Les instabilités plastiques désignent une famille de comportements non-linéaires que l’on rencontre dans plusieurs matériaux solides. Elles correspondent à une évolution hétérogène de la déformation sous un chargement homogène, et se manifestent par un écrouissage irrégulier accompagné de bandes de localisation d’épaisseur millimétrique dont la cinétique est sensible, entre autres, à la température et à la vitesse de chargement. Ce phénomène freine considérablement l’usage des tôles d’aluminium-magnésium dans l’industrie. En effet, il a des conséquences esthétiques et mécaniques néfastes dont il est difficile de prédire l'évolution à l'étape de conception. Des modèles de comportement dédiés peuvent reproduire les bandes de localisation mais peinent à estimer précisément leur cinématique. De plus, ils sont sujets à des complications comme la sensibilité à la discrétisation, un coût de calcul considérable ou encore l’identification expérimentale délicate de leurs paramètres. L’objectif de ces travaux est donc de proposer un cadre dans lequel la cinématique des bandes de localisation est prédite de façon fidèle. Dans un premier temps, l’alliage d’étude est caractérisé par des essais de traction où la cinétique de bandes individuelles est traquée à l'aide de la corrélation d'images numériques. Les quantités d'intérêt sont identifiées à l'échelle non-locale des bandes de déformation : leur géométrie, leur distribution spatio-temporelle, la déformation qu'elles portent et l'énergie qu'elles échangent. S'appuyant sur ces résultats expérimentaux, un modèle de comportement est formulé à l'échelle des bandes de localisation. Il encapsule toutes les conséquences macroscopiques des instabilités plastiques et s’émancipe donc des complications évoquées plus tôt. Finalement, une stratégie numérique est proposée pour la simulation unidimensionnelle des essais, avec pour objectif de démontrer la faisabilité de l'approche. Ce travail constitue une première contribution à la simulation des bandes de localisation au travers d'une modélisation directe de leur cinétique. Les perspectives suggérées portent en particulier sur trois aspects. D'abord, la caractérisation de la cinétique des bandes de déformation à l'échelle inférieure à la nucléation. Aussi, le déploiement en 2D et l'amélioration du modèle proposé pour le traitement robuste de cas industriels. Enfin, l'utilisation du cadre développé pour la prise en charge d'autres physiques non-locales. / Plastic instabilities refer to a wide family of material nonlinearities met in several solid materials. They correspond to a heterogeneous strain response under homogeneous loading conditions, and manifest as an erratic workhardening accompanied by strain localization bands that kinetics are sensitive to temperature and loading rate, among other material properties. This phenomenon hinders the industrial use of aluminium-magnesium alloys. It involves harmful mechanical and aesthetic consequences that can hardly be predicted at the design step. Constitutive models can recreate localization bands but they fail to accurately predict their kinematics. Moreover, they are subjected to several issues such as mesh sensitivity, a high computational cost or a complex parameters identification. The purpose of this work is to build a framework in which bands kinematics can be reliably predicted. First, the studied alloy is characterized by means of tensile tests in which the kinetics of individual bands are tracked using digital image correlation. Quantities of interest are then identified at the non-local scale of bands: their morphology, spatiotemporal distribution, the strain they carry and the energy they exchange. Based on these experimental results, a constitutive model is derived at the scale of localization bands. It embeds all the aforementioned macroscopic consequences of plastic instabilities. A numerical strategy is then proposed to tackle unidimensional simulations, with the purpose of justifying the feasibility of the approach. This work constitutes a first contribution to the simulation of localization bands through a direct modeling of their kinetics. The considered outlooks focus on three main aspects. First, the experimental characterization of instabilities beneath the bands scale. Also, the twodimensional deployment and the improvement of the model to fit concrete and industrial applications. Lastly, the use of the proposed framework for a greater variety of non-local behaviors.

Aluminium has great properties that are utilised the world over, but the production of primary aluminium is very energy intensive. In order to reduce the energy-cost, the aluminium can be recycled by re-melting aluminium scrap. This results in a circularity of the aluminium, as it is produced from ore to a metal and then the metal scrap can be re-melted again for other use.  The study also focuses on secondary production in Sweden. Through interviewing diverse actors in Sweden and analysing literature, an understanding of how the circulatory systems work was developed and the problems that can occur within it.  The major problems found is that through re-melting, the previous alloying elements can become impurities in the new scrap-based material. These impurities can change the properties in the aluminium. Separating these impurities from the aluminium is not an easy process, but a growing research question. Easiest is to minimise these contaminations, companies do this by sourcing where scrap is coming from and its compositional information, so to better organize or use the scrap for a similar purpose aluminium alloy.  This study looked at how the circulation of aluminium scrap works and how used scrap is once again returned to new reusable aluminium. With an understanding of how the processes it is easier to locate problems to improve the processes. / Aluminium har mycket goda mekaniska egenskaper som används i hela världen, men att producera primär aluminium är extremt energikrävande. För att minska energikostnaden kan man återvinna aluminiumet, det görs genom att återanvända gammalt aluminiumskrot. När man gör detta så leder det till ett cirkulärt kretslopp, där det börjar från malm som produceras till metall, när metallen blir till skrot så kan det återanvändas för att producera nytt aluminium.  Genom att intervjua folk inom branschen och att analysera litteratur inom ämnet, så skapades en förståelse hur det cirkulär kretsloppet fungerar och problem som kan uppstå inom systemet.  Det största problemet som hittades var att genom att återvinna aluminium skrot, så kan det tidigare legeringselement bli föroreningar i den nya skrot baserade materialet. Dessa föroreningarna kan ändra egenskaperna hos aluminiumet. För att får bort dessa föroreningar kan vara en svår process eller fortfarande utvecklande processen. Det är mycket lättare att försöka undvika dessa föroreningarnas från börja. Företagen gör detta genom att veta var skrotet kommer ifrån och skrotets legeringsämnen innan de återanvänder det. Då kan de organisera skrotet bättre och använda det till liknande skrot material i framtiden.  Denna studien fokuserar på hur skrotbaserat aluminium fungerar i ett kretslopp och hur gammalt skrot kan återanvändas till ny användbar aluminium. Med en förståelse på hur processen fungerar, så är det mycket lättare att hitta problem som kan leda till möjligheter att förbättra processen.

The amount of aluminium sheets in future body-in-white concepts is still on the rise. There is a need for optimizing the joining techniques, caused by the different characteristics compared to the established steel components. Especially the electrode life for resistance spot welding as a reliable and established process needs to be improved. One reason for the short electrode life when welding aluminium is the insulating effect of the aluminium oxide layer. One possibility to reduce the electrode wear is the mechanical destruction of the oxide layer before the welding. This paper describes the influence of a translational and rotational electrode movement on the electrode wear. The oxide layer destruction is detected by resistance measurement. It could be shown that the destruction of the oxide layer already occurs at low movements. However, a homogeneous, large-area destruction is necessary for a wear reduction.

No description available.

Die Arbeit ruht auf zwei Säulen: Die eine besteht in der Aufbereitung, Erprobung und konsequenten Anwendung von Methoden der Skaleninvarianzanalyse, die andere in einem breiten Fundus an experimentellen Daten für aushärtbare Aluminiumknetlegierungen in der Form dünner Bleche, die unter gleichartigen, streng kontrollierten Bedingungen gewonnen worden sind. Als methodische Weiterentwicklungen sind die Fundierung des Umgangs mit der algebraischen Korrelation zwischen Vorfaktor und Exponent einer beliebigen Potenzgleichung, die Übertragung des Ansatzes der finiten Skaleninvarianz auf die Ermüdungsrißausbreitung sowie die Kombination der Idee eines geschwindigkeitsbestimmenden Schrittes mit der Dimensionsanalyse der umgebungsabhängigen Ermüdungsrißausbreitung bis hin zur Kartierung der geschwindigkeitsbestimmenden Schritte zu nennen. Auf experimenteller Seite wurde eine Datensammlung mit gemessenen Streubändern für die Ermüdungsrißausbreitung und das Verfestigungsverhalten von 39 Orientierungen bzw. Auslagerungszuständen von Aluminiumlegierungen aufgebaut. Diese Sammlung wird durch ausgewählte Messungen der Ermüdungsrißausbreitung im schwellenwertnahen Bereich, Restfestigkeitsversuche, Rißschließmessungen, Rauheitsmessungen an Bruchflächen, frequenzabhängige Messungen zum Umgebungseinfluß sowie Untersuchungen an drei Stählen und einer Magnesiumlegierung sinnvoll ergänzt. Auf der Basis der Meßdaten und der Analysemethoden wurde der Werkstoffeinfluß auf die Ermüdungsrißausbreitung in dünnen Blechen aus Aluminiumknetlegierungen bei Belastung mit konstanter Amplitude im Gültigkeitsbereich der linear-elastischen Bruchmechanik untersucht. Dabei wurden folgende Größen als wesentliche Einflußfaktoren identifiziert: - für die Gruppenzugehörigkeit: der Kohärenz- und Ordnungsgrad der festigkeitsbestimmenden Ausscheidungen und die resultierende Gleitverteilung, - für den gemeinsamen Vorfaktor der Legierungen der Gruppe 1: die elastischen Eigenschaften und das Spannungsverhältnis (Translation der Paris-Geraden), - für die Exponenten der Legierungen der Gruppe 1: 0,2%-Dehngrenze, athermischer Verfestigungsparameter, Probendicke und Kc-Wert als dimensionsloses Potenzprodukt (Rotation der Paris-Geraden), - für die Legierungen der Gruppe 2: das Ausmaß der Rißablenkung und eine bleibende Mode-II-Komponente der Rißöffnungsverschiebung, - für den Umgebungseinfluß der Legierung 6013 T6: Frequenz und Schwingbreite des Spannungsintensitätsfaktors. Die Diskussion umfaßt den wertenden Vergleich der experimentellen Ergebnisse mit Befunden und Modellen aus der Literatur, Erklärungsansätze für die Ursachen der Einflußnahme der wesentlichen Parameter sowie einen Modellansatz für die Legierungen der Gruppe 1 auf der Basis einer Mischungsregel. Dabei hatte sich erwiesen, daß keines der aus der Literatur bekannten Modelle alle Befunde richtig wiedergibt. Einige der ausgearbeiteten Erklärungsansätze bedürfen der zukünftigen Vertiefung. / The work is based upon two essentials: the first one is the preparation and application of techniques of scale invariance analysis, the second one consists in a database of experimental results for heat-treatable thin-sheet wrought aluminium alloys obtained under uniform conditions. Progress with respect to methodology was achieved regarding, first, the algebraic correlation between sets of coefficients and exponents of any power law, second, the transfer of the concept of finite scale invariance to the phenomenon of fatigue crack growth (FCG), and third, the combination of the ideas of a rate-controlling step and dimensional analysis of environmental-assisted FCG including the mapping of rate-controlling steps. In the experimental part, a database containing both measured scatterbands of FCG and strengthening characteristics for several orientations and aging conditions of aluminium alloys amounting to a total of 39 different material conditions was established. This database was supplemented with results of selected measurements of near-threshold FCG rates, residual strength, crack closure, roughness of fatigue cracks, and frequency-dependent environmental-assisted FCG as well as investigations of three plain-carbon steels and a magnesium alloy. Based on these prerequisites, the influence of the material on the FCG behaviour of thin-sheet wrought aluminium alloys under constant-amplitude loading was investigated within the limits of validity of linear-elastic fracture mechanics. The following influence factors were identified to be essential: The assignment of alloys to one out of two groups is mainly determined by the degrees of coherency and order of the strength-controlling precipitates and the resulting type of slip distribution. The normalized-Paris-law coefficient for the first group is mainly dependent on the modulus of elasticity and the stress ratio. The Paris-law exponents for the first group are dominated by a dimensionless power monomial of the 0.2% proof stress, the athermal strengthening coefficient, sheet thickeness and the critical stress intensity factor. The retardation of the FCG rates of alloys of the second group relative to the first group is mainly determined by the amount of crack deflection and by a residual mode-II component of crack opening displacement. Finally, the environment-assisted FCG for aluminium alloy 6013 T6 reveals a coupled dependence on loading frequency and cyclic stress intensity factor. The discussion covers the evaluation of the results in relation to observations and models from the literature, the explanation of the modes of operation of the major influence factors and a model based on a mixing rule for the alloys of the first group. It turned out that there is not any model that reflects all of the observations simultaneously. Some of the ideas presented require to be worked out in more detail.

Dans le domaine des matériaux métalliques, les techniques d’assemblage par soudageconduisent à des réductions de masse et de coûts importantes susceptibles d’intéresserles industries aéronautiques. Néanmoins, les procédés de soudage classiquespar fusion ne s’appliquent pas aux dernières générations d’alliages d’aluminium aéronautiques.Dans ce contexte, le procédé de soudage Friction Stir Welding présentedes atouts considérables, de nature à rendre compétitives les structures métalliquesface à la montée en puissance des matériaux composites.L’objectif de cette thèse est double. Il s’agit d’une part d’améliorer notre compréhensiondu procédé de soudage Friction Stir Welding Bobbin Tool puis dans undeuxième temps de proposer une méthodologie visant à prédire les paramètres desoudage optimaux.Afin de mener à bien ces objectifs, des essais de soudage ont été menés pour troisalliages d’aluminium aéronautique, incluant deux alliages d’aluminium-lihtium, etdeux épaisseurs, représentatives d’une jonction de peau de fuselage. Les résultatsd’essais ont par la suite été exploités et ont permis de mettre en évidence des corrélationsentre paramètres de soudage, température, puissance et malaxage du noyausoudé.Dans un troisième temps, afin de supporter la démarche expérimentale, des outilsde simulation ont été utilisés. Un modèle thermo-fluide local a été développé afinde simuler les phénomènes de malaxage dans le noyau soudé. A l’échelle globale, unmodèle thermique a permis de reproduire fidèlement les phénomènes de diffusion dela chaleur dans la structure. Enfin, le couplage des deux modèles a montré qu’il étaitpossible de simuler puis de prédire un domaine de soudabilité. / In the field of metallic materials, welding technologies can provide significantmass reductions and cost savings to aircraft industries. Nevertheless, classical fusionwelding processes can not be applied to last generations of aeronautical aluminiumalloys. In this context, Friction Stir Welding offers many advantages and can helpmetallic parts to face the build up of composite materials.This thesis has mainly two objectives. We aim first at improving our understandingof Friction Stir Welding with Bobbin Tool and then at proposing a kind ofmethodology able to predict optimal welding parameters.Welding trials were carried out using three aeronautical aluminium alloys includingtwo aluminium lithium and two thicknesses representative of a fuselagejunction. Results were analyzed and some correlations were found between weldingparameters, temperature and stirring of the weld nugget.This work was also supported by several modeling tools. A local thermo-fluidapproach has been used to simulate stirring of the material in the weld nugget. Aglobal thermal model has been used to simulate heat diffusion in the structure. Then,a coupled approach of these previous modeling tools shows that it was possible tonumerically predict a processing window.

La recherche permanente de solutions d’allègement des structures aéronautiques a conduit au développement de nouveaux alliages comme les Al-Cu-Li et les Al-Mg-Li qui se caractérisent par une densité inférieure aux alliages conventionnels et par des propriétés améliorées. De manière générale, la formabilité de ces alliages, que ce soit à froid ou à chaud est encore assez mal connue. Le projet « Formage avancé des alliages basses densité pour application aéronautique » se propose donc de caractériser précisément la plage de formabilité de ces nouveaux alliages et d’investiguer les voies de mise en œuvre les plus adaptées : procédé d’étirage conventionnel ou procédé de mise en forme pendant une étape de traitement thermique. Ce projet regroupe les entreprises AEROLIA SAS, ACB, AIRBUS Operation SAS et CONSTELLIUM.Ces développements seront destinés au fuselage métallique et plus particulièrement à la structure pointe-avant qui présente une géométrie en double courbure ; ils concernent à la fois les panneaux de fuselage et les profilés. / The ongoing researches to lighten aeronautical structures have led to the development of new materials like Al-Cu-Li and Al-Mg-Li alloys. These alloys exhibit lower density and higher mechanical properties than conventional alloys. However, their ability to be formed either by cold or hot forming process is not well known. The aims of this PhD research works are thus to characterize the formability of these new alloys and to suggest the most appropriate forming sequence to elaborate complex aeronautic parts. Various forming processes will be studied such as cold forming by stretching of sheet metal parts or hot forming by stamping of sheet metal parts after or during different heat treatments. An experimental as well as a numerical approach will be used to develop the forming process of these new alloys to elaborate fuselage panels with more or less complex shapes. These PhD research works are a component of a larger project led by IRT Jules Verne and entitled “Advanced forming of low density alloys for aeronautic applications”. This project includes several firms from aeronautic domain (AEROLIA SAS, ACB, AIRBUS SAS and CONSTELLIUM).

O NbAl3 e algumas ligas intermetálicas do sistema Nb-Ni-AI foram sintetizadas por combustão a partir dos pós de seus elementos constituintes. O efeito de variáveis de processo, como o tamanho de partícula dos pós, a composição química, a pressão de compactação, o tratamento de desgaseificação e a taxa de aquecimento, foram investigados na síntese do NbAl3 na forma de pastilhas cilíndricas. A síntese de ligas do sistema Nb-Ni-AI foi realizada a partir de misturas com as composições Nb10Ni70AI, Nb20Ni65AI e Nb30Ni60AI. A microestrutura das amostras reagidas foi caracterizada por microscopia óptica, microscopia eletrônica de varredura, EDS e difração de raios-X (método de Rietveld). Foram obtidas pastilhas de NbAl3 com 98,5 % da densidade teórica, superior ao valor encontrado na literatura (95%), mediante o controle de variáveis de processo. Nas pastilhas contendo níquel, a combustão ocorreu nas pastilhas de todas as composições. Fases metaestáveis, presentes na microestrutura das pastilhas baitas de reação, foram transformadas após tratamento térmico, originando ligas trifásicas com diferentes concentrações de fases (NbAl3, NiAI e NbNiAI), conforme a composição inicial do compactado. Algumas propriedades mecânicas de amostras brutas de reação e tratadas termicamente foram determinadas pela técnica da impressão (microdureza e tenacidade). Os resultados obtidos são comparáveis aos da literatura, salvo algumas discrepâncias atribuídas a processos de fabricação distintos. As etapas de reação da síntese do NbAl3 e de ligas Nb-Ni-AI foram posteriormente investigadas mediante interrupção da reação durante sua propagação ao longo de barras paralelepipédicas compactadas. Verificou-se que a síntese do NbAl3 ocorre pela dissolução de nióbio no alumínio fundido, seguida da precipitação do NbAl3. Nas amostras contendo níquel, a síntese ocorre em dois estágios: no primeiro estágio formam-se o Ni2Al3 ou o NiAl3, em quantidades relativas dependentes da composição geral. As reações deste primeiro estágio podem disparar as reações do segundo estágio, referentes à síntese do NbAl3. / NbAl3 and Nb-Ni-AI intermetallic alloys have been obtained by pressureless combustion synthesis from elemental powders. The effects of process variables as powder particle size, composition, compaction pressure (green density), degassing treatment and heating rate on the combustion (thermal explosion mode) of NbAl3 cylindrical pellets were studied. Combustion synthesis of Nb-Ni-AI alloys was performed on powder mixtures with nominal compositions Nb10Ni70AI, Nb20Ni65AI and Nb30NI60AI. The microstructure of reacted samples was characterized by optical microscopy, scanning electron microscopy, EDS and X-ray diffraction (Rietveld method). It was shown that careful control of the processing conditions allowed near full (98,5%) dense pellets of NbAl3. In the nickel containing pellets, reaction occurred for all the compositions investigated. Metastable phases were seen to be present in the as reacted pellets, which were transformed after a heat treatment, producing a three phase alloy (NbAl3, NiAI and NbNiAI) with different phase concentrations, depending on the initial compact composition. Some mechanical properties, like microhardness and tenacity were measured by microidentation technique on the as reacted and heat-treated samples. The results are comparable with the literature, excepted for some discrepancies caused by different fabrication processes. The reaction sequence for both cases (NbAl3 and Nb-Ni-AI alloys) was further investigated by DSC analysis and also by interrupting the reaction during its propagation along compacted parallelopipedal bars. It was found that the NbAl3 synthesis occurs through niobium dissolution in molten aluminum and precipitation of NbAl3. In the nickel containing samples, synthesis occurs as two-stage reaction: Ni2Al3 or NiAl3 are formed in the first stage, with relative amounts depending on the general composition. This first stage reaction can trigger the second one, related to the formation of NbAl3.

This thesis systematically investigates the effects of a recently developed modified ageing procedure of aluminium alloys, termed the T6I6 temper, on the microstructural development and mechanical properties of the Al ??? Mg ??? Si - Cu alloy 6061. For the T6I6 temper, a conventional single stage T6 temper is interrupted by an ageing period at a reduced temperature (65??C) to facilitate secondary precipitation, before resuming the final ageing at the temperature of the initial T6 treatment. The T6I6 temper was found to cause simultaneous increases in tensile properties, hardness, and toughness as compared with 6061 T6. Al ??? Mg ??? Si ??? Cu alloys are medium strength alloys widely used in the automotive industry and their further improvement is underpinned by stringent demands for weight reduction placed on the transportation industry in recent years. The potential for further improvement of the mechanical properties was found in the control of secondary precipitation that may take place even in some fully aged alloys when exposed to reduced temperatures. The overall improvement in the mechanical properties of 6061 T6I6 was attributed to the formation of finer and more densely dispersed precipitates in the final microstructure. The refinement of precipitates was facilitated by control of the precipitation processes and gradual evolution of the microstructure throughout each stage of the T6I6 treatment. The results indicated that the concentration and the chemical environment of the vacancies controlled the precipitation processes in this alloy. Findings also show that the proportion of the different precipitate phases present in the final microstructure, as well as the amount of the solute in these precipitates, can be controlled and modified utilizing secondary precipitation. A number of analytical techniques were used in this study. The evolution of the microstructure was studied using Transmission Electron Microscopy (TEM), High Resolution TEM (HRTEM) and Three Dimensional Atom Probe (3DAP). Vacancy-solute interactions were studied using Positron Annihilation Lifetime Spectroscopy (PALS) and 3DAP. The distribution of the solute was studied using 3DAP and Nuclear Magnetic Resonance (NMR). Differential Scanning Calorimetry (DSC) was used to identify precipitation reactions and to determine the stability of vacancy-associated aggregates.

In several applications of casting, dendritic microstructure is not desirable as it results in poor mechanical properties. Enhancing fluid flow in the mushy zone by stirring is one of the means to suppress this dendritic growth. Strong fluid flow detaches the dendrites formed at the solid-liquid interface and carries them into the mould to form slurry. When this slurry solidifies, the microstructure is characterized by globular, non-dendritic primary phase particles, separated and enclosed by a near-eutectic lower-melting secondary phase. This property represents a great potential for further processing in semisolid forming (SSF) by various techniques such as pressure die casting and forging. Among all currently available methods, linear electromagnetic (EM) stirring is considered as one of the most suitable routes for large scale production of semisolid feed stock. One of the biggest advantages of EM stirring is that the stirring intensity and direction can be modulated externally and in a non-intrusive manner. With this viewpoint, the primary objective of the present research is to investigate rheocasting using linear electromagnetic stirring. A systematic development of a linear electromagnetic stirrer (LEMS) is the subject of the first part of the thesis. The LEMS consists of a set of six primary coils displaced in space. These coils are excited by a three-phase power supply to produce an axially travelling magnetic field. The metal to be stirred is placed in the annular space of the stirrer. The travelling field induces secondary current in the molten metal. The current and magnetic fields interact to generate a net mechanical force in the metal, commonly termed as the Lorentz force. The molten metal is stirred under the influence of this force. Two prototype stirrers, one for low melting alloys and the other for aluminium alloys are developed. The stirrers are characterized by measuring forces on low melting point alloy and on solid aluminum cylinders placed inside the annular space of the stirrer. As an outcome of these tests, a non-intrusive method of detecting stirring of liquid metal is developed. The development of a rheocasting mould for the LEMS forms the second part of the work presented in the thesis. The mould design and cooling arrangement are such that solidification in the mould is primarily unidirectional. Heat from the solidifying metal is extracted at the bottom of the mould, so that the axisymmetric EM stirring effectively shears the dendrites formed at the solid-liquid interface. The outer surface of the mould is cooled with water or air exiting from 64 jets, each of 4 mm diameter. Such an arrangement provides a high heat transfer coefficient and a wide range of cooling rate in the metal ranging from 0.01 to 10 K/s. Temperature is measured at various depths in the solidifying melt and at other key locations in the mould to assess the various heat transfer mechanisms. The results from the rheocasting experiments using the above mould and LEMS are presented in the third and final part of the thesis. Such studies are required for understanding the solidification process in presence of electromagnetic stirring and for highlighting the important issues connecting solidification, fluid flow, dendrite fragmentation and the resulting microstructure. A series of experiments are performed with A356 (Al-7Si-0.3Mg) alloy. Experiments are conducted with various combinations of operating parameters, and the resulting microstructures and cooling curves at various locations are examined. The key process parameters are stirring current, cooling rate, pouring temperature, and stirring current frequency. The parametric studies also include the case without EM stirring in which liquid aluminium is poured into the rheocast mould without powering the LEMS. It is found that stirring at high currents produces non-dendritic microstructures at all locations of the billet. For lower currents, however, dendritic microstructures are observed in regions outside the zone of active stirring. Stirring also enhances heat loss from the exposed top surface, leading to solid front advancement from the top as well. Without EM stirring, microstructures are found to be dendritic everywhere. The percentage of primary α-Al phase and its number density are found to increase with stirring intensity. With a decrease in cooling rate with air as the coolant, the average grain size of primary α-Al phase increases. Excitation frequency is found to be an important parameter, with lower frequencies generating a more uniform force field distribution, and higher frequencies enhancing induction heating. At higher frequencies, the effect of higher induction heating results in the formation of larger and coarser primary phase grains. This phenomenon has led to the development of a one-step process for rheocasting and heat treatment of billets.