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Fernández, Gustavo Jorge. "Proceso de extrusión de la aleación de Magnesio AZ91D." Bachelor's thesis, Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Escuela de Ingeniería Aeronáutica, 2016. http://hdl.handle.net/11086/5577.
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Proyecto Integrador (IA)--FCEFN-UNC, 2016Analiza la posibilidad de deformación plástica de la Aleación de Magnesio AZ91D, obtenida a partir de un proceso de re fusión de virutas de mecanizado. Los ensayos consisten en someter este material a un proceso de extrusión en caliente, para lo cual se realiza un estudio completo del material, del proceso de extrusión, se diseña un dispositivo para extruir y se desarrolla una metodología de trabajo. Los resultados muestran que el material se deforma plásticamente bajo la acción de cargas de compresión a alta temperatura.
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Milne, Rodrigo. "Recuperación pulvimetalúrgica de aleación de magnesio AZ91D con fines estructurales." Bachelor's thesis, Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Escuela de Ingeniería Aeronáutica, 2015. http://hdl.handle.net/11086/2201.
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Proyecto Integrador (IA)--FCEFN-UNC, 2015Desarrolla un método que permite la recuperación de la viruta de aleación de magnesio AZ91D, producto del mecanizado de carcasas de cajas de velocidades, mediante técnicas de pulvimetalurgia con la finalidad de poder aplicarse en componentes estructurales aeroespaciales. Se propone estudiar el efecto que poseen las variables más importantes del proceso sobre las propiedades mecánicas de la pieza final.
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Dini, Hoda. "As-cast AZ91D Magnesium Alloy Properties- Effect of Microstructure and Temperature." Licentiate thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH. Forskningsmiljö Material och tillverkning – Gjutning, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-28467.
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Magnesium and magnesium alloys are used in a wide variety of structural applications including automotive, aerospace, hand tools and electronic industries thanks to their light weight, high specific strength, adequate corrosion resistance and good castability. Al and Zn are the primary alloying elements in commercial Mg alloys and commonly used in automotive industries. AZ91 is one of the most popular Mg alloys containing 9% Al and 1% Zn. Hence, lots of research have been done during last decades on AZ91D. However, the existing data concerning mechanical properties and microstructural features showed large scatter and is even contradictory. This work focused on the correlation between the microstructure and the mechanical properties of as-cast AZ91 alloy. An exhaustive characterization of the grain size, secondary dendrite arm spacing (SDAS) distribution, and fraction of Mg17Al12 using optical and electron backscattered diffraction (EBSD) was performed. These microstructural parameters were correlated to offset yield point (Rp0.2), fracture strength and elongation to fracture. It was understood that the intermetallic phase, Mg17Al12, plays an important role in determining the mechanical and physical properties of the alloy at temperature range from room temperature up to 190oC. It was realized that by increasing the Mg17Al12 content above 11% a network of intermetallic may form. During deformation this rigid network should break before any plastic deformation happen. Hence, increase in Mg17Al12 content resulted in an increase in offset yield point. The presence of this network was supported by study of thermal expansion behaviour of the alloy containing different amount of Mg17Al12. A physically-based model was adapted and validated in order to predict the flow stress behaviour of as-cast AZ91D at room temperature up to 190ºC for various microstructures. The model was based on dislocation glide and climb in a single-phase (matrix) material containing reinforcing particles. The temperature dependant variables of the model were quite well correlated to the underlying physics of the material.
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Liu, Guojun. "A study on twin-screw rheo-diecasting of AZ91D Mg-alloy." Thesis, Brunel University, 2006. http://bura.brunel.ac.uk/handle/2438/5227.
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A newly developed one-step semisolid process by BCAST for semisolid processing of magnesium alloy was studied in this thesis - the Twin-Screw Rheo-Diecasting (RDC) of AZ91D Mg-alloy. The RDC process is an innovative process which combines the dispersive mixing power of the Twin-Screw Slurry Maker (TSSM) for creation of high quality semisolid slurry and the existing cold chamber High-Pressure Die-Casting (HPDC) process for component shaping. Magnesium alloys, due to their low density and superior strength/weight ratio, offer distinct advantages in weight savings, and are gaining increasing interests in applications. The research on the new RDC technology aimed to eliminate the limitations of the conventional HPDC and to meet the requirements from extensive application of Mg-alloys. In this thesis, the major tasks were to optimise of the RDC technology, to evaluate the microstructure and mechanical properties of RDC AZ91D Mg-alloy in both as-cast and heat treated conditions, and to understand the solidification process in the TSSM. The results of the RDC as-cast state indicated that the microstructure of primary a-Mg particles had a fine size (around 40μm), extremely spherical morphology and uniform distribution throughout the entire castings; the RDC AZ91D samples had extremely low levels of porosity. Due to the unique microstructure and much reduced level of defects, the RDC AZ91D alloy exhibited a substantial improvement in mechanical properties. In addition, a traditional full heat treatment was performed for RDC AZ91D alloy. Compared with HPDC alloy, the RDC AZ91D alloy was found to exhibit an accelerated dissolution of ß-Mg17A112during solution treatment, and a faster age-hardening kinetics of the ß-phase during subsequent ageing. The microstructural investigations showed that under intensive forced convection, heterogeneous nucleation occurred continuously throughout the entire volume of the solidifying melt and the nuclei grew spherically. Ostwald ripening took place by dissolution of the smaller particles but at a very slow coarsening rate. Increasing the intensity of forced convection enhanced nucleation and reduced volume fraction of primary phase solidified in the slurry maker. This study has demonstrated that the novel RDC process possesses a number of advantages and it is suitable for production of high integrity Mg-alloy components.
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Dini, Hoda. "As-cast AZ91D magnesium alloy properties : Effects of microstructure and temperature." Doctoral thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH, Material och tillverkning, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-38148.
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Today, there is an essential need for lightweight, energy-efficient, environmentally benign engineering systems, and this is the driving force behind the development of a wide range of structural and functional materials for energy generation, energy storage, propulsion, and transportation. These challenges have motivated the use of magnesium alloys for lightweight structural systems. Magnesium has a density of 1.74 g/cm3, which is almost 30% less than that of aluminium, one quarter of steel, and almost identicalto polymers. The ease of recycling magnesium alloys as compared to polymers makes them environmentally attractive, but their poor mechanical performance is the primary reason for the limited adoption of these alloys for structural applications. The Mg-Al-Zn alloy AZ91D exhibits an excellent combination of strength, die-castability, and corrosion resistance. However, its mechanical performance with regard to creep strength, for example, at evaluated temperatures is poor. Moreover, very little is known about the correlation between its mechanical properties and microstructural features. This thesis aims to provide new knowledge regarding the role played by microstructure in the mechanical performance of the magnesium alloy. The properties/performance of the material in relation to process parameters became of great interest during the investigation. An exhaustive characterisation of the grain size, secondary dendrite arm spacing (SDAS) distribution, and fraction of Mg17Al12 was performed using optical and electron backscatter diffraction (EBSD). These microstructural parameters were correlated to the offset yield point (Rp0.2), fracture strength, and elongation to failure of the material. It was proposed that the intermetallic phase, Mg17Al12, plays an important role in determining the mechanical and physical properties of the alloy in a temperature range of room temperature to 190°C by forming a rigid network of intermetallic. The presence of this network was confirmed by studying the thermal expansion behaviour of samples of the alloy containing different amounts of Mg17Al12. A physically based constitutive model with a wide validity range was successfully adapted to describe the flow stress behaviour of AZ91D with various microstructures. The temperature-dependent variables of the model correlated quite well with the underlying physics of the material. The model was validated through comparison with dislocation densities obtained using EBSD. The influence of high-pressure die-cast parameters on the distortion and residual stress of the cast components was studied, as were distortion and residual stress in components after shot peening and painting. Interestingly, it was found that intensification pressure has a major effect on distortion and residual stresses, and that the temperature of the fixed half of the die had a slight influence on the component's distortion and residual stress.Numera finns det ett väsentligt behov av lätta, energieffektiva och miljövänliga tekniksystem. Detta behov är drivkraften för utveckling av ett brett utbud av material för energigenerering, energilagring, framdrivning och transport. Dessa utmaningar motiverade användningen av magnesiumlegeringar för lättviktskonstruktioner. Magnesium har en densitet på 1,74 g/cm3, vilket är ca 30% lägre än för aluminium, en fjärdedel av densiteten för stål och nästan i nivå med många polymerer. Då magnesiumlegeringar dessutom är lätta att återvinna, jämfört med polymerer, gör det dem miljömässigt attraktiva. Låga mekaniska egenskaper är den främsta orsaken till begränsad användning av dessa legeringar för lastbärande tillämpningar. Mg-Al-Zn-legeringen AZ91D uppvisar en utmärkt kombination av styrka, gjutbarhet och korrosionsbeständighet. Dess mekaniska egenskaper vid förhöjd temperatur, som tex kryphållfasthet, är låga. Dessutom är korrelationen mellan mikrostruktur och mekaniska egenskaper oklar. Denna avhandling syftade till att ge ny kunskap om mikrostrukturens roll för magnesiumlegeringars mekaniska egenskaper. Slutligen var materialets egenskaper i förhållande till processparametrar vid tillverkningen av stort intresse. En omfattande karaktärisering av kornstorleks-, sekundära dendritarmavstånds (SDAS)-fördelning och fraktion av Mg17Al12 utfördes med hjälp av optisk mikroskopering och diffraktion av bakåtspridda elektroner (EBSD). Mikrostrukturen korrelerades till sträckgränsen (Rp0.2), brottstyrkan och brottförlängningen. Det föreslogs att den intermetalliska fasen, Mg17Al12, spelar en viktig roll vid bestämning av legeringens mekaniska och fysikaliska egenskaper vid temperaturintervall från rumstemperatur upp till 190°C genom att bilda ett styvt nätverk av intermetaller. Uppkomsten av ett sådant nätverk stöddes genom en studie av den termiska expansionen av legeringen för olika fraktioner av Mg17Al12. En fysikalisk konstitutiv modell med ett brett giltighetsområde användes framgångsrikt för att beskriva det plastiska flytbeteendet hos AZ91D för olika mikrostrukturer. De temperaturberoende variablerna i modellen korrelerade ganska väl med materialets underliggande fysik. Modellen validerades genom att jämföra dislokationstätheten som predikterades av modellen och den med EBSD uppmätta dislokationstätheten. Påverkan av pressgjutningsparametrar på geometrisk tolerans och restspänning hos de gjutna komponenterna studerades. Vidare studerades geometrisk tolerans och restspänning av komponenter efter pening och målning. Intressant nog hade eftermatningsfasen en stor effekt på geometrisk tolerans och restspänningar. Dessutom hade temperaturen på den fasta formhalvan av verktyget även ett visst inflytande på komponentens geometriska tolerans och restspänning.
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Cavallo, María Sara, and Mariana Lucía Flores. "Recubrimientos biodegradables para AZ91D, evaluación del desempeño en fluido fisiológico simulado." Bachelor's thesis, Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales, 2017. http://hdl.handle.net/11086/6491.
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Proyecto Integrador (I.Biom.)--FCEFN-UNC, 2017Realiza la aplicación de técnicas para generar recubrimientos sobre muestras de aleación de magnesio AZ)!D con la finalidad de evaluar el carácter protector frente a la corrosión en un medio fisiológico simulado. Enmarcado en el uso del magnesio y sus aleaciones como metales para implantes biodegradables
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戴有志 and Yo-Zhi Dai. "鎂基複合材料AZ91D/SiCp之磨耗研究." 碩士, 國立中正大學, 1995. http://ndltd.ncl.edu.tw/cgi-bin/gs32/gsweb.cgi/login?o=dnclcdr&s=id=%22095CCU05311078%22.&searchmode=basic.
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Paradis, Mathieu. "Évaluation et identification des inclusions dans les alliages de magnésium AM50A et AZ91D." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2003. http://theses.uqac.ca.
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Ribeiro, Eloana Patrícia. "Desenvolvimento de revestimentos de conversão à base de cério em liga de magnésio AZ91D." reponame:Repositório Institucional da UFABC, 2017.
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Orientador: Prof. Dr. Renato Altobelli AntunesDissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Nanociências e Materiais Avançados, 2017.
Neste estudo foram avaliadas três técnicas de dispersão para o processamento de nanocompósitos de matriz de epóxi com nanopartículas de diferentes geometrias: lamelares, fibrilares e esféricas. Para isso, foram preparados nanocompósitos com montmorilonita, laponita, nanotubos de haloisita, nanotubos de carbono e nanossílica por meio de mistura mecânica, sonicação e moagem de alta energia. A dispersão das nanopartículas na matriz foi avaliada por microscopia eletrônica de varredura, difração de raios X e espalhamento de raios x a baixo ângulo. Os resultados mostraram que o processo de sonicação foi o melhor para dispersar as nanopartículas em epóxi, sendo, portanto, utilizado para a fabricação de nanocompósitos híbridos com matriz de epóxi. Esses materiais apresentam duas fases sólidas nanométricas dispersas na matriz e, neste estudo, foram combinadas nanopartículas de diferentes geometrias, a fim de avaliar as propriedades mecânicas e reológicas dos híbridos e compará-las com as dos nanocompósitos com apenas uma nanopartícula (nanocompósitos convencionais). As propriedades mecânicas foram medidas por meio de ensaios de resistência à flexão, de resistência ao impacto (Izod) e análise dinâmico-mecânica. As propriedades reológicas foram medidas por meio de ensaios de cisalhamento oscilatório de pequenas amplitudes das dispersões não curadas. Com exceção da ductilidade, os nanocompósitos convencionais exibiram propriedades inferiores às da matriz. Já os nanocompósitos híbridos apresentaram propriedades mecânicas superiores às dos nanocompósitos convencionais, e em alguns casos, superiores às da matriz, indicando algum nível de efeito sinergético entre as nanopartículas. As propriedades reológicas das dispersões não curadas indicaram que algumas partículas apresentaram boa dispersão na matriz, antes do processo de cura. Contudo, tal característica não foi convertida em ganhos reais de propriedades mecânicas e os nanocompósitos correspondentes exibiram propriedades muito similares às das amostras supostamente mal dispersas. Esse foi um indicativo de que as propriedades finais dos nanocompósitos foram essencialmente determinadas pelos parâmetros envolvidos no processo de cura do material.
In this study, three dispersion techniques were evaluated for the processing of nanocomposites with epoxy matrix and nanoparticles with different geometries: lamellar, fibrillar and spherical. Therefore, nanocomposites with montmorillonite, laponite, halloysite nanotubes, carbon nanotubes and nanosilica were prepared via magnetic stirring, sonication and high energy milling. The dispersion of the nanoparticles in the epoxy matrix was evaluated using scanning electron microscopy, X-ray diffraction and small angle X-ray scattering. The results showed that sonication was the best method to disperse the nanoparticles in epoxy. Thus, it was used to manufacture hybrid nanocomposites with epoxy matrix. These materials have two different nanometric solid phases, dispersed in the matrix and, in this study, nanoparticles of different geometries were combined, aiming to evaluate the mechanical and rheological properties of the hybrids and compare them to those of the nanocomposites which have only one nanoparticle (conventional nanocomposites). The mechanical properties of the nanocomposites were evaluated through flexural testing, impact strength (Izod) and dynamic-mechanical analysis. The rheological properties were measured by small amplitude oscillatory shear tests of the uncured dispersions. Apart from ductility, the conventional nanocomposites showed inferior properties to those of the matrix. However, the hybrid nanocomposites exhibited superior properties to those of conventional nanocomposites and in some cases, even superior to those of the matrix, suggesting some level of synergistic effects between the nanoparticles. The rheological properties of the uncured dispersions indicated that some particles had good dispersion in the matrix, prior to the curing process. However, such feature was not converted into real gains on mechanical properties and the corresponding nanocomposites exhibited very similar properties to the supposedly poorly dispersed samples. This was an indicative that the final properties of nanocomposites were essentially determined by the parameters involved in the material curing process.
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Fritzsch, Katja. "Beitrag zur Verbesserung des Korrosions- und Verschleißverhaltens der Magnesiumlegierung AZ91D mittels lokaler Elektronenstrahl-Flüssigphasen-Randschichtbehandlung." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2018. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-232556.
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Magnesiumwerkstoffe sind aufgrund ihrer geringen Dichte und hohen spezifischen Festigkeit für den Leichtbau prädestiniert. Ziel der vorgelegten Arbeit ist es, durch die gleichzeitige Verbesserung des Korrosions- und Verschleißverhaltens neue Anwendungsfelder für Magnesiumlegierungen zu erschließen. Anhand der Magnesiumlegierung AZ91D wurden die Möglichkeiten einer lokalen beanspruchungsgerechten Modifikation von Struktur und Gefüge im oberflächennahen Bereich durch eine Elektronenstrahl(EB)-Flüssigphasen-Randschichtbehandlung ohne Zusatzstoff (EB-Umschmelzen) und unter Verwendung von Al-Si-Zusatzstoffen (EB-Umschmelzlegieren) aufgezeigt. Die mittels verschiedener hochfrequenter Strahlablenktechniken erzeugten Schichten weisen eine deutliche Gefügefeinung, neue Gefügemorphologien sowie eine veränderte Phasenverteilung und/oder -neubildung auf, sind riss- und porenfrei und haben eine ausgezeichnete schmelzmetallurgische Anbindung an den Grundwerkstoff. Anhand von Tauchversuchen und potentiodynamischen Polarisationsmessungen in verschieden konzentrierten NaCl-Lösungen konnte eine signifikante Verbesserung des Korrosionsverhaltens der generierten Schichten im Vergleich zum Ausgangszustand nachgewiesen werden. EB-umschmelzlegierte Schichten weisen im Ergebnis von Trockenverschleißtests (Stift-Scheibe) eine deutliche Reduzierung des spezifischen Verschleißkoeffizienten auf.
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La, Sala Carlos Alberto, and Maximiliano Omar Solis. "Obtención y caracterización de espuma metálica a partir de viruta de aleación de Magnesio AZ91D." Bachelor's thesis, Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales, 2016. http://hdl.handle.net/11086/4767.
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Proyecto Integrador (IM)--FCEFN-UNC, 2016Desarrolla un método pulvimetalúrgico que permita la obtención de una espuma metálica en base magnesio que sirva para aplicaciones de absorción de energía, más específicamente de relleno de paneles sándwich, utilizando como material de partida viruta de aleación de magnesio AZ91D
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Russo, James. "The Effects of Laser Shock Peening on the Residual Stress and Corrosion Characteristics of Magnesium Alloy AZ91D for use as Biodegradable Implants." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1354550566.
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Fritzsch, Katja [Verfasser], Rolf [Akademischer Betreuer] Zenker, Rolf [Gutachter] Zenker, and Olaf [Gutachter] Keßler. "Beitrag zur Verbesserung des Korrosions- und Verschleißverhaltens der Magnesiumlegierung AZ91D mittels lokaler Elektronenstrahl-Flüssigphasen-Randschichtbehandlung / Katja Fritzsch ; Gutachter: Rolf Zenker, Olaf Keßler ; Betreuer: Rolf Zenker." Freiberg : Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2018. http://d-nb.info/1221070126/34.
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Azad, Amit. "Grain refinement of magnesium alloy AZ91E." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/42280.
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Spark Plasma Sintering (SPS) process has been used to develop a novel grain refiner Al-SiC master alloy for AZ91E Mg alloys. When the Al-SiC master alloy was added to molten AZ91E alloy, the Al matrix melted and allowed the SiC particles to distribute homogeneously throughout the molten AZ91E alloy. After addition of 0.1 wt.% Al-SiC master alloy to AZ91E alloy, the mean grain size decreased from 227.5 ± 5.0 µm to 197.5 ± 5.0 µm; however, the mean grain size increased when the amount of added Al-SiC exceeded 0.1 wt.%. The grain refining and coarsening mechanisms were investigated using scanning electron microscope (SEM), energy dispersive spectroscopy (XEDS) and differential scanning calorimetry (DSC).
It is proposed that the binary carbides (e.g., MgC), possibly acted as heterogeneous nucleation sites for grain refinement. The formation of ineffective nuclei AlCMn₃ with the increased amount of grain refiner exceeding 0.1 wt.% Al-SiC has inhibited formation of MgC, resulting in grain coarsening. The effect of Al-SiC on the mean area percentage of β-Mg₁₇Al₁₂ phase and porosity were investigated using optical microscopy, while hardness was measured using a Rockwell hardness tester. It was found that increasing the addition of Al-SiC had an effect on β-phase and porosity. The highest mean area percentage of β-phase was found 6.6 ± 1.3 % with the addition of 1 wt.% Al-SiC, while the lowest mean area percentage of porosity was 1.9 ± 0.5 % with the addition of 0.1wt.% Al-SiC. It was found that adding the Al-SiC master alloy to AZ91E alloy had no influence on hardness.
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Sobola, Petr. "Únavová odolnost extrudované Mg-slitiny AZ91E." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-231941.
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This thesis deals with fatigue behaviour of magnesium alloy AZ91E produced by extrusion. In the frame of this work, basic mechanical characteristics and data from performed fatigue tests were obtained. Further metallographic analysis of microstructure and fractographic analysis of broken specimens after fatigue tests were carried out.
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Erchov, Sergej. "Research on the Mechanical Properties of the Sand Cast Magnesium Alloy AZ91 /." [S.l. : s.n.], 2001. https://fridolin.tu-freiberg.de/archiv/html/WerkstoffwissenschaftenErchovSerguei82974.html.
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Zeng, Ruilin. "Precipitation hardening in AZ91 magnesium alloy." Thesis, University of Birmingham, 2013. http://etheses.bham.ac.uk//id/eprint/4695/.
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The microstructure evolution of a sand cast AZ91 magnesium alloy during heat treatment (solution treatment and subsequent ageing) were characterized quantitatively using a combination of optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The area fraction of discontinuous precipitates and number density of continuous precipitates (N\(_V\)) in the AZ91 alloys with and without pre-deformation were measured using OM and TEM, respectively. Based on these metallurgical evidences, the existing precipitation strengthening mode for AZ91 was modified and the effect of pre-deformation on the precipitation strengthening of AZ91 was investigated. Al-Mn-(Mg) particles in the size range of 20-200 nm have been found in the as-cast AZ91. Their morphologies, chemical composition and structures were investigated using TEM. It was found that these particles have a chemical composition of (Al \(_6\)\(_.\)\(_5\)\(_2\)Mn) \(_1\)\(_-\)\(_x\)Mg\(_x\) (x < 0.13) and a decagonal quasi-crystalline structure. These particles were stable during a solution treatment and acted as preferential nucleation sites for continuous Mg\(_1\)\(_7\)Al\(_1\)\(_2\) precipitates during the subsequent ageing. The results obtained using two electron tomography (ET) approaches were also summarized in this thesis. One uses HAADF-STEM for Mg\(_1\)\(_7\)Al\(_1\)\(_2\) precipitates on Al-Mn-(Mg) particles. The other technique is BF-STEM applied to study Mg\(_1\)\(_7\)Al\(_1\)\(_2\) precipitates on the dislocations.
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Darida, Jiří. "Mechanické vlastnosti hořčíkové slitiny AZ91E připravené metodou ECAP." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2016. http://www.nusl.cz/ntk/nusl-254287.
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This thesis deals with mechanical and fatigue properties of magnesium alloy AZ91 processed by EX-ECAP method. This method involves the application of extrusion followed by equal-channel angular pressing. To obtain basic mechanical characteristics, the tensile test were carried out at room and elevated temperatures. Further the fatigue tests were performed and obtained data were used to compile S-N curve. The work also includes metallographics analysis of microstructure and fractographic analysis of fracture surfaces of tensile and fatigue test specimens.
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Krauss, Martin. "Zur thermischen Ermüdung der Magnesiumbasislegierungen AZ31 und AZ91." Kassel Kassel Univ. Press, 2006. http://deposit.d-nb.de/cgi-bin/dokserv?id=2912633&prov=M&dok_var=1&dok_ext=htm.
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Krauß, Martin. "Zur thermischen Ermüdung der Magnesiumbasislegierungen AZ31 und AZ91." Kassel : Kassel Univ. Press, 2007. http://nbn-resolving.de/urn:nbn:de:0002-2686.
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Esho, Faris Nora. "Creep Properties of Magnesium Alloys AE44 and AZ91." Thesis, Högskolan i Jönköping, Tekniska Högskolan, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-44261.
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Al-Zubaydi, Ahmed. "High-pressure torsion processing of AZ91 magnesium alloy." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/386345/.
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AZ91 magnesium alloy has been successfully processed at room temperature by high–pressure torsion as well as at elevated temperatures. Ultrafine grains and nano–sized particles of β–phase have developed with increasing number of turns. The hydrostatic pressure, the geometry of the processing zone and the unidirectional nature of torsional straining during the HPT processing have facilitated processing of AZ91 alloy at room temperature. Extensive grain refinement and twinning segmentation of the coarse grains have been observed in the microstructures processed at room temperature and elevated temperatures, respectively. The twins have been observed at all processing temperatures during processing and their distribution was proportional to the processing temperature and number of turns. The morphology and distribution of the β–phase have altered during processing, with fragmentation of coarse clusters of the β–phase into nano–sized particles and the alignment of these particles in the direction of torsional strain being observed. Microstructural homogeneity has gradually developed at a relatively low number of turns using the lower processing temperature and continued with increasing number of turns. A significant improvement in the strength of the alloy has been found after HPT processing at all processing temperatures. The dislocation density has developed significantly for the alloy processed at room temperature rather than at elevated temperatures with increasing number of turns. An experimental Hall–Petch relationship has emphasized a significant dependence of the strength on grain size for the alloy processed at room temperature. The high–strain rate superplasticity, low–temperature superplasticity, and thermal stability of the processed alloy have been observed and attributed to the ultrafine–grained microstructures produced by HPT at room temperature and the dispersion of nano–sized β–phase particles. Grain–boundary sliding was the main deformation mechanism during the high–strain rate superplasticity regime. Glide–dislocation creep accommodated by grain–boundary sliding was the deformation mechanism operating during the low–temperature superplasticity regime. At high temperature and slow strain rate grain–boundary sliding was accommodated by a diffusion creep mechanism.
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Unal, Ogun. "Characterization of Tensile Deformation in AZ91 Mg Alloy Castings." UNF Digital Commons, 2016. http://digitalcommons.unf.edu/etd/632.
Full textAbstract:
Tensile deformation characteristics of cast aluminum alloys have been investigated extensively. Cast Mg alloys have remained mostly neglected by researchers, despite their potential for weight savings. This present study is motivated by this gap in the literature and consists of two stages; in Stage 1, analysis of tensile data gathered from literature were reanalyzed, and in Stage 2, data generated from tensile testing of 60 specimens of AZ91 Mg alloy castings in both T4 and T6 conditions were analyzed to characterize work hardening behavior.
In Stage 1, more than 1600 data were collected from the literature for various Mg alloy families. After plotting these data in yield strength-elongation charts, highest points were identified and interpreted as the maximum ductility, i.e., ductility potential (eFmax). The trend in maximum points indicated a linear relationship with yield strength (σY), expressed as;
eF(max) = 41.8 - 0.106σY (1)
This ductility potential equation can be used as a metric to compare elongation obtained from tensile specimens to measure the structural quality of Mg alloy castings. Moreover, results indicated that ductility potential was not affected by heat treatment, grain size (within 30-120 μm), casting geometry, size, the type of casting process nor chemical composition.
In Phase 2, AZ91 cast Mg alloy specimens in T4 and T6 conditions were tested in tension to obtain stress-strain data for each specimen. Fits of four constitutive equations, namely, the Hollomon, Voce, Ludwik and Swift, to true stress-true plastic strain data in the elastoplastic region were characterized for the specimens with highest elongation values for T4 and T6 specimens. The coefficient of determination, R2, values for all equations were in excess of 0.99, suggesting that all four equations provide excellent fits to tensile data in both conditions.
The change in work hardening rate with true stress was investigated for all specimens by using Kocks-Mecking (KM) plots. It was determined that work hardening behavior of Mg alloy castings in T4 and T6 is distinctly different. In T4 specimens, there is a plateau in work hardening rate at approximately E/25 which was observed in all specimens. The presence of this plateau is consistent with results given in the literature for pure Mg. However, this plateau was not observed in any of the T6 specimens. The reasons for the absence of the plateau in T6 specimens are unknown at this time. In both T4 and T6 specimens, the KM work hardening model in which work hardening rate changes linearly with true stress was found to be applicable. This is the first time that KM model was found to be valid for Mg alloys. Moreover in all specimens, there was a sudden drop in work hardening rate just prior to final fracture. This drop was first hypothesized to be due to structural defects in specimens, which was subsequently validated via fractography. Structural defects were found in all specimens whose fracture surfaces were investigated, indicating low to medium levels of quality.
The quality index method, originally developed for cast aluminum alloys as the ratio of elongation to ductility potential, was found not to be applicable to Mg alloys, at least in its original form. This is due to the fact that work hardening behavior of cast aluminum alloys follows the KM model and there is no plateau where work hardening rate is constant. Hence the work hardening behavior of cast aluminum alloys and AZ91 specimens in T6 condition was similar. However the plateau of constant work hardening rate had a strong effect on elongation in T4 specimens. Therefore quality index analysis, which is supposed to be independent of alloy condition, did show that T4 and T6 specimens had different quality index levels. This finding contradicted the result from Stage 1 that aging has no effect on ductility potential. However because of the presence of structural defects in all specimens, quality index levels were low (0.30-0.45). Therefore it is unclear at this point whether the work hardening behavior of T4 and T6 specimens would still be different if elongation values were in the proximity of the ductility potential line. More research is needed to characterize work hardening behavior of cast Mg alloys in the absence of major structural defects and also address other questions raised in this study.
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Noster, Ulf. "Zum Verformungsverhalten der Magnesiumbasislegierungen AZ31 und AZ91 bei zyklischen und quasi-statischen Beanspruchungen im Temperaturbereich 20-300C." Kassel : Kassel Univ. Press, 2003. http://deposit.d-nb.de/cgi-bin/dokserv?idn=970518994.
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Krauß, Martin [Verfasser]. "Zur thermischen Ermüdung der Magnesiumbasislegierungen AZ31 und AZ91 / Martin Krauß." Kassel : Kassel Univ. Press, 2007. http://d-nb.info/986600679/34.
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Šomanová, Pavlína. "Příprava a charakterizace vysoce hydrofobních povlaků na hořčíkové slitině AZ91." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2021. http://www.nusl.cz/ntk/nusl-444211.
Full textAbstract:
Magnesium and its alloys have many interesting properties and thanks to them it can be used in many applications (transport industry, medicine etc.). Disadvantage of these materials is their high corrosion rate. For this reason, there is an effort to achieve high corrosion resistance through different modifications of magnesium and its alloys. In recent years the superhydrophobization of the surface seem to be an attractive solution for this question. This type surface modification minimalize contact between the surface and water. In this diploma thesis the superhydrophobic surface was created on the magnesium alloy AZ91. The first step included pretreatment of AZ91 surface by etching in solution of SnCl2 or ZnCl2. Next step was superhydrophobization in the ethanolic solution of stearic acid. The surface morphology and elemental analysis of the superhydrophobic coating were explored by use of scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS). The adhesion properties of the coating on the AZ91 were analysed by means of scratching test. Contact and sliding angles were measured for superhydrophobic coatings. Electrochemical characterization of the coatings was determined using potentiodynamic polarization (PD) and electrochemical impedance spectroscopy (EIS). Finally, the analysis of composition and the functional groups was made using Fourier-transform infrared spectroscopy (FTIR) and the phase composition analysis was performed using X-ray diffraction (XRD). The results show that the coatings prepared by etching did not lead to good corrosion properties, even though the value of contact angle was about 150 °. The reduction of corrosion resistance could be caused by not obtaining required surface morphology or insufficient binding of stearic acid in the form of stearate to the sample surface.
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Štěpánek, Roman. "Teplotní stabilita Mg-slitiny AZ91 připravené pomocí intenzivní plastické deformace." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2012. http://www.nusl.cz/ntk/nusl-230220.
Full textAbstract:
This thesis dealt with thermal stability of magnesium alloy AZ91 prepared by severe plastic deformation, which leeds to fine grained structure. This structure is characterised by its inherent instability and this thesis tries to find out the value of critical temperature and rate of this instability, which manifests as grain coarsening.
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Prakash, D. G. Leo. "Microstructural influences on macro properties of hpdc magnesium alloy AZ91 quantification and FE simulations." Magdeburg Docupoint-Verl, 2005. http://deposit.ddb.de/cgi-bin/dokserv?id=2747367&prov=M&dok_var=1&dok_ext=htm.
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Erchov, Serguei. "Research on the mechanical properties of the sand cast magnesium alloy AZ91." Doctoral thesis, [S.l. : s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=963699164.
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CHEN, CHIH-YI, and 陳志亦. "Processing of AZ91D/SiCp magnesium matrix composite." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/67294651779601581396.
Full textAbstract:
碩士國立中正大學
機械系
93
Abstract Due to the petroleum crisis, vehicle weight reduction has been recognized as the main stream of the vehicle technology development. This study tries to use the lightweight materials to achieve the purpose of weight reduction. In general, lightweight materials are aluminum alloy and magnesium alloy. Magnesium alloy is the lightest structural material, but has smaller elastic modulus, tensile strength and yield strength than that of aluminum alloy. Hence, we want to use the magnesium alloy based metal matrix composite materials as the lightweight materials, in order to improve the elastic modulus, yield strength, creep life...et al. , which is also the goal of this thesis. We try to make magnesium matrix composites with mirco-sized SiC particles. This experiment first uses the simple casting system to fabricate the magnesium matrix composites and discuss the influence of adding different size and different volume ratio SiC particles on AZ91. The experimental results reveal that the hardness of AZ91D adds SiC particles is better than AZ91D. The SiC size has not affected to AZ91D. There is a trend that the hardness of different SiC particle sizes increases with the volume ratio of the SiC within AZ91D.
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Bin, Won Jen, and 翁仁斌. "Solid State Recycling of Mg Alloy AZ91D." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/25467635775066003108.
Full textAbstract:
碩士中華大學
機械與航太工程研究所
94
Abstract Mg alloy with the specific weight of 1.74 g/cm3 is the lightest structural metal and possesses a number of advantages such as specific strength、specific stiffness and material recycling. Therefore Mg alloy has been used prevalently at 3C、automobile and bicycle industries. The applications of Mg alloy having been highly developed recently, a large amount of waste materials have been produced due to the low yield rate of manufacturing processes, it is revealing the problem of recycling. The liquid-phase recycling process has been commonly used in the industry. However, this process is with high cost and hazard, it is also harmful to the ozonosphere due to using SF6 during melting process. In order to meet the requirements of environment protection and cost reduction, the development of new technology for Mg alloy recycling is urgent. This paper proposed a solid-state method for Mg alloy recycling. In this new method, the chips of waste material was first pressed into an ingot, the ingot was then plastically deformed at a high temperature to make the final or semi-finished products. In this research, the scraps of Mg alloy AZ91D used as the raw material. Part of the scraps were oxidized at 300C. Both the scraps with and without oxidization were compacted by using an 100 ton press. The compacted ingots were then extruded into a rod with a diameter of 20 mm for scraps without oxidization and a plate with rectangular cross section of 110 mm 10 mm for oxidized scraps at a billet preheating temperature of 350C. Heat treatment was performed to explored the characteristics of age hardening of the recycled material without oxidation. Annealing heat treatment was carried out to investigate the effects of annealing on the mechanical properties of the recycled material with oxidation. The experimental results showed that the ultimate tensile strength, yield strength, and elongation of the as extruded bar with an average grain size of 7.5 μm were 289.5 MPa, 79.7 MPa, and 6.9%, respectively. After age hardening treatment the maximum ultimate tensile strengths increase to 330MPa and 317.5 MPa for aging at 170C and 215C, respectively. From microstructural analysis, it was found that the aging treatment would advance the formation of eutectic-like lamellar structure, and the lamella structure increased with aging time. The as extruded plate revealed an ultimate tensile strength and elongation of 271 MPa and 2.3%, respectively. The ultimate tensile strength increased to 310 MPa; an increase about 40 MPa, and elongation increased to 12.7 % for annealing at various temperatures between 250C and 400C. It seems that annealing temperature did not affect the mechanical properties. The microstructural analysis showed that annealing treatment would not cause grain growth during heat treating. The precipitation of fine β-phase tremendously improved the mechanical properties.
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Chen, Hung-Chih, and 陳竑志. "Study of Powders Cladding on AZ91D Magnesium Alloy." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/50008511105323512461.
Full textAbstract:
碩士國立臺灣科技大學
機械工程系
103
In this thesis, the Al-Si mixed powders with SiC ceramic powders were clad on AZ91D magnesium alloy by the gas tungsten arc welding (GTAW) method to investigate improvement of wear resistance. A modified surface layer free of cracks and pores was formed with appropriate processing parameters and the suitable weight ratio of Al to Si powders. The microstructure, chemical composition and phase analyses of the cladding layer were studied by scanning electron microscopy (SEM), Energy Dispersive Spectrometer (EDS), Electron probe microanalyzer (EPMA) and X-ray Diffraction (XRD). SEM shows the GTAW clad layer have very good bonding with the AZ91D magnesium alloy substrate. EPMA and XRD confirmed the main phases in the layer to be Mg2Si, Mg17Al12, Mg2Zn11, and Mg2Al3 phases. The hardness distrubtion of the clad layers was obtained by Vickers microhardness tester. Microhardness of the surface cladding layer was significantly improved to as high as Hv152 as compared to Hv60 of the AZ91D substrate. A roating tribometer with a pin-on-disc type was conducted to evaluate the wear behaviors of various clad specimens in oil-lubricated condition. 10% SiC clad layer has the best wear resistance as compared to AZ91D magnesium alloy.
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Wang, Shing-Ping, and 王行平. "Chromate-Free Conversion Coating on AZ91D Magnesium Alloy." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/58541072706773691118.
Full textAbstract:
碩士元智大學
化學工程學系
93
Recently, chromating conversion treatment on magnesium alloys has provided good corrosion protection worldwide. However, the liquid wastes generated from surface coating may cause serious environmental pollution on the earth and the contamination of Cr species are strictly prohibited in Taiwan. Chromate-free conversion technique on magnesium alloys is prevailing and may be an appealing environmental friendship alternative. Therefore, the main objective of this study was to investigate a phosphating conversion treatment on magnesium alloys by chromate-free solution routes. Due to the phosphating treatment on AZ91D alloy surfaces required a longer reaction time of 10 min, adding proper surfactant for accelerating agent may decease reaction time approximately of 3 min that can reach commercial thickness of coated films determined by metallographic optical macroscope (MOM). Experimentally, 10~30 mL/L surfactant of triethanolamine (TEA) having a low molecular weight was added to the treating solution in order to decrease the required treating time. By MOM tenique, a thickness of 1.4 μm for treated AZ91D alloy was also obtained by non-accelerator bath within 10 min. Thickness of 4.1 and 18.5 μm were separately formed on AZ91D alloys in the treating solution bath containing 30 mL/L accelerator within 4 and 20 min, respectively. In other words, by adding the treating solution of 20 mL/L optimially of 0.8 μm/min treating rate calculated bascally with non-accelerator solution within 2 min, that it is enough to reach the required thickness of 1.4 μm. Generally, the thickness of 1 mm or less formed by AZ91D alloy on notebook casing. Due to the reqirement of thinner thickness of AZ91D alloy, the grinding and polishing procedures of AZ91D alloy were needed before surface modification. The innovatory fixed tools used for AZ91D alloy polishing were therefore designed successfully. This fixed tool with 100-600 rpm (rate per minute) could meet the commercial standard of grinding and polishing procedures of surface-modified AZ91D alloy. Understanding of the equations used for the formation of chromate-free conversion film, may provide the reasons for investigating the phosphating procedure in the surface treatment of AZ91D alloys. Investigating the properties of using a pH value of 3-4 in phosphating bath and formation of the unstable intermediates of Mn(H2PO4)2 or MnHPO4, may enhance the clarification of the original additives of different commercial formula used for the surface treatment of AZ91D alloys.
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Cho, Hsuen-Yuan, and 卓學淵. "Study on Die Casting Defects of AZ91D Magnesium Alloys." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/47711052735983562027.
Full textAbstract:
碩士國立東華大學
材料科學與工程學系
90
Abstract In recent years, the die casting of magnesium alloy had been prevailing in the marking of parts in the automotive industry as such items as the covers of notebook, computers as well as cellular phones. However, these alloys are prone to micro-shrinkage and some kinds of casting defects. Therefore, in this research, the as-cast defects of NB panel products by pressure die casting will be collected and studied. The defects of casting products are investigated by optical and scanning electron microscopy, and EDX. The phase identification was conducted using X-ray diffractometer. At the same time, the computer simulation of mold filling and solidification during die casting was also performed to understand the effect of varying processing parameter on the fluid flow and solidification behavior of AZ91D and the influence on the causes of casting defects. From the results of collecting and checking the surface of as-cast products, defects including hot checked mold, hot tearing, and ejector caused bent, flow marks as well as surface oxide were found. This thesis describes the experimental observations, compares with the simulation and relates their occurrence to the operating conditions. Mechanisms are proposed to explain the different defects that are found.
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Wang, Kai Dei, and 王凱迪. "Study of Corrosion Resistance of AZ91D Alloy by Dimethyl Acetamide." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/01912277312146989031.
Full textAbstract:
碩士高苑科技大學
化工與生化工程研究所
99
Abstract Anodic oxide film on AZ91D ally was prepared by micro-ace oxidation process using pulse-reverse plating. The additive , Dimethyl acetamide ,in the plating solution is a key factor to improve the characteristic of anodic oxide film. When Dimethy acetamide concentration was adjusted at 0.12M,the anodic oxide film was formed in the plating solution with long passive potential of 12V and low corrosion current desity of 0.0158mA/cm2. Moreover , the hardness , thickness , and dense structure were also improved by the additive ,Dimeyhyl acetamide. Finally, the optimum operating condition, pulse-plating potential of 500V , reveres-plating potential of 50V , pulse-plating period of 50ms,reveres-plating of 50ms and 6000 duty cycles , could form the anodic oxide film with thickness of 113µm and 1763 HV.
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Chia-ChangChang and 張家彰. "Study of semisolid processing AZ91D Mg alloy via electromagnetic stirring." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/83511140852221880771.
Full textAbstract:
碩士國立成功大學
材料科學及工程學系碩博士班
98
The purpose of this study is to improve the equipment of the electromagnetic stirring process and the parameters of the process. We can get a reliable and effective method to prepare magnesium alloy with equi-axis and tiny grains after optimizing the process. Expect that it could apply to the follow-up forming and manufacturing, then it could be used in industrialization for the final goal. This study mainly discusses the effects of parameters of the electromagnetic stirring on the morphologies of the ingots, macroscopic defects and microstructures. And processing parameters include the stirring current, the stirring time, the cooling rate, the initial cooling temperature and the temperature of the temperature controller. By mean of the improvement of the equipment and the revising of the parameters, the improvements of the structures of magnesium alloy have obtained some preliminary achievements.
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Tsai, Hao-Jan, and 蔡浩然. "The Heat Treatment & Surface Treatment of AZ91D Magnesium Alloy." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/spjz4t.
Full textAbstract:
碩士國立東華大學
材料科學與工程學系
95
AZ91D has higher content of aluminums, it can precipitate the β phase(Al12Mg17) of BCC structure in the magnesium base of HCP with the proper heat treatment. Because of this precipitates are located slip plane（0001）under the room temperature, this kind of precipitates can not resisted the dislocation to slide very effective and it caused the purpose of precipitation hardening are very limited. In consequence, this study will use the different heat treatment ways which like T6 treatment（solid solution＋aging hardening）、T8 treatment（solid solution＋TMT＋aging hardening）and T9 treatment（solid solution＋aging hardening ＋TMT）on AZ91D magnesium alloy（As－Extruded）and survey the morphological distribution of samples after solid solution treatment、aging hardening treatment、TMT； and then, comprehend the effect of hardness and tensile strength for AZ91D magnesium alloy. The experimental result shows, the magnesium alloy of AZ91D is in the rising that after T6, T8 and T9 treatment are achieved with its hardness value will be obvious, especially T8, T9 treatment, It can make Al12Mg17 produced the discontinuous particle precipitates directly by the TMT, make its distributed evenly in the magnesium base, and then improve the effect of precipitation hardening. Can know by the result of tensile test, after T6 treatment, 200 degrees Centigrade of aging hardening temperature makes tensile strength value that can be obviously higher than the extruded magnesium alloy；and then, the T8、T9 treatment can also find the tensile strength of the two is higher than the extruded magnesium alloy, superior to the tensile strength value that T6 treatment. In consequence, after comprehensive hardness and result of tensile test, AZ91D extruded magnesium alloy can change morphological distribution ofβ phase(Al12Mg17) by the TMT to reach higher strength. The corrosion resistance of magnesium alloys was, however, very poor. Without proper corrosion-prevention treatment, their applications can be severely restricted, In this study, DC magnetron sputtering was used to deposit a thin film of photo-catalytic TiO2 on AZ91D Mg-alloy to enhance the corrosion-resistance and photo-catalytic properties of the AZ91D substrate. Experimental results showed that the contact angles of AZ91D surface, when coated with a thin film of TiO2 , decreased substantially down to 5° after exposure to UV light, From the experimental of photo-catalytic activity via methyllene blue, can knows that the methylene blue were catalyzed by TiO2 film，thus exhibiting photo‐induced hydrophilicity effect. On the other hand, the potentiodynamic polarization curves indicated that the corrosion potential of TiO2-deposited AZ91D was higher than that of the uncoated AZ91D Mg-alloy. While for TiO2-deposited samples this data suggested an increase in the intrinsic corrosion resistance, the current density of the TiO2-deposited samples was much higher than that for the uncoated samples. The overall corrosion resistance of TiO2-deposited samples deteriorated as compared with that of the uncoated samples. FE-SEM observation of the TiO2 thin film showed polycrystalline structure characteristics of anatase phase, as well as the presence of pinholes on the TiO2 thin film. EDS analysis revealed the pinholes to be locales of incomplete deposition, which caused accelerated corrosion by Galvanic corrosion effect, on the other hand, AZ91D substrate which coated TiO2 film to use voltage and which coated TiO2 film after conversion coating both can advanced the corrosion resistance of magnesium alloys.
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Lim, Tiong-wei, and 林長偉. "Quality evaluation of AZ91D recycling magnesium alloy in die-casting process." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/86721732930185342635.
Full textAbstract:
碩士國立臺灣科技大學
機械工程系
95
In general die casting factory, large volume of recycling AZ91D magnesium alloy materials were used. Although the recycled manufacturing supplier’s materials meet the standard norm, due to the difference of recycled material used the quality of the die casting parts was influenced widely and the understanding of the causes are limitedly. The main purpose of this research is to understand the influences of recycling AZ91D magnesium alloy to the mechanical property and corrosion resistance of the die casting parts. By choosing three existing reputed brand AZ91D material, to compare with own manufacturing magnesium alloy by using 100% pure magnesium, mixture of 30% pure magnesium with 70% recycling magnesium, mixture of 70% pure magnesium with 30% recycling magnesium, and 100% recycling magnesium. Different testing specimens are made by ingot without fabrication and by die-casting process. Through the analysis of chemical compositions, metallography, tensile strength test, impact test, hardness test and corrosion resistance testing, we try to clarify the characteristic of different combination of magnesium. From the analysis of a large number of test data, we realign that the main compositions like Al, Mn, Zn, Si, Fe, Ni, Cu, etc. which can influence the properties of the die-casting parts. Besides, the pollution of casting oxides, plunger lubrication oil and die release agents during die-casting process and the impurities of flux and residue during smelting are also influence the properties of the parts. To widen the use of all recycling AZ91D magnesium alloy can significantly reduce the manufacturing cost. The results detained in this study can be offered to the recycled material manufacturer and die casting factory for reference.
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Lien, Chao-Chien, and 連昭鑑. "Analysis of a Fatigue Crack Growth Equation for Magnesium Alloy AZ91D." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/36827896758853109359.
Full textAbstract:
碩士中原大學
機械工程研究所
103
ABSTRACT In this study, according to the experimental results that presented by Bag et al for magnesium alloy AZ91D, the data of fatigue crack growth rate are estimated with the scale. The predicting da/dN values in this study compared with experimental results are similarity.
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Pan, Han-Tsung, and 潘漢宗. "Study on the semisolid process of spray-formed AZ91D Mg alloys." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/99482253031090364964.
Full textAbstract:
碩士國立成功大學
材料科學及工程學系碩博士班
93
The study on the behavior of metals and alloys in the semi-solid state was discovered by Flemings and Spencer in MIT in 1971. In the same year, two kinds of semi-solid forming process were presented, including of rheocasting and thixocasting. The rheo-route involves the preparation of a SSM slurry from liquid alloys and transferring the prepared slurry directly to a die or mould for component shaping. The thixo-route involves the preparation of roll materials or ingot with equiaxed microstructure and reheating the solid feedstock material to semisolid temperature, then shaping the semisolid slurry to component. In this research, the semisolid forming process was employed to study the deformation behavior of as-cast、spray-formed and extruded AZ91D Mg alloys. In the study of coarsening behavior of material, the modified LSW equation was used to discuss the variation of grain size of material. Finally, to make use of Shimadzu Universal Test Machine, the semisolid forming test was used to study the effects of temperatures and ram speeds on the deformation loads and microstructures.
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Chen, Bo-Cun, and 陳柏村. "Using Electroless Method to Improve Corrosion Resistance of Magnesium Alloy (AZ91D)." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/93245907363277636156.
Full textAbstract:
碩士高苑科技大學
機械與自動化工程研究所
102
Abstract Oxide coating on AZ91D alloy was prepared to improve anti-corrosion property by pulse- reverse plating and micro-arc oxidation technique. In this study, the pulse-reverse plating structure a homogeneous oxide coating to increase the hardness, thickness and corrosion resistance. The up limit voltage of pulse plating potential is an important factor to improve anti-corrosion character of oxide coating on AZ91D alloy. When the up limit voltage is fixed as 240V, the intensity of MgO crystalline peak was shown as XRD pattern. The MgO crystalline peak indicate the oxide coating with a dense layer with anti-corrosion ability. Those composition, sodium hydroxide, sodium citrate, sodium tetraborate, tetramethyl ethylene diamine, phosphoric acid and sodium silicate, in plating solution were studied. Moreover, pre-treatment period, solution temperature, up-limit potential, low-limit potential and duty cycles, were studied for oxide coating on AZ91D alloy for a better anti-corrosion ability. Keywords: AZ91D, magnesiumalloy, magnesium oxide, corrosion resistant, sodium silicate
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BAI, JIA-SIANG, and 白家祥. "Using Electroless Method to Improve Corrosion Resistance of Magnesium Alloy (AZ91D)." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/92160211156323269804.
Full textAbstract:
碩士高苑科技大學
化工與生化工程研究所
101
Electroless plating is used to prepare Si film on AZ91D ally before micro arc oxidation process. In this work, oxide film on AZ91D alloy is detected hardness, morphology, crystalline, composition and corrosion resistance. When AZ91D alloy immerses during 24 hours in eletroless process to get a high Si content of 3.78 atm.% and hardness of 285Hv. Moreover, the oxide film has a better OCP value of 0. According to the results, the optimal preparation parameter to form a better corrosion resistance of oxide film on AZ91D alloy is up-limit potential of 170V, low-limit potential of 30V, pulse-plating period of 50ms, reveres-plating of 50ms and 12000 duty cycles. The optimal preparation condition can form a low corrosion current of 0.011mA/cm 2 with long passivation potential from -2 to 10 V. Keywords: AZ91D, Magnesium alloy, Silicon oxide, Oxide film, Electroless, Corrosion resistance
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Wu, Ping-Hsing, and 吳炳興. "The Effect of Aging Precipitates to Mechanical Properties on AZ91D Magnesium Alloy." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/37595094639457413703.
Full textAbstract:
碩士大葉大學
車輛工程研究所
90
In the new century, the lightweight materials will be on the dominated position. Therefore, the investigations relating to magnesium and aluminum alloys were never interrupted. Not only the 3C electronic industries make use of lightweight materials, but also widely applied in vehicle and aerospace industries to reduce the weight of body. These efforts will reach the goals of increasing fuel efficiency, decreasing fuel consumption and controlling exhaust gases emission. In recent years, the fully aluminum vehicles were developed and fabricated. Due to the progress of the technetronic generation and people seek the superior quality of products (lightweight、multi-function、etc.), which help to materialize the magnesium alloys to be the dominated material in the new generation. As we known, the magnesium alloys exist many excellent characteristics (ex. low specific density、high specific strength and rigidity、large thermal conductivity、high damping capacity、better corrosion resistance and good electromagnetic interference, etc.). Nevertheless, the HCP crystal structure inhibits the low temperature formability and the techniques of heat treatment、welding and forging are not well developed yet. For above reasons, the applications of magnesium alloy were temporarily constrained. The AZ91D magnesium alloy is the most popular material to fabricate the magnesium products. Therefore, in this research program, extruded AZ91D magnesium alloy plate with 5 mm thickness was selected to do the heat-treated experiments. From a series of temperature vs. time combinations, try to correlate the relationship among grain size、micro-hardness、mechanical strength、elongation and toughness. Also, analyze the chemical composition、elements combination and morphology with various types of precipitates which formed during different heat-treated processes. Analyzing the obtained data, we can figure out the correlation between precipitation mechanisms and mechanical properties. After that, we can easily determine the parameter to control the precipitate formation and to promote the material properties (ex. strength、toughness, etc.). According to the preliminary tensile tests shown that the grain size within the range of 15~20μm exists better toughness values. Therefore, the parameter with maximum tensile strength and adequate grain size can be obtained and applied it to the dual ageing treatment. Hopefully, after the dual ageing treatment, the optimized mechanical properties can be achieved and enlarged the application fields of magnesium alloys.
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Jhou, Wei-Ping, and 周偉萍. "The technology of micro-arc oxidation black coating on AZ91D magnesium alloys." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/23721871717897269811.
Full textAbstract:
碩士大同大學
材料工程學系(所)
100
The anodized oxide film of magnesium alloy has many defects(poor bond strength, low wear and corrosion resistance, easy fading , uneven color, etc) in traditional surface coloring technology. These defects have largely limited the applications of magnesium alloy. In this paper, black ceramic film with uniform color, smooth surface, compact structure and excellent corrosion on AZ91D alloys was successfully obtained by micro-arc oxidation. Micro-arc oxidation (MAO) is a new electrochemical surface treatment technology, suitable for treating the aluminum, magnesium and titanium and other light metal alloys. In electrolyte by the arc discharge plasma generated of the substrate oxidation and high temperature melting, the film were formed with high hardness and corrosion resistance. In order to blacken the magnesium alloy AZ91D under plasma electrolytic oxidation (MAO) technology in silicate electrolyte containing copper sulfate and individual concentrations of K2FeO4, the characteristics of MAO coatings formed at different treatment time were investigated and dectection by XRD、 SEM 、XPSand color analysis instrument.
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Lee, Yueh-Lien, and 李岳聯. "Microstructure and Properties of Cr-free Conversion coating on AZ91D Magnesium alloy." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/32105661207435123541.
Full textAbstract:
博士國立臺灣大學
材料科學與工程學研究所
99
In the first part of this paper, the effect of the different die-casting microstructures on the stannate conversion coating treatment has been investigated on AZ91D magnesium alloy, with emphasis on the die-chill skin and α/β (Mg17Al12) eutectic structure. Prior to the immersion in the stannate bath, AZ91D substrates were pickled in 11wt﹪HF solution at room temperature, respectively. After thorough cleaning in running water, the substrates were immersed in a stannate bath for 60s and 600s. SEM, TEM, EDS and XRD were employed to analyze the surface morphology and detailed microstructure of the coating on the AZ91D substrate. In addition, the electrochemical polarization measurement was performed to compare the corrosion resistance of the coating on the AZ91D with and without the die-chill skin. The results showed that the die-chill skin contain a lot of pores and those pores are covered with oxide. Besides, the stannate coatings on the substrate with die-chill skin after 10 minutes immersion show higher corrosion potential and smaller anodic current. In the second part, the formation characteristics of conversion coating on the AZ91D magnesium alloy were discussed. Comparing to the α phase, the hydroxides films formed on the β phase at the beginning of conversion process provide insufficient protection. Since the galvanic effect between β phase and eutectic α + βcould occur most easily, the nucleation of stannate conversion coating depending on sufficient Mg2+ took place predominantly in the vicinity of β phase. In the contrast, formation of ceirum conversion coating on AZ91D was largely relied on the increase of the pH value. Since α phase is more active than β phase in the acid solution, the severe Mg2+ dissolution causes the production of H2 bubbles, leading the formation of blisters on the α phase at the beginning of cerium conversion process. In the last part of this papar, a new approach for alternative of toxic hydrofluoric acid (HF) in the magnesium pretreatment process was investigated. The hydrochloric acid, hydrofluoric acid and vanadate solution were made on the AZ91D magnesium alloy before cerium/hydrogen peroxide conversion coating respectively. The microstructure of coatings was observed by transmission electron microscopy (TEM), and the electrochemical impedance spectroscopy (EIS)、Polarization curves and salt spray test (SST) were carried out to evaluate the corrosion resistance. The results show that, comparing with HF and HCl pretreated samples, the passive layer formed in vanadate-containing bath (pH=8) effectively restrained the reaction rate of Ce conversion coating and apparently reduced the number of blisters and partial peel-off of the coating. Both the EIS and SST results show that the better corrosion resistance coating can be obtained when the samples were pretreated in the vanadate-containing bath.
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cheng, young chang, and 楊承璋. "the structure strength and growth mechanism of az91d magnesium alloy conversion coatings." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/69088341662823358236.
Full textAbstract:
碩士大葉大學
車輛工程學系碩士班
93
As result of the development of technology and consumers’ demands, the designs of new products become smaller and lighter, also the fully functional outfits are equipped. In addition, due to the prosperity of environmental protection, the lightness of transportation vehicle, reducing the emission of pollution, and the consideration of increasing the fuel efficiency, the use of lightening material gradually attracts attentions nowadays. In recent years, the prosperity of information industry has leaded to the significant use of light-materials which mainly refer to magnesium, aluminum and titanium. Among these materials, magnesium alloys will be the dominated material because of its excellent characteristics including low specific density, high specific strength and rigidity, good thermal conductivity, high damping capacity and electromagnetic interference, etc. However, magnesium alloys exists high activity, low electrochemical potential behaviors which will oxidize easily. It is necessary applying appropriate surface treatment to prevent corrosion. In this study, AZ91D magnesium alloy is used as experimental material. Meanwhile, permanganate and phosphate conversion coatings, which are widely used for surface treatment in industries, are adapted to have fundamental discussions. The operation parameters studied included the solution temperature and immersion time, used OM, SEM (EDS) and XRD to observe the surface morphology of coatings and analyze the chemical composition. Normally, products would follow-up coating after conversion treatment, thus, conversion coating plays the role of corrosion resistance in a short time. In the last, using adhesives to do the adhesion test and obtain the shear strength of conversion coatings directly. Obeying these data, we can judge the capability of adhesion and wear resistance. From experimental results shown that the surface cracks of permanganate conversion coatings were amorphous, and the thickness and weight increased with increasing immersion time. However, the coating of phosphate conversion is non-crystal layers and randomly distributed. The size of surface product grows with immersion time increased and the morphology without change apparently. In the aspect of shear strength, at 60℃and 80℃permanganate conversion specimens, the coating strength increased after 10 minute immersion time which is due to the dense MgO structure formation. However, in phosphate conversion treatment, the strength do not show apparently changed under various operation conditions. The fracture surface always occurs between adhesives and base metal or at the interface of adhesives and coatings. Overall, the non-crystal phosphate conversion coating exist better shear strength than permanganate coating. This result illustrate phosphate coating with regard to follow-coating layer has better adhesion ability, also can provide better corrosion resistance protection.
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Hegde, Adarsh K. "Dry Sliding Wear of Saffil Short Fibre Reinforced AZ91D Mg Alloy Composite." Thesis, 2016. http://hdl.handle.net/2005/3211.
Full textAbstract:
Magnesium alloys have emerged as a promising material for light-weighting due to their potential for higher weight saving compared with advanced high-strength steel, aluminium alloys and glass fibre reinforced polymer composites based on equal stiffness or strength. Even though magnesium alloys offer low density, high strength to weight ratio and excellent machinability their poor creep resistance and low yield strength at elevated temperatures (~150oC) restricts their use in automotive powertrain applications. Possible ways of improving the creep resistance include development of creep resistant alloys and/or reinforcing the alloy with ceramic particulates, fibres/whiskers.
Several magnesium alloys such as – Mg-Zr based alloys, Mg-Al-RE alloys (RE: rare earth), Mg-Al-Ca alloys, Mg-Al-Sr alloys, Mg-Al-Sr-Ca alloys, Mg-Al-Si alloys offer improvement in creep resistance to different extent. However, these alloys are relatively expensive than the widely used Mg-Al-Zn alloys. Some of these alloys are unsuitable for die casting application due to cracking or die filling problems for example, in Ca and Sr containing alloys their content must be controlled to avoid castability problems.
Discontinuous reinforcement of magnesium alloys opens up wide variety of casting techniques for production. Most of the components do not require high performance capability all throughout the component. Squeeze casting technique can be used to economically produce selectively reinforced composites having complex near-net-shape components. By selectively reinforcing only the regions of stress concentration, material property can be optimised at the same time lowering both the cost of manufacturing and machining.
In the present study, wear behaviour of Saffil short fibre reinforced AZ91D Mg alloy composite prepared by squeeze casting is explored. The Mg-Saffil composite had a two dimensional planar random fibre orientation which was inherent to the fabrication process of porous fibre preform. In the as-polished specimen fibres protrude out of the Mg matrix due to differential polishing. The Mg-Saffil composites were subject to unidirectional sliding wear against steel counterface under nominally dry condition in ambient atmosphere at low velocities, to simulate the piston reversal at the top dead centre of an engine wherein lubrication starvation results in wear of engine cylinder. The fibres protruding out of the magnesium matrix prevent the softer Mg matrix coming in contact with the counterface material. The worn surface was examined by means of scanning electron microscopy and the physical and chemical changes caused by the wear processes were characterised using different spectroscopic techniques.
The effect of fibre distribution and fibre orientation on wear of the composite was studied. Depending on the radius of curvature of the counterface, inhomogeneities in the fibre distribution up to a certain length scale were permissible without deteriorating the wear resistance of the composite. The normal fibre orientation proved deleterious to the wear of the counterface. But wear of the composite was independent of the fibre orientation of the wear surface.
In contrast to unreinforced AZ91 Mg alloy which undergoes extensive wear, the steel counterface was machined by the hard alumina fibres protruding out of the matrix. With progressive sliding a discontinuous patch of transferred material formed on the worn surface. Eventually, an oxidised iron-rich transfer layer formed on the worn surface due to compaction of the transferred material and wear debris under the combined action of applied normal load and frictional force. The coefficient of friction plateaus following an initial rapid increase with the increase in the areal coverage of the transfer layer. The abrupt increase in friction coincides with the change in contact at the sliding interface from protruding alumina fibres/steel counterface to mostly between the transferred layer and steel counterface. The increase in friction due to the iron-rich transfer layer formed on the worn surface induced bending stresses in the fibre.
A correlation between the incipient fibre fracture and build-up of the transfer layer was observed. Wear of the composite was governed by the dawn of the fibre fracture event, which in turn leads to three-body wear.
Diamond-like carbon coatings are well-known for their low friction, high hardness and elastic modulus, chemical inertness and optical transparency. They have found widespread use due to their superior tribological characteristics as protective coatings for magnetic storage media (hard-disk drives), in micro-electromechanical devices (MEMS), biomedical applications (joint implants, artificial heart valves), optical windows (anti-reflection coating) and razor blades. The physical and mechanical properties of these coatings can be tailored by controlling the sp3 /sp2 ratio and modification via alloying with metals such as W, Ti, Cr, Al; or non-metallic elements such as B, N, F, Si.
A tungsten doped hydrogenated diamond-like carbon coated steel counterface was used to rule out or minimise any chemical and physical interaction between the composite and the counterface. The composite exhibited a higher wear resistance when slid against a DLC coated steel counterface due to ease of interfacial sliding between the carbon-rich transfer layer and the DLC coated counterface. The transition from ultra-mild to mild wear was not altogether suppressed but delayed to higher loads, prolonging the ultra-mild wear regime. As a result of reduced friction the point of maximum shear stress recedes from the surface, which manifests as subsurface cracks. The dominant wear mechanism of Mg-Saffil composite sliding against the DLC coated counterface was delamination wear.
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Yi, Lin Tsung, and 林宗毅. "The Structure and Growth Mechanism of Phosphate Conversion Coatings on AZ91D Magnesium Alloy." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/16746871522043286690.
Full textAbstract:
碩士大葉大學
機械工程研究所碩士班
95
In this study, AZ91D magnesium alloy is selected as experimental material. Meanwhile, choose zinc phosphate and sodium phosphate conversion solutions to process the experiment. The operating parameters studied included the solution temperature and immersion time. Using SEM, EDS and XRD to observe the surface morphology and analyze the chemical composition of coatings. At the same time, not only measure the thickness and weight of coatings, but examine the adhesives strength and corrosion resistance of conversion coatings by adhesion test and polarization test. From experimental results shown that the zinc phosphate coating contains two layers which including the upper crystalline layer and the lower cracking layer. However, for the sodium phosphate conversion coating, the coating is belong a non-crystalline layer which appear full of cracks and bulk area. The thickness、bulk area and cracks become larger and wider with increasing immersion time. In the aspect of shear strength of coatings, the test of zinc phosphate coating only can obtain the strength between layers, and the value of strength is not quite good. The components of zinc phosphate coating is formed by Zn3(PO4)2．4H2O and AlPO4, which analyzed by EDS and XRD. The Zn3(PO4)2 is the major form of compound at the upper crystalline layer. And the components of sodium phosphate coatings is form by AlPO4 and Mg. The test of polarization did show both the zinc phosphate and sodium phosphate coatings can improve the corrosion resistance of the AZ91D magnesium alloy. Comparing the relationship between thickness of coatings and their corrosion current density, we can figure out the capability of resistance from upper crystalline layer is much weaker than the lower cracking layer. We also believed that the main factors determined the corrosion resistance are the thickness of coating, the width of cracks, and the quantity of cracks. Therefore, how to equalize these three factors to obtain the best corrosion resistance are the major concerns. The best operating parameters for zinc phosphate coating is at 45℃ solution temperature and 25 minutes immersion time. If immersion time further increased which will result in the corrosion resistance decreased, the main reason is due to the wideness of cracks in the lower cracking layer increased. While, in sodium phosphate conversion coatings, the thicker the thickness of coating, the performance of corrosion resistance is better, and the best corrosion resistance parameters is under 70℃ and 30 minutes immersion time. Although the performance of corrosion resistance in phosphate conversion coatings is not good as the chromate and vanadate coatings. But these results still can offer a good reference for future study. Hopefully, the researchers can toward the goal of non-chromate coating developing for better anti-corrosive result together.
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Chen, Hsien-Ming, and 陳憲銘. "Numerical Simulation and Control of Thermal Deformation in AZ91D Magnesium Alloy Frame Shell." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/b82p3y.
Full textAbstract:
碩士國立臺北科技大學
材料及資源工程系研究所
97
Magnesium alloy products are superior to plastic materials in many aspects including their lightweight, electromagnetic interference property, high specific strength, and recyclability. The 3C applications often require them to be die cast into thin shells. These shells are subject to thermal deformation due to temperature increase in use. In this study, computer aided engineering software ANSYS combined with finite element method is utilized to simulate the thermal deformation of AZ91D magnesium alloy shell structure. The simulations consider the changes in shell sizes, shell thickness, and temperatures. It is found that there exists a critical shell thickness of 1mm above which the thermal deformation remains nearly constant. Whereas the thermal deformation raises greatly with shell area indicating the importance of thermal deformation upon shell size design. In order to control the thermal deformation, this study considers adding ribs to reduce structure deformation. L9 (34) orthogonal array of Taguchi method is used to minimize the thermal deformation and rib weight for discussions. It is found that the rib height and thickness are the main controlling factors in rib design for thermal deformation. Ribs are effective in reducing the deformation at the side of shell surface with the ribs. On the side of shell surface that does not have the ribs, very limited deformation reduction is observed.
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Paradis, Mathieu. "Évaluation et identification des inclusions dans les alliages de magnésium AM50A et AZ91D." Thèse, 2003. http://constellation.uqac.ca/758/1/17729707.pdf.
Full textAbstract:
La demande grandissante pour le magnésium et ses alliages, ainsi que la grande production de rebuts des procédés de coulées, poussent les producteurs de magnésium à se tourner vers le recyclage pour subvenir à la demande du marché. Le magnésium est un métal aux propriétés très intéressantes : faible densité, bonne résistance à la traction, bonne coulabilité et bonne résistance à la corrosion. Cependant, ses propriétés sont grandement affectées par les inclusions présentes dans le métal. Or, le recyclage du magnésium apporte son lot d'inclusions de toutes sortes.
Dans le but de fournir un produit de qualité, les producteurs ont à leur disposition une panoplie d'appareils mesurant la propreté du métal. Toutefois, certains de ces appareils sont très onéreux et nécessitent un technicien qualifié pour les opérer. Les facteurs temporels et économiques étant très importants, il est nécessaire de trouver de nouvelles techniques plus économiques tout en demeurant tout aussi fiables.
La présente étude porte sur le magnésium pur : l'alliage AM50A et l'alliage AZ91D. L'étude inclue l'utilisation du « Brightimeter » pour quantifier la concentration des inclusions. L'identification des inclusions a été effectuée par un microscope optique et un analyseur d'images, ainsi que par un microscope à microsondes électroniques couplé à un système de spectroscopie à longueurs d'ondes et à énergie dispersive aussi bien qu'à une cartographie couleur. L'effet de la composition des alliages a été évalué par des essais de traction à la température ambiante. En complément aux essais de traction, la surface de rupture des éprouvettes de traction a également été analysée.
Les principaux résultats montrent une baisse notable de l'indice de « Brightimeter » quand le niveau d'oxydes de magnésium dans l'alliage augmente. Lorsque le niveau d'oxydes de magnésium est bas, la variation de l'indice de « Brightimeter » devient très faible. L'analyse électronique révèle la présence de plusieurs types d'inclusions. Les oxydes de magnésium sont les principaux. D'autres oxydes, comme ceux d'aluminium et de fer, sont présents en plus des particules d'origine étrangère comme la silice et les sels.
La porosité peut être un défaut majeur dans les alliages. Celles observées dans nos alliages sont les retassures. Leurs effets sur l'indice de « Brightimeter » n'est pas notable, l'appareil semble plutôt insensible à la porosité. La taille des grains peut s'avérer un facteur influençant l'indice de « Brightimeter », mais il n'en est rien. Le joint de grain est de la même couleur que la matrice; c'est seulement après une attaque chimique qu'il est révélé.
L'étude portait également sur l'identification et la quantification des phases intermétalliques présentes dans les alliages. Les deux principales phases observées sont la phase Mg-Al-Zn et la phase Mn-Al. La phase Mg-Al-Zn est grandement affectée par l'ajout d'aluminium dans l'alliage; un changement de la taille et de la morphologie des particules de la phase est observé. La phase Mn-Al, quant à elle, n'est pas affectée par l'ajout d'aluminium. La taille des particules de la phase dépend essentiellement de la quantité de manganèse.
Les essais de traction sur les éprouvettes de composition chimique différente montrent une relation directe entre la taille, la morphologie et la densité des particules de la phase versus les propriétés mécaniques des alliages. La ductilité diminue avec l'augmentation de la concentration d'aluminium, tandis que les limites d'élasticité et limite ultime semblent plutôt stables.
L'analyse de la surface de rupture des éprouvettes de tractions montre un changement du mode de fracture : de ductile, pour les alliages pauvres en aluminium à fragile, pour les alliages riches en aluminium. Ce changement s'observe par l'apparition de plans de clivage sur la surface de rupture.
En tenant compte de tous les paramètres étudiés, nous en venons à la conclusion que l'appareil « Brightimeter » est capable de détecter et de mesurer efficacement les oxydes de magnésium dans les alliages. Sa sensibilité est accrue lorsque les niveaux d'oxydes sont à leur plus haut. Pour ce qui est des bas niveaux d'oxydes, l'appareil est bon, mais avec quelques réserves. La sensibilité est affectée par plusieurs paramètres, qui ne doivent pas être négligés. La plupart de ces paramètres dépendent du processus de solidification. Pour établir une relation entre l'indice de « Brightimeter » et le niveau d'oxydes, les paramètres métallographiques doivent être clairement établis.