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Este proyecto tiene como objetivo desarrollar un estudio reológico de la aleación de aluminio A356 durante su formación en estado semisólido, mediante el proceso de rheocasting, para ser utilizada en una máquina de impresión de piezas en 3D. A través de la investigación teórica y experimentación, se pretende controlar los parámetros que influyen en la calidad final del material y conseguir que obtenga mejoras en sus propiedades mecánicas. Se define lo que es un material en estado semisólido, sus características principales y su relación con la fabricación de piezas en la industria. Se estudia el concepto de reología examinando a fondo sus propiedades más relevantes y se hace una revisión de la viscosidad y de la clasificación de los fluidos existentes. Se citan ejemplos de rutas de tixo y rheo casting empleadas en la industria del conformado de SSM y se discute el papel que cumplen las aleaciones de aluminio en este contexto. Se describe el intento de realización de la fase experimental, consistida en analizar la morfología y el comportamiento de los parámetros del A356 fundido y sometido a varios experimentos a diferentes velocidades y tiempo de agitación mecánica. Se especifican los problemas sucedidos en este periodo y se discute propuestas de mejora para sus futuras y/o posibles soluciones. Se lleva a cabo el diseño de una mesa de altura regulable cumpliendo con los requerimientos del departamento de ciencia de materiales de la universidad EPSEVG y se describen los impactos positivos y negativos que este proyecto puede ser capaz de ocasionar al medioambiente. Por último, se informa los aspectos más relevantes que han sido observados y que se deben de tener en cuenta en los proyectos posteriores y relacionados con este. En conclusión, debido a problemas eléctricos y mecánicos que se presentan durante el montaje y desmontaje del prototipo PMSM, no se alcanza realizar la parte experimental de esta investigación. Sin embargo, se logra entender la teoría del procesamiento de piezas en estado semisólido y cómo pueden afectar los parámetros reológicos la calidad final de los elementos. Finalmente, se ha diseñado la mesa regulable cumpliendo con los requerimientos del departamento de materiales de la universidad y cómo información adicional se ha elaborado un manual de uso para el horno de fundición del edificio A de la EPSEVG, destacando sus principales limitaciones, mediante un caso práctico. The objective of this project is to develop a rheological study of the aluminum alloy A356 during its formation in semi-solid state, by means of the rheocasting process, to be used in a 3D printing machine. Through theoretical research and experimentation, the aim is to control the parameters that influence the final quality of the material and to obtain improvements in its mechanical properties. It is defined what is a material in semi-solid state, its main characteristics and its relation with the manufacture of parts in the industry. The concept of rheology is studied by examining in depth its most relevant properties and a review of viscosity and the classification of existing fluids is made. Examples of thixo and rheo casting routes employed in the SSM forming industry are cited and the role of aluminum alloys in this context is discussed. The attempt to perform the experimental phase, consisting of analyzing the morphology and parameter behavior of molten A356 subjected to various experiments at different speeds and mechanical stirring time, is described. The problems that occurred during this period are specified and improvement proposals for future and/or possible solutions are discussed. The design of a height adjustable table is carried out in compliance with the requirements of the materials science department of the EPSEVG university and the positive and negative impacts that this project may be able to cause to the environment are described. Finally, the most relevant aspects that have been observed and that should be taken into account in subsequent projects related to this one are reported. In conclusion, due to electrical and mechanical problems that occurred during the assembly and disassembly of the PMSM prototype, the experimental part of this research could not be carried out. However, it is possible to understand the theory of the processing of parts in semi-solid state and how the rheological parameters can affect the final quality of the elements. Finally, the adjustable table has been designed according to the requirements of the materials department of the university and as additional information, a user's manual has been elaborated for the melting furnace of the EPSEVG building A, highlighting its main limitations, by means of a practical case.

The car industry is constantly under pressure to be competitive in their product development which includes not only safety and increased performance, but also in their environmental impact. Volvo Cars strives to be more environmental and high performing in their product development, which of course includes manufacturing methods since these highly effect a components environmental impact and mechanical performance. To optimize these aspects of car components it is important to have good knowledge of current manufacturing processes and the possibilities and challenges that come with them and their relationship to already well-established processes. This report focuses on the relatively new RheoMetal-process (called rheocasting in this report), a process that uses a partly solidified slurry to fill the mold, and the conventional high pressure die casting (HPDC) which uses a liquid melt, and their differences in casting aluminum-alloys from both a process-and design perspective. The RheoMetal-process is also compared to a few other semi-solid processes on the market, thixocasting, GISS and SEED. This report is meant to work as a foundation for product developers at Volvo Cars to learn about rheocasting, and eventually use to make future choices for manufacturing processes for aluminum alloys. With a literature review, interviews with experts and professionals and analysis of casting simulations, information of the processes and their effect on material properties was collected and compiled. What could be concluded from these methods was that the slurry in the RheoMetal process has a globular microstructure, unlike the melt in HPDC which is dendritic. The globular microstructure in rheocasting is caused from shearing the slurry which makes it run more easily. The thicker consistency of the slurry makes the flow more laminar when filling a mold which makes for less air entrapment and defects in the material. The reduced number of defects opens the possibility of using T6 heat treatment on rheocasted components to reach improved mechanical properties, which would normally not be recommended for components made with HPDC. The globular microstructure makes the slurry flow easier which means, in combination with less defects, thinner components can be cast with similar strength as thicker components made with HPDC. This would contribute to weight reduction in a car, and in turn less fuel consumption. With rheocasting, a wider range of alloys can be used because of the ability of using non-eutectic alloys for the slurry. From research and analysis of simulations it could also be concluded that a combination of a high solid phase fraction and low gate velocity result in a more laminar flow and therefore fewer porosities in the final component.

In this study, TiB2/7075 aluminum matrix composites were prepared via in situ synthesis. It was found that TiB2 particles are mainly quadrate. Large TiB2 particles (1&ndash, 2 &mu, m) agglomerate at grain boundaries, but most of the particles are on the submicron scale. Adding 4.5 wt.% TiB2 particles effectively optimizes &alpha, Al grains in the 7075 aluminum alloy. By combining in situ reinforcing particles with the self-stirring effect of a serpentuator, rheocasting of the 7075 aluminum alloy was achieved in a simple and economical way. The average grain size of the specimen after rheocasting and heat treatment was smaller than 33 &mu, m, and the shape factors were greater than 0.85. The wear resistance of the 4.5 wt.% TiB2/7075 aluminum matrix composite that was prepared via rheocasting and gravity casting was tested with loads of 30, 60, 90, and 120 N at a friction speed of 0.15 m/s for a duration of 30 min. Because of the optimized microstructure and increased hardness, the wear resistance of the 4.5 wt.% TiB2/7075 aluminum matrix composite was significantly better than that of the 7075 aluminum alloy, and the wear resistance of the rheocast TiB2/7075 aluminum matrix composite was better than that of the gravity cast one.

A possibilidade de obtenção de peças near-net-shape faz com que o magnésio tenha destaque na indústria, que vem buscando redução de peso e aumento de eficiência. Porém a anisotropia microestrutural, causada pelo processo de fundição, e a baixa resistência mecânica em temperaturas elevadas é um problema para a utilização em larga escala. Assim, o objetivo principal desse trabalho é estudar a influência do tempo de agitação e da temperatura de agitação na fabricação de lingotes de magnésio pelo método de Reofundição. Para isso, lingotes com a composição química nominal de Mg-6Al-3La-1Ca foram fundidos em forno resistivo com atmosfera inerte e agitados mecanicamente no estado semissólido por meio de um agitador mecânico. Variou-se o tempo de agitação de 1 até 10 minutos e a temperatura de 585°C a 605°C, obtendo-se frações sólidas entre 29% até 57%. Dos lingotes reofundidos obtidos foram extraídos corpos de prova que foram submetidos a ensaios mecânicos de tração e de dureza e também foram realizadas análises em microscopia óptica e eletrônica para identificar a evolução morfológica dos lingotes agitados mecanicamente Também foram realizados ensaios de difração de raios X para identificar as fases encontradas. Os resultados mostraram que houve a formação de glóbulos na matriz do material e que houve a precipitação das fases α-Mg, Al11La3, (Mg,Al)2Ca e Mg2Ca. O melhor nível de globularização foi atingido para o tempo de agitação de 2 minutos. A melhor resistência mecânica foi atingida para a temperatura de agitação de 605°C. Nessa temperatura, a resistência à tração apresentou incremento de 75% e a deformabilidade atingiu um aumento de 83% em comparação a um lingote sem agitação. A agitação na temperatura de 605°C influenciou a formação da fase Al11La3 fazendo-a precipitar na região interglobular. Para agitação abaixo de 605°C a fase Al11La3 precipitou tanto no centro quanto na fronteira dos glóbulos. The industry's demand for weight reduction due to environmental restrictions and the research for more efficient products have made the demand for magnesium alloys to increase in recent decades. The research for light materials, with good creep resistance and easy manufacturing has increased in recent years. Thus, the main objective of this work is to study the influence of both time and processing temperature on magnesium by the Rheocasting method. For this purpose, commercial ingots of Mg-6Al-3La-1Ca were melted in a resistive furnace with an inert atmosphere and it was agitated through a mechanical stirrer inserted in the bath when they were in the semissolid state. It was used 1 to 10 minutes stirring time and the temperatures changed from 585°C to 605°C. Specimens were extracted from the cast ingots obtained and subjected to both mechanical tensile and hardness tests. In order to study morphological evolution in magnesium alloy images have been performed in optical and electron microscopy. X-ray diffraction were also performed to identify the microcompounds The results allowed to conclude that there was a great amount of globularization of the structures and there was a precipitation of globular α-Mg, Al11La3, (Mg,Al)2Ca and Mg2Ca phases. Acicular structures Al11La3 changed their solidification route: to temperatures above 605°C they have precipitated at globules boundary; however, to temperatures below 605°C they have precipitated both at globules center and boundary. The manganese presence led to a precipitation of a faceted microcompounds formed by Al-La-Mn. The tensile strength results increased 75% and a deformability increased 83% when compared to non-stirred ingot solidified at same condition at 605°C. The stirring time variation has confirmed the theory about dendrite’s break followed by Ostwald Ripening phenomenon due to globularization of structures and subsequent thickening.

Recent studies regarding semi-solid casting as a viable alternative to conventional liquid metal casting have been met with considerable interest. The dual nature of semi-solid materials results in a marked decrease in internal defects otherwise associated with conventional casting methods. In recent years, the National Research Council Canada - Aluminum Technology Centre (NRC-ATC) has dedicated itself to better understanding the behaviour of semi-solid aluminum alloys, notably 357, using the SEED (Swirled Enthalpy Equilibration Device) rheocasting method. SEED is a novel process which relies on the mechanical agitation and cooling of molten aluminum to produce a semi-solid billet. This billet is then injected into a die to yield the desired cast shape. The current work focuses on the rheocasting of a 357 aluminum alloy support bracket, consisting of four rings. Material flow around a ring is known to result in a welding of the two metal fronts. Traces of porosity and oxides can sometimes be found at the weld, unless preventative measures are taken. These include the use of overflows attached to the ring via a web as well as a careful control of the casting parameters. At NRC-ATC, several parts were rheocast and then subjected to both destructive and non-destructive testing, in an effort to better understand the material flow behaviour around these rings. The results obtained are presented herein., 12th International Conference on Semi-Solid Processing of Alloys and Composites, October 8-11 2012, Cape Town, South Africa