• Title/Summary/Keyword: AZ91D

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Mutual Solubility of Mn and Fe in AZ91 Alloy Melts and Its Application to Composition Control of AZ91D Recycled Ingots (AZ91 합금 용탕내 Mn과 Fe의 상호용해도 측정 및 AZ91D 재생지금의 성분조정에의 활용)

  • Kwon, Soon-Il;Byun, Ji-Young;Kim, Seon-Jin;Shim, Jae-Dong
    • Korean Journal of Materials Research
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    • v.13 no.9
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    • pp.619-624
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    • 2003
  • This paper describes a method to control Mn and Fe contents in recycled AZ91D ingots, based on the mutual solubility of Mn and Fe in AZ91 alloy melts. For this purpose, Fe solubility with the change of Mn content and temperature was investigated in the homogenized and re-precipitated liquid AZ91 alloy. The increase of the amount of Mn added to the melt resulted in the decrease of Fe content. The data obtained in this study was adopted to the pilot plant for recycling of the scrap. As a result, Mn and Fe contents measured in the recycled ingot were in good agreement with ASTM B93 standard.

Effect of Heat Treatment on Microstructure and Tensile Properties of AZ91-CaO Alloy (AZ91-CaO 합금의 미세조직과 인장 특성에 미치는 열처리의 영향)

  • Jun, Joong-Hwan
    • Journal of the Korean Society for Heat Treatment
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    • v.25 no.4
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    • pp.190-195
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    • 2012
  • This study aims to investigate and compare the microstructures and room temperature tensile properties for AZ91 and ECO-AZ91 (AZ91+0.3%CaO) alloys in as-cast, T4 and T6 states, respectively. In as-cast state, the ECO-AZ91 alloy has finer microstructure than the AZ91 alloy. The AZ91 alloy exhibits greater ductility, while YS and UTS are inferior to those of the ECO-AZ91 alloy. After T4 treatment, most of ${\beta}$ compounds disappear in the AZ91 alloy, whereas ${\beta}$ phase is still observed in the ECO-AZ91 alloy due to its enhanced thermal stability, resulting in lower values of ductility and UTS. In T6 state, YS and UTS are better in the ECO-AZ91 alloy.

Microstructure and Corrosion Properties of AZ91D Magnesium Alloy treated by Plasma Electrolytic Oxidation (플라즈마 전해 산화 처리한 AZ91D 마그네슘합금 피막의 미세조직 및 부식 특성)

  • Chang, Si-Young;Kim, Ye-Lim;Kim, Yang-Do
    • Journal of Korea Foundry Society
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    • v.28 no.1
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    • pp.20-24
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    • 2008
  • The characteristics, such as roughness, thickness, microhardness and corrosion resistance, of plasma electrolytic oxide coatings on AZ91D alloy were investigated under the processing condition of various coating times. The coatings on AZ91D alloy consisted of MgO, $MgAl_{2}O_{4}$ and $Mg_{2}SiO_{4}$ oxides. The surface roughness and thickness of coatings became larger with increasing the coating time. The microhardness in cross section of coatings was much higher than not only that in surface but that in the conventional anodic oxide coatings, which increased progressively as the coating time increased. After being immersed in 3.5%NaCl solution and methyl alcohol, the corrosion resistance of AZ91D alloy was markedly improved by plasma electrolytic oxidation coating treatment, and the AZ91D alloy coated for 50min revealed excellent corrosion resistance.

Fast laser welding with scanner on the joint between AZ31 thin sheet and die-casted AZ91D frame for smart phone application (스캐너를 이용한 AZ31 극박판재와 AZ91D 다이캐스팅 프레임의 고속레이저용접)

  • Lee, Mok-Young;Seo, Min-Hong
    • Laser Solutions
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    • v.18 no.1
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    • pp.1-6
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    • 2015
  • High welding speed and narrow weld seam are favorable for welding of magnesium alloy. Magnesium alloy is recommended for the smart frame because it has several advantages such as low density, high thermal conductivity, EMI shielding capability and good cast ability. This study is for the assembly welding of the magnesium smart frame with high productivity, good performance and low cost. The window for battery on AZ91D frame produced by die-casting was prepared by CNC machining. Corresponding AZ31 blank of 0.2mm thickness was prepared by die-blanking cut. All system set was fixed at the stationary bed but the laser beam was manipulated by scanner up-to 1,000mm/s speed. The weld joint between AZ31 sheet and AZ91D frame was welded by fiber laser on 850~1,000W output power. The joint showed penetration enough but some humping bead. The distortion by the weld heat was almost free because of the quick dissipation of the heat by small beam size and fast welding. Consequently, the thinner magnesium foil was assembled successfully to the magnesium frame of mobile phone.

Effect of CaO Addition on Age Hardening Behavior of AZ91 Alloy (AZ91 합금의 시효경화 거동에 미치는 CaO 첨가의 영향)

  • Jun, Joong-Hwan
    • Journal of the Korean Society for Heat Treatment
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    • v.24 no.4
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    • pp.193-198
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    • 2011
  • Effect of CaO addition on age hardening response has been studied by using optical microscopy, scanning electron microscopy and differential thermal analysis in AZ91 and CaO-containing ECO-AZ91 alloys. After solution treatment, the ${\beta}$($Mg_{17}Al_{12}$) phase formed during solidification mostly disappeared in the microstructure in the AZ91 alloy, whereas numerous ${\beta}$ precipitates containing Ca were still observed in the ECO-AZ91 alloy due to its enhanced thermal stability. The ECO-AZ91 alloy showed the delayed peak aging time and higher peak hardness compared with those of the AZ91 alloy. The activation energies for ${\beta}$ precipitation calculated by means of Kissinger method increased from 71.4 to 85.6 kJ/mole by the addition of CaO, which implies that CaO plays a role in reducing ${\beta}$ precipitation rate in the AZ91 alloy.

The characteristic of low pressure casting AZ91D Magnesium alloy wheel (저압주조방식에 의한 AZ91D 마그네슘 휠 특성)

  • Kim, Kwang-Hee
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.13 no.11
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    • pp.4963-4967
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    • 2012
  • In this study, 18-inch wheels, magnesium alloy AZ91D was developed and we compared overseas go on sale magnesium wheels and same specifications of the aluminum wheels mechanical properties. Prototype 18-inch magnesium wheels by a low-pressure casting method to achieve the same specifications of aluminum wheels and reduced 26% of the weight, the new edition of magnesium wheels compared to the same level of elongation, tensile strength, hardness. Casting and heat treatment process to improve future need to improve the yield strength is expected.

Effect of Power Mode of Plasma Anodization on the Properties of formed Oxide Films on AZ91D Magnesium Alloy

  • Lee, Sung-Hyung;Yashiro, Hitoshi;Kure-Chu, Song-Zhu
    • Korean Journal of Materials Research
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    • v.28 no.10
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    • pp.544-550
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    • 2018
  • The passivation of AZ91D Mg alloys by plasma anodization requires deliberate choice of process parameters due to the presence of large amounts of structural defects. We study the dependence of pore formation, surface roughness and corrosion resistance on voltage by comparing the direct current (DC) mode and the pulse wave (pulse) mode in which anodization is performed. In the DC plasma anodization mode, the thickness of the electrolytic oxide film of the AZ91D alloy is uneven. In the pulse mode, the thickness is relatively uniform and the formed thin film has a three-layer structure. The pulse mode creates less roughness, uniform thickness and improved corrosion resistance. Thus, the change of power mode from DC to pulse at 150 V decreases the surface roughness (Ra) from $0.9{\mu}m$ to $0.1{\mu}m$ and increases the corrosion resistance in rating number (RN) from 5 to 9.5. Our study shows that an optimal oxide film can be obtained with a pulse voltage of 150 V, which produces an excellent coating on the AZ91D casting alloy.

Microstructures and Mechanical Properties of Diecast 0.7wt% CaO added Eco-Mg Parts (0.7wt% CaO 첨가 AZ91D Eco-Mg 다이캐스팅 부품의 미세조직 및 기계적 특성)

  • Seo, Jung-Ho;Lim, Hyun-Kyu;Kim, Shae-K.
    • Journal of Korea Foundry Society
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    • v.30 no.6
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    • pp.224-230
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    • 2010
  • To prevent oxidation of Mg melt, $SF_6$ gas has been generally used for Mg alloys during melting and casting as a cover gas. The use of $SF_6$ gas, however, will be restricted owing to its crucial impact on global warming. Non-$SF_6$ process during melting and casting in diecasting industry has been proved with Eco-Mg alloys by a simple addition of small amount of CaO into Mg alloys. This paper shows non-$SF_6$ diecasting procedures for 0.7wt% CaO added AZ91D Eco-Mg alloys. Cold-chamber diecasting was performed under $CO_2$ atmosphere without $SF_6$ gas. An increment of mechanical properties, especially strength and ductility of Eco-Mg alloys is, in part, due to high-quality melt, refined grain size and $Al_2Ca$ second phase strengthening. Microstructures and mechanical properties of 0.7wt% CaO added AZ91D Eco-Mg alloys are evaluated in comparison with those of conventional AZ91D Mg alloy.

Melt Protection Property and Ignition Resistance Property of CaO added AZ91D Mg Alloy (CaO이 첨가된 AZ91D 마그네슘 합금의 발화저항특성 및 용탕보호특성 평가)

  • Lee, Jin-Kyu;Ha, Seong-Ho;Kim, Young-Jig;Jo, Hyung-Ho;Kim, Shae-K.
    • Journal of Korea Foundry Society
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    • v.27 no.3
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    • pp.131-134
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    • 2007
  • [ $SF_6$ ] gas that is used as a protective cover gas for Mg and Mg alloys during melting and casting has extremely high greenhouse effect. CaO added Mg alloys could maintain their original mechanical properties and original abilities such as fluidity and hot tearing susceptibility. The ignition temperature increased with increasing CaO addition under ambient atmosphere and nitrogen atmosphere. The minimum amount of $SF_6$ gas decreased by 0.13 wt%CaO added AZ91D Mg alloy in the sealed condition.

Fabrication of Plasma Electrolytic Oxidation Coatings on Magnesium AZ91D Casting Alloys

  • Lee, Sung-Hyung;Yashiro, Hitoshi;Kure-Chu, Song-Zhu
    • Journal of the Korean institute of surface engineering
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    • v.50 no.6
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    • pp.432-438
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    • 2017
  • AZ91D casting alloy requires an advanced plasma anodizing processing because large amount of defects are liable to generate during anodization. In this study, plasma electrolytic oxidation (PEO) of AZ91D Mg alloy was conducted by the application of either constant voltage or current using a pulse mode and its effects on pore formation, surface roughness and corrosion resistance were investigated. The PEO films showed a three-layer structure. The PEO film thickness was found to increase linearly with voltage. The surface roughness, Ra, ranged between $0.2{\mu}m$ and $0.3{\mu}m$. The corrosion resistance increased from RN 3.5 to 9.5 by the PEO treatment when evaluated according to the 72 hour salt spray test. The PEO-treated surface exhibited higher pitting potential than the raw material.