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    Effect of Plasma Electrolytic Oxidation Process on Corrosion Resistance of Al-Coated AZ61 Magnesium Alloy
    (Sakarya University, 2025) Durna, İdris; Catar, Recep; Altun, Hikmet
    Magnesium alloys are extensively utilized in aerospace, aviation, and automotive sectors due to their low density and high specific strength, which offer significant advantages for lightweight structural applications. Their low density especially directs the attention of the aviation sector, where lightness is necessary, to these alloys. However, one of the disadvantages that restricts their use in the industry is their low corrosion resistance. In this study, the Plasma Electrolytic Oxidation (PEO) process was applied in a silicate-based electrolyte to AZ61 magnesium alloy pre-coated with aluminum using the electric arc spraying technique. To examine the characteristics of the fabricated coatings, their phase structures, surface features, and elemental compositions were investigated through XRD, SEM, and EDS analyses. Corrosion performances of coatings were investigated by potentiodynamic polarization test in 3.5% NaCl solution. As a result of electrochemical tests, corrosion current density values for the base sample (AZ61) and PEO coating (AZ61-PEO) were determined as 36,29 ?A. cm?2 and 6,53 ?A. cm?2, respectively. The findings highlight that the Al?O? layer formed following PEO treatment significantly enhanced the corrosion resistance compared to the base sample. © 2025, Sakarya University. All rights reserved.
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    Improvement of corrosion and stress corrosion properties of magnesium alloys by coating aluminum with the electric arc spray method
    (Wiley-V C H Verlag Gmbh, 2022) Catar, Recep; Altun, Hikmet
    In this study, corrosion and stress corrosion behaviors of AZ31, AZ61, and AZ91 magnesium alloys coated with aluminum by the electric arc spray method were investigated in 3.5 wt.% NaCl solution. Structural properties of coated materials were investigated by scanning electron microscopy (SEM), energy dispersive X-ray analysis, and X-ray diffraction. Electrochemical properties were determined using the potentiodynamic polarization method in 3.5 wt.% NaCl solution. Potentiodynamic polarization curves showed that corrosion current density values did not change with coating in aluminum-coated samples by the electric arc spray method. In contrast, corrosion potential value increased toward positive values. Slow strain rate test (SSRT) was used to determine the stress corrosion behavior and stress corrosion indexes (I-SCC), ultimate tensile strength (UTS), and elongation of AZ31, AZ61, and AZ91 magnesium (Mg) alloys were determined. As a result of the SSRT, the aluminum coating process decreased significantly the stress corrosion indexes of AZ31, AZ61, and AZ91 Mg alloys. The fracture of surface images was also examined in the SEM, and both intergranular and transgranular stress corrosion cracking were observed in all three alloys.
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    Investigation of radiation shielding parameters of AZ61 magnesium alloy after electric arc spray and micro arc oxidation processes
    (Pergamon-Elsevier Science Ltd, 2026) Durna, Idris; Yilmaz, Demet; Catar, Recep; Altun, Hikmet
    In this study, the radiation shielding parameters of AZ61 magnesium (Mg) alloy, which is used in automotive, aerospace, and biomedical fields due to its low density, high specific strength, and biocompatible properties, were determined to investigate its usability in nuclear protection applications. Firstly, Al coating was applied to AZ61 Mg alloy by electric arc spray process and then ceramic oxide layer was obtained by micro arc oxidation (MAO) method. Then, the radiation shielding properties of AZ61 alloy were investigated. The radiation shielding parameters such as mass attenuation coefficient (MAC), mean free path (MFP), half-value layer (HVL) and effective atomic numbers (Zeff) were measured in gamma spectrometer with Ba-133 radioactive sources. The fast neutron removal cross-sections (Sigma R), exposure buildup factors (EBF) were theoretically determined. The results revealed that the duplex coating (AZ61-Al-O) significantly enhanced the gamma shielding capability compared to the uncoated AZ61 alloy, achieving about 8.0 % higher MAC at 383.8 keV. Therefore, the AZ61-Al-O sample can be considered a promising lightweight material for radiation protection applications.
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    Investigation of Stress Corrosion Cracking Behaviour of Mg-Al-Zn Alloys in Different pH Environments by SSRT Method
    (Sciendo, 2019) Catar, Recep; Altun, Hikmet
    In this study, stress corrosion behaviors of AZ31, AZ61 and AZ91 Mg alloys which contain different amounts of Al were investigated under acidic, basic and neutral environments having chloride ions using Slow Strain Rate Test (SSRT) method. Stress corrosion indexes (I-SCC), ultimate tensile strength (UTS) and elongation of AZ31, AZ61, and AZ91 Mg alloys were determined and compared. Slow strain rate test showed that three Mg alloys in basic environments were the least stress corrosion susceptible, while the most stress corrosion susceptible occurred in acidic environments. Also, it has been shown that the stress corrosion indexes of AZ91 Mg alloys are less than AZ31 and AZ61 Mg alloys in all environments. UTS and elongation of A7,61 Mg alloys were higher than those of AZ31 and AZ91 in all media. The fracture of surface images also examined in the scanning electron microscope (SEM) and both intergranular stress corrosion cracking (IGSCC) and transgranular stress corrosion cracking (TGSCC) were observed in all three alloys.
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    Investigation of the Structural and Corrosion Properties of Duplex Surface Treated AZ31 Magnesium Alloy
    (Springer, 2025) Durna, Idris; Catar, Recep; Altun, Hikmet
    The AZ31 alloy was first completely coated with pure aluminum in this study using the electric arc spray coating method. Then, considering the existing benefits of the micro-arc oxidation process (MAO), a ceramic oxide coating was formed by applying MAO to the Al-coated surface. Thus, a duplex coating was obtained on the base material. The structural properties of both the Al-coated samples and the duplex coatings obtained after the MAO process were investigated by scanning electron microscopy, energy-dispersive x-ray analysis (EDS), and x-ray diffraction devices. The electrochemical behavior of the coatings was carried out in a 3.5 wt.% NaCl solution. The samples were polarized from the potential value - 0.2 V below the corrosion potential to the maximum value of 2 V at a scanning rate of 1 mV/s, and potentiodynamic polarization curves were recorded. According to the electrochemical experiments, Al coatings and duplex coatings improved the corrosion resistance of AZ31 alloy. The corrosion current density values were 298.23 mu A/cm2 for the base material, 0.415 mu A/cm2 for the Al coating, and 0.014 mu A/cm2 for the duplex coating, respectively. The best corrosion resistance among all samples was obtained in duplex-coated samples obtained by MAO. Due to their low corrosion resistance, magnesium alloys are restricted in many areas, especially aviation, automotive, and biomedical. Therefore, this study aimed to improve the corrosion resistance of AZ31 magnesium alloy.