• Title/Summary/Keyword: Mg-alloy

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A study on corrosion resistance and surface properties of AZ31 alloy according to Ca-GP addition during PEO treatment (PEO 처리시 Ca-GP첨가에 따른 AZ31합금의 내식성 및 표면특성에 관한 연구)

  • Lee, Jun-Su;Park, Je-Shin;Park, Il-Song
    • Journal of the Korean institute of surface engineering
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    • v.54 no.5
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    • pp.238-247
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    • 2021
  • PEO (plasma electrolytic oxidation) was applied to modify the surface of AZ31 magnesium alloy in this study. The mixed solution of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) was used as the electrolyte, and 0 - 0.05 g/L of Ca-GP (Glycerol Phosphate Calcium salt) was added in the electrolyte as an additive. PEO treatment was conducted at a current density of 30mA/cm2 for 5 minutes using a DC power supply. The surface properties were identified by SEM, XRD and surface roughness analyses, and the corrosion resistance was evaluated by potentiodynamic polarization and immersion tests. In addition, the biocompatibility was evaluated by immersion test in SBF solution. As the concentration of Ca-GP was increased, the surface morphology was denser and more uniform, and the amount of Ca and the thickness of oxide layer increased. Only Mg peak was observed in XRD analysis due to very thin oxide layer. The corrosion resistance of PEO-treated samples increased with the concentration of Ca-GP in comparision with the untreated sample. In particular, the highest corrosion resistance was identified at the group of 0.04g Ca-GP through potentiodynamic polarization and immersion tests in saline solution (0.9 wt.%NaCl). During the immersion in saline solution, pH rapidly increased at the beginning of immersion period due to rapid corrosion, and then increase rate of pH decreased. However, the pH value in the SBF temporarily increased from 7.4 to 8.5 during the day, then decreased due to the inhibition of corrosion with HA(hydroxyapatite) formation.

Investigating the Effect of Homogenization Heat Treatment on the Microstructure and Texture of Magnesium Alloy Sheet Manufactured via Twin Roll Casting (트윈롤 주조법으로 제조된 마그네슘합금 판재의 균질화 열처리에 따른 미세조직 및 집합조직 발달)

  • Lee, Hee Jae;Park, No Jin
    • Journal of the Korean Society for Heat Treatment
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    • v.34 no.3
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    • pp.122-129
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    • 2021
  • This study focuses on the microstructural development of 99% magnesium alloy sheet manufactured using twin roll casting (TRC) process. Herein, a plate with a thickness of 5 mm was manufactured using the TRC process, homogenization heat treatment was performed at 400℃ for 2-32 h, and finally, the change in microstructure was evaluated via optical microscopy and textural analysis. The results suggest that the plate manufactured using the TRC process was not destroyed and was successfully rolled into a plate. Microscopic observation suggested that the dendritic cast structure was arranged along the rolling direction. And the central layer of the rolled plate, where was present in a liquid state at the beginning of rolling, solidified later during the TRC process to form central segregation. The initial cast structure and inhomogeneous structure of the plate were recrystallized by homogenization heat treatment for only 2 h, and it was confirmed that the segregated part of the central layer became homogeneous and recrystallization occurred. Grain growth occurred as the heat treatment time increased, and secondary recrystallization occurred, wherein only some grains were grown. The textural analysis, which was conducted via X-ray diffraction, confirmed that the relatively weak basal plane texture developed using the TRC process was formed into a random texture after heat treatment.

Effects of Extrusion Ratio and Extrusion Temperature on Microstructure and Tensile Properties of SEN6 Magnesium Alloy (SEN6 마그네슘합금의 미세조직과 인장 특성에 미치는 압출비와 압출 온도의 영향)

  • H. J. Kim;J. Y. Lee;S. C. Jin;S. H. Park
    • Transactions of Materials Processing
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    • v.33 no.3
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    • pp.178-184
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    • 2024
  • In this study, we investigated the effects of extrusion ratio and extrusion temperature on the microstructure and tensile properties of extruded Mg-6Al-0.3Mn-0.3Ca-0.2Y (SEN6) alloy. As the extrusion ratio and temperature increase, dynamic recrystallization during extrusion is promoted, leading to the formation of a fully recrystallized microstructure with increased grain size. Additionally, the increases in extrusion ratio and temperature lead to texture strengthening, exhibiting a higher maximum texture intensity. The extruded materials contain three types of secondary phases, i.e., Al8Mn4Y, Al2Y, and Al2Ca, with irregular or polygonal shapes. The quantity, size, distribution, and area fraction of the second-phase particles are nearly identical between the two materials. Despite its larger grain size, the tensile yield strength of the material extruded at 450 ℃ and an extrusion ratio of 25 (450-25) is higher than that of the material extruded at 325 ℃ and an extrusion ratio of 10 (325-10), which is mainly attributed to the stronger texture hardening effect of the former. The ultimate tensile strength is similar in the two materials, owing to the higher work hardening rate in the 325-10 extrudate. Despite differences in grain size and recrystallization fraction, numerous twins are formed throughout the specimen during tensile deformation in both materials; consequently, the two materials exhibit nearly the same tensile elongation.

The Performance of NI/$MgAl_2O_4$ Coated Metal Monolith in Natural Gas Steam Reforming for Hydrogen Production (NI/$MgAl_2O_4$코팅된 금속 모노리스 촉매의 수소 생산을 위한 천연가스 수증기 개질 반응특성에 관한 연구)

  • Choi, Eun-Jeong;Koo, Kee-Young;Jung, Un-Ho;Rhee, Young-Woo;Yoon, Wang-Lai
    • Transactions of the Korean hydrogen and new energy society
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    • v.21 no.6
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    • pp.500-506
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    • 2010
  • The metal monolith catalyst coated with 15wt% Ni/$MgAl_2O_4$ is applied to the natural gas steam reforming for hydrogen production. To address the improvement of adherence between metal monolith and catalyst coating layer, the pre-calcination temperature as well as the coating conditions of $Al_2O_3$ sol are optimized. When the Fe-Cr alloy monolith is pre-calcined at $900^{\circ}C$ for 6 h, $Al_2O_3$ layer was formed uniformly on the entire surface of the metal substrate. It is seen that the formation of $Al_2O_3$ layer on the monolith surface is essential for the uniform coating of $Al_2O_3$ sol onto the monolith substrate. The monolith catalyst coated with 10wt% $Al_2O_3$ sol shows high $CH_4$ conversion and good thermal stability as compared with the monolith catalyst without $Al_2O_3$ sol coating under severe reaction conditions with high GHSV of 30,000 $h^{-1}$ at $700^{\circ}C$. In addition, the metal monolith catalyst shows higher catalytic activity and better thermal conductivity than 15wt% Ni/$MgAl_2O_4$ pellet catalyst.

The effect of gap between ingot and crucible on the distribution of initial melt concentration in Bridgman crystal growth (Bridgman 결정성장시 장입 주괴와 도가니 사이의 틈이 용액이 초기농도에 미치는 영향)

  • Seung-Mo Chung;Man-Sug Kang;Zin-Hyoung Lee
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.4 no.2
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    • pp.169-177
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    • 1994
  • Dilute Al-Cu and Al-Mg alloys were solidified unidirectionally upward by Bridgman method. It is necessary that solute concentration of initial melt is uniform to be able to control the concentration of crystal. When solute concentration is not uniform, it can cause unusual macro-segregation in grown solid. A non-steady state solidification was observed where the solute concentration in the grown solid decreased with the progress of solidification, when a dilute Al-Cu melt with positive axial temeprature gradient was solidified. This was caused by leaking out of Cu-rich melt into the gap between ingot and crucible during melt-down and its sedimentation after complete melting. In the case of Al-Mg alloy, the solute concentration has a minimum in the middle of grown specimen because Mg-rich melt flowed down the gap between ingot and crucible and floated after complete melting. Uniform initial melt concentration can be achieved by the homogenization of the ingot or by the absence of the gap between ingot and crucible.

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Bone-like Apatite Formation on Ti-6Al-4V in Solution Containing Mn, Mg, and Si Ions after Plasma Electrolytic Oxidation in the SBF Solution

  • Lim, Sang-Gyu;Choe, Han Cheol
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2017.05a
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    • pp.157-157
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    • 2017
  • Titanium and its alloys that have a good biocompatibility, corrosion resistance, and mechanical properties such as hardness and wear resistance are widely used in dental and orthopedic implant applications. They can directly connect to bone. However, they do not form a chemical bond with bone tissue. Plasma electrolytic oxidation (PEO) that combines the high voltage spark and electrochemical oxidation is a novel method to form ceramic coatings on light metals such as titanium and its alloys. This is an excellent reproducibility and economical, because the size and shape control of the nano-structure is relatively easy. Silicon (Si), manganese (Mn), and magnesium (Mg) has a useful to bone. Particularly, Si has been found to be essential for normal bone, cartilage growth and development. Manganese influences regulation of bone remodeling because its low content in body is connected with the rise of the concentration of calcium, phosphates and phosphatase out of cells. Insufficience of Mn in human body is probably contributing cause of osteoporosis. Pre-studies have shown that Mg plays very important roles in essential for normal growth and metabolism of skeletal tissue in vertebrates and can be detected as minor constituents in teeth and bone. The objective of this work was to study nucleation and growth of bone-like apatite formation on Ti-6Al-4V in solution containing Mn, Mg, and Si ions after plasma electrolytic oxidation. Anodized alloys was prepared at 270V~300V voltages. And bone-like apatite formation was carried out in SBF solution for 1, 3, 5, and 7 days. The morphologies of PEO-treated Ti-6Al-4V alloy in containing Mn, Mg, and Si ions were examined by FE-SEM, EDS, and XRD.

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Analysis of Tube Extrusion Process Conditions Using Mg Alloy for Automotive Parts (자동차 부품용 마그네슘 합금 관재 압출공정조건 분석)

  • Park, Chul Woo;Kim, Ho Yoon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.36 no.12
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    • pp.1675-1682
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    • 2012
  • Weight reduction is increasingly being considered very important in light of air pollution and the exhaustion of resources. As a result, many automotive components are being replaced by Al and Mg alloys, and studies are increasingly focusing on the same. However, the use of Mg alloys is limited because they have higher material cost and lower productivity owing to the difficult forming conditions compared with Al alloys. In this study, the tube extrusion process conditions of an automotive bumper back beam were analyzed using FEA. Material tests were performed to determine the properties, and experiments and analyses for a simple shape were performed to define the data for heat generation during plastic deformation. Then, the analyses of the product were carried out by considering various temperatures and ram speeds. The conditions were then established, and a product without surface defects was extruded successfully.

Low Temperature Thermal Conductivity of Sheath Alloys for High $T_{c}$ Superconductor Tape

  • Park, Hyung-Sang;Oh, Seung-Jin;Jinho Joo;Jaimoo Yoo
    • Transactions on Electrical and Electronic Materials
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    • v.1 no.2
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    • pp.32-37
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    • 2000
  • Effect of alloying element additions to Ag on thermal conductivity and electrical conductivity of sheath materials for Bi-Pb-Sr-Ca-Cu-O(BSCCO) tapes has been characterized. The thermal conductivity at low temperature range (10~300K) of Ag and Ag alloys were evaluated by both direct and indirect measurement techniqueas and compared with each other, It was observed that the thermal conductivity decreases with increasing the content of alloying element such as Au, Pd and Mg. Thermal conductivity of pure Ag at 3 0K was measured to be 994.0 W(m.K) on the other hand, the corresponding values of $Ag_{0.9995}Mg_{0.0005}$, $Ag_{0.974}$, $Au_{0.025}$, $Mg_{0.001}$, $Ab_{0.973}$, $Au_{0.025}$, $Mg_{0.002}$ and $Ag_{0.92}$, $Pb_{0.06}$, $Mg_{0.02}$ were 342.6, 62.1, 59.2 and 28.9 W(m.K), respectively, indicating 3 to 30 times lower than that of pure Ag. In addition, the thermal conductivity of pure Ag measured by direct and indirect measurement techniques was 303.2 and 363.8 W(m.K) The difference in this study is considered to be within an acceptable error range compared to the reference data.

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Dielectric functions of $Cd_{1-x}Mg_xTe(0\leqx\leq0.43)$ alloy films studied by ellipsometry (타원편광분석기를 이용한 $Cd_{1-x}Mg_xTe(0\leqx\leq0.43)$ 박막 화합물의 유전율 함수 연구)

  • 구민상;이민수;김태중;김영동;박인규
    • Journal of the Korean Vacuum Society
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    • v.9 no.3
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    • pp.254-257
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    • 2000
  • We report spectroscopic ellipsometric (SE) measurements on $Cd_{1-x}Mg_x/Te$ (0$\leq$x$\leq$0.43) films grown on GaAs substrate. When compared with previous bulk data, at first, current spectrum shows clear interference oscillations below $E_0$ band gap energy, which means the transparent characteristic of direct transition material below $E_0$ edge. It proves that the film samples used for this work have the most interrupted surface of high quality reported so far by SE. Secondly the best resolution of $E_2$-peak is observed, so we can report clear splitting of E$_2$and $E_0'$ band gap energies. We also performed the multilayer calculation necessary to remove this interference oscillations to observe $E_0'$ band gap energy of $Cd_{1-x}Mg_x/Te$ (x=0.23) film.

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Microstructure and Mechanical Properties of Mg-Al-Zn-X Alloys Fabricated by Rotation-Cylinder Method (교반관법으로 제조한 Mg-Al-Zn-X합금의 기계적 특성)

  • Lee, Jung-Il;Lee, Joo-Ho;Kim, Young-Ho;Hong, Tae-Whan;Lee, Hoo-In;Park, Jintae;Kim, Joon-Soo;Park, Hyungkyu
    • Journal of the Korean Society for Heat Treatment
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    • v.19 no.2
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    • pp.96-102
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    • 2006
  • Development of Rotation-Cylinder Method(RCM) is given for Mg-Al-Zn-X(X=Sr) alloys, identifying some of the key factors that need to be controlled and indicating subsequent casting processes. Effects of Sr addition on the microstructure and mechanical properties of as-cast and T6 heat-treated Mg-Al-Zn-X alloys fabricated by the RCM were investigated. The microstructural and mechanical characterizations were performed by utilizing optical microscope, scanning electron microscope, transmission electron microscope, hardness test and ultimate tensile test. The solution and aging treatment time was varied to optimize the T6 heat treatment conditions, and experimental results were discussed. The grain size of Sr containing alloys was refined by increasing Sr content, but the tensile and yield strengths were increased by addition up to 1wt% Sr.