• Title/Summary/Keyword: AZ91D

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Influence of subsequent-annealing on the oxide layer of AZ91 Mg alloy prepared by plasma electrolytic oxidation (PEO 코팅 처리된 AZ91 합금의 산화층에 미치는 후-열처리의 영향)

  • Kim, Y.M.;Ko, Y.G.;Shin, D.H.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2009.10a
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    • pp.429-432
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    • 2009

  • The influence of the subsequent-annealing (SA) treatment on plasma electrolytic oxidation (PEO)-treated Mg-based alloy was investigated and the dependence of the dehydration reaction on the SA temperature was also studied. For this purpose, a series of the SA treatments were carried out on the coated samples at two different temperatures, i.e. 423 and 523 K for 10 h. In contrast to the sample without SA treatment, the sample annealed at 523 K exhibited a significant difference in term of surface morphology since the MgO content in the oxide layer increased with increasing SA temperature. With increasing SA temperature, the dehydration of $Mg(OH)_2$ led to the increase in the relative amount of the MgO, which was a hard phase. From the nano-indentation results, the applied loads of the samples were seen to increase as SA temperature increased. However, the corrosion resistance of the sample annealed at 423 K was higher than that of the samples annealed at 523 K.

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The Composition of the Rare Earth Based Conversion Coating Formed on AZ91D Magnesium Alloy

  • Chang, Menglei;Wu, Jianfeng;Chen, Dongchu;Ye, Shulin
    • Corrosion Science and Technology
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    • v.17 no.1
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    • pp.1-5
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    • 2018

  • As structural materials, magnesium (Mg) alloys have been widely used in the fields of aviation, automobiles, optical instruments, and electronic products. There are few studies on the effect of coating conditions on the compositional variation during the formation process of the conversion coatings. Rare-earth based conversion coating on AZ91 magnesium alloy was prepared in ceric sulfate and hydrogen peroxide contained solution. The element composition and valence as well as their distribution in the coating were analyzed with energy dispersive X-ray spectroscopy (EDS), Electron probe micro-analyzer (EPMA), X-ray photoelectron spectroscopy (XPS). The effect of treating process on the element composition were also studied. It was found that the conversion coating surface consists of Mg, Al, O, Ce, and the weight content of Ce in the coating was affected by the treating solution concentration and immersion time; the Ce element was distributed in the coating non-uniformly and existed in the form of $Ce^{+3}$ and $Ce^{+4}$, while the O element existed in the form of $OH^-$, $O^{2-}$, $H_2O$. Based on microscopic analysis results, the electrochemical deposition mechanism on the micro-anode and micro-cathode in the process of the coating growth was suggested.

  • https://doi.org/10.14773/cst.2018.17.1.1 인용 PDF KSCI HTML

FRICTION STIR WELDING OF MAGNESIUM ALLOYS

  • Kazuhiro Nakata;Kim, Young-Gon;Masao Ushio
    • Proceedings of the KWS Conference
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    • 2002.10a
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    • pp.511-515
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    • 2002

  • Extruded and cast plates of AZ type magnesium alloys were successfully joined by friction stir welding (FSW). Effect of FSW conditions on the formation of the defect was revealed in relation to tool rotation speed and specimen travel speed. Magnesium alloy with higher aluminum content became difficult to be joined and the optimum condition without defect was restricted into narrow condition range. The structure of the stirred zone was a fine-grained recrystallized structure even in the case of cast AZ91D. FSW joint had better mechanical properties than those of GTA welded joint. Especially the toughness of the stirred zone increased more than that of the base metal.

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Computer Simulation for Die Filling Behavior of Semi-Solid Slurry of Mg Alloy

  • Lee, Dock-Young;Moon, Jung-Hwa;Seok, Hyun-Kwang;Kim, Sung-Bin;Kim, Ki-Bae
    • Journal of Korea Foundry Society
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    • v.27 no.1
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    • pp.31-35
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    • 2007

  • In order to develop the semi-solid forming technology for magnesium alloy the rheological and thixotropic behavior of Mg alloy slurry with varying shear rates and cooling rates was investigated and simulated with considering the viscosity based on microstructures and processing variables. The viscosity of slurry of Mg alloy (AZ91D) in semi-solid region was exponentially increased with a solid fraction, and was decreased with increasing a shear rate. In order to analyze precisely the rheological behavior, the ANYCAST program modified with the Carreau model and the different heat transfer coefficient between the cast and mold was used to simulate the flow behavior of Mg semi-solid slurry during the injection into a casting mold in a high pressure diecasting machine. The simulated rheological behavior of Mg alloy slurry was matched well with the experimental results.

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