Дисертації з теми "Magnesium rare-earth alloys"
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Griffiths, David Glyndwr John. "Understanding texture weakening in magnesium rare earth alloys." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/understanding-texture-weakening-in-magnesium-rare-earth-alloys(3823f6a8-bba7-415f-9326-adc1b1655c8c).html.
Повний текст джерелаFreeney, Timothy Alan. "Friction stir processing of cast magnesium alloys." Diss., Rolla, Mo. : University of Missouri-Rolla, 2007. http://scholarsmine.mst.edu/thesis/pdf/Freeney_09007dcc804a9022_3_09007dcc8055e79b.pdf.
Повний текст джерелаVita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed June 17, 2008) Includes bibliographical references.
Yong, Ming S. "Process optimisation of squeeze cast magnesium-zinc-rare earth alloys and short fibre composites." Thesis, Loughborough University, 1999. https://dspace.lboro.ac.uk/2134/15363.
Повний текст джерелаShekhe, Ahmad Mustafa Abussalam b. "Microstructure and corrosion characteristics of excimer laser melted elektron 21-T6 rare-earth magnesium alloy." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/microstructure-and-corrosion-characteristics-of-excimer-laser-melted-elektron-21t6-rareearth-magnesium-alloy(e352ad12-9362-41e2-bd0c-a1eebc3f4e92).html.
Повний текст джерелаBasu, Indranil [Verfasser], Günter [Akademischer Betreuer] Gottstein, and Brita Daniela [Akademischer Betreuer] Zander. "Recrystallization mechanisms in wrought magnesium alloys containing rare-earth elements / Indranil Basu ; Günter Gottstein, Brita Daniela Zander." Aachen : Universitätsbibliothek der RWTH Aachen, 2016. http://d-nb.info/1130871770/34.
Повний текст джерелаSilva, Campos Maria del Rosario [Verfasser]. "The role of intermetallic phases in the corrosion of magnesium-rare earth alloys / Maria del Rosario Silva Campos." Hamburg : Universitätsbibliothek der Technischen Universität Hamburg-Harburg, 2016. http://d-nb.info/1114820385/34.
Повний текст джерелаApps, Peter Joseph. "The effects of the rare earth elements yttrium, gadolinium and dysprosium on the microstructure and properties of precipitation hardening magnesium alloys." Thesis, University of Manchester, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488095.
Повний текст джерелаZARPELON, LIA M. "Estudo das características eletroquímicas e microestruturais de eletrodos de hidreto metálico à base de LaNi com adições de elementos de liga." reponame:Repositório Institucional do IPEN, 2016. http://repositorio.ipen.br:8080/xmlui/handle/123456789/27133.
Повний текст джерелаMade available in DSpace on 2017-03-10T15:20:01Z (GMT). No. of bitstreams: 1 22060.pdf: 3959215 bytes, checksum: 0a58b276270c30e02d2f6935bafba229 (MD5)
Neste trabalho avaliou-se a ação positiva da substituição de lantânio por praseodímio e de lantânio por magnésio na performance eletroquímica de eletrodos de ligas de armazenamento de hidrogênio em estado bruto de fusão e com tratamento térmico. O La foi substituído por Mg nas ligas La0,7-xMgxPr0,3Al0,3Mn0,4Co0,5Ni3,8 (x=0,0-0,7) e por Pr nas ligas La0,7-yPryMg0,3Al0,3Mn0,4Co0,5Ni3,8 (y=0,0-0,7). Os parâmetros eletroquímicos analisados foram ativação, capacidade de descarga, retenção da capacidade de descarga, autodescarga e alta taxa de descarga. As ligas apresentaram comportamento passivo em relação à corrosão. As análises por MEV/EDS e por DRX com refinamento por Rietveld revelaram a presença majoritária de fases similares às fases LaNi5, PrNi5, LaMg2Ni9 e PrMg2Ni9 em função das composições das ligas estudadas. Os parâmetros de rede e os volumes da célula unitária das fases diminuíram com a substituição crescente de La por Mg e de La por Pr. As capacidades de descarga máxima decresceram com a substituição crescente de La por Mg e de La por Pr, acompanhando o decréscimo da abundância da fase similar à fase LaNi5 e o aumento da abundância da fase similar à fase LaMg2Ni9. Comparativamente, menores taxas de autodescarga e maior estabilidade cíclica foram observadas para o eletrodo da liga na condição x=0,1, ao passo que o eletrodo da liga na condição y=0,0 apresentou maiores valores de alta taxa de descarga, indicando melhor performance cinética.
Tese (Doutorado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
Buzolin, Ricardo Henrique. "Mechanical properties and corrosion behaviours of the as-cast ZK40 alloys modified with individual additions of CaO, Gd, Nd and Y." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/18/18158/tde-13012017-093623/.
Повний текст джерелаO efeito da adição individual de óxido de cálcio (CaO), Gd, Nd e Y foi investigado na microestrutura, propriedades mecânicas e resistência à corrosão de ligas ZK40 fundidas. As características microestruturais foram analisadas via microscopia óptica, microscopia eletrônica de varredura, microscopia eletrônica de transmissão, difração de Raios-X e \"Scanning Kelvin Atomic Probe Force Microscopy\". O comportamento à compressão e à tração das ligas à temperatura ambiente foi investigado. Espectroscopia eletroquímica de impedância, evolução de hidrogênio e ensaios de imersão em solução de 0.5% em peso de NaCl foram utilizados para avaliar a resistência à corrosão. Os resultados dos ensaios mecânicos e corrosão foram relacionados com a microestrutura. A adição de 2% em peso de Gd melhorou a ductilidade, ao passo que a adição de Nd resultou na piora das propriedades mecânicas. A adição de 2% em peso de Gd e 1% em peso de Y resultou na melhora da ductilidade. A adição de 1% em peso de Y causou uma melhora na ductilidade e a adição de CaO não teve impacto benéfico nas propriedades mecânicas. A resistência à corrosão foi melhorada com a adição de CaO e Gd. A modificação da liga ZK40 com a adição de Gd abre novas perspectivas no desenvolvimento de ligas Mg-Zn.
Brownsmith, Tomas. "Thermomechanical processing of magnesium alloy Elektron 43." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/thermomechanical-processing-of-magnesium-alloy-elektron-43(460a4e6e-1744-4f6f-b056-ba8f93920a04).html.
Повний текст джерелаKao, Vincent, and 高銘辰. "Micro-arc anodizing of magnesium-lithium alloys add rare-earth element." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/94582263154077992325.
Повний текст джерела國立中央大學
機械工程研究所
96
This research tries to improve corrosion resistance of LAZ1110, LAZ1110 +Be, LAZ1110 +Sc, LAZ1110 +Be +Sc magnesium alloys by means of micro-arc anodizing. In the experiment, the electrolytic solution is composed of 40gl-1 Na2SiO3, 100gl-1 NaOH, 20gl-1 NaPO2and 80gl-1(COOH)2.2H2O in distilled water. After the micro-arc anodizing treatment, it will discuss to various parameters. The results indicated that the anodic oxidation film has better corrosion performance under the pulse current condition. In four materials of LAZ1110, LAZ1110 +Be, LAZ1110 +Sc, LAZ1110 +Be +Sc magnesium alloys, LAZ1110 +Be have the worst of corrosion resistance, and LAZ1110 +Sc have the best of corrosion resistance, in the basic extrapolate, add the Be element have decrease the oxidation on the magnesium alloys surface, this phenomenon destroy the anodic oxidation film of LAZ1110 +Be during micro-arc anodizing treatment, add the Sc element have increase the effect of corrosion resistance. Temperature, frequency, time, current density, duty cycle and electrolytic concentration have an influence on micro-structure and corrosion performance of anodic films. In our research, it fixed current density and another parameter, and it used various of time parameter to find out the best operate condition, the results indicated that at 8min of operate condition of micro-arc anodizing treatment have the best of anodic oxidation film.
Jain, Chao-Chi, and 簡朝棋. "The Study of Creep Behavior and Weld Properties of Rare Earth Containing Magnesium Alloys." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/81047496173366425340.
Повний текст джерела國立臺灣大學
材料科學與工程學研究所
95
In this study, the effect of RE content on the microstructure, creep behavior, weld and corrosion properties of Mg-8Al-xRE (x=0, 1, 2 or 3 wt.%) alloys were investigated. The alloys were prepared by melting and casting in a vacuum induction melting furnace in an atmosphere of argon gas. Chemical analysis of the alloys was performed by inductively coupled plasma-atomic emission spectrometer (ICP-AES). To avoid the possible casting defects, such as micro-pore or micro-segregation, the cast ingots were indirect hot extrusion to remove the cast-defects. The microstructural analysis and phase characterizations of alloys were performed by optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM), and X-ray diffraction (XRD). The fracture surfaces of crept specimens were examined by SEM. Corrosion tests were carried out by potentiodynamic polarization and immersion tests. The study of weld property was accomplished by tungsten-arc inert gas and CO2 laser beam welding. The microstructure analysis, mechanical properties, and corrosion properties of welded specimens were investigated. The microstructure of Mg-8Al alloy with 1-3 wt.% RE additions were conducted: (i) The as-extruded Mg-8Al-xRE alloys consisted of α-Mg matrix, with β (Mg17Al12) and Al11RE3 compounds. (ii) Raising the extent of RE in the alloy also increases the amount and coarsening of the Al11RE3 compounds, but the amount of β phase diminishes and turns into the fine particles. The creep rupture life increment measured at 150℃ is around 40-100 MPa, and the creep rupture life over 150℃ is also prolonged. The marked improvement of the high-temperature tensile creep properties is attributed to the fine rod-like Al11RE3 compound having high thermal stability in the alloys. The stress exponent of the Mg-8Al-xRE alloys is approximately 2, which suggested the creep mechanism of the alloys is controlled by the grain boundary sliding. The creep activation energy of Mg-8Al and Mg-8Al-2RE alloys are 114 and 104 kJ mol-1, respectively. In addition, the aluminum content also has great effects on the creep property of the Mg-Al alloy; when comparing the AZ31-1RE with the Mg-8Al-1RE alloys. The creep resistance of the AZ31-1RE is inferior to that of the Mg-8Al-1RE, as the applied load is high; at either higher or lower test temperature. On the contrary, the creep resistance of the AZ31-1RE is superior to that of the Mg-8Al-1RE, as the applied load is low at any test temperature. Therefore, the effect of aluminum content on the creep properties of Mg-Al alloy is great. The close-grain boundary microstructure of pose-crept Mg-8Al shows that high volume fraction of lamellar β precipitates close-grain boundaries during the creeping. Since the lamellar precipitation occurring during the creeping may effectively multiply the grain boundary area available for easy deformation by grain boundary sliding through the elevated temperature creep. Therefore the creep resistance of Mg-8Al is poor at elevated temperature. Oppositely, no significant change in the microstructure morphology after creep exposure has been observed in the RE-containing alloys. The addition of RE to the Mg-8Al alloy forms the Al11RE3 intermetallic phase, which may suppress the precipitation of lamellar β phase during the creep test. Consequently, the sliding of grain boundaries and the slip of dislocations in the matrix are effectively prevented at elevated temperature, improving the creep resistance of Mg-8Al base alloy. The optimization welding parameters of TIG welding are current 110 A and welding speed 7 m/min. Because the TIG welding has low energy density and high heat input characteristics, the macrostructure of welded Mg-8Al-xRE alloys possess three clearly distinguished regions, including weld metal, heat-affected zone, and parent metal. The aspect ratio of the weld pool is low, about 0.5. Microstructure of weld metal is refined with the increased RE content; and a lot of needle-like or rod-like RE-containing compounds precipitated. The join efficiency is approximate 85%, and the bonding strength is increased with the increasing RE content. However, when the RE content over 2 wt.%, the strength is decreased. The hardness of weld metal is lower than the parent metal, and close to the heat-affected zone. Corrosion rate of the alloy may slightly decrease with the increase of the added RE contents. The corrosion resistance of welded specimens is poor, comparing with the as-extruded alloys. The optimized welding parameters of CO2 laser beam welding are power 2.0 kW and welding speed 2,500 mm/s. The CO2 laser beam welding has high energy density and low heat input characteristics, so the cooling rate of the weld metal is high. The microstructure of the welds is finer than that of TIG welding; and no obviously heat-affected zone is observed, which is due to the laser welded alloys owns fine structure, thus the hardness is higher than that of the TIG welded alloy. In this study, the hardness of the welded metal is slightly lower than that of the parent metal. The aspect ratio of the laser welds is higher than that of the TIG welding, which is about 1.5.
Hung, Ting dung, and 洪廷東. "Study the Growth Mechanism and Corrosion Resistance of Rare Earth Magnesium Alloy Conversion Coating." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/89660247296225491143.
Повний текст джерела大葉大學
機械與自動化工程學系
101
In this pursuit of lightness, versatility and recycling generation, magnesium alloys have been increasingly used in products of various fields, which is due to its low specific gravity, high specific strength and specific stiffness, good electromagnetic shielding and high recycling rates, etc. However, due to the nature of great activity, poor electrochemical performance, it is vulnerable to corrode by environment, therefore, appropriate surface treatment is generally required to impart corrosion-prevention function to magnesium metal. In this conversion treatment study, the AZ80A magnesium alloy plate with yttrium element containing as the experimental substrates, and this research divide into two stages. The first stage selects six types of conversion solution which commonly used in industries, under the selected conversion temperature to carry out with different immersion times, and then to observe the surface morphology by SEM and examine the corrosion current density of coating layer. The second stage is to carry out with different drying processes, and investigate the influences of corrosion resistance with drying methods. The first stage experimental results show that the conversion treatment with pH=3.5 manganate solution (nitric acid) for 10 minutes, and pH=9 vanadate solution for 5 minutes have the best corrosion resistance data and adequate coating morphology. It is because that coating completely covered with specimen in a short time, with intense and moderate thickness, also without found crack penetrating into substrate, which is believed to be beneficial to following adhesion processing. The results of second stage experiment (natural shade-drying or oven air-drying) show that all coating layers have relatively flat status without obvious cracks. Only the manganate layer separate out more precipitated phase rich with manganese during oven air-drying processing; believing the precipitated phase may affect the corrosion resistance performance. However, the morphology of vanadate coatings treats with different drying ways showing quite similar, which results in the same corrosion resistance behavior. From a viewpoint of the industrial manufacturing process demand (corrosion resistance and production rate), recommend to use pH=9 vanadate conversion solution for such AZ80A rare earth magnesium alloy, select 60℃with 5 minutes immersion time, and choose the method of 25℃oven air-drying 20 minutes for rapid drying, which should be the best combination of processing parameters. It is believed that can not only effectively improve the production rate, but also maintain the quality and economic benefit.
Chen, Guan-Ting, and 陳冠廷. "To Study the Effect of Aging Treatment on Fatigue Resistance Properties of Rare Earth Magnesium Alloy Welds." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/15660535440863060100.
Повний текст джерела大葉大學
醫療器材設計與材料碩士學位學程
104
Consumer demand on products has risen with today’s technological improvement. To adhere to the varying needs, products have evolved from the thick and heavy materials to thin and light materials that are fashionably appealing. To account for environmental protection, material selection and use must exhibit the characteristics of lower pollution and emission, lower power consumption, higher energy efficiency, and high recycle and renewability. Thus, magnesium alloys have become an essential and emergent material. According to industrial needs for fatigue-resistance and light-weight materials. This study applied solid-solution aging treatment in AZ80A extruded magnesium sheet with yttrium (0.25 wt.%) addition, and explored the influence on mechanical and fatigue-resistance properties of this alloy. By applying gas tungsten arc welding, adjusting the aging treatment parameters, and using the S-N curve obtained from fatigue tests, this study determined the optimal aging parameters for predicting the change in durability of such magnesium welds under various stress states. From experimental results show that administering 32 ampere current will completely penetrate the 2.6 mm sheet, and exhibit the optimal welding heat input control. The weld also exist favorable performance in mechanical properties. Thus, this current value was used as the welding current value in subsequent welding for investigating the aging treatment. To examine the microstructure of aged welding sheets revealed that the amount of precipitate increased with increasing aging time, which in turn of enhanced the hardness. The types of precipitate from the aging-treated welds were quite similar. However, differences were observed in shape at different aging times. Under short aging treatment period, the continuous layer-shaped precipitate assisted more evidently in enhancing the tensile strength and hardness of weld. However, it had a detrimental influence on elongation. Rod-shaped precipitates were uniformly precipitated inside the grains with increasing aging time, but these precipitates did not enhance weld strength. In addition, the continuous increase in precipitate negatively affected the elongation. Properties of fatigue resistance were evidently enhanced with increasing the aging time. After aging, the β phase particles exhibited delayed crack growth and hindered dislocation movement. Especially, precipitates obtained with 8 hours treatment evidently enhanced the weld fatigue strength, but those obtained after 16 hours did not and instead exhibited a decreasing trend. Although the mechanical properties and S-N fatigue curve performance were less favorable than those of the original extruded material. However, for applying this type of rare-earth AZ80A alloys to industrials, recommended to use gas tungsten arc welding processes with AC current output should obtain favorable mechanical properties. Regarding post-weld aging treatment, one could apply quenching after 400°C、1 hours solid solution, and followed by aging treatment at 200°C for 8 hours, may effectively enhance weld strength.
SU, Sheng-Hao, and 蘇聖皓. "Effect of Pulsing Current and Aging Treatment on Microstructure and Mechanical Properties of Rare Earth Magnesium Alloy Welds." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/20135466126373742066.
Повний текст джерела大葉大學
機械與自動化工程學系
101
Due to the highly development of technology, consumers have extended the requests of product from functional oriented to higher quality and light weight property. Also, according to the environmental awareness, the material’s selection, such as reducing pollution emission, improving fuel efficiency and high recycling ratio, are considered to fabricate the products. Therefore, magnesium alloys become the dominant material in new generation. Research was carried out the TIG weld and post-weld heat treatment on yttrium containing AZ80 magnesium alloy plate. By changing the frequency of pulsing current and heat treating parameters, to find the best combination of pulsing frequency and precipitating mechanism enhance the weld quality of this types magnesium alloys. From experimental results shown, with increasing the frequency of pulse current, grain was refined on the fusion zone which will also reveal from the mechanical properties, especially at the frequency of 9 Hz has the best performance than other parameters. Therefore, welds with 9 Hz and 0 Hz frequency were selected to study the difference in the following post-weld aging treatment experiment. Types of precipitates on 0 Hz and 9 Hz aging weld are quite similar. In short aging time, the discontinuous layer-shaped precipitates are able to enhance the hardness and tensile strength of welds, but show inferior influence to elongation. Further increasing the aging time, the short-rod-shaped and mat-shaped precipitates will uniformly precipitate inside the grain, but these precipitates unable to further increase the strength of weld, and the elongation is still decreasing. Based on experimental results, selecting 9 Hz pulse current can obtain better mechanical properties in this rare earth containing AZ80 magnesium alloy TIG weld. For post-weld aging treatment, choosing 400℃- 1 hour for solid solution and following with 200℃- 8 hours for aging treatment, can effectively improve the strength of pulsed weld.