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Este trabajo presenta un estudio detallado sobre la aleación de aluminio A356, enfocándose en la formación de microestructuras globulares durante el proceso de conformado en estado semisólido. Las aleaciones de aluminio son ampliamente utilizadas en diversas industrias, como la automotriz y aeroespacial, debido a su combinación de ligereza y resistencia mecánica. El objetivo principal de este estudio es identificar las condiciones óptimas de temperatura y velocidad de agitación que permiten obtener una microestructura globular en la aleación A356, mejorando así sus propiedades mecánicas. El proceso experimental se llevó a cabo utilizando un equipo especializado, diseñado para medir y analizar la reología de los materiales en función de la temperatura y la velocidad de agitación. Se realizaron ensayos a diferentes temperaturas y velocidades, utilizando técnicas de conformado en estado semisólido como el rheocasting, un método que reduce defectos y mejora la calidad de las piezas. Los resultados mostraron que tanto la velocidad de agitación como la temperatura de inicio del proceso son críticos para la obtención de una microestructura globular. En particular, se observó que una velocidad de agitación de 400 rpm combinada con una temperatura inicial de 680°C ofrecía los mejores resultados en términos de calidad de la microestructura para esta aleación. Estos hallazgos tienen implicaciones significativas para la producción industrial, ya que permiten optimizar el proceso de fabricación y mejorar la calidad del producto final., This work presents a detailed study of aluminum alloys A356 and A380, focusing on the formation of globular microstructures during the semisolid forming process. Aluminum alloys are widely used in various industries, such as automotive and aerospace, due to their combination of lightness and mechanical strength. The main objective of this study is to identify the optimal conditions of temperature and stirring speed that allow obtaining a globular microstructure in A356 and A380 alloys, thereby improving their mechanical properties. The experimental process was carried out using specialized equipment designed to measure and analyze the rheology of materials as a function of temperature and stirring speed. Tests were conducted at different temperatures and speeds, using semisolid forming techniques such as rheocasting, a method that reduces defects and improves the quality of the parts. The results showed that both the stirring speed and the initial process temperature are critical for obtaining a globular microstructure. In particular, it was observed that a stirring speed of 400 rpm combined with an initial temperature of 680°C offered the best results in terms of microstructure quality for both alloys. These findings have significant implications for industrial production, as they allow optimizing the manufacturing process and improving the quality of the final product.

Aquest projecte presenta una anàlisi d’un procés d’extrusió sub-sòlidus de l’aliatge d’alumini A356 mitjançant l’avaluació termodinàmica, la mesura de forces de procés, la microscòpia òptica i electrònica i la interpretació estadística. L’anàlisi termodinàmica implica la caracterització dels paràmetres d’escalfament per a diferents temperatures, proporcionant informació sobre el seu comportament en estat sòlid. Les mesures de forces d’extrusió quantifiquen les forces involucrades en la conformació i el tractament del material, revelant les diferències entre els diferents valors de temperatura estudiats. Per realitzar l’estudi metal·logràfic s’utilitza tant la microscòpia òptica, per identificar les fases presents, com l'electrònica, per examinar la composició de l'aliatge, oferint més detalls sobre les fases presents i les seves característiques. Finalment, es realitzen assajos de duresa per, posteriorment, analitzar estadísticament les dades experimentals identificant factors i interaccions significatives que afecten els resultats del procés. La utilització d’aquestes tècniques permeten una comprensió exhaustiva del procés metal·lúrgic., This project presents an analysis of a sub-solidus extrusion process of the aluminum alloy A356 through thermodynamic evaluation, process force measurement, optical and electron microscopy, and statistical interpretation. The thermodynamic analysis involves characterizing the heating parameters at different temperatures, providing information about its behavior in the solid state. The extrusion force measurements quantify the forces involved in the shaping and treatment of the material, revealing differences between the various temperature values studied. For the metallographic study, both optical microscopy, to identify the present phases, and electron microscopy, to examine the alloy composition, are used, offering more details about the present phases and their characteristics. Finally, hardness tests are conducted and subsequently, the experimental data is statistically analyzed to identify significant factors and interactions affecting the process results. The use of these techniques allows for a comprehensive understanding of the metallurgical process.

The comparative analysis of the two hybrid composites, obtained by the compocasting process, based on A356 and ZA-27 alloys and reinforced with 10 wt. % SiC and 0, 1 and 3 wt. % graphite (Gr) is presented. Optimisation of their tribological behaviour was performed by the Taguchi method and the artificial neural network (ANN). Tribological tests were performed on a block-on-disk tribometer, at three sliding speeds, three normal loads and a sliding distance of 600 m, without lubrication. Results obtained by the ANOVA showed that the hybrid composites based on A356 alloy have the better wear resistance and that the composite reinforced with 10 wt. % SiC and 1 wt. % Gr has the lowest wear rate. The lowest coefficient of friction was obtained for a composite based on ZA-27 alloy reinforced with 10 wt. % SiC, at a normal load of 10 N and sliding speed of 1 m/s.

The comparative analysis of the two hybrid composites, obtained by the compocasting process, based on A356 and ZA-27 alloys and reinforced with 10 wt. % SiC and 0, 1 and 3 wt. % graphite (Gr) is presented. Optimisation of their tribological behaviour was performed by the Taguchi method and the artificial neural network (ANN). Tribological tests were performed on a block-on-disk tribometer, at three sliding speeds, three normal loads and a sliding distance of 600 m, without lubrication. Results obtained by the ANOVA showed that the hybrid composites based on A356 alloy have the better wear resistance and that the composite reinforced with 10 wt. % SiC and 1 wt. % Gr has the lowest wear rate. The lowest coefficient of friction was obtained for a composite based on ZA-27 alloy reinforced with 10 wt. % SiC, at a normal load of 10 N and sliding speed of 1 m/s.

The comparative analysis of the two hybrid composites, obtained by the compocasting process, based on A356 and ZA-27 alloys and reinforced with 10 wt. % SiC and 0, 1 and 3 wt. % graphite (Gr) is presented. Optimisation of their tribological behaviour was performed by the Taguchi method and the artificial neural network (ANN). Tribological tests were performed on a block-on-disk tribometer, at three sliding speeds, three normal loads and a sliding distance of 600 m, without lubrication. Results obtained by the ANOVA showed that the hybrid composites based on A356 alloy have the better wear resistance and that the composite reinforced with 10 wt. % SiC and 1 wt. % Gr has the lowest wear rate. The lowest coefficient of friction was obtained for a composite based on ZA-27 alloy reinforced with 10 wt. % SiC, at a normal load of 10 N and sliding speed of 1 m/s.

The comparative analysis of the two hybrid composites, obtained by the compocasting process, based on A356 and ZA-27 alloys and reinforced with 10 wt. % SiC and 0, 1 and 3 wt. % graphite (Gr) is presented. Optimisation of their tribological behaviour was performed by the Taguchi method and the artificial neural network (ANN). Tribological tests were performed on a block-on-disk tribometer, at three sliding speeds, three normal loads and a sliding distance of 600 m, without lubrication. Results obtained by the ANOVA showed that the hybrid composites based on A356 alloy have the better wear resistance and that the composite reinforced with 10 wt. % SiC and 1 wt. % Gr has the lowest wear rate. The lowest coefficient of friction was obtained for a composite based on ZA-27 alloy reinforced with 10 wt. % SiC, at a normal load of 10 N and sliding speed of 1 m/s.

The comparative analysis of the two hybrid composites, obtained by the compocasting process, based on A356 and ZA-27 alloys and reinforced with 10 wt. % SiC and 0, 1 and 3 wt. % graphite (Gr) is presented. Optimisation of their tribological behaviour was performed by the Taguchi method and the artificial neural network (ANN). Tribological tests were performed on a block-on-disk tribometer, at three sliding speeds, three normal loads and a sliding distance of 600 m, without lubrication. Results obtained by the ANOVA showed that the hybrid composites based on A356 alloy have the better wear resistance and that the composite reinforced with 10 wt. % SiC and 1 wt. % Gr has the lowest wear rate. The lowest coefficient of friction was obtained for a composite based on ZA-27 alloy reinforced with 10 wt. % SiC, at a normal load of 10 N and sliding speed of 1 m/s.

The comparative analysis of the two hybrid composites, obtained by the compocasting process, based on A356 and ZA-27 alloys and reinforced with 10 wt. % SiC and 0, 1 and 3 wt. % graphite (Gr) is presented. Optimisation of their tribological behaviour was performed by the Taguchi method and the artificial neural network (ANN). Tribological tests were performed on a block-on-disk tribometer, at three sliding speeds, three normal loads and a sliding distance of 600 m, without lubrication. Results obtained by the ANOVA showed that the hybrid composites based on A356 alloy have the better wear resistance and that the composite reinforced with 10 wt. % SiC and 1 wt. % Gr has the lowest wear rate. The lowest coefficient of friction was obtained for a composite based on ZA-27 alloy reinforced with 10 wt. % SiC, at a normal load of 10 N and sliding speed of 1 m/s.

Aquest estudi es va centrar en examinar les característiques reològiques de l'aliatge d'alumini A356 en un estat semisòlid i agitat mecànicament a velocitats entre 200-300 rpm (20,94-31,42 rad/s) durant 15 segons, obtenint una estructura aproximadament globular. Es va utilitzar el prototip PMSM per crear lingots amb una microestructura no dendrítica, mesurant paràmetres com el corrent elèctric, el parell i la viscositat de l'aliatge a diferents velocitats de rotació i refredament sostingut. Els lingots es van tallar en mostres més petites i preparats per a l'anàlisi microscòpica, per observar la microestructura de l’aliatge mitjançant un microscopi. Aquest aspecte no es va poder dur a terme a causa de les dificultats d’accés a la xarxa necessària per a l’anàlisi requerida. Als experiments inicials amb el prototip es van trobar problemes a causa del desgast de la barra agitadora de l'aliatge. Després de reparar la barra i reduir el frec variable entre aquesta i el seu suport de refrigeració, es van repetir els experiments, aconseguint resultats satisfactoris en termes de viscositat amb la nova configuració. Se suggereix modificar la part inferior del suport de refrigeració, afegint-hi un rodament per minimitzar-ne l'impacte en el consum elèctric i, per tant, en els resultats obtinguts. Com a segona part de l'estudi reològic, es va realitzar una anàlisi de les micrografies obtingudes prèviament, caracteritzant les partícules detectades a les mostres metal·logràfiques preses a temperatures de 670-690 °C i velocitats de 100-200 rpm (10,47-20,94 rad /s) durant 10 segons. Es va utilitzar el programari d'anàlisi ImageJ per caracteritzar la mida, la forma, la densitat i la distribució de les partícules detectades. Els resultats de l'anàlisi metal·logràfic es consideren satisfactoris, ja queconcorda amb els valors literaris i es va aconseguir una caracterització més quantitativa de la microestructura., Este estudio se centró en examinar las características reológicas de la aleación de aluminio A356 en un estado semisólido y agitado mecánicamente a velocidades entre 200 y300 rpm, con una estructura aproximadamente globular. Se utilizó el prototipo PMSM para crear lingotes con una microestructura no dendrítica, ajustando parámetros como la corriente eléctrica, el par y la viscosidad de la aleación a diferentes velocidades de rotación y enfriamiento continuo. Tras la solidificación de los lingotes se prepararon las muestras para el análisis metalográfico de la microestructura resultante usando un microscopio, aunque este aspecto del estudio no pudo llevarse a cabo debido a problemas informáticos con el equipo necesario Los experimentos iniciales con el prototipo encontraron problemas debido al desgaste de la barra agitadora de la aleación. Tras reparar la barra y reducir el roce entre esta y su soporte de refrigeración, se repitieron los experimentos, logrando resultados satisfactorios en términos de viscosidad con la nueva configuración. Se sugiere modificar la parte inferior del soporte de refrigeración, añadiendo un rodamiento para minimizar su impacto en el consumo eléctrico y, por ende, en los resultados obtenidos Como segunda parte del estudio reológico, se realizó un análisis de las micrografías obtenidas previamente, caracterizando las partículas detectadas en las muestras metalográficas tomadas a temperaturas de 670-690 °C y velocidades de 100-200 rpm (10,47-20,94 rad/s) durante 10 segundos. Se utilizó el software de análisis ImageJ para caracterizar el tamaño, forma, densidad y distribución de las partículas detectadas. Los resultados del análisis metalográfico se consideran exitosos, ya que concuerda con los valores literarios y se logró una caracterización más cuantitativa de la microestructura., This study examined the rheological characteristics of A356 aluminium alloy in a semi-solid state and mechanically stirred at low speeds (200-300 rpm or 20,94-31,42 rad/s), with an approximately globular structure. The PMSM prototype was used to create ingots with a non-dendritic microstructure, adjusting parameters such as electrical current, torque, and alloy viscosity at different rates of rotation and sustained cooling. After creating the ingots, the ingots are cut into smaller samples for microscopic analysis. This analysis involved examining the microstructure of the alloy using a microscope and observing the resulting globular structure. This particular aspect of the study was unable to be conducted due to difficulties in accessing the network that was necessary for the required analysis. Initial experiments with the prototype found problems due to wear on the alloy stirrer bar. After repairing the bar and reducing the friction between it and its cooling support, the experiments were repeated, achieving satisfactory results in terms of viscosity with the new configuration. It is suggested to modify the lower part of the cooling support, adding a bearing to minimize its impact on electrical consumption and, therefore, on the results obtained. As a second part of the rheological study, an analysis of the previously obtained micrographs was carried out, characterizing the particles detected in the metallographic samples taken at temperatures of 670-690 °C and speeds of 100-200 rpm (10,47-20,94 rad /s) for 10 seconds. ImageJ analysis software was used to characterize the size, shape, density, and distribution of the detected particles. The metallographic analysis is successful since it agrees with the literary values and a more quantitative characterization of the microstructure was achieved. .

Heat treatable aluminum alloys require post-fabrication steps to achieve the desired properties. The conditions to treat cast aluminum parts are well established, however the same processes are not well studied for additive manufactured (AM) parts. This study evaluated the effects of post-printing processes on the hardness of metal parts fabricated by AM. The research focused on the intermediate period from print completion to immersion of the sample into the quenching bath and how delays can influence the part’s hardness. Those results were compared to samples that were then solution treated. Aging procedures were conducted to evaluate the influence of diverse time and temperature on hardness. In addition to post-printing process studies, an experiment was conducted to evaluate the effects of introducing additional argon into the printing environment as the 3D part is produced. It was found that quenching after the initial minute of print completion has lasting effects on hardness that are not reversed by the solution treatment step at the temperatures and times employed. Modifying the standard aging time and temperature by ± 15ºC or ± 20 minutes did not show a significant effect on the mechanical properties of the prints (<3% change in hardness). Samples that were heat treated increased in hardness, demonstrating the usefulness of the T6 heat treatment. The 3D printer was employed to fabricate the component used to distribute extra argon into the printing environment., Lieutenant, United States Navy, Approved for public release. Distribution is unlimited.

Additive manufacturing (AM) applications continue to gain traction as a viable and advantageous means of manufacturing compared to traditional manufacturing (TM) techniques. Liquid metal printing is an AM technique in which a metal filament is melted in a nozzle and delivered onto a heated bed, layer by layer, to build a part. This work studied the mechanical properties and microstructural features of liquid metal printed Al-4008 by performing tensile and microhardness tests, along with X-ray diffraction (XRD), optical microscopy (OM) and scanning electron microscopy (SEM) analysis. Mechanical properties of Al-4008 parts produced via liquid metal printing were compared to A356 cast aluminum parts following T6 heat treatment. Microhardness tests revealed that the hardness, tensile, and yield strength increase 2-3 times after the solution treatment and artificial aging. Print direction directly affects mechanical properties, specifically tensile strength (UTS) and yield strength., Lieutenant, United States Navy, Approved for public release. Distribution is unlimited.

Purpose This study aims to present a novel methodology for the evaluation of tribological properties of new nanocomposites with the A356 alloy matrix reinforced with aluminium oxide (Al2O3) nanoparticles. Design/methodology/approach Metal matrix nanocomposites (MMnCs) with varying amounts and sizes of Al2O3 particles were produced using a compocasting process. The influence of four factors, with different levels, on the wear rate, was analysed with the help of the design of experiments (DoE). A regression model was developed by using the response surface methodology (RSM) to establish a relationship between the observed factors and the wear rate. An artificial neural network was also applied to predict the value of wear rate. Adequacy of models was compared with experimental values. The extreme values of wear rate were determined with a genetic algorithm and particle swarm optimization using the RSM model. Findings The combination of optimization methods determined the values of the factors which provide the highest wear resistance, namely, reinforcement content of 0.44 wt.% Al2O3, sliding speed of 1 m/s, normal load of 100 N and particle size of 100 nm. Used methods proved as effective tools for modelling and predicting of the behaviour of aluminium matrix nanocomposites. Originality/value The specific combinations of the optimization methods has not been applied up to now in the investigation of MMnCs. In addition, using of small content of ceramic nanoparticles as reinforcement has been poorly investigated. It can be stated that the presented approach for testing and prediction of the wear rate of nanocomposites is a very good base for their future research.

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 procesam, 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 eleme

Optimization of tribological behaviour of hybrid composites based on A356 and ZA27 alloys reinforced with 10 wt. % SiC and 0, 1 and 3 wt. % Gr is presented in this paper. Optimization was performed using the Taguchi method and the artificial neural network (ANN). Hybrid composites were obtained by compocasting procedure. The analysis shows that hybrid composites based on A356 alloy have better tribological characteristics, while the one reinforced with 10 wt. % SiC and 1 wt. % Gr shows the least wear.

Se lleva a cabo un estudio del contexto histórico y una revisión de las técnicas más importantes de la actualidad en el campo de la industria de los semisólidos para obtener un mejor entendimiento del funcionamiento del prototipo PMSM y cómo se llegó a su diseño. A la vez, se exponen las ventajas de los procesos de conformado de semisólidos con respecto a las técnicas tradicionales. Un breve estudio de la reología y los diferentes tipos de fluidos, junto a sus características más diferenciales ha sido realizado para entender cómo se comportan y obtienen las propiedades del lodo semisólido. El método para medir la viscosidad en el prototipo PMSM ha sido revisado. Se han estudiado las características que definen la aleación de aluminio A356 y su viabilidad para la industria del semisólido, junto a sus opciones de posprocesado. Más adelante, se lleva a cabo la experimentación y pruebas del prototipo PMSM con aluminio A356. Los resultados obtenidos son analizados y los mejores parámetros para el proceso se ponen bajo debate. Se realiza adicionalmente una comprobación con la bibliografía obtenida para comprobar la veracidad de los resultados. Finalmente, los conflictos durante el proceso y opciones de mejora para un mejor funcionamiento futuro y la posibilidad de obtener más versatilidad en la obtención de datos son expuestas., A review of the most important techniques and the historical background of the semisolid forming industry is done in order to understand the functioning of the PMSM prototype and what led to its design. Advantages of SSM forming processes in comparison to conventional processing techniques are discussed. A rheology study is carried out, analyzing and discussing the different fluid types and its features, along with the different models and equations used to represent the behavior of each one. A rheological characterization of semisolid slurries and the reasons of it are showcased, and the best way to measure the viscosity properties in the PMSM prototype is analyzed. Aluminum A356 alloy’s properties are showcased and its viability for the semisolid processing industry is discussed, along its advantages and posttreatment options. Later on, experimentation with Aluminum A356 is carried out in the PMSM prototype. The obtained samples are analyzed and the process data is put under observation in order to find the best combination of the local process parameters. A comparison with current bibliographic data is done in order to prove the veracity of the obtained data. Finally, process issues and improvement options for the future are debated in order to obtain better results, more testing options and versatility and to improve the process stability in the future.

This project aims to complete the validation and improve and optimize the experimentation process to obtain a globular microstructure of Aluminum A356 using a crucible and a stir bar, to obtain results from the viscosity data. On the other hand the improvement of the processes developed to obtain this microstructure, such as heating times, and the process of obtaining the ingots. The base of the crucible has been modified, adding one with a larger surface for better stability and a reduction in possible accidents. Experimentation with the foundry has been affected due to the covid-19 pendemic and the confinement that did not allow attendance at the laboratory. Improvements have been proposed for the optimization of time when melting aluminum by parallelizing tasks and preparing castings in secondary ovens for better production in order to obtain ingots. And improvements to the stir bar cooling. The results obtained from the tests performed are positive, as they face where to go, what values to work with, and most importantly, a procedure for calibrating the machine to obtain reliable results. It is recommended to maintain a regime below 150 revolutions per minute to obtain the globular microstructure and keep the crucible without any residual water by preheating it to evaporate any drop left of water in the crucible and the mold as the combination of aluminum and water is very dangerous., Aquest projecte té com a objectiu completar la validació i millorar i optimitzar el procés d'experimentació per obtenir una microestructura globular de l'Alumini A356 utilitzant un crisol i una barra de remenar, i obtenir resultats a partir de les dades de viscositat. Per altra banda la millora dels processos desenvolupats per a l'obtenció d'aquesta microestructura, com són els temps d'escalfament, i el procés d'obtenció dels llingots. S'ha modificat la base del crisol, afegint una amb una superfície més gran per una millor estabilitat d'aquest i una reducció de possibles accidents. L'experimentació amb la fundició s'ha vist afectada degut a la pendèmia del covid-19 i el confinament que no va permètre l'asssistència al laboratori. S'ha proposat millores per a la optimització del temps a l'hora de fondre l'Alumini paral·lelitzant tasques i preparant colades en forns secundaris per una millor producció de cara a obtenció de llingots. I millores en la refrigeració de la barra de remenar. Els resultats obtinguts de les proves realitzades són positius, ja que s'encaren cap a on s'ha d'anar, amb quins valors s'ha de treballar, i el més important, un procediment de calibració de la màquina per obtenir uns resultats fiables. Es recomana mantenirun règim per sota de les 150 revolucions per minut per a la obtenció de la microestructura globular i mantenir el crisol sense cap resta d'aigua pre-escalfant-lo per evaporar qualsevol gota que quedi tant al crisol com en el motlle ja que la combinació d'aquests és molt perillosa.

Two types of A356 alloy castings in initial and modified with nanoparticles condition produced by gravitational casting were studied. Samples, as-cut from the castings, were subjected to light optical microscopy (LM), thermal analyses, Electron Backscattered Diffraction (EBSD) and Scanning Transmission Electron Microscopy (STEM) analyses. Results, obtained by EBSD, confirmed that there is grain refinement in samples from castings with added nanoparticles compared to the initial ones. STEM analysis shows agglomerates of nanoparticles in examined foils. Nanoparticles’ position in the microstructure confirms the hypothesis that they act as nucleating sites during the alloy solidification, which is the reason for observed fine-grained microstructure., (OLD) MSE-3

This paper presents the investigation of tribological behaviour of aluminium hybrid composites with Al–Si alloy A356 matrix, reinforced with 10 wt% silicon carbide and 0, 1 and 3 wt% graphite (Gr) with the application of Taguchi’s method. Tribological investigations were realized on block-on-disc tribometer under lubricated sliding conditions, at three sliding speeds (0.25, 0.5 and 1 m/s), three normal loads (40, 80 and 120 N) and at sliding distance of 2400 m. Wear rate and coefficient of friction were measured within the research. Analysis of the results was conducted using ANOVA technique, and it showed that the smallest values of wear and friction are observed for hybrid composite containing 3 wt% Gr. The prediction of wear rate and coefficient of friction was performed with the use of artificial neural network (ANN). After training of the ANN, the regression coefficient was obtained and it was equal to 0.98905 for the network with architecture 3-20-30-2.

This paper presents the investigation of tribological behaviour of aluminium hybrid composites with Al-Si alloy A356 matrix, reinforced with 10 wt% silicon carbide and 0, 1 and 3 wt% graphite (Gr) with the application of Taguchi's method. Tribological investigations were realized on block-on-disc tribometer under lubricated sliding conditions, at three sliding speeds (0.25, 0.5 and 1 m/s), three normal loads (40, 80 and 120 N) and at sliding distance of 2400 m. Wear rate and coefficient of friction were measured within the research. Analysis of the results was conducted using ANOVA technique, and it showed that the smallest values of wear and friction are observed for hybrid composite containing 3 wt% Gr. The prediction of wear rate and coefficient of friction was performed with the use of artificial neural network (ANN). After training of the ANN, the regression coefficient was obtained and it was equal to 0.98905 for the network with architecture 3-20-30-2.

This paper presents the investigation of tribological behaviour of aluminium hybrid composites with Al–Si alloy A356 matrix, reinforced with 10 wt% silicon carbide and 0, 1 and 3 wt% graphite (Gr) with the application of Taguchi’s method. Tribological investigations were realized on block-on-disc tribometer under lubricated sliding conditions, at three sliding speeds (0.25, 0.5 and 1 m/s), three normal loads (40, 80 and 120 N) and at sliding distance of 2400 m. Wear rate and coefficient of friction were measured within the research. Analysis of the results was conducted using ANOVA technique, and it showed that the smallest values of wear and friction are observed for hybrid composite containing 3 wt% Gr. The prediction of wear rate and coefficient of friction was performed with the use of artificial neural network (ANN). After training of the ANN, the regression coefficient was obtained and it was equal to 0.98905 for the network with architecture 3-20-30-2.

This paper analyses wear behaviour of Al-Si alloy A356 (AlSi7Mg) based composite reinforced with 10 wt. % SiC, and compare it with the base A356 alloy. Composite are obtained using the compocasting procedure. Tribological testing have been conducted on a block-on-disc tribometer with three varying loads (10, 20 and 30 N) and three sliding speeds (0.25, 0.5 and 1 m/s), under dry sliding conditions. Sliding distance of 300 m was constant. The goal of the paper was to optimize the influencing parameters in order to minimize specific wear rate using the Taguchi method. The analysis showed that the sliding speed has the greatest influence on specific wear rate (39.5 %), followed by the load (23.6 %), and the interaction between sliding speed and load (19.4 %). A regression analysis and experiment corroboration was conducted in order to verify the results of the optimization. Specific wear rate prediction was done using artificial neural network (ANN).

In this work the heat treatment response of SSM processed A356 and A357 casting alloys was analysed. The development of a new T6 heat treatment, with solution times less than 30 mm has been allowed. In this new short heat treatment, the alloy showed better mechanical properties compared to the same alloy which heat treated in standard conditions (solution time between 6 h and 8 h). This new heat treatment, carried out at the solution temperature of 540 degrees C, enabled the complete magnesium dissolution, while minimizing the grain growth of the alpha-phase and the eutectic silicon. Although this experiment was carried out on A356 and A357 aluminium alloys, conformed by Sub-Liquidus-Casting process (SLC), the results may be applied to the components produced with other semi-solid technologies or others Al-Si hardenable alloys that form coherent magnesium inter-metallic precipitates. (C) 2014 Elsevier B.V. All rights reserved., Peer Reviewed, Postprint (published version)

Se estudian los cambios microestructurales que tienen lugar en los tratamientos térmicos de las aleaciones AlSi, con- formadas en estado semisólido, durante las etapas de puesta en solución y envejecimiento. El estudio ha permitido proponer nuevos tratamientos T6, con tiempos de puesta en solución inferiores a los 30 min, manteniendo o mejorando las propiedades mecánicas que se obtienen con los actuales procesos de tratamiento de 6 a 8 h. Estos tratamientos de corta duración, realizados a 540 o C, permiten una completa disolución del magnesio, minimizando al mismo tiempo el crecimiento de los granos y del silicio eutéctico. Si bien la experimentación se ha realizado con componentes producidos por Sub-Liquidus Casting (SLC) con aleaciones A356 y A357, se considera que los resultados obtenidos pueden ser aplicables a los componentes producidos en estado semisólido por otras tecnologías, con diferentes aleaciones AISi que se endurecen por formación de precipitados coherentes de magnesio. La caracterización del material se ha realizado mediantes análisis micrográficos, ensayos de dureza y ultramicrodureza., Peer Reviewed, Postprint (published version)

This work is an experimental approach to understand the effect of the microstructure on large strain deformation behavior of A356 alloy (with various additions of titanium and strontium) under uniaxial tensile, compressive and V-bend loading conditions. The studies were carried out on unmodified and Sr-modified A356 Al alloy, where Sr was added to refine the morphology of the eutectic Si phase particles. The two variants were then used to study the effect of size and shape distributions of Si eutectic phase particles within the material on the deformation behavior under uniaxial tension, compression and V-bending conditions. The alloy with a modified and refined eutectic Si phase particles showed significant improvement in ductility and bendability, whereas the differences in compression were not appreciable. In addition to Sr addition, Ti was also added as a grain refiner to the alloys at three different levels to obtain microstructures with different grain sizes. The results in the form of full field strain maps show that the larger grained alloy exhibits extensive strain inhomogeneity, whereas the grain refined alloy shows a more homogenous loading pattern., Master of Applied Science (MASc)

En este trabajo se revisan los antecedentes en la conformación de aleaciones de aluminio en estado semisólido, y se describen algunos procesos de acuerdo con la bibliografía consultada. Mediante la técnica de Sub Liquidus Casting se han fabricado, con la aleación A356, componentes de motocicleta. A estos materiales se les han realizado tratamientos térmicos de envejecimiento T5 y T6 con objeto de mejorar sus propiedades mecánicas, dado que esta tecnología de inyección permite estos tratamientos. Esta es una de las grandes ventajas de estos procesos frente a la inyección a alta presión convencional. Se ha estudiado también el efecto de los tratamientos térmicos en las propiedades mecánicas, mediante ensayos de tracción. A continuación se ha profundizado en el estudio de la influencia de los parámetros velocidad y temperatura de ensayo en las propiedades mecánicas de estos materiales a tracción. Así mismo, se han obtenido los coeficientes de endurecimiento por deformación n y de resistencia K del material, que nos permiten conocer en profundidad el comportamiento plástico de estos materiales. Los resultados obtenidos podrán ser aplicados a programas de simulación de procesos de conformación así como en la aplicación industrial de estos componentes. La experimentación ha de permitir obtener la influencia que ejercen los parámetros tratamiento térmico, temperatura y velocidad en el módulo elástico, límite elástico, resistencia a la tracción, alargamiento, coeficiente de endurecimiento n y coeficiente de resistencia K.

Depuis quelques années, les recherches qui portent sur les procédés de mise en forme par voie semi-solide ne cessent d'augmenter. Cette popularité s'explique par les nombreux avantages que procure ce type de moulage par rapport au moulage traditionnel en phase liquide. Le procédé SEED (Swirled Enthalpy Equilibration Device) est une méthode de mise en forme de l'aluminium semi-solide actuellement développée par Alcan International Limited et le Centre des technologies de l'aluminium. Ce procédé utilise la masse thermique d'un creuset pour absorber une quantité définie de chaleur d'un lopin pour qu'il atteigne la température et la fraction solide voulues. L'avantage principal du procédé SEED est qu'il ne requiert pas de contrôle de températures sophistiqué. Le transfert de chaleur peut être aisément contrôlé par la masse et le matériau du creuset. L'objectif des travaux réalisés dans le cadre de cette maîtrise concerne l'évolution de la fraction solide en fonction de la température dans les lopins semi-solides produits par le procédé SEED. Comme les lopins sont destinés au moulage sous pression, il est essentiel de bien connaître les propriétés d'écoulement de la pâte pour obtenir des pièces ayant de bonnes propriétés mécaniques. Or, les propriétés rhéologiques de la pâte dépendent fortement de la fraction solide, d'où l'intérêt de la caractériser. Deux modèles théoriques sont fréquemment utilisés pour connaître la fraction solide en fonction de la température, soit le modèle de Scheil et celui de solidification à l'équilibre. Par contre, ces modèles demeurent des approximations et il est impossible de dire jusqu'à quel point l'évolution de la fraction solide dans les lopins semi-solides produits par le procédé SEED concorde avec ces modèles. Pour caractériser l'évolution de la fraction solide de l'aluminium, quatre approches ont été utilisées. Le logiciel Thermo-Cale a d'abord été utilisé pour tracer l'évolution de Penthalpie et de la fraction solide pour un alliage

Les alliages d'aluminium sont de plus en plus utilisés dans le monde du transport. Pour répondre à cette demande, les pièces moulées doivent respecter de hauts critères de performances. Ainsi, de nouvelles méthodes de moulage sont développées parce que les procédés traditionnels de moulage ne peuvent satisfaire ces nouvelles exigences. Une technique privilégiée de ces nouvelles technologies est le moulage des alliages semi-solides. Ce type de procédé implique l'utilisation de métal en cours de solidification impliquant la présence de particules de phase solide incluses dans la phase liquide. Le procédé SEED est l'un de ces procédés qui a comme avantage de procurer une grande intégrité aux pièces moulées augmentant ainsi les propriétés mécaniques des pièces. Le lopin semi-solide produit par le procédé SEED se doit de satisfaire des critères de qualité afin de mouler une pièce qui rencontre les spécifications désirées. Ce projet a donc pour mission de déterminer la faisabilité d'une méthodologie pour évaluer la conformité d'un lopin d'alliage d'aluminium semi-solide avant son injection dans le moule et d'établir des corrélations entre les mesures, la morphologie des grains et le pourcentage de la fraction solide du lopin semi-solide. Suite aux travaux réalisés par le CTA et Alcan avant le début de ce projet, les paramètres du procédé produisant des lopins d'aluminium A356 conformes ont été identifiés. En se basant sur ces paramètres, quatre signatures ont été déterminées pour caractériser les lopins considérés conformes. Ces mesures sont la base du système de contrôle de la qualité. Elles se divisent en deux volets. L'un est le volet de mesures non destructives qui comporte l'évolution temporelle de la température à deux endroits sur la surface du creuset et l'évolution temporelle de la masse d'aluminium drainée pendant l'étape de drainage du procédé SEED. L'autre est le volet de mesures destructives qui est l'évolution de la force appliquée pour la coupe longitudinal

Le traitement du métal semi-solide, MSS, fait référence a des gelées semi-solides contenant des particules non dendritiques qui sont dispersées dans une matrice liquide, le tout ayant une viscosité apparente voisine de celle du liquide. Cette masse peut s'écouler facilement sous pression et remplir les cavités complexes d'un moule pour fabriquer des produits de qualité et de haute-intégrité. La gelée de MSS peut être préparée par différentes méthodes. Dans la présente étude la coulée conventionnelle et la procédure SEED ont été utilisées pour produire des billettes de MSS avec différentes morphologies de la phase primaire a-Al dans l'alliage Al-Si A356. Pour la coulée conventionnelle, une gamme de morphologies de particules solides et de microstructures, ont été obtenues en variant température d'alimentation. Pour les billettes SEED, nouveau brevet d'ALCAN international pour la coulée semi-solide, les changements de morphologies ont été réalisés en contrôlant les paramètres du procédé pendant la solidification de la masse. Afin d'étudier l'évolution morphologique due à l'effet des différents paramètres du procédé, la température d'alimentation et les intensités de brassage, les billettes MSS préparées par les deux méthodes ont été étudiées en utilisant la métallographie quantitative. La microstructure de l'alliage de MSS A356 a été également caractérisée en utilisant une méthode innovatrice, soit la viscométrie par la compression entre plaques parallèles, ce qui a permis d'obtenir une corrélation entre la morphologie et la viscosité. L'objectif principal de la présente recherche était de tirer partie de principes rhéologiques pour étudier le comportement à la déformation de l'alliage A3 56 pour différentes morphologies et fractions solides, en traitent des billettes de MSS comme des fluides newtoniens et non newtoniens, respectivement. En outre, deux relations empiriques ont été proposées pour mettre en évidence le lien entre la viscosité, la fraction solide et la m

En tant qu'une des familles principales des alliages d'aluminium, les alliages Al-Si offrent une excellente coulabilité, une bonne résistance à la corrosion et des bonnes propriétés physiques et mécaniques. L'alliage A356.2 commercialement populaire, appartenant au système Al-Si-Mg, a d'excellentes caractéristiques de coulée, soudabilité, étanchéité de pression et résistance à la corrosion. L'alliage est généralement soumis à un traitement thermique (traitement T6) pour fournir de diverses combinaisons des propriétés de traction et physiques qui sont attrayantes pour plusieurs d'applications en industrie de l'automobile et de l'aérospatiale telles que des blocs de moteur, des têtes de cylindre et des roues. De tels composants critiques exigent que les pièces coulées présentent des propriétés conformes de résistance et de ductilité dans tout le matériel solidifié. Il est bien connu que la morphologie des particules eutectiques de silicium dans les alliages Al-Si soit un facteur principal qui détermine les propriétés mécaniques de ces alliages. Dans les conditions de tel que coulé, la microstructure d'alliage contient des particules fragiles et aciculaires de silicium sous forme de plaquettes avec des côtés pointus aux extrémités. D'un point de vue mécanique, la présence de telles particules sous forme plaquettes dégradera les propriétés mécaniques parce que des efforts inhérents seront centralisés sur les côtés et les extrémités pointus, ce qui entraîne une rupture rapide. D'autre part, si les particules eutectiques de silicium sont obtenues sous une forme fine et fibreuse (silicium fibreux), une telle morphologie contribue aux meilleures propriétés de traction avec des valeurs légèrement plus élevées de résistance à la traction finale et à des valeurs de ductilité considérablement plus grandes. En plus de la taille et de la forme des particules eutectiques de silicium, la taille de grain et le DAS (espacement de bras de dendrite) sont également importants pour les p

Avec leurs caractéristiques de basse masse volumique, de bas point de fusion, d'excellente coulabilité et de bonne résistance à la corrosion, les alliages aluminium-silicium (Al-Si) sont intensivement utilisés dans les applications d'automobiles. Les pièces produites à partir de ces alliages s'étendent dans plusieurs utilisations, à savoir, des blocs de moteur, des culasses et des roues. Deux des alliages commerciaux les plus populaires utilisés dans de telles applications sont les alliages de type A3 5 6 et 319, appartenant respectivement aux systèmes Al-Si-Mg et Al-Si-Cu. La qualité et les propriétés des pièces coulées sont déterminées par la qualité de leur microstructure, commandée par de divers paramètres tels que l'espace interdendritique (DAS, contrôlé lui même par le taux de solidification), le degré de modification de silicium eutectique et le degré d'affinage de grain, et la quantité de microporosités, d'intermétalliques et d'inclusions observées dans la microstructure. Parmi ces derniers facteurs, le taux de solidification est le plus important, car il affecte directement ou indirectement presque tous les autres paramètres microstructuraux. La modification de la morphologie du silicium eutectique de la forme aciculaire à une forme fibreuse est habituellement effectuée par l'addition du strontium (Sr) pour améliorer la ductilité de l'alliage. Les intermétalliques qui sont présents généralement en ces alliages sont les intermétalliques du fer B-Al5FeSi et a-Al5(Fe, Mn)3Si2, plaquettes, Mg2Si et, dans le cas des alliages 319, les intermétalliques de cuivre, CuAl2. En raison de leur fragilité, les intermétalliques de fer dont la nature est sous forme de plaquettes peuvent être tout à fait délétères aux propriétés de l'alliage, de même la présence de la porosité, en particulier en termes de qualité extérieure et solidité. Le but du travail actuel est d'étudier les paramètres métallurgiques contrôlant l'évolution microstructurale dans les alliages de type Al-Si