Browsing by Keyword "Magnesium alloys"
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Item Analysis of the upward direct chill casting of magnesium alloys(Curran Associates, 2006) Landaberea, A.; Pedros, P.; Anglada, E.; Garmendia, I.; CIRMETALThe upward direct chill casting, where the continuous casting is operated vertically against gravity, is a novel technology which has been applied to the production of high quality magnesium alloys circumventing the main disadvantages of using conventional continuous casting processes, since the risks of burning and explosion are practically eliminated. This represents a key aspect to increase the industrial application of magnesium wrought products. In order to help on the understanding of the process, a mathematical model for the simulation of the upward continuous casting of round billets of magnesium alloys has been developed. The equations for the flow field with heat transfer are numerically solved by a finite volume method and the solidification is accounted via an enthalpy-porosity formulation where the mushy region is modeled as a pseudo porous medium. The obtained temperature distribution is then used as input for a thermo-mechanical analysis to determine the deformation and stress field developed in the billet during the casting process. Several configurations have been simulated and comparison of computed results with available experimental data is provided.Item Development of a squeeze semisolid high pressure die casting process for magnesium structrural parts(Stowarzyszenie Techniczne Odlewnikow Polskich/Polish Foundrymen's Association, 2018) Vicario, I.; Crespo, I.; Val, D.; Weiss, U.; Cao, D.; Martinez De La Pera, I.; PROMETALItem Development of a Squeeze Semisolid High-Pressure Die Casting Process for Magnesium Structural Parts(2019-07-15) Vicario, Iban; Crespo, Iñigo; Val, D.; Weiss, U.; Cao, D.; Martinez de la pera, Ignacio; Sanchez, Jon Mikel; PROMETAL; CIRMETALHigh-pressure die casting is the most common method used to produce magnesium castings, due to the excellent balance of cost and properties for high production volumes with limitations in terms of final mechanical properties. A newly developed process based on employing low injection speeds, in a range slightly over the standard semisolid speeds with a modified die, with thick gates and high die temperatures has been developed. Despite working with speeds that are not in the lamellar flow, the obtained parts present very low porosity, allowing the use thermal treatments to increase the ductility without producing blisters. The demonstration has been performed in a AM60B magnesium body joint produced by the squeeze casting process. Finally, the microstructure and the mechanical properties of as-cast and T4 heat-treated samples were studied. The results indicate the improvement of the mechanical properties in T4 heat-treated parts; specifically, a 40% improved deformation-to-failure, 40-60% improved penetration force and 90% of energy absorption were possible to obtain employing the newly developed SC + T4 process.Item Improvement of mechanical and corrosion behaviour in die casting magnesium alloys with the addition of grain refiners.(World Foundry Organization, 2014) Posada, Tomás; García, José Carlos; Vicario, Ibán; Crespo, Iñigo; Plaza, Luis María; Val, Diego; Borge, Gregorio; CIRMETAL; PROMETAL; Tecnalia Research & InnovationThis paper shows a work carried out to obtain better properties in magnesium alloys used on high pressure die casting process (predominantly AM60B and AZ91D). This study starts with the selection of grain refiner materials to be employed for these alloys. Simple elements such as Mn, Ti, C, Si⋯ and compound elements as ZnO, TiB2 were selected as promising grain refiners. Tensile strength and elongation were chosen as main mechanical properties to be tested employing a design of experiments and laboratory tests. The determination of the fading effect of the grain refiner on the magnesium melt bath is also discussed. This work shows also the results obtained after the addition of selected grain refiners on corrosion resistance, by a new corrosion evaluating method based on affected surface area instead of weight loosing. Finally the best refiner elements for the analysed alloys are assessed, determining their concentration and dissolving time to obtain the best mechanical and corrosion properties. Tensile strength increases up to 6% for AZ91D alloy and up to 12% for AM60B alloy, elongation is also increased and corrosion resistance is even improved in both alloys.Item Influence of thermomechanical processing on superplastic forming of Mg-Al alloys(2007-04) Pérez-Prado, M. T.; Del Valle, J. A.; Salort, F.; Peñalba, F.; Gómez, X.; Ruano, O. A.; EXTREMATThe aim of this paper is to study the influence of the initial microstructure of several Mg-Al alloys on their superplastic formability and on their post-forming microstructure and mechanical properties. Various thermomechanical processing routes, such as annealing, conventional rolling, severe rolling and cross rolling, were used in order to fabricate AZ31 and AZ61 alloys with different grain sizes. These materials were then blow formed into a hat shaped die. It was found that the processing route has only a small effect in the formability of Mg-Al alloys or on the postforming microstructures and properties due to rapid dynamic grain growth taking place at the forming temperatures. Nevertheless, good formability is achieved as a result of the simultaneous operation of grain boundary sliding and crystallography slip during forming.Item Investigation of particle flattening behaviour and bonding mechanisms of APS sprayed coatings on magnesium alloys(2007-02-04) Parco, Maria; Zhao, Lidong; Zwick, Jochen; Bobzin, Kirsten; Lugscheider, Erich; EXTREMATMagnesium alloys are promising alternatives to other lightweight materials due to their high specific strength and stiffness. However, the use of magnesium alloys is limited by their poor wear behaviour and low corrosion resistance for many industrial applications. The thermal spray technology offers a wide range of possibilities to improve the surface properties of Mg-based components. In this study, three different coating materials, namely Al, NiAl5 and Al2O3, were applied on AZ91 and AE42 substrates using the atmospheric plasma spray technology. The investigation was focused on the bonding strength of the coatings and the related bonding mechanisms. For a better understanding of the bonding mechanisms, the flattening behaviour of the spray particles was investigated in correlation with the substrate pre-heating temperature. It was found that NiAl5-particles could well melt the substrate at the surface and deformed it locally; Al-particles did the same but to a lower extent. The dominating bonding mechanism for NiAl5-coatings could be attributed to a metallurgical bonding. For Al-coatings, this mechanism played a more important role once the substrate pre-heating temperature was increased. Al2O3 particles in contrast, were less able to deform the substrate in spite of their higher thermal load and the mechanical anchoring remained the main bonding mechanism. The thermo physical properties of the Mg substrate showed also to have an influence on the adhesion of the coatings.Item Rare Earths and the Balance Problem: How to Deal with Changing Markets?: How to Deal with Changing Markets?(2018-03-01) Binnemans, Koen; Jones, Peter Tom; Müller, Torsten; Yurramendi, Lourdes; VALORIZACIÓN DE RESIDUOSThe balance between the market demand and the natural abundance of the rare-earth elements (REEs) in ores, often referred to as the Balance Problem (or the Balancing Problem), is a major issue for REE suppliers. The ideal situation is a perfect match between the market demand for and the production of REEs, so that there are no surpluses of any of the REEs. This means that the rare-earth industry must find new uses for REEs that are available in excess and search for substitutes for REEs that have either limited availability or are high in demand. We present an overview of the trends in the applications for the different REEs and show that the demand for REEs for use in magnets, catalysts, and alloys is still increasing, while the application of REEs in polishing agents, glass, and ceramics are stable. On the other hand, the use of REEs in nickel–metal-hydride (NiMH) batteries and lamp phosphors is decreasing. These changes in the REE market have an influence on the Balance Problem, because the REEs that can be recycled from fluorescent lamps, cathode-ray tubes (CRTs), and NiMH batteries have to be at least partly reused in other applications. Magnesium and aluminum alloys offer an opportunity to mitigate the Balance Problem caused by these changes in the REE market. This is illustrated for REEs that can be recycled from fluorescent-lamp phosphor waste, CRT phosphors, and NiMH batteries. At present, five REEs (Nd, Eu, Tb, Dy, and Y) are being considered as very critical by Europe, the United States, and Japan, but we forecast that in the medium term, only neodymium will remain a critical REE. This paper discusses the relationship between criticality and the Balance Problem and shows how this relationship influences the market for specific REEs.