<p>The reduction behaviour of the olivine iron ore pellet MPBOwas studied in laboratory scale at KTH as well as in the LKABexperimental blast furnace. Initially, a newreduction-under-load, or so-called reduction/softening/melting,test equipment was developed. Experiments using differentreducing conditions, corresponding to different radialpositions of the blast furnace, were conducted. The experimentsincluded different temperature profiles, reducing atmospheresand mechanical loads applied on the sample bed to simulate thevarying conditions in the blast furnace process. The progressof reduction was investigated, as well as the processes ofsintering and contraction during reduction. A model of thecarburisation (pick-up of carbon by the reduced iron) andmelt-down process during rapid contraction was presented.</p><p>Laboratory testing of MPBO pellets was compared with resultsfrom the LKAB experimental blast furnace. The reduction of ironore pellets in the experimental blast furnace was surveyed by adissection of the furnace after quenching. The high temperaturephenomena occurring when reducing the MPBO pellet, with limitedsoftening and a short temperature range of the melting process,resulting in a thin cohesive zone, were found to be the same inlaboratorytests and in the experimental blast furnace. Thereduction down through the burden of the experimental blastfurnace was similar, but not identical to the results of theRUL experiments. The differences were found to be due todifferent reducing conditions. Therefore, it was concluded thata simulation of the reduction occurring in the blast furnacecan be performed in laboratory scale, provided the experimentalconditions are correctly chosen.</p><p>Finally, a modification to further improve the properties ofthe MPBO pellets was examined. With the aim to improve theblast furnace process, coating of blast furnace pellets wasinvestigated in laboratory scale, as well as in the LKABexperimental blast furnace. Olivine, dolomite and quartzitewere used as coating agents. In laboratory scale the stickingprevention action of the different coating materials wasverified, in established test methods as well as in new testmethods, modified for blast furnace conditions. Testing of thecoated pellets in the experimental blast furnace revealedseveral advantages; significantly reduced blast furnace fluedust generation, improved gas utilisation and a smoother blastfurnace operation with a potential for a lowered fuel rate.</p><p><b>Keywords:</b>Olivine, pellets, pellet testing,reduction/softening/melting, MPBO, blast furnace, reduction,quenching, dissection, coating, sticking, coated pellets.</p>

The major goal of this PhD project is to investigate the fundamental properties of energetic materials, including their atomic and electronic structures, as well as mechanical properties, and relate these to the fundamental mechanisms of shock wave and detonation propagation using state-of-the-art simulation methods. The first part of this PhD project was aimed at the investigation of static properties of energetic materials (EMs) with specific focus on 1,3,5-triamino-2,4,6-trinitrobenzene (TATB). The major goal was to calculate the isotropic and anisotropic equations of state for TATB within a range of compressions not accessible to experiment, and to make predictions of anisotropic sensitivity along various crystallographic directions. The second part of this PhD project was devoted to applications of a novel atomic-scale simulation method, referred to as the moving window molecular dynamics (MW-MD) technique, to study the fundamental mechanisms of condensed-phase detonation. Because shock wave is a leading part of the detonation wave, MW-MD was applied to demonstrate its effectiveness in resolving fast non-equilibrium processes taking place behind the shock-wave front during shock-induced solid-liquid phase transitions in crystalline aluminum. Next, MW-MD was used to investigate the fundamental mechanisms of detonation propagation in condensed energetic materials. Due to the chemical complexity of real EMs, a simplified AB model of a prototypical energetic material was used. The AB interatomic potential, which describes chemical bonds, as well as chemical reactions between atoms A and B in an AB solid, was modified to investigate the mechanism of the detonation wave propagation with different reactive activation barriers. The speed of the shock or detonation wave, which is an input parameter of MW-MD, was determined by locating the Chapman-Jouguet point along the reactive Hugoniot, which was simulated using the constant number of particles, volume, and temperature (NVT) ensemble in MD. Finally, the detonation wave structure was investigated as a function of activation barrier for the chemical reaction AB+B ⇒ A+BB. Different regimes of detonation propagation including 1-D laminar, 2-D cellular, and 3-D spinning and turbulent detonation regimes were identified.

科学研究費補助金 研究種目:一般研究(C) 課題番号:04640413 研究代表者:藤吉 康志 研究期間:1992-1993年度

Selective laser melting (SLM) is a powder-based additive manufacturing technique consisting of the exact reproduction of a three dimensional computer model (generally a computer-aided design CAD file or a computer tomography CT scan) through an additive layer-by-layer strategy. Because of the high degree of freedom offered by the additive manufacturing, parts having almost any possible geometry can be produced by SLM. More specifically, with this process it is possible to build parts with extremely complex shapes and geometries that would otherwise be difficult or impossible to produce using conventional subtractive manufacturing processes. Another major advantage of SLM compared to conventional techniques is the fast cooling rate during the process. This permits the production of bulk materials with very fine microstructures and improved mechanical properties or even bulk metallic glasses. In addition, this technology gives the opportunity to produce ready-to-use parts with minimized need for post-processing (only surface polishing might be required). Recently, significant research activity has been focused on SLM processing of different metallic materials, including steels, Ti-, Ni- and Al-based alloys. However, most of the research is devoted to the parameters optimization or to feasibility studies on the production of complex structures with no detailed investigations of the structure-property correlation. Accordingly, this thesis focuses on the production and structure-property correlation of Al-12Si samples produced by SLM from gas atomized powders. The microstructure of the as-prepared SLM samples consists of supersaturated primary Al with an extremely fine cellular structure along with the residual free Si situated at the cellular boundaries. This microstructure leads to a remarkable mechanical behavior: the yield and tensile strengths of the SLM samples are respectively four and two times higher than their cast counterparts. However, the ductility is significantly reduced compared with the cast samples. The effect of annealing at different temperatures on the microstructure and resulting mechanical properties of the SLM parts has been systematically studied by analyzing the size, morphology and distribution of the phases. In addition, the mechanical properties of the SLM samples have been modeled using micro- structural features, such as the crystallite and matrix ligament sizes. The results demonstrate that the mechanical behavior of the Al-12Si SLM samples can be tuned within a wide range of strength and ductility through the use of the proper annealing treatment. The Al-Si alloys are generally used as pistons or cylinder liners in automotive applications. This requires good wear resistance and sufficient strength at the operating temperature, which ranges between 373 – 473 K. Accordingly, the tensile properties of the SLM samples were also tested at these temperatures. Changing the hatch style during SLM processing vary the texture in the material. Hence, samples with different hatch styles were produced and the effect of texture on their mechanical behavior was evaluated. The results show that the hatch style strongly influences both the mechanical properties and the texture of the samples; however no direct correlation was observed between texture and mechanical properties. The wear properties of the Al-12Si material was evaluated using pin-on-disc and fretting wear experiments. These experiments show that the as-prepared SLM samples exhibit better wear resistance than their cast counterparts and the SLM heat-treated samples. Finally, the corrosion investigations reveal that the SLM samples have similar corrosion behavior as the cast specimens under acidic conditions. A major drawback for the wide application of SLM as an industrial processing route is the limited size of the products. This is a direct consequence of the limited dimensions of the available building chambers, which allow for the production of samples with volumes of about 0.02 m3. A possible way to overcome this problem would be the use of the welding processes to join the small SLM objects to form parts with no dimensional limitations. In order to verify this possibility, friction welding was employed to join Al-12Si SLM parts. The results indicate that friction welding not only successfully permits the join materials manufactured by SLM, but also helps to significantly improve their ductility. This work clearly demonstrates that SLM can be successfully used for the production of Al-12Si parts with an overall superior performance of the mechanical and physical properties with respect to the conventional cast samples. Moreover, the mechanical properties of the SLM samples can be widely tuned in-situ by employing suitable hatch styles or ex-situ by the proper heat treatment. This might help the development of SLM for the production of innovative high-performance Al-based materials and structures with controlled properties for automotive and aerospace applications.

Die vorliegende Arbeit beinhaltet die theoretische Betrachtung des Glasschmelzprozesses in Glasschmelzöfen und die Darstellung von fünf Bewertungsprinzipien zur qualitativen Bewertung von Glasschmelztechnologien für die Abschmelz-, Restquarz- und Läuterzone. Es konnte gezeigt werden, dass zum verbesserten Einschmelzen des Gemenges nicht nur der Energieeintrag, sondern auch der Abtransport der neu entstehenden Schmelze intensiviert werden muss. Bei der qualitativen Bewertung und der Auswahl von Schmelztechnologien zur Beschleunigung der Restquarzlösung wurde dargestellt, dass der Einfluss der Schmelztechnologie auf das Verweilzeitverhalten und damit rückwirkend auf die Effizienz der Restquarzlösezone bei der Vorauswahl von Schmelztechnologien berücksichtigt werden muss. Für die Läuterzone wurde nachgewiesen, dass zwei teils in der Literatur diskutierte Bewertungsprinzipien zur Läuterung von Glasschmelzen abzulehnen sind bzw. zu überschätzten Aussagen zur Effizienz von Läutertechnologien führen. Weiterhin konnte gezeigt werden, dass für den theoretischen Fall einer Läuterbank ohne Konvektionsströmungen die Blasenwachstumsgeschwindigkeiten für Konstruktionen mit minimalen Kosten im Bereich von 4-12*10-7 m/s mit möglichen Ausreißern zu 5*10-6 m/s bei Massengläsern liegen sollten.

Doping allows us to modify semiconductor materials for desired properties such as conductivity, bandgap, and / or lattice parameter. A small portion replacement of the highly mismatched isoelectronic dopants with the host atoms of a semiconductor can result in drastic variation of its structural, optical, and / or electronic properties. Here, the term "mismatch" describes the properties of atom size, ionicity, and / or electronegativity. This thesis presents the fabrication of two kinds of highly mismatched semiconductor alloys, i.e., Ge(1-x)Sn(x) and GaAs(1-x)N(x). The structural and optical properties of the prepared Ge(1-x)Sn(x) and GaAs(1-x)N(x) have been investigated. The results suggest an efficient above-solubility doping induced by non-equilibrium methods of ion implantation and ultrashort annealing. Pulsed laser melting promotes the regrowth of monocrystalline Ge(1-x)Sn(x), whereas flash lamp annealing brings about the formation of high quality GaAs(1-x)N(x) with room temperature photoluminescence. The bandgap modification of Ge(1-x)Sn(x) and GaAs(1-x)N(x) has been verified by optical measurements of spectroscopic ellipsometry and photoluminescence, respectively. In addition, effective defect engineering in GaAs has been achieved by flash lamp annealing, by which a quasi-temperature-stable photoluminescence at 1.3 µm has been obtained. / Dotierung ermöglicht es, die Eigenschaften von Halbleitermaterialien, wie Leitfähigkeit, aber auch Bandabstand und / oder Gitterkonstanten gezielt zu verändern. Wenn ein Halbleiter mit einer kleinen Menge unterschiedliche Fremdatome dotiert wird, kann dies in einer drastischen Modifikation der strukturellen, optischen und / oder elektronischen Eigenschaften resultieren. Der Begriff "unterschiedlich" bedeutet hier die Eigenschaften von Atomgröße, Ioniztät und / oder Elektronegativität. Diese Doktorarbeit beschreibt die Herstellung von zwei Arten von stark fehlangepassten Halbleiterlegierungen: Ge(1-x)Sn(x) und GaAs(1-x)N(x). Die strukturellen und optischen Eigenschaften von Ge(1-x)Sn(x) und GaAs(1-x)N(x) wurden untersucht. Die Ergebnisse deuten auf eine effiziente Dotierung oberhalb der Löslichkeit, induziert durch die Nicht-Gleichgewichtsverfahren Ionenimplantation und Ultrakurzzeit-Ausheilung. Gepulstes Laserschmelzen ermöglicht das Nachwachsen von monokristallinem Ge(1-x)Sn(x), während die Blitzlampenausheilung in der Bildung von GaAs(1-x)N(x) hoher Qualität mit Photolumineszenz bei Raumtemperatur resultiert. Die Änderung der Bandlücke von Ge(1-x)Sn(x) und GaAs(1-x)N(x) wurde durch die optischen Methoden der spektroskopischen Ellipsometrie und Photolumineszenz verifiziert. Darüber hinaus konnte in ausgeheiltem GaAs eine quasi-temperaturstabile Photolumineszenz bei 1,3 µm beobachtet werden.

In this thesis we study thermal properties and melting behavior of crystals using Monte Carlo simulations. The Monte Carlo method is very difficult to implementfor melting investigation, unlike for problems where particles (such as spins) are localized on lattice sites. However, once it is well conceived, it is among themost efficient numerical techniques, to be able to study melting.We have created a high-performance algorithm based on an optimized Verlet procedure, which allowed us to investigate thermalproperties up to the melting. This optimization was necessary for treating an important number of atoms in very long runsto have good statistics, without prohibitive CPU time.We applied our algorithm to rare-gas crystals using the Lennard-Jones potential with parameters given by Bernardes which are widely used in the literature since 1958.Our results, thanks to their precision, show that we should modify these parameters in order to have a good agreement with experimental data.We studied melting of bulk semiconductors and metals by considering the case of Si and Ag. These materials have been chosen to serve our project about Silicene. Silicon has a diamond structure, and silver has the FCC lattice structure, both of them have been well experimentallystudied with well-known experimental melting temperatures. In spite of this, no good simulations have been done. For Si, one of the major problems is thechoice of a potential which stabilizes the diamond structure at finite temperatures. We have applied our algorithm to these materials using the multi-body Stillinger-Weber and Tersoff potentials for Si and the Gupta and EAM(embedded atom method) potentials for Ag. We obtained results much more precise than in early simulations and in good agreement with experiments.We also studied the Ag(111) surface trying to elucidate the long-standing controversy whether or not there is the ''anomalous'' thermal expansion whichhappens, for certain metals, when the inter-layer distances between the topmost atomic planes changes from a contracted situation to an expansion with respect tothe bulk distance. We showed that, depending on the potential, the anomalous crossover exists and the surface melting can occur at a temperature very far belowthat of the bulk melting. This is the case of EAM potential, but not the Gupta potential where surface melting occurs just belowbulk the melting.Finally, we studied the thermal stability of a stand-alone silicene sheet. Silicene is the Si counterpart of 2D carbon sheet called ''graphene". Siliceneattracts the attention of many researchers, because of its electronic and thermal properties which seem to be comparable to those of graphene which is actually oneof the most studied materials, due to its unusual properties susceptible for revolutionary device applications. Furthermore, because it is a Si-based material, thecompatibility, with the actual Si-based electronic industry, is expected to be better than for graphene. We show that, using the Tersoff potential with twosets of parameters (the original and the modified ones), the silicene 2D honeycomb structure is stable up to high temperatures without buckling. We have tested the Stillinger-Weberpotential: it yields a buckled honeycomb sheet at low temperatures but the 2D structure is destroyed in favor of a tri-dimensional structureat the melting. Discussion on this point is given.A general conclusion with some open perspectives is given at the end.

The Voter and Chen version of an embedded-atom model, derived by fitting to experimental data of both the diatomic molecule and bulk platinum simultaneously, has been applied to study the locally stable structures, energetics, growth patterns and melting behavior of free platinum clusters in the size range of N=2-56 and N=75. Using the constant-energy molecular dynamics simulations, thermal and conjugate-gradient minimization techniques, the global minima and the other locally stable structures have been distinguished from those stationary structures that correspond to saddle points of the potential energy surface. The number of isomers and the probabilities of sampling different basins of attractions of the clusters from 2 to 22 atoms are obtained. The energy spectra of these clusters have been analyzed. The correlations between the total energy of the 75-atom cluster and the isomer number and the energy-spectrum-width of the isomers are investigated. The number of isomers of 75-atom cluster as a function of the total energy is presented, and the isomer probability distribution is discussed. The melting behavior of Pt_N clusters in the size range of N=12-14, 54-56, and N=75 has been studied. An atom-resolved analysis method including physical quantities such as the root-mean-square bond-length fluctuations and the coordination numbers for indivudual atoms as the functions of the temperature has been presented. Comparisons have been made with the results of previous calculations using electronic structure and empirical potential methods. The results show that the global minima have structures based on either octahedral, decahedral or icosahedral packing.

Το θέμα αυτής της διπλωματικής είναι παρασκευή άμορφων μεταλλικών συμπαγών κραμάτων με τήξη σε βολταϊκό τόξο και ο χαρακτηρισμός της δομής τους και των μηχανικών ιδιοτήτων τους. Στο πρώτο κεφάλαιο γίνεται εισαγωγή στη δομή των υλικών και επεξηγούνται βασικές έννοιες των άμορφων υλικών και επίσης παρουσιάζονται οι κυριότερες εφαρμογές των άμορφων μεταλλικών συμπαγών κραμάτων. Στο δεύτερο κεφάλαιο περιγράφονται οι τεχνικές που χρησιμοποιούνται για την παρασκευή άμορφων συμπαγών μεταλλικών κραμάτων και στο τρίτο κεφάλαιο αναφέρονται οι κυριότερες φυσικές ιδιότητες των άμορφων μεταλλικών συμπαγών κραμάτων. Στο τέταρτο κεφάλαιο παρουσιάζεται η βαθμονόμηση της συσκευής περίθλασης ακτίνων Χ και της συσκευής παραγωγής και μέτρησης υπερήχων που χρησιμοποιήθηκαν για την μέτρηση των δειγμάτων που παρασκευάστηκαν στο εργαστήριο. Στο πέμπτο κεφάλαιο περιγράφεται ο τρόπος παρασκευής των άμορφων κραμάτων ζιρκονίου (Zr) και σιδήρου (Fe) και επίσης παρουσιάζονται και αναλύονται τα XRD διαγράμματα τους και τα μέτρα ελαστικότητας Young (E), διάτμησης (G) και όγκου (B). Τέλος στο έκτο κεφάλαιο αναφέρονται άλλες μετρήσεις που θα μπορούσαν να γίνουν για να χαρακτηριστούν τα παραπάνω δείγματα και περιγράφονται οι προοπτικές των άμορφων κραμάτων σιδήρου ως αντικείμενο έρευνας για το μέλλον. / The subject of this diploma thesis is the preparation of bulk amorphous metallic alloys with arc-melting technique and the characterization of their structure and their mechanical properties. The first chapter is an introduction to the structure of materials and it is explaine the basic concepts of amorphous materials. It is also present the main applications of bulk amorphous metallic alloys. The second chapter describes the techniques that used in the preparation of bulk amorphous metallic alloys and the third chapter refers the main physical properties of bulk amorphous metallic alloys. The fourth chapter describes the calibration of X-ray diffractοmeter and ultrasound measurement system that used for measuring the samples that have been prepared in the laboratory. In the fifth chapter is described the preparation of amorphous zirconium based (Zr) and iron based (Fe) alloys and also is presented and isanalyzed their XRD patterns and also their elastic moduli, like Young modulus(E), shear modulus (G) and bulk modulue (B). Finally the sixth chapter refers to other measurements that could be used to charactirize the samples that prepared and describes the prospects of amorphous iron based alloys as a research subject for the future.

[pt] Solidificação e fusão fazem parte de uma classe de problemas transientes de transferência de calor conhecidos como problemas de mudança de fase ou de fronteira móvel. A solução desta classe de problemas envolve uma dificuldade inerente ao processo que é o movimento da interface entre as fases sólida e líquida. Este movimento está relacionado à absorção ou remoção do calor latente na interface. Como conseqüência a localização da interface sólido/líquido não é conhecida a priori tornando-se parte da solução. No presente trabalho, considera-se a mudança de fase em regime transiente de um material puro, na presença de convecção natural, em uma cavidade fechada bidimensional. A interface entre as fases sólida e líquida se comporta como um contorno bem definido com temperatura igual à temperatura de mudança de fase do material. O material na fase líquida é considerado um fluido Newtoniano e a aproximação de Boussinesq é utilizada. Tanto na região líquida, quanto na região sólida, as propriedades termofísicas são constantes e uniformes, porém, diferentes entre si. O sistema de coordenadas adotado é aquele onde suas coordenadas adaptam-se ao contorno da geometria, e considera, quando existe movimento de fronteira e/ou interface, sua velocidade de deslocamento. A intensidade na qual o fluido se movimenta provoca mudanças na forma da interface e é de fundamental importância no fenômeno da mudança de fase. No começo do processo de mudança de fase, o modo de transferência de calor na fase líquida é devido somente à condução de calor. À medida que a velocidade do fluido aumenta, o processo de transferência de calor por convecção começa a dominar. O escoamento ocorre no regime laminar mas eventualmente torna- se turbulento, o que aumenta significativamente as taxas de transferência de calor ao longo da interface. Além disso, como as partículas fluidas se deslocam mais rapidamente há uma melhor distribuição destas taxas ao longo da interface, com uma diminuição em sua curvatura. O modelo de turbulência selecionado pertence à família de modelos k-e. O modelo k-e tradicional é utilizado no núcleo turbulento, e um outro conjunto de equaçõesdesenvolvido a partir de dados de simulação numérica direta, é utilizado na região próxima às paredes. A metodologia implementada permite determinar naturalmente a transição do regime laminar para o turbulento. O presente trabalho apresenta uma nova metodologia no tratamento da interface entre as regiões sólida e líquida. Um volume de controle de espessura zero representa a posição da interface. Uma vez resolvida a equação do balanço combinado de massa e energia na interface, nenhum artifício é necessário para se avaliar sua nova posição. Devido ao salto de massa específica na interface alguma variação no volume total do material é esperada. Entretanto, o modelo atual não prevê aumento no volume total do material e algum artifício deve ser utilizado para adicionar ou retirar massa do domínio. A utilização do volume de controle zero na interface permite retirar ou adicionar massa sem a necessidade de termos de fonte adicionais. Também é utilizado o artifício de redistribuir os pontos nodais entre as fases sólida e líquida no intuito de não alocar muitos pontos nodais em regiões de pequenas espessuras. A redistribuição de pontos garante um refinamento melhor junto à interface e, possibilita a utilização de maiores intervalos de tempo sem introduzir dificuldade de convergência. Os resultados numéricos são comparados a dados experimentais e resultados numéricos para os processos de fusão e solidificação de materiais puros. A boa concordância com dados experimentais revela que a metodologia apresentada resulta numa melhora na resolução deste tipo de problemas. / [en] Solidification and fusion belong to a class of transient heat transfer problems known as phase change problems or moving boundary problems. The solution of this class of problems presents an additional difficulty concerning the movement of the interface. This movement is due to the absorption or removal of the latent heat at the interface. As a consequence the position of the interface is not known, being part of the solution. At the present work, the transient phase change of a pure substance is considered in the presence of natural convection in a closed two dimensional cavity. The interface is a well-defined boundary at the phase change temperature. The liquid phase is assumed to be Newtonian and the Boussinesq approximation is adopted. The properties of both liquid and solid phases are constant, although different of each other. A non-orthogonal coordinate system, which adapts to the geometry, is employed. This coordinate system moves with time to adapt to the varying interface position. The intensity of the fluid movement promotes changes in the interface shape, and it is extremely important for the phase change phenomena. At the beginning of the phase change process, the heat transfer mechanism at the liquid phase is due only to conduction. As the fluid velocity increases, the heat transfer by convection begins to dominate the process. The flow is laminar, and eventually the fluid flow becomes turbulent, substantially increasing the heat transfer rate along the interface. Further, since the fluid particles move more rapidly, theses heat fluxes along the interface are better distributed, causing a reduction of the interface curvature. The turbulence model selected belongs to the k-e family. The traditional k-e é employed at the turbulent core and another set of equations, developed based on direct numerical simulation data, is employed at the near wall region. The methodology is capable of determining the transition from laminar to turbulent flow. The present works presents a new methodology to determine the interface between solid and liquid regions. A zero thickness control volume represents the interface position. Once the mass and energy balance equations are solved at the interface, no further schemeis necessary to evaluate its new position. The zero thickness control volume at the interface allows the mass to be conserved at the liquid region without the need of any special treatment, in spite of the specific mass jump across the interface. The grid distribution is adjusted between the liquid and solid phase during the phase change process, in order to optimize the grid distribution in the domain. Further, the grid redistribution allows the use of larger time steps, without convergence difficulties. The numerical results are compared with experimental and numerical data available in the literature for fusion and solidification of pure substances. The good agreement reveals that the presented methodology furnishes an improved solution for this type of problems. The point redistribution allows the specification of larger time steps without compromising the convergence and precision. / [es] Solidificación y fusión forman parte de una clase de problemas de transferencia de calor conocidos como problemas de cambio de fase o de frontera movil. La solución de esta clase de problemas envuelve una dificuldad inherente al proceso: el movimiento de la interfaz entre las fases sólida y líquida. Este movimiento está relacionado con la absorción o extracción del calor latente en la interfaz. Como consecuencia, la localización de la interfaz sólido/líquido no se conoce a priori, por lo que forma parte de la solución. En el presente trabajo, se considera el cambio de fase en régimen transitorio de un material puro, en presencia de convección natural, en una cavidad cerrada bidimensional. La interfaz entre las fases sólida y líquida se comporta como un contorno bien definido con temperatura igual a la temperatura de cambio de fase del material. El material en fase líquida es considerado un fluido Newtoniano, por lo que se utiliza la aproximación de Bousinesq. Tanto en la región líquida como en la sólida, las propiedades termofísicas son constantes y uniformes, aunque diferentes entre sí. El sistema de coordenadas adoptado es aquel donde las coordenadas se adaptan al contorno de la geometría; y considera su velocidad de deslizamiento cuando existe movimiento de fronteira y/o interfaz. La intensidad del fluido provoca cambios en la forma de la interfaz lo que resulta de fundamental importancia en el fenómeno del cambio de fase. Al inicio del proceso de cambio de fase, el modo de transferencia de calor en la fase líquida se debe solamente a la conducción de calor. A medida que la velocidad del fluido aumenta, el proceso de transferencia de calor por convección comienza a dominar. El fujo ocurre en el régimen laminar, pero eventualmente se vuelve turbulento, lo que aumenta significativamente las tasas de transferencia de calor a lo largo de la interfaz. Además de esto, como las partículas fluidas se desplazan más rapidamente, hay una mejor distribución de estas tasas a lo largo de la interfaz, con una disminución en su curvatura. El modelo de turbulencia seleccionado pertence a la família de modelos k-y. El modelo k-y tradicional se utiliza en el núcleo turbulento, y se desarrolla otro conjunto de ecuaciones a partir de datos de simulación numérica directa, que es utilizado en la región próxima a las paredes. La metodología implementada permite determinar naturalmente la transición del régimen laminar para el turbulento. Este trabajo presenta una nueva metodología en el tratamiento de la interfaz entre las regiones sólida y líquida. El volúmen de control de espesura cero representa la posición de la interfaz. Una vez resuelta la ecuación del equilibrio combinado de masa y energía en la interfaz, no se necesita evaluar su nueva posición. Debido al salto de masa específica en la interfaz, se espera alguna variación en el volúmen total del material. Sin embargo, el modelo actual no prevee un aumento en el volumen total del material y se debe utilizar cierto artificio para adicionar o retirar masa del dominio. La utilización del volumen de control cero en la interfaz permite retirar o adicionar masa sin necesidad de términos de fuente adicionales. También es utilizado el artificio de redistribuir los puntos nodales entre las fases sólida y líquida con el objetivo de no considerar muchos puntos nodales en regiones de pequenas espesuras. Esta redistribución garantiza un mejor refinamiento junto a la interfaz y, posibilita la utilización de mayores intervalos de tiempo sin introducir mayores problemas de convergencia. Los resultados numéricos son comparados con datos experimentales y con resultados numéricos para los procesos de fusión y solidificación de materiales puros. La concordancia con datos experimentales revela que la metodología presentada mejora la resolución de este tipo de problemas.