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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Springer Science and Business Media Deutschland GmbH  

The effects of the chlorine content used as electrolyte should be controlled in the recycle process of Mg-air battery. The influence of MgCl2 and NaCl in Si-thermic reduction of MgO has been studied in this study. The mixture of MgO with MgCl2 or NaCl was reduced by metallic Si at 1150 °C for 3 h, and the reduction rate was estimated. The reduction rate without MgCl2 or NaCl addition was about 55% under our reduction condition, and 1 mol% addition of MgCl2 rarely affected the reduction rate. However, the reduction rate decreased with added amount of MgCl2, and became about 15% in 10 mol% addition. Even 1 mol% addition of NaCl worsened the reduction rate, and the reduction rate decreased with the addition amount. It is confirmed that the chlorine should be removed before Si-thermic reduction in the recycle of Mg-air battery.

DOI： 10.1007/978-3-030-72432-0_26

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Springer Science and Business Media Deutschland GmbH  

It was shown in our previous study that the contact condition between MgO, CaO, and Si strongly affected Mg metal production by silicothermic reduction of magnesium oxide derived from salt evaporation ponds. In this study, the influence of the contact condition of MgO, CaO, and Si in the reduction was studied
the dependence of the reduction rate on the preparation procedure of MgO–CaO mixture and pre-sintering before the reduction was examined. A short-term sintering improved the reduction rate, but a longer sintering worsened the rate. Sintering seems effective in the improvement of contact condition, but causes the surface oxidation on Si. In this study, Si reduction with Ca2SiO4 instead of CaO was also attempted to reduce CaO consumption, but it was shown that MgO was lost by CaMgSiO4 formation.

DOI： 10.1007/978-3-030-72432-0_2

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Springer Science and Business Media Deutschland GmbH  

Mg–14mass%Li–3mass%Al (LA143) alloy has higher corrosion resistance than previous Mg-Li alloys such as Mg–14mass%Li–1mass%Al (LA141). However, the corrosion properties of the alloy are not enough to apply for practical use without corrosion protection coatings. The anodization for Mg alloys is an effective technique to prevent metal surface from exposure to corrosion environment. Phosphoric acid-based solutions containing metal cation are useful electrolytes to form a thick oxide layer on the Mg surface. In this study, the effect of cation species on the oxidized film was investigated. The film formed by each electrolytic solution was mainly composed of Mg3(PO4)2, AlPO4, MgAl2O4, and the phosphate and oxide-containing each additive element were slightly present. Particularly, in the electrolyte containing Ca, the dissolution of LA143 was suppressed about twice as much as other electrolytes, and the most uniform and thick film was formed.

DOI： 10.1007/978-3-030-72432-0_18

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Springer Science and Business Media Deutschland GmbH  

There is the deleterious influence of corrosion resistance of Mg alloy by contaminant of impurity element Ni during Mg recycling. Mg2Ni precipitates trigger the galvanic corrosion with Mg matrix phase. Zn addition into Mg alloy may reduce the detrimental impact of impurities because a small amount of Ni element is dissolved into Mg-Zn intermetallic phase. Therefore, the microstructure and corrosion behavior were investigated by changing the amount of Zn in Mg alloy with a trace amount of Ni. From the results of the microstructural observation, Ni element existed in MgZn2 intermetallic phase when the Zn content exceeded 6 mass%, to change the existing state of Ni whereas Mg2Ni phase was dispersed in Mg-Zn alloy with a few percent of Zn.

DOI： 10.1007/978-3-030-72432-0_21

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Springer Science and Business Media Deutschland GmbH  

The anodic formation of an oxide film on MoSi2 in molten MgCl2–NaCl–CaCl2 containing oxide ions has been investigated based on our former study, and the compatibility as an inert anode in the melt is discussed in contradistinction in molten LiCl–KCl. A small anodic current flew continuously during potentio-static electrolysis, and gas bubble generation was seen. The weight of MoSi2 was changed by the electrolysis, and an oxide film consisting of SiO2 and MgSiO3 was formed by the electrolysis above 1.9 V (vs. Mg/Mg2+). The current contributions estimated from the weight change and the film thickness indicate that the reaction other than the Mo dissolution and the oxide film formation enlarged with the increase in the electrolysis duration and the raise in the electrolysis potential. The current contribution other than the Mo dissolution and the oxide film formation became above 90%, which suggests MoSi2 is promising as an inert anode. A SiO2 film was formed on MoSi2 in molten LiCl–KCl containing oxide ions, but most of the current was consumed for the Mo dissolution and the oxide film formation. It is considered that the formation of MgSiO3 influences the anodic behavior of MoSi2.

DOI： 10.1007/978-3-030-72432-0_3

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Springer Science and Business Media Deutschland GmbH  

Mg–Li system alloy has excellent formability at room temperature due to its crystal structure. However, exfoliation corrosion appears during the progress of corrosion. Therefore, it is difficult to apply for the actual metallic products without corrosion protection. Previously, the suppression of exfoliation could be attained by recrystallization of cold-rolled alloy. The microstructural characteristics were completely changed by recrystallization, so a detailed investigation is required for the explanation of exfoliation corrosion origination. In this study, the origination of exfoliation corrosion of Mg–14 mass%Li–1 mass%Al alloy with various microstructures such as as-rolled, only recovered and recrystallized state. As the results, the induced strain during severe deformation is a major factor of expression of exfoliation corrosion.

DOI： 10.1007/978-3-030-72432-0_19

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Institute of Metals (JIM)  

The change in TiO2 solubility in molten CaCl2 at 1573 K with CaO addition was studied to clarify the influence of CaO on TiO2 dissolution. The solubility of TiO2 in molten CaCl2 remarkably enlarged with CaO addition, which suggests that a titanate ion (TixOy Z1) was preferentially formed in it. The cathodic behavior in molten CaCl2 containing various species of calcium titanate at 13731573 K was investigated by cyclic voltammetry, and electrodeposition of Ti metal was attempted by potentio-static electrolysis. The reduction behavior was affected by the species of calcium titanate, and the components in the deposit changed consequently. These results indicate that the reduction behavior of Ti was strongly influenced by the species of titanate ion, and that the bath consisting of Ca3Ti2O7 is found suitable.

DOI： 10.2320/matertrans.MBW201702

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Trans Tech Publications Ltd  

Anodic oxidation of Mg-Li-Al alloys using phosphoric acid-based bath were processed to obtain the corrosion-proof surface coating. The specimen oxidized at low voltage anodically dissolved without the formation of oxidized film. Anodic oxidation film could be formed at higher voltage due to thin layer preferentially formed on tthe active surface, this layer develops to stable thick film. There were no significant differences in film thickness between LA141 and LA143 alloys.

DOI： 10.4028/www.scientific.net/MSF.941.1194

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN INST METALS  

The solubility of calcium titanate in CaCl2 melt was investigated above 1373 K, and electrodeposition of Ti metal in the melt was attempted. Many pits were formed on the surface of sintered CaTiO3 compact by the immersion in CaCl2 melt above 1373 K. The weight of the compact decreased with the increase in the immersion time, and the decrease got faster with the increase in temperature. Cathodic current in cyclic voltammetry increased with the addition of CaTiO3 powder in the bath, and the increase in the cathodic currents depended on the bath temperature and the added amount of CaTiO3. From the results by the electrochemical measurement, the solubilities of CaTiO3 in CaCl2 melt were estimated about 7 mol% at 1573 K, and less than 1 mol% at 1373 K. Metallic Ti was detected by XRD analysis in the electrodeposit obtained by potentio-static electrolysis in the bath containing CaTiO3 above 1373 K, but the amount of Ti metal seemed a little. The similar results were obtained in CaCl2 melt containing Ca3Ti2O7 though the detailed study has not been completed. It was concluded that calcium titanate was soluble in molten CaCl2 above 1373 K, and that the CaCl2 bath containing calcium titanate could be applied to Ti electrolysis.

DOI： 10.2320/matertrans.MK201615

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Electrochemical Society Inc.  

The current efficiency (CE) for aluminium electrolysis in modern cells can be as high as 96 %. The main reason for loss in current efficiency is the so-called back reaction between dissolved metal and the anode product of CO2 Decreasing temperature of the cell may give higher current efficiency. However, low superheat may cause solidification of melt. A laboratory cell to determine the current efficiency was recently modified to obtain more reliable results. Electrolysis was performed at constant current density and the current efficiency was determined from the weight of deposited aluminium. Effects of electrolyte composition by addition of LiF and temperature were studied. The loss in current efficiency is strongly related to the content of dissolved metal in the electrolyte. The effect of LiF addition on the current efficiency was discussed in this study.

DOI： 10.1149/07711.0997ecst

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELECTROCHEMICAL SOC INC  

The so-called metal fog sometimes formed during the molten salt electrolysis. In this paper, the effect of the surface shape of electrode on the metal fog formation was investigated in LiCl-KCl. Cyclic voltammetry and potentiostatic electrolysis were carried out at Mo wire electrode with/without screw cutting. The dark blue metal fog was formed at both types of electrodes, while the gray metal fog was generated only at the screw-cut electrode. The gray fog formation also depended on the diameter of the electrode; the formation was intenser at a small electrode than at a large electrode. It is concluded that the shape of electrode strongly affects the gray metal fog formation, and it is suggested that the current concentration at the edge causes the formation.

DOI： 10.1149/07515.0233ecst

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN INST METALS  

Mg-Li system alloys have poor corrosion properties, especially cold-rolled sheet leads to exfoliation corrosion as a result of long-term immersion test. Addition of aluminum element to Mg-14 mass% Li alloy could be suppressed the occurrence of exfoliation corrosion. However, excess addition of aluminum to Mg-14 mass% Li alloy causes the degradation of corrosion resistance. In this study, the composition of aluminum in Mg-14 mass% Li was optimized to improve the corrosion property. 3 mass% of Al addition could be suppressed the corrosion rate because enough aluminum element dissolved into matrix and precipitation of the second phase was inhibited.

DOI： 10.2320/matertrans.M2016247

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELECTROCHEMICAL SOC INC  

The electrolysis condition to obtain Ti metal in a CaF2-MgF2 with CaO and TiO2 has been studied at 1573K. It was shown by cyclic voltammetry that cathodic current increased below 0.8V ( vs. Mg/Mg2+) with CaO and TiO2 addition and that three reduction steps of Ti was suggested. The particles containing Ti were obtained by potentio-static electrolysis; only Ti oxide particles were detected by the electrolysis above 0.5V, while Ti metal particles did by the electrolysis below 0.4V. This result indicates that Ti metal can be electrodeposited below 0.4V (vs. Mg/Mg2+).

DOI： 10.1149/07515.0199ecst

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN INST METALS  

As increasing the demand of Mg alloys, recycling of these alloys require for securing a metallic resource and energy conservation. A commercial metal scrap includes other structural materials such as iron, copper and aluminum alloys. These metal elements deteriorate mechanical properties or corrosion properties of Mg alloys. Therefore, these different materials were possibly removed from Mg scrap during recycling process. The separation of Al and Mg materials has difficulty except for the gravity separation. However, there is a limited difference in density between Mg and Al. In this study, Mg recovery from mixed metal scrap was attempted by dry gravity separation using solid particulate vibrating bed. Mg separation with high recovery ratio was achieved by adjusting the density of the particulate bed. It was suggested that the bulk density of the particulate bed affected the behavior of separation materials for the favorable recovery.

DOI： 10.2320/matertrans.M2015226

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The purification process is required for recycling Mg process. Selective impurity removal has an efficient purification process in the purity level of commercial Mg metal and alloys. Especially, iron impurity deteriorates the corrosion resistance of Mg alloys. Carbon addition to Mg-3 mass% Al alloy melt is an effective method for the removal of iron impurity by the formation of Fe-Al-C compounds. In this study, gas injection of carbon dioxide (CO2) into Mg alloy melt as the method of carbon addition was investigated for the separation of iron compounds. Carbon dioxide was decomposed by Mg melt and carbon substance affected the formation of iron carbide in the melt. Magnesium oxide and Fe-Al-C compound were formed in the melt slag and floated to the top of the solidified Mg-3 mass% Al alloy.

DOI： 10.2320/matertrans.MBW201407

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN INST METALS  

Mg-Li system alloys with over 11 mass% Li have an excellent cold-workability in Mg alloys due to the bcc-structured crystal system. However this system alloys have poor corrosion resistance caused by Li solid-solution alloy. The corrosion resistance of conventional hcp-Mg alloys is influenced by the composition of impurity elements. Particularly, minute iron element deteriorates the corrosion resistance of Mg alloy and there is a threshold concentration on the corrosion rate in Mg alloys. In this study, the effect of iron element on the corrosion resistance of Mg-Li alloy was investigated by addition of iron. The corrosion resistance of Mg-Li with no Fe addition was higher than conventional Mg alloy. The corrosion rate of Mg-Li alloy increased with increasing iron concentration. However, there is no threshold iron concentration affected to the corrosion resistance on Mg-Li alloy.

DOI： 10.2320/matertrans.MAW201405

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Language：English   Publishing type：Part of collection (book)   Publisher：Wiley Blackwell  

The cathodic phenomena in Li electrolysis in LiCl-KCl eutectic melt were studied by means of in situ visual observation linked with electrochemical measurement. It was shown that the so-called metal fog was observed even in Li electrolysis under particular conditions. The results in this study suggested the phenomenon in Li electrolysis seemed different from those of Na and Ca electrolysis. The cathodic reaction of H2 bubble generation due to residual moisture in the bath was evaluated from this link-view, and it was indicated that the reduction of the residual moisture strongly influenced the efficiency of Li electrolysis. The link between the in situ visual observation and the electrochemical response was shown helpful for better understanding of electrochemical investigation in a molten salt bath.

DOI： 10.1002/9781118448847.ch2d

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELECTROCHEMICAL SOC INC  

The cathodic reaction of Ti has been studied in a CaF2-MgF2 bath with CaO and TiO2 at 1373K. Cyclic voltammograms were measured in the baths of various compositions, and the dependence of the cathodic reaction of Ti on the bath composition was discussed. With reference to the results of the cyclic voltammetry, Ti metal deposition by potentio-static electrolysis was attempted. It was shown that the reduction sequence of Ti consisted of three steps, and Ti metal was deposited under the suitable condition. The cathodic behavior of Ti was influenced by the molar ratio of TiO2 to CaO in the melt. Considering the previous results of Ti electrolysis by using DC-ESR unit, it is strongly suggested that a binuclear complex ion of Ti with O, such as Ti2O76-, affects the reduction sequence of Ti in CaF2-CaO-TiO2 and CaF2-MgF2-CaO-TiO2 baths.

DOI： 10.1149/06404.0275ecst

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Language：Japanese   Publisher：Japan Foundry Engineering Society  

<p>  The effects of Friction Stir Processing (FSP) on the hardness of Al-Cu binary alloys with various copper contents up to 9mass%Cu were investigated. Prepared Al-Cu samples were divided in two groups. Samples in one group were used as cast sample plate. Samples in the other group were annealed at 673K for 108ks. The hardness of as cast samples increased with increasing copper content before FSP treatment. The hardness of the annealed samples increased in the same way as the as cast sample at low copper ranges up to 5mass%Cu. At higher copper content ranges from Al-5%Cu, the rate of hardness increment of annealed samples however slowed down before FSP. Sample plates were treated by FSP, and microstructure and hardness were measured. Samples containing less than 4%Cu including pure aluminum showed hardness increment by 10HV after FSP regardless of heat treatment. For as-cast series specimens however, the FSP treatment never increased the hardness in copper content ranges from 5mass% to 9mass%. On the other hand, annealed samples were slightly hardened by FSP. This is because the annealed samples have a weaker network of harder phase than as-cast samples, and the breakdown of such networks and distribution of the fragments weaken the material of as-cast samples.</p>

DOI： 10.11279/jfes.85.837

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN INST METALS  

Cold-rolled Mg-Li system alloys represent the exfoliation corrosion on the surface of the longitudinal and the transverse sections. In this study, the origination of the exfoliation corrosion of the cold-rolled Mg-Li alloy was clarified. In the initial stage of the corrosion, the oxide film formed immediately on the surface of each section, and then the film destruction with a remarkable bubble generation was observed in a certain spot. There were microcracks on the trace of the film destruction along the grain boundary. The corrosion resistance in the annealed specimen was more than that in the as-rolled specimen because the microstructure of the as-rolled specimen has elongated and thinned grains by severe cold rolling. The exfoliation corrosion was not observed in the annealed specimen, because the annealed specimen has homogeneous equiaxial grains. The successive film destruction in annealed specimen progressed along the grain boundary to random direction. Moreover, the initiation time of the bubble generation was delayed in the annealed specimen.

DOI： 10.2320/matertrans.MAW201301

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Iron should be removed in the Mg recycling flow because of its ill effect to the corrosion property. In this study, the Fe elimination from Mg and its alloys has been investigated by carbon addition in liquid Mg metal containing Fe. Iron in liquid Mg metal was hardly removed by only the carbon addition. The existence of Ca in Mg melt was helpful for the Fe removal, but the excess Ca addition resulted in an adverse effect. In Mg metal containing Al, Fe was removed by C addition, and AlFe3C was detected. In all the cases, Fe and its compound tended to concentrate around the bottom and the shrinkage cavity, but the Fe compounds still remained even in the purified ingot. The control of Fe precipitation should lead to the better Fe elimination. Copyright © 2013 MS&amp
T'13®.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELECTROCHEMICAL SOC INC  

The anodic reactions on some materials in LiCl-KCl eutectic melt have been investigated. Palladium and Mo were dissolved though Mo showed passivation behavior. In the melt including Li2O, O-2 gas generation occurred at both metal anodes along with their anodic dissolution. At the graphite anode, some anodic reactions besides the Cl-2 gas generation reaction were observed in the melt with Li2O. The visual observation and the weight change of the anode indicated that the anodic reaction without gas generation and the electrode consumption preceded the CO2 gas generation. The potential of the CO2 gas generation reaction on graphite looked more positive than that of the O-2 gas generation on Pd and Mo, which suggested the overpotential of the CO2 generation reaction on graphite was rather large in the melt.

DOI： 10.1149/05011.0127ecst

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Friction stir processing (FSP) is one of the severe plastic deformation processes that have been developed to improve the mechanical properties of both metals and alloys by producing an ultrafine-grained structure. In this study, it was used to realize the minimum grain size in Al-Mg alloys. The results indicate that the grain size in Al-Mg alloy decreases with increasing Mg content because of the influence of stacking fault energy in the Al-Mg alloy. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.scriptamat.2010.10.033

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：JOHN WILEY & SONS  

A friction stir processing (FSP) technique has been developed for use with aluminum and magnesium alloys. The microstructure was evolved into fine grains by the dynamic recrystallization during FSP. In this study, FSP was used to pure aluminum and aluminum alloys and the influence of alloying element on the grain size was investigated. In addition, the relationship between the grain size and the Zener-Hollomon parameter was investigated. There was observed difference in grain size between these materials. The recrystallized grain of FSP-ed ultra-high-purity (99.999%) aluminum was particularly large, compared to the grain sizes of other materials, when subjected to the same processing conditions. In contrast, grain sizes decreased with an increase in the Zener-Hollomon parameter in all materials. However, the grain size reached a certain minimum value at high-strain-rates of processing. Compared to other processed aluminum materials, the minimum grain size was found for each material.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

A friction stir processing (FSP) technique has been developed for use with aluminum and magnesium alloys, with the goal of high-strain-rate processing. In this study, we treat the microstructures of aluminum samples, of three levels of purity, manipulating their grain sizes, making them finer, using FSP. Grain sizes decreased with an increase in the Zener-Hollomon parameter, at all purity levels. However, the recrystallized grain of FSP-ed ultra-high-purity (99.999%) aluminum was particularly large, compared to the grain sizes of lower-purity (99% and 99.99%) aluminum, when subjected to the same processing conditions. The grain size reached a certain minimum value at high-strain-rates of processing, which we report for each purity level herein. (C) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.matlet.2010.06.003

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Post-weld properties of dissimilar friction stir welds of mild steel/A7075-T6 aluminum alloy were investigated. The joint strength increased with reduction in thickness of the intermetallic compound at the weld interface. During tensile tests of the composite weld, no weld failed in the aluminum base metal. Comprehensive analysis using the heat input parameter showed that the apparent interface strength between the steel and aluminum was lower than the joint strength of the friction-stir-welded A7075-T6 alloy. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.scriptamat.2009.06.022

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Formation of a protective thin surface of pure aluminum on Mg-14mass%Li alloy by plasma thermal spraying and the cold rolling was investigated. An Mg-14mass%Li-1mass%Al alloy ingot was melted and cast in a pressurized argon atmosphere. After homogeneous heat treatment, the ingot was rolled to 3 mm-thick plate with a reduction ratio of 98%. The plate specimens were annealed again. Plasma sprayings of pure aluminum were carried out with various conditions after grit blasting. The coated layer thickness was about 100 mu m. There was slight increase in temperature during spraying on substrates. The first pass of rolling was carried out at 250 degrees C; then several cold rolling passes were processed to reduce the entire thickness up to 90% in reduction ratio of the sprayed specimens&apos; thickness. It was found that the determining factor for sound rolled sheet without separation of aluminum coating was the maximum temperature of the substrate at plasma processing. There were no separation, for specimen heated in the temperature range between 300 and 400 degrees C during thermal spraying, at rolling up to 90% in total reduction ratio. Sectional observation revealed a continuous thin aluminum layer adhered on the Mg-14mass%Li alloy.

DOI： 10.1002/ppap.200932408

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MANEY PUBLISHING  

Cast Mg alloys were processed using friction stir processing (FSP) to acquire a fine grained structure and high strength. Actually, FSP is a novel grain refinement method for light metal alloys. Using FSP, a cast microstructure with coarse grain size was refined to equiaxial fine grain through dynamic recrystallisation; second phase particles were finely dispersed by FSP. Moreover, FSP is effective to eliminate cast defects such as microshrinkages or porosities. Commercial die cast Mg alloy (AZ91D) and high strength Mg-Y-Zn alloy plates were prepared for FSP. Heat input using a rotational tool during FSP closely affected the microstructure in the stirred zone. Actually, FSP with lower heat input produced a finer grain size and higher hardness. Changes in the friction stir processed microstructures affecting mechanical properties were not only grain refinement, but also second phase particle distributions. Results show that alloys with high hardness by FSP have finely dispersed second phase particles without dissolution during FSP.

DOI： 10.1179/136404608X361774

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN INST METALS  

Microstructures and mechanical properties of dissimilar welding joint between Al alloy and Mg alloy by Friction Stir Welding (FSW) were investigated in comparison with laser welding of the same combination. Dissimilar joint of At and Mg alloy by laser welding was very brittle because of building up Mg17Al12 inter metallic compounds in fusion zone. On the other hand, FSW is anticipated to welding dissimilar alloys with enough joint strength because it is a solid-state process without melting. In this paper, FSW was carried out to make dissimilar butt joints of Al alloy and AZ31 magnesium alloy with various tool rotational speed and welding speed. These joints showed higher hardness in their stir zones than that of parent AZ31 alloy because of Mg-Al inter metallic compound formation. However, the hardness of stir zone was lower than that of fusion zone of laser welding, and was changed with the welding parameters of tool rotational speed and welding speed (i.e. heat input ratio of FSW). The optimum welding conditions of Mg and Al dissimilar FSW joint and the influence of inter metallic compound distribution with mixing of materials in stir zone were discussed.

DOI： 10.2320/matertrans.MC200768

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Cast Mg-Y-2-Zn-1 alloy was friction stir (FS) processed to obtain fine grain structure. Then the elevated temperature tensile tests were carried out to investigate the deformation behavior of the FS processed alloy. The starting structure for FS processing was coarse dendritic microstructure (secondary dendrite arm spacing ca. 75 mu m) with a plate-like second phase, which developed from inter-dendritic eutectic pockets after homogenization heat treatment. The alpha-Mg matrix and second phases were broken mechanically and distributed homogeneously by FS processing. The refined grain size at the fully stirred zone had the average size of ca. 2.0 mu m. Different deformation behavior occurred as a result of varying microstructural evolution according to temperatures (623 K and 723 K).

DOI： 10.2320/matertrans.48.618

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：MINERALS, METALS & MATERIALS SOC  

Friction stir processing (FSP) was carried out for cast Mg-1at.%Zn-2at.%Y alloy. Bulk fine-grained microstructure including second phase was obtained, Lamella structure was developed from quasi-crystal by heat treatment. At room temperature, FSP-ed Mg-1at.%Zn-2at.%Y alloy showed higher hardness when compared to those made by other processes. Main deformation mechanism was controlled by the dislocation-climb creep (n similar to 4.5) in the range of strain rates 10-3 to 10-1 (s-1) and temperature 623K to 723K. Ductility was up to 240 % at strain rate of 10-3 (s-1) arid at 723K.

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The ability to form protective thin surface of aluminum alloy on the Mg-14mass%Li alloy by the lap friction stir welding and the rolling was investigated. Mg-14mass%Li-1mass%Al alloy ingot was melted and cast in argon atmosphere. After homogeneous heat treatment, the ingot was rolled to plate with 3 mm in thickness under reduction ratio of 90%. Then the plate specimens were annealed again. Lap welding of A5052 alloy plate with 1 mm in thickness was carried out t after grit blasting and wire brushing. Both good adhesiveness and low mixing were necessary. Optimum FSW conditions for the purpose were searched. First pass of rolling was carried out at 300 degree C, and then several passes were processed to reduce the entire thickness to 50%. The sectional observation revealed the continuous thin aluminum layer adhered on the Mg-14mass%Li alloy.

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Cast magnesium alloys were processed by friction stir processing (FSP) to acquire fine grain and high strength. FSP is a novel grain refinement method for light metal alloys. By using FSP, cast microstructures were refined by dynamic recrystallization (DRX) and second phase particles could be finely dispersed by FSP. Moreover, FSP is effective process to eliminate cast defects like micro porosities. Thick plate of commercial Mg alloy for die-casting AZ91D or Mg-Y-Zn alloys of two different chemical compositions have been prepared for FSP. Changes in the FSP-ed microstructures that affect mechanical properties were not only grain size refinement, but also the distributions of second phase particles. As-cast Mg-2at.%Y-2at.%Zn alloy, differs from Mg-2at.%Y-1at.%Zn, has icosahedral quasi-crystalline phase in grain boundaries. It has higher elevated temperature stability than inter-metallic compound of Al12Mg 17. The distribution of fine second phase particles and mechanical properties were discussed.

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Language：English   Publisher：MANEY PUBLISHING  

Cast Mg alloys were processed using friction stir processing (FSP) to acquire a fine grained structure and high strength. Actually, FSP is a novel grain refinement method for light metal alloys. Using FSP, a cast microstructure with coarse grain size was refined to equiaxial fine grain through dynamic recrystallisation; second phase particles were finely dispersed by FSP. Moreover, FSP is effective to eliminate cast defects such as microshrinkages or porosities. Commercial die cast Mg alloy (AZ91D) and high strength Mg-Y-Zn alloy plates were prepared for FSP. Heat input using a rotational tool during FSP closely affected the microstructure in the stirred zone. Actually, FSP with lower heat input produced a finer grain size and higher hardness. Changes in the friction stir processed microstructures affecting mechanical properties were not only grain refinement, but also second phase particle distributions. Results show that alloys with high hardness by FSP have finely dispersed second phase particles without dissolution during FSP.

DOI： 10.1179/136404608X361774

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Language：English   Publisher：JAPAN INST METALS  

Microstructures and mechanical properties of dissimilar welding joint between Al alloy and Mg alloy by Friction Stir Welding (FSW) were investigated in comparison with laser welding of the same combination. Dissimilar joint of At and Mg alloy by laser welding was very brittle because of building up Mg17Al12 inter metallic compounds in fusion zone. On the other hand, FSW is anticipated to welding dissimilar alloys with enough joint strength because it is a solid-state process without melting. In this paper, FSW was carried out to make dissimilar butt joints of Al alloy and AZ31 magnesium alloy with various tool rotational speed and welding speed. These joints showed higher hardness in their stir zones than that of parent AZ31 alloy because of Mg-Al inter metallic compound formation. However, the hardness of stir zone was lower than that of fusion zone of laser welding, and was changed with the welding parameters of tool rotational speed and welding speed (i.e. heat input ratio of FSW). The optimum welding conditions of Mg and Al dissimilar FSW joint and the influence of inter metallic compound distribution with mixing of materials in stir zone were discussed.

DOI： 10.2320/matertrans.MC200768

Web of Science

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Language：English   Publisher：MINERALS, METALS & MATERIALS SOC  

Cast magnesium alloys were processed by friction stir processing (FSP) to acquire fine grain and high strength. FSP is a novel grain refinement method for light metal alloys. By using FSP, cast microstructures were refined by dynamic recrystallization (DRX) and second phase particles could be finely dispersed by FSP. Moreover, FSP is effective process to eliminate cast defects like micro porosities. Thick plate of commercial Mg alloy for die-casting AZ91D or Mg-Y-Zn alloys of two different chemical compositions have been prepared for FSP. Changes in the FSP-ed microstructures that affect mechanical properties were not only grain size refinement, but also the distributions of second phase particles. As-cast Mg-2at.%Y-2at.%Zn (Mg-6.7wt.%Y-5.0wt%Zn) alloy, differs from Mg-2at.%Y-1at.%Zn (Mg-6.8wt.%Y-2.5wt.%Zn), has icosahedral quasi-crystalline phase in grain boundaries. It has higher elevated temperature stability than inter-metallic compound of Al12Mg17. The distribution of fine second phase particles and mechanical properties were discussed.

Web of Science

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J-GLOBAL

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J-GLOBAL

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J-GLOBAL

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Language：English   Publisher：TRANS TECH PUBLICATIONS LTD  

Grain refinement of magnesium alloy by Friction Stir Processing (FSP) was investigated. It is assumed that dynamic recrystallization (DRX) is occurred by frictional heat and plastic flow during FSP. This process is the effective method of the grain refinement for light metals. In this study, FSP was conducted to cast Mg alloys for and the difference of the grain refinement by DRX in these alloys was examined. As a result, in comparison with commercial Mg-Al-Zn alloy and Mg-Y-Zn alloy have finer microstructure. The grain size of FSP-ed Mg-Y-Zn alloy was similar to 1.7 [mu m], however, that of AZ31 alloy was 20 similar to 30 [mu m].

DOI： 10.4028/www.scientific.net/AMR.26-28.465

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Language：English   Publisher：TRANS TECH PUBLICATIONS LTD  

A high strength at room temperature and at high temperature was reported for the extremely fine-grained RS P/M Mg-2at%Y-1at%Zn (Mg-6.8mass%Y-2.5mass%Zn) alloy. This property was attributed to the fine grain size. However, such alloys have very poor productivity. Therefore, they are far from from practical applications.
The aim of this study is to acquire the fine-grained bulk Mg-Y-Zn alloy by ingot metallurgy route much lower in cost. Friction-Stir-Processing (FSP) was performed on this alloy ingot, and the mechanical properties and the microstructures were examined. FSP was conducted on allover the plate of this alloy for both surfaces by the rotational tool with FSW machine. The stirring passes were shifted half of the probe diameter every execution.
The microstructure of as-cast material was dendrite. The dendrite are spacing was 72.5 [mu m], and there are the lamellar structures in it. The dendrite structures disappeared after FSP, but the lamellar structure could be observed by TEM. the grain size of FSP materials were measured as ca. 1 mu m by TEM micrographs.

DOI： 10.4028/www.scientific.net/AMR.15-17.369

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Language：English   Publisher：TRANS TECH PUBLICATIONS LTD  

Friction stir processing (FSP) is the effective method of the grain refinement for light metals. The aim of this Study is to acquire the fine grained bulk Mg-Y-Zn alloy by ingot metallurgy route much lower in cost. Such bulk alloy can be formed by the superplastic forging. The microstructure of as-cast Mg-Y-Zn alloy was dendrite. The dendrite arm spacing was 72.5 [mu m], and there are the lamellar structures in it. FSP was conducted on allover the plate of Mg-Y-Zn alloy for both surfaces by the rotational tool with FSW machine. The stirring passes were shifted half of the probe diameter every execution. The dendrite structures disappeared after FSP, but the lamellar structure could be observed by TEM. The matrix became recrystallized fine grain, and interdendritic second phase particles were dispersed in the grain boundaries. By using FSP, cast Mg-Y-Zn alloy could have fine-grained. This result compared to this material produced by equal channel angular extrusion (ECAE) or rapid-solidified powder metallurgy (RS P/M). As the result, as-FSPed material has the higher hardness than materials produced by the other processes at the similar grain size.

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Event date： 2014.3

Venue：大阪府立大学  

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Event date： 2013.12

Venue：Las Vegas, NV  

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Event date： 2013.11

Venue：慶應義塾大学日吉キャンパス  

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Event date： 2013.11

Venue：慶應義塾大学日吉キャンパス  

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Event date： 2013.11

Venue：慶應義塾大学日吉キャンパス  

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Event date： 2013.11

Venue：慶應義塾大学日吉キャンパス  

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Event date： 2013.11

Venue：慶應義塾大学日吉キャンパス  

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Event date： 2013.10

Venue：Montreal, QC, Canada  

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Event date： 2013.9

Venue：金沢大学角間キャンパス  

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Event date： 2013.9

Venue：金沢大学角間キャンパス  

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Event date： 2013.8

Venue：Hawaii, HI  

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Event date： 2013.3

Venue：東京理科大学神楽坂キャンパス  

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Event date： 2013.3

Venue：東京理科大学神楽坂キャンパス  

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Event date： 2012.7

Venue：Vancouver, BC, Canada  

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Event date： 2012.6

Venue：江戸東京博物館  

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Event date： 2012.5

Venue：九州大学伊都キャンパス  

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Event date： 2012.3

Venue：横浜国立大学常盤台キャンパス  

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Event date： 2012.3

Venue：横浜国立大学常盤台キャンパス  

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Event date： 2011.11

Venue：沖縄コンベンションセンターおよびカルチャーリゾートフェストーネ  

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Event date： 2011.11

Venue：沖縄コンベンションセンターおよびカルチャーリゾートフェストーネ  

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Event date： 2011.11

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Event date： 2011.9

Venue：Yoshida-south Campus, Kyoto University  

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Event date： 2011.9

Venue：Yoshida-south Campus, Kyoto University  

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Event date： 2011.8

Venue：Quebec city convention centre  

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Event date： 2011.5

Venue：名古屋大学  

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Event date： 2011.5

Venue：名古屋大学  

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Event date： 2011.2 - 2011.3

Venue：San Diego, California  

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Venue：Vienna, Austria  

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Venue：Vienna, Austria  

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