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 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 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.