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Improvement of corrosion properties of MgAl-LDH coating on AZ31
Gromov, Egor ; Buchtík, Martin (referee) ; Doskočil, Leoš (advisor)
The subject of this bachelor thesis was the preparation and characterization (morphological and chemical) of layered double hydroxide (LDH) coatings with and without the addition of organic substances on AZ31 magnesium alloy treated by plasma electrolytic oxidation (PEO) to improve the corrosion resistance of the alloy. The samples were prepared at three different temperatures (100, 110 and 120 °C) for 4 or 24 h to determine the effect of the conditions on the quality of the LDH coating formed. For testing, samples were prepared with the addition of salicylic and tartaric acid. The corrosion resistance of the AZ31 alloy with coatings was described using the potentiodynamic polarization method and compared with the AZ31 alloy containing PEO coating. This was followed by a description of the morphological and elemental composition by SEM-EDS analysis, which confirmed the formation of MgAl-LDH. The best corrosion properties, according to the PDP method, were exhibited by the sample without the addition of acids, prepared at 100 °C for 4 h, but the greatest thickness of the LDH coating was obtained under conditions of 120 °C and 24 h. The samples with the addition of salicylic acid or tartaric acid showed poorer corrosion resistance compared to the LDH coatings prepared in the absence of organic substances.
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Modification of Elektron 21 magnesium alloy microstructure via electron beam treatment
Hanáček, Josef ; Šiška, Filip (referee) ; Čížek, Jan (advisor)
This work presents a basic research on the influence of electron beam technology modification on chemical, structural and phases changes of Elektron 21 magnesium alloy. The samples were systematically modified under various parameters of the electron beam and coatings on their respective surfaces were deposited via controlled plasma electrolytic oxidation (PEO) subsequently. The influence of the EB modification on the PEO coating formation was observed. Several samples with remelted fine-grained surface layer were obtained. Having a thickness of 10^1 to 10^3 µm, the average grain sizes in this layer were quantitatively evaluated. The performed EDS analysis revealed in identical chemical composition of the remelted surface layer and the original alloy material, despite the detected sample weight loss upon the EB treatment. XRD analysis revealed an increased content of Mg3(Nd,Gd) intermetallic phase in the remelted area. The PEO coatings were more compact and less porous as compared with their counterpart coatings on the original, unmodified alloy material.The results of the presented work showed, among others, a suitable microstructure and chemical composition of some of the modified samples that could potentially exhibit enhanced corrosion resistance as opposed to the unmodified material. The corrosion testing will be part of a follow-up study. More compact PEO coatings formed on some of the modified surface layers likely represent, too, a more durable variant as compared to the original material.
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Modification of Elektron 21 magnesium alloy microstructure via electron beam treatment
Hanáček, Josef ; Šiška, Filip (referee) ; Čížek, Jan (advisor)
This work presents a basic research on the influence of electron beam technology modification on chemical, structural and phases changes of Elektron 21 magnesium alloy. The samples were systematically modified under various parameters of the electron beam and coatings on their respective surfaces were deposited via controlled plasma electrolytic oxidation (PEO) subsequently. The influence of the EB modification on the PEO coating formation was observed. Several samples with remelted fine-grained surface layer were obtained. Having a thickness of 10^1 to 10^3 µm, the average grain sizes in this layer were quantitatively evaluated. The performed EDS analysis revealed in identical chemical composition of the remelted surface layer and the original alloy material, despite the detected sample weight loss upon the EB treatment. XRD analysis revealed an increased content of Mg3(Nd,Gd) intermetallic phase in the remelted area. The PEO coatings were more compact and less porous as compared with their counterpart coatings on the original, unmodified alloy material.The results of the presented work showed, among others, a suitable microstructure and chemical composition of some of the modified samples that could potentially exhibit enhanced corrosion resistance as opposed to the unmodified material. The corrosion testing will be part of a follow-up study. More compact PEO coatings formed on some of the modified surface layers likely represent, too, a more durable variant as compared to the original material.
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