were synthesized by a very simple one-step solvothermal method from a mixture of pure lanthanum oxide and boron without using water or any acidic solvent or surfactant. The practical synthesis was made for two different solvothermal time durations. The synthesized nanocomposites were investigated by XRD, FIB-SEM imaging, EDS, FTIR, UV-vis absorbance, Raman, Ellipsometry, and TG-DTA analyses. The pure precursors lanthanum oxide (La2O3) and boron converted to La(OH)3 and LaB3O6. EDS elemental mapping showed the homogeneous distribution of elements in the nanocomposites. A strong deep-UV absorbance band was detected. The very low reflectance and excellent visible transmittance (exceeding 86% for the sample with a longer solvothermal process time) reaching infrared region were achieved. The direct and indirect band gap energies were estimated by the Tauc plot method for both of the composite samples. Adding boron reduced the literature given direct band gap value (around 4.5-5.5 eV) of pure La(OH)3. DTA and TGA results revealed the steps of mass losses, including decomposition of La(OH)3. FTIR analyses confirmed the presence of the formed compounds. All results showed that the La(OH)3+LaB3O6 nanocomposites can be suitably used in related applications, including electro-optic, photonic, solar cell, catalysts etc.

İncele

Özkul, İskender; Kalay, Ece; Güler, Seval Hale; Karaduman, Oktay; Şimşek, Telem; Bülbül, Zeynel Abidin; Aksu Canbay, Canan; Sen Baykal, Duygu; ALMisned, Ghada; Tekin, H.O.

Rare-earth substitution provides a route for tailoring the structural, magnetic, and gamma-ray attenuation behaviour of Ho-based Co-Mn double perovskites; however, the combined effects of rare-earth ionic size, magnetic character, and substitution level remain insufficiently understood. In this study, Ho1.5La0.5CoMnO6, Ho1.2Er0.8CoMnO6, Ho1.3Sm0.7CoMnO6, and Ho2CoMnO6 were synthesized through a two-step route involving mechanical alloying to obtain precursor powders, followed by annealing at 1000 °C in air to promote oxidation and double-perovskite phase formation. Their structural, thermal, surface-chemical, magnetic, and gamma-ray attenuation properties were examined by X-ray diffraction, thermal analysis, X-ray photoelectron spectroscopy, SEM-EDS, vibrating-sample magnetometry, and theoretical shielding calculations based on half-value layer (HVL) and transmission factor (TF) parameters. The XRD patterns were consistent with predominantly monoclinic P21/n type double-perovskite structures, while weak additional reflections suggested possible minor secondary phases. SEM-EDS showed homogeneous elemental distributions, and XPS analysis indicated Co2+ dominated and mixed Mn-valence characteristics in the spectra where reliable component analysis was possible. All compositions exhibited a low-temperature ferromagnetic-like field response but did not reach magnetic saturation at 3 T. Ho2CoMnO6 and Ho1.3Sm0.7CoMnO6 showed the highest field-dependent magnetization values at 10 K, whereas Ho1.2Er0.8CoMnO6 displayed the lowest response. The theoretical gamma-ray attenuation calculations showed clear composition-dependent differences. At 0.662 MeV, the HVL values were 1.0650, 0.9972, 1.0438, and 0.9967 cm for Ho1.5La0.5CoMnO6, Ho1.2Er0.8CoMnO6, Ho1.3Sm0.7CoMnO6, and Ho2CoMnO6, respectively. At the same photon energy and a thickness of 1.0 cm, the corresponding TF values were 0.0896, 0.0858, 0.0882, and 0.0860. Thus, Ho1.2Er0.8CoMnO6 and Ho2CoMnO6 exhibited the lowest HVL and TF values among the investigated compositions. The shielding calculations identified Ho1.2Er0.8CoMnO6 and Ho2CoMnO6 as the most effective attenuators, with lower HVL and TF values across the investigated energy range. These results show that rare-earth substitution enables compositional tuning of magnetic and theoretical gamma-ray attenuation behaviour, with the observed trends reflecting the combined influence of rare-earth ionic size, magnetic character, substitution level, and valence-state complexity.

İncele

Karaduman, Oktay; Doğan, Fatih; Dehghanpour, Heydar; Yüzüak, Gizem Durak; Yüzüak, Ercüment; Canbay, Canan Aksu

Cu-Al-Mn-Fe high-temperature shape memory alloys containing 0-1.0 wt.% La2O3 were fabricated by vacuum arc remelting to investigate oxide-dispersion effects on microstructure, martensitic transformation, wear, and corrosion behavior. XRD and SEM analyses revealed that low La2O3 additions (0.2-0.4 wt.%) promoted β1′ martensite refinement and enhanced crystallinity, while higher contents induced structural heterogeneity. The alloy with 0.4 wt.% La2O3 exhibited the highest transformation enthalpy (7.49 J g−1), reduced friction coefficient (~0.55), and the narrowest wear scar (~501 µm). Electrochemical tests in 3.5 wt.% NaCl showed a fivefold decrease in corrosion current density and increased charge-transfer resistance (2512 Ω cm2) for the same composition. Excessive La2O3 led to performance degradation due to particle agglomeration and interfacial defects. The results demonstrated that controlled La2O3 addition enabled microstructural refinement and multifunctional performance enhancement in Cu-based shape memory alloys.

İncele

Özkul, İskender; Kalay, Ece; Güler, Ömer; Karaduman, Oktay; Canbay, Canan Aksu; Hameed, Louis Ibrahim; Almisned, Ghada; Baykal, Duygu Sen; Tekin, H.O.

This study investigates the effect of 1 at.% rare-earth (RE = Sm, Gd, Dy) addition on the structural, mechanical, magnetic, and radiation shielding properties of CoFeNiMnTi high-entropy alloys produced by arc melting. X-ray diffraction results reveal an FCC-dominant structure accompanied by secondary Laves-type phases, with increased phase complexity observed in Gd- and Dy-containing alloys. Mechanical evaluation shows a significant hardness enhancement, reaching 581 HV for Gd and 548 HV for Dy, compared to 447 HV for the reference alloy. Magnetic measurements indicate soft-ferromagnetic behaviour for all compositions, with magnetization increasing in the order S0<S1<S2<S3, highlighting the strong influence of Dy on magnetic response. Elemental mapping confirms a homogeneous distribution with minor local compositional variations contributing to phase evolution. Thermodynamic analysis suggests that rare-earth addition increases lattice distortion and chemical complexity without strongly differentiating among RE types. In terms of radiation shielding, linear attenuation coefficients and effective atomic number values demonstrate improved gamma-ray attenuation, particularly at low energies, with Dy exhibiting the highest performance. In contrast, fast neutron removal cross section values remain nearly unchanged, indicating limited sensitivity to dilute RE addition. It can be concluded that the incorporation of Dy results in the most balanced multifunctional performance, whereas Gd primarily enhances mechanical strength, emphasizing the importance of rare-earth selection in the design of high-entropy alloys for radiation-related applications.

İncele

Karaduman, Oktay; Kalay, Ece; Ozkul, Iskender; Kurgun, Mehmet Ali; Canbay, Canan Aksu; Guler, Omer; ALMisned, Ghada; Baykal, Duygu Sen; Tekin, H.O.

A novel Cu-based high-temperature shape memory alloy (HTSMA) with the composition 70.84Cu–23.80Al–4.14Mn–1.22Fe (at. %) was successfully synthesized via arc melting in this study. The effects of thermal aging duration on the alloy’s martensitic transformation behavior, shape memory effect (SME), and microstructural evolution were systematically investigated. Six samples were prepared from the as-cast ingot: one was homogenized in the β-phase region and quenched into ice-brine to induce a martensitic structure, while five others were subsequently aged at 350 ℃ for varying durations and air-cooled. Thermal and structural characterizations were conducted. These included differential scanning calorimetry (DSC), X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), and optical microscopy. Prolonged aging altered transformation temperatures and reduced both enthalpy and entropy values. It also promoted the formation of observed precipitates, vacancies, and coarsened 2H martensites. Prolonged aging altered the microstructure and thermal response, leading to partial SME degradation. Additionally, the alloy’s gamma-ray and fast neutron shielding parameters were theoretically estimated using simulation software to explore its potential functional scope. The calculated results indicate that the CuAlMnFe HTSMA is predicted to exhibit favorable attenuation performance across a wide energy spectrum, with appropriate values of mass attenuation coefficient (MAC) and half-value layer (HVL). In particular, the fast neutron removal cross-section was calculated as 0.139 cm−1, which is significantly higher than those of water (0.1023 cm−1), graphite (0.0773 cm−1), and B4C (0.0714 cm−1). In conclusion, the CuAlMnFe HTSMA developed in this study offers a unique profile combining tailorable shape memory behavior with a computationally predicted potential for nuclear radiation shielding. These properties offer novel insights into the alloy’s potential for applications in high-radiation environments that require both mechanical actuation and radiation protection, pending experimental validation of its shielding performance.

AtıfScopus1·OpenAlex1

İncele

Özkul, İskender; Karaduman, Oktay; Şimşek, Tuncay; Şimşek, Telem; Canbay, Canan Aksu; Güler, Ömer; ALMisned, Ghada; Tekin, H.O.

This study systematically investigates the influence of Cr and Mn additions on the structural, magnetic, and radiation shielding properties of NiFeGaCo-based ferromagnetic high-entropy shape memory alloys (FHESMAs) synthesized via the arc melting method. The fabricated NiFeGaCo, NiFeGaCoCr, and NiFeGaCoMn alloys were comprehensively characterized in terms of their phase formation, microstructure, martensitic transformation behavior, and magnetic performance. The results demonstrated that Mn addition significantly improved the magnetic properties, yielding the highest saturation magnetization (56.64 emu/g) and lowest coercivity (5.55 Oe), making NiFeGaCoMn highly suitable for soft magnetic applications. In contrast, Cr addition provided moderate magnetic behavior but enhanced structural stability with the largest crystallite size and lowest lattice strain. Moreover, gamma-ray and fast neutron shielding investigations revealed that the Cr-containing alloy exhibited superior performance in terms of linear attenuation coefficient, half-value layer, effective electron density, and fast neutron removal cross-section values, while Mn addition slightly reduced these shielding capabilities. It can be concluded that Cr addition offers a balanced advantage in designing FHESMAs with combined magnetic sensitivity and radiation shielding efficiency, whereas Mn addition is more effective for maximizing magnetic performance with a compromise in shielding characteristics.

AtıfScopus2·OpenAlex2

İncele

Özkul, İskender; Kalay, Ece; Karaduman, Oktay; Kizilgün, Yasİn; Güler, Ömer; Canbay, Canan Aksu

This study investigates the effects of different cerium additions on the properties of Cu-Al-Mn high-temperature shape memory alloy (HTSMA), such as the characteristic martensitic transformation temperatures, transformational kinetic parameters, and martensitic microstructures which are related to its shape memory mechanism and also to its magnetic behavior. Polycrystalline alloys with a base composition of Cu77.32Al21.02Mn1.67 (at.%) were synthesized, and varying concentrations of cerium (Ce-1 to Ce-4) were added for comparison. Differential scanning calorimetry tests revealed notable increments in transformation temperatures with cerium additions. Specifically, the austenite start temperature of the reference alloy increased from 143.75 °C to 194.88 °C by 0.05 at.% of Ce addition (Ce-3 alloy), corresponding to the formation of CeCu5 and Mn1.15Cu3.85Ce phases. However, excessive Ce addition in Ce-4 led to the over-stabilization of secondary phases, reducing the transformation temperatures. Microstructural analysis indicated that Ce addition of refined grains changed the crystallite size of the martensite structure and reduced lattice strain (from 0.72% to 0.34%). Magnetic characterization demonstrated that Ce addition shifted the alloy towards paramagnetic behavior, with M-H curves showing no significant coercive field or remanent magnetization across the studied alloy samples. These findings suggest that cerium can enhance the high-temperature performance of Cu-Al-Mn HTSMAs, with potential applications in environments requiring both shape memory and magnetic properties.

AtıfScopus3·WoS3

İncele

Kalay, Ece; Özkul, İskender; Karaduman, Oktay; Kızılgün, Yasin; Güler, Ömer; Canbay, Canan Aksu; Kilic, G.; Baykal, Duygu Sen; ALMisned, Ghada; Tekin, H.O.

This study systematically investigates the effect of Ce addition on the thermal, structural, and radiation shielding properties of CuAlMn-based high-temperature shape memory alloys (HTSMAs). Among the different compositions, Ce-III demonstrated the most balanced performance, exhibiting optimized phase transformation behavior, microstructural refinement, and enhanced gamma-ray attenuation. Differential Scanning Calorimetry (DSC) analysis revealed that Ce-III exhibited lower transformation temperatures, with austenite start (As) and finish (Af) temperatures of 378.13 °C and 429.75 °C, respectively, and martensite start (Ms) and finish (Mf) temperatures of 402.52 °C and 341.91 °C, suggesting improved thermal stability. Microstructural analysis indicated significant grain refinement, attributed to Ce's dislocation pinning effect, which contributed to enhanced strength and radiation attenuation. X-ray diffraction (XRD) patterns confirmed the formation of Ce-rich intermetallic phases, such as Mn1.15Cu3.85Ce and Cu8Ce4, which increased density and photon interaction probability. The Ce-III alloy exhibited superior linear attenuation coefficients and reduced half-value layer, reinforcing its effectiveness as a radiation shielding material. It can be concluded that Ce-III represents an optimal composition with a synergistic combination of structural stability, phase transformation control, and enhanced radiation shielding capabilities, making it a promising candidate for nuclear and high-radiation applications.

AtıfOpenAlex1

İncele

Özkul, İskender; Karaduman, Oktay; Şimşek, Tuncay; Şimşek, Telem; Canbay, Canan Aksu; Güler, Ömer; ALMisned, Ghada; Baykal, Duygu Sen; Tekin, Huseyin Ozan

High-entropy alloys (HEAs) are a novel class of materials known for their complex compositions and exceptional multifunctional properties. In this study, NiCoMnTi-based HEAs were modified with Fe, Cr, and Cu as fifth elements to systematically investigate their structural, magnetic, thermodynamic, and nuclear radiation shielding characteristics. The alloys were synthesized via arc melting and characterized using XRD, SEM-EDS, VSM, and theoretical modeling methods. The findings reveal that each additional element uniquely alters the alloy’s properties. The Fe-containing alloy exhibited a well-defined lamellar microstructure, the highest saturation magnetization (10.79 emu/g), and a Curie temperature near 450 K, along with strong gamma-ray shielding performance across both low and high energy ranges. The Cr-containing alloy demonstrated soft magnetic behavior, featuring the lowest coercivity (29.64 Oe) and the highest fast neutron removal cross-section. In contrast, the Cu-containing alloy enhanced low-energy photon attenuation due to its higher atomic number but exhibited limited magnetic homogeneity. Despite these differences, all samples displayed stable thermodynamic behavior and comparable buildup factor trends. Overall, the addition of Fe led to a synergistic improvement in both magnetic and radiation shielding capabilities of the NiCoMnTi-based HEA system.

AtıfScopus3·OpenAlex3

İncele

Özkul, İskender; Karaduman, Oktay; Şimşek, Telem; Şimşek, Tuncay; Canbay, Canan Aksu; Güler, Ömer; Şan, Mert Hüseyin; ALMisned, Ghada; Tekin, H.O.

This study investigates the thermal, structural, magnetic, and radiation shielding properties of CuAlNi-based high-temperature shape memory alloys (HTSMAs) enhanced through sequential alloying with Co, Fe, Mn, and Cr. Five different variants were produced, designated as CRef (reference CuAlNi alloy), CCo (CuAlNiCo), CFe (CuAlNiCoFe), CMn (CuAlNiCoFeMn), and CCr (CuAlNiCoFeMnCr). Differential scanning calorimetry (DSC) confirmed the presence of reversible martensitic transformations in all alloys, with Co and Mn additions significantly enhancing thermal stability. Structural analyses using X-ray diffraction (XRD) and microscopy showed significant grain refinement and phase transitions, while magnetic measurements highlighted the strong ferromagnetic response of CCo (CuAlNiCo) and the increased coercivity of CMn (CuAlNiCoFeMn) due to domain-pinning effects. Moreover, radiation shielding analyses demonstrated the critical influence of density and elemental composition, with CRef exhibiting superior linear attenuation coefficients (LAC), effective atomic number (Zeff), and energy absorption buildup factor (EBF) performance, attributed to its optimized Cu fraction and high density (7.1296 g/cm3). In contrast, CMn (CuAlNiCoFeMn) showed the weakest shielding properties due to reduced density and Mn content. Among the samples, CRef emerged as the superior alloy, demonstrating exceptional multifunctionality across all evaluated parameters, while CCr (CuAlNiCoFeMnCr) displayed synergistic properties, combining shape memory behavior with competitive shielding efficiency. It can be concluded that CuAlNi-based HTSMAs hold significant potential as multifunctional materials, particularly for nuclear safety and aerospace engineering applications, where adaptive functionality and radiation protection are critical.

AtıfScopus2·OpenAlex2

İncele

Özkul, İskender; Karaduman, Oktay; Canbay, Canan Aksu

CuAlMn alloys are cheaper and more promising alloy types compared to NiTi alloys. In this study, based on CuAlMn shape memory alloy, thermodynamic and structural characteristics of some new alloys containing four elements were investigated in detail. In this study, five new quaternary shape memory alloys, each containing a CuAlMn base alloy and a different fourth additive element (Ga, Nb, V, Zr, and Cr), were produced. The properties of the obtained alloys were characterized using a series of analysis methods such as X-ray diffraction (XRD), optical microscopy, differential scanning calorimetry (DSC), and differential thermal analysis (DTA). The results showed the effects of different elements on the crystal structures of the alloys and how different elements could change the thermal behavior of the alloys.

AtıfScopus4·WoS3·OpenAlex6

İncele

Demirelli, Kadir; Barım, Esra; Tuncer, Hülya; Dere, Ayşegül; Canbay, Canan Aksu; Karaduman, Oktay; Al-Sehemi, Abdullah G.; Al-Ghamdif, Ahmed A.; Yakuphanoğlu, Fahretttin

The synthesis of poly[4-(4-vinylbenzyl)oxy)phthalonitrile-co-styrene] [P(VBOPN5 %-co-St)] was carried out by free radical polymerisation at 60 °C. The successful formation of a green coloured single-chain polymer molecule with the formation of cobalt phthalocyanine (SCP-CoPc) was performed at 140–150 °C in the presence of dilute cyclohexanol. The characterization of SCP-CoPc was confirmed by FT-IR and UV/vis spectroscopic techniques. The absorption filtration process of the SCP-CoPc polymer/Sudan III composite was investigated. The introduction of Sudan III into the SCP-CoPc polymer matric strongly affected the optical transmission spectrum of the composite films. The optical transmission measurements of the SCP-CoPc/Sudan III thin film show a high absorption in the visible region (400–800 nm). In the SCP-CoPc/Sudan III composites, the optical band gaps (Eg1 and Eg2) of each of its components has changed significantly. The Eg1 and Eg2 were found to be between 1.90 and 2.83 eV, respectively. Depending on the sudan III content, a wide range from 600 nm to 730 nm indicates complete absorption filtration. The dc electrical conductivity and dielectric behavior of the SCP-CoPc/Nanografene (NG) 6 wt% nanocomposite increased with increasing temperature. From the dc conductivity plot, the Ea values of I. and II. regions were found to be 0.75 eV and 0.27 eV, respectively and it was found that the calculated activation energy obeyed the Arrhenius relationship. The refractive index and the optical permittivity of SCP-CoPc/NG 6 wt% have been estimated.

AtıfScopus2·OpenAlex3

İncele

Karaduman, Oktay; Özkul, İskender; Aksu Canbay, Canan

Cu-based shape memory alloys (SMAs), except for exhibiting shape recovery, superelasticity, and high damping, are desirable because these smart materials have higher electrical and thermal conductivity and much lower prices than NiTi SMAs. However, they also have some downsides in mechanical strength and brittleness (mostly stemming from their coarse grain structure) and thermal instability. Therefore, adding some grain refining elements to these SMAs to improve their shape memory effect (SME), and thermal, structural, and mechanical properties is a widespread and simple way that significantly affects their martensitic phase transitions, structure, and mechanical properties. One of these grain-refining elements is titanium. Its thermal conductivity is lower than those of Cu and Al elements and has a low solubility in Cu-matrix. Besides the effects of small Al variations, the use of minor amounts of titanium in binary CuAl-base alloys can show impressive effects on all characteristics of these shape memory alloys, such as shape memory effect properties, martensitic transformation kinetics parameters, and microstructural features. In this research work, CuAlTi ternary high-temperature shape memory alloys (HTSMAs) with new compositions were produced by the arc melting method without a complicating use of Mn or Ni components in usual ternary CuAlMn and CuAlNi shape memory alloys. Thermal analyses of the prepared samples of the alloys were investigated by using differential scanning calorimetry (DSC) and differential thermal analysis (DTA) measurements. In contrast, x-ray diffraction (XRD) test results and optical micrographs were used for analyzing the structure of the alloy samples. The effect of different amounts of low soluble and grain refining Ti element on the binary CuAl alloy system was investigated.

AtıfScopus2·WoS2·OpenAlex2

İncele

Karaduman, Oktay; Canbay, Canan Aksu; Dere, Aysegul; Orman, Yusuf; Al-Ghamdi, Ahmed A; Al-Sehemi, Abdullah G; Yakuphanoglu, Fahrettin

In this work, a novel smart (shape memory) alloy metalized photonic silicon wafer photodiode with Schottky type CuAlV/n-Si/Al contact structure as a nano-electro-mechanical-system (NEMS) photodevice was fabricated by thermal evaporation technique. The CuAlV memory alloy used as the top Schottky metal contact electrode was produced by arc melting technique and a subsequent quenching in an iced-brine water medium, and its shape memory effect characteristics were revealed by thermal and structural tests. The fabricated photonic NEMS photodiode was characterized by different photo-electrical (I-V, I-t) and frequency/time dependent and illuminated capacitance (C-V/f, C-t, C-V/ill.) and conductance-voltage (G-V) measurements under different frequencies and artificial light intensity power conditions. The I-V tests showed an excellent current rectifying ability and very well net photocurrent generation features of the photodiode. The specific detectivity of the photodiode was found as high as almost approaching 1011 Jones. The SCLC (space charge limited current conduction) analyses made on the double-log I-V plots of the photodiode revealed that the trap-filling TFL-SCLC and trap-free SCLC current conduction mechanisms are the two prevailing conduction mechanisms in the forward bias voltage region. The density of interface states (Dit) of the fabricated photodiode was determined. Moreover, an excellent reproducibility of light-induced photocapacitance formation of the novel photodiode was demonstrated by C-V/t measurements under different artificial light power intensities.

AtıfScopus5·OpenAlex5

İncele

Karaduman, Oktay; Özkul, İskender; Güler, Seval Hale; Aksu Canbay, Canan

In this study, two high-temperature shape memory alloys (HTSMAs) of CuAlV with unprecedented chemical compositions were fabricated using the arc melting technique, followed by traditional ice-brine water quenching after the melting process. To characterize the shape memory properties and structure of the alloys, a series of tests including differential calorimetry (DSC and DTA), EDS, optical microscopy, and XRD were conducted. The DSC tests, performed at different heating and cooling rates, demonstrated highly stable reversible martensitic phase transformation peaks at high temperatures, which were also confirmed by the results of DTA tests. Microstructural XRD and optical microscopy tests were conducted at room temperature, revealing the martensitic structure of the alloys in both cases. Based on all the results, the effects of different minor amounts of vanadium additives directly on the CuAlV alloy were discussed.

AtıfScopus2·WoS2·OpenAlex3

İncele

Karaduman, Oktay; Boyrazli, Mustafa; Canbay, Canan Aksu; Özkul, İskender; Çelik, Emrah; Başbağ, Güneş

For the first time, CuAlVMg high-temperature shape memory alloy (HTSMA) with unprecedented alloy composition and with extended solubility of vanadium element was fabricated as-cast ingot by arc melting method, then homogenization of the alloy in high β-phase temperature region and quenching in iced-brine water were performed, respectively. The characteristic forward martensite to austenite martensitic transformation (MT) temperatures were detected at around 390 °C, which put the novel alloy in the category of HTSMAs. The thermal response of the alloy at high-temperatures was observed by DTA test as coherent with usual Cu-based HTSMAs. The residual sub-eutectoid precipitations emerging at around 500 °C hindered the direct martensitic transformation. The martensite structure of the alloy was revealed by XRD, SEM and optical microscopy tests.

İncele

Özkul, İskender; Boyrazli, Mustafa; Aksu Canbay, Canan; Başbağ, Güneş; Karaduman, Oktay

Shape memory alloys (SMAs) constitute the second largest commercial smart material class after piezoelectric materials. Different SMA alloy systems or SMAs with miscellaneous functionalities and characteristic properties have been designed for using in different applications until today. High temperature shape memory alloys (HTSMAs) are also widely desired to be used in various smart materials applications. HTSMAs with different functional and characteristic properties are muchly demanded for different tasks to be done by these alloys or devices designed by these alloys. A common and practical way to fabricate SMAs or HTSMAs with different shape memory effect (SME) and other properties is to fabricate them with different alloying compositions and add different additive elements. In this work, a quaternary CuAlZnMg HTSMA with an unprecedented composition consisting minor amount of zinc and magnesium additives was produced by arc melting method. As a result of applying post-homogenization in high β–phase temperature region and immediate quenching, the microstructural mechanism of a SME property was formed in the produced alloy. After then, to examine SME characteristics of the CuAlZnMg alloy some differential thermal analysis (DTA), microstructural (XRD) and magnetization (VSM) characterization tests were carried out. The DTA results showed that the alloy is a HTSMA exhibiting reverse martensitic transformations at temperature range between 167 °C and 489 °C. The XRD pattern obtained at room temperature revealed the martensite phases formed in the alloy, which phases are the base mechanism of the reversible martensitic transformation (the SME property) of the alloy. The VSM test showed that the alloy exhibit a diamagnetic property with a weak ferromagnetic coercivity contribution.

İncele

Başbağ, Güneş; Karaduman, Oktay; Canbay, Canan Aksu; Özkul, İskender; Boyrazlı, Mustafa

In this work, the new quaternary CuAlTiMg high-temperature shape memory alloy (HTSMA) with an unprecedented composition and with extended solubility of Ti was produced by the arc melting method. The thermal shape memory effect characterization tests were done by performing a series of differential calorimetric (DSC and DTA) measurements. The obtained thermograms of the alloy displayed the martensitic phase transformation peaks. The forward (martensite to austenite) phase transformation was found to occur at above 350◦C, which qualifies the produced alloy as an HTSMA. The microstructural XRD measurement was performed to reveal the atomic planes of martensite structures formed in the alloy, which constitute the shape memory effect property of the fabricated alloy. The alloy surface was monitored by optical microscopy image taken at room temperature, and finely dispersed Ti-rich X-phases were observed.

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