O presente trabalho apresenta um estudo sobre o amolecimento após laminação e recozimento da AA 7075, uma liga de alumínio endurecível por precipitação . As amostras recebidas no estado T6 foram caracterizadas com auxílio das técnicas de microscopia óptica de luz polarizada, microscopia eletrônica de varredura, espectroscopia de raios X por dispersão de energia, difração de raios X, condutividade elétrica e dureza Vickers . As amostras foram então separadas em dois grupos. O primeiro sofreu um tratamento térmico de solubilização (485°C por 5 horas) enquanto o segundo foi submetido a um tratamento de superenvelhecimento (300°C por 5 horas) e, em seguida, ambos os grupos de amostras tratadas foram novamente caracterizadas pelas técnicas descritas anteriormente (exceto microscopia óptica) e laminadas a frio. Durante a etapa de laminação, constatou-se a dificuldade em causar deformação plástica na amostra solubilizada. Optou-se em conduzir o estudo com as amostras superenvelhecidas, que foram laminadas com reduções de 45%, 75% e 90% em espessura. A seguir, estas foram submetidas a tratamentos isotérmicos e isócronos com o objetivo de estudar a cinética de amolecimento das amostras deformadas a frio. As amostras superenvelhecidas e deformadas em 45% em redução de espessura, apresentaram somente indícios de início de recristalização (nas amostras tratadas a partir de 250°C por 1 hora) via EBSD, sendo que a maior parte do amolecimento pode ser explicada pelo mecanismo de recuperação. Além disso, a cinética de amolecimento das amostras recozidas nesse grupo apresentaram boa concordância com a lei logarítmica proposta por Kulhmann (1948) e (coincidentemente) também com o consolidado modelo JMAK. As amostras superenvelhecidas e deformadas em 75% e 90% apresentaram comportamento similar (isso é, principalmente recuperação) para recozimentos realizados em temperaturas de até 350°C por uma hora. Recozimentos realizados a 400°C promoveram a recristalização total das amostras desse grupo para tempos inferiores a 15 minutos. Dessa forma, não foi possível estudar a cinética de recristalização para esse segundo grupo de amostras. / This work presents a study about the softening after cold rolling and annealing of aluminium alloy AA 7075. Firstly, polarized light optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, electrical conductivity and Vickers hardness have been used at the starting material (T6). The samples were then separated in two groups. The former underwent a solubilization heat treatment (485°C for 5 hours) whilst the latter underwent an overaging treatment to grow up the existing precipitates (300°C for 5 hours). Both groups of treated samples were again characterized by the techniques described above (except optical microscopy). In the rolling stage, the difficulty in straining the solubilized sample and the relative ease for doing so to the overaged sample was verified. It was therefore decided to conduct the study with the samples of the second group, which were 45%, 75% and 90% rolled in thickness reduction. Then, they underwent isothermal and isochronous treatments in order to study its softening kinetics by Vickers hardness measurements, polarized light optic microscopy and EBSD. The overaged and rolled samples (45% in thickness reduction) didn\'t present evidences of recrystallization except by very few grains found via EBSD (in samples treated from 250 ° C for 1 hour). So, most of the observed softening can be explained by recovery. In addition, the softening kinetics of the annealed samples in this group showed good agreement with the logarithmic law proposed by Kulhmann (1948) and (coincidentally) also with the consolidated JMAK model. The overaged samples that underwent thickness reduction of 75% and 90% showed a similar behavior (that is, mainly recovery) for annealing at temperatures up to 350 ° C. Annealing at 400 ° C promoted total recrystallization of the samples from this group (75% and 90% in thickness reduction) in less than 15 minutes. Thus, it was not possible to study the kinetics of recrystallization for this second group of samples.

Made available in DSpace on 2014-10-09T12:35:20Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:11Z (GMT). No. of bitstreams: 0 / O processo de conformação por spray é interessante devido à capacidade de conjugar, em apenas uma etapa do processo, a vantagem da técnica de solidificação rápida combinada com alta produtividade dos processos de fundição convencional. Este processo permite a obtenção de materiais livre de macrossegregações, livre de porosidades e com microestrutura refinada. A evolução recente das pesquisas está levando ao desenvolvimento de novas ligas e os resultados têm sido interessantes. O processo de solidificação rápida inerente da conformação por spray permite a produção de ligas com composições diferentes das obtidas pela fundição convencional. O objetivo deste trabalho foi o de caracterizar mecanicamente uma liga de alumínio AA-6082 conformada por spray. Os resultados de testes de dureza Vickers são apresentados para seções de um preformado em relação a sua altura (em um arranjo tridimensional). O material foi avaliado na condição como conformado por spray e após tratamento térmico de solubilização a 525 ºC por 1 h, seguido por envelhecimento a 125 ºC por períodos distintos de 1 h, 10 h, 100 h e 500 h. É mostrado que o a liga AA 6082 conformada por spray mostra uma boa estabilidade térmica em relação a variação da dureza durante o envelhecimento. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2014-10-09T12:54:14Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:09:24Z (GMT). No. of bitstreams: 1 12433.pdf: 20959730 bytes, checksum: a98e9829a642f5e597da179c95c176ef (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Quimica, Universidade de Sao Paulo - IQ/USP

O objetivo deste trabalho foi determinar a influência do ferro e do manganês em uma liga de alumínio com 9% de silício (% em peso). Para isto, foram elaboradas duas famílias de liga Al-9%Si: uma com os teores de 0,1%, 0,4%, 0,8% e 1,2% de Fe e uma segunda liga de Al-9%Si-0,8%Fe com teores de 0,1%, 0,4% e 0,7% de Mn. Para a realização deste estudo, foram produzidos corpos de prova de tração fundidos em coquilha, segundo a norma ASTM B108. Os corpos de prova obtidos foram tracionados para avaliação das propriedades mecânicas, em seguida, foram submetidos a uma análise microestrutural por microscopia óptica (MO) e eletrônica de varredura (MEV). As superfícies de fratura dos corpos de prova tracionados foram também observadas por MEV com a finalidade de comparar o efeito das adições de Fe e Mn. O efeito da adição crescente de Fe na liga Al-9%Si foi observado no ensaio de tração que mostrou queda tanto nos limites de resistência e de escoamento como no alongamento, decorrentes da formação da fase β-Al5FeSi que apresentou morfologia em plaquetas, interrompendo a continuidade da matriz de alumínio. Para teores abaixo de 0,4% de Fe, ocorreu um ligeiro aumento da resistência mecânica que pode ser atribuído à formação da fase α-Al8Fe2Si, que apresentou morfologia tipo escrita chinesa, que não interrompe a continuidade da matriz. Com adição de teores crescentes de Mn na liga Al-9%Si-0,8%Fe ocorreu uma elevação do limite de resistência e do alongamento, mas uma queda do limite de escoamento, quando comparados com a mesma liga sem adição de Mn. Conclui-se que esse comportamento pode ser atribuído a mudança de morfologia do intermetálico de plaquetas para escrita chinesa que intercala a matriz dúctil com a fase frágil, devido a adição do Mn. / This study aims to determine the influence of iron and manganese in an aluminum alloy with 9% silicon (% by weight). Were prepared two families of alloy Al-9%Si: one with the content of 0.1%, 0.4%, 0.8% and 1.2% Fe and a second alloy of Al-9% Si-0,8%Fe content of 0.1%, 0.4% and 0.7% Mn. For this study, tensile specimens were produced in permanent mold casting according to ASTM B108. The specimens obtained were pulled for quantitative evaluation of the mechanical properties and were subjected to a qualitative metallographic evaluation. Qualitative analysis of the bodies of tensile fracture test was conducted in order to compare the effect of additions of Fe and Mn. The effect of incremental addition of Fe in the alloy Al-9% Si was observed in the tensile test that showed a decrease in both the tensile and elongation flow as resulting from the formation of β-Al5FeSi phase platelet morphology showed that interrupting the continuity of aluminum matrix. To levels below 0.4% Fe, there was a slight increase in strength can be attributed to the formation of α-Al8Fe2Si phase morphology presented in chinese script that does not interrupt the continuity of the matrix. With addition of increasing concentrations of Mn in the alloy Al-9% Si-0, 8% Fe was an increase in the tensile strength and elongation but fall of yield stress when compared to the same alloy without Mn addition. We conclude that this behavior can be attributed to a change in morphology of the intermetallic platelets to chinese writing interspersing the ductile matrix with brittle phase due to the addition of Mn.

A cinética da transformação de fase UAl3 + Al → UAl4 foi estudada em duas ligas Al-U, com 31,4 % e 33,4 % U em peso respectivamente, através de metalografia quantitativa. Os resultados mostraram que esta transformação é um processo de nucleação e crescimento termicamente ativado, com a nucleação ocorrendo heterogeneamente nas interfaces UAl3/AI(∞) e o crescimento sendo controlado por difusão em volume. A energia de ativação empírica do processo foi determinada, cujo valor médio é da ordem de 54,8 kcal/mol. Foi verificado que a cinética de crescimento da fase UAl4 obedece uma lei parabólica. As interfaces UAl4/ UAl3 e UAl4/Al(∞) migram em direções opostas, sendo que a velocidade da interface UAl4/ UAl3 é aproximadamente cinco vezes maior que aquela da interface UAl4/Al(∞). O coeficiente de difusão química do Al e do U na fase UAl4 foi avaliado ser da ordem de 10-9 cm 2/s a 600°C. / The kinetics of phase transformation UAl3 + Al → UAl4 of two Al-U alloys, with 31.4 and 33.4 wt % U respectively, was studied by quantitative microscopy. The results have shown that this transformation is a nucleation and thermally activated growth process. The nucleation occurs heterogeneously at the UAl3/AI(∞) interfaces and growth is controlled by volume diffusion. The empirical activation energy of the process was determined, whose mean value is of about 54.8 kcal/mol. It was verified that a parabolic growth law is obeyed. The UAl4/ UAl3 and UAl4/Al(∞) interfaces migrates in opposite directions, with the UAl4/ UAl3 interface velocity was approximately 5 times greater than that of UAl4/Al(∞) interface. The chemical diffusion coefficient of Al and U in the UAl4 phase were evaluated to be of the order of 10-9 cm 2/s at 600°C.

Orientadores: Amauri Garcia, Ivaldo Leão Ferreira / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-20T13:38:54Z (GMT). No. of bitstreams: 1 Gomes_LaercioGouvea_D.pdf: 17047245 bytes, checksum: 5fae42e8e6af30ec0ed1e1c1ea889af5 (MD5) Previous issue date: 2012 / Resumo: As ligas de alumínio para fundição possuem propriedades de grande interesse industrial, como: baixa massa especifica, boa resistência a corrosão, elevadas condutibilidade térmica e elétrica, boas combinações de propriedades mecânicas, boa trabalhabilidade em processos de usinagem e conformação mecânica. Atualmente, essas ligas são produzidas em vários sistemas e dezenas de composições. A literatura apresenta vários estudos tanto teóricos quanto experimentais focando na evolução microestrutural de ligas binárias a base de alumínio. Leis de crescimento celular e dendritico experimentais e teóricas foram propostas e devidamente validadas. As analises de macrossegregação e formação de poros de ligas binárias de alumínio também foram contempladas em vários estudos recentes. Entretanto, são escassos os estudos abordando importantes famílias de ligas multicomponentes a base de alumínio. Nesse sentido, o presente trabalho se propôs a analisar ligas da família Alumínio-Silício-Cobre (A319.1 e A333.1) [Al-5,5%Si-3,0%Cu e Al-9,0%Si-3,0%Cu] no que diz respeito a evolução da microestrutura dendrítica, macrossegregação e formação de porosidade na solidificação. Para a produção das ligas ternárias foram utilizados Alumínio e Silício comercialmente puros e Cobre eletrolítico. A macrossegregação de soluto e a formação de microporosidade são investigadas tanto experimentalmente quanto por meio de simulações numéricas. A microestrutura dendrítica e quantificada através de seus espaçamentos primários, secundários e terciários, que são devidamente correlacionados com os parâmetros térmicos da solidificação. Os perfis de macrossegregação de soluto, densidade teórica e densidade aparente são apresentados ao longo dos comprimentos dos lingotes. Os perfis de segregação de soluto experimentais foram obtidos através da técnica de espectrometria de fluorescência de raios-X e para a simulação foram calculados levando-se em conta transformações de fase secundarias que ocorrem ao longo da solidificação. As medições de microporosidade foram realizadas utilizando-se a técnica de picnometria...Observação: O resumo, na íntegra, poderá ser visualizado no texto completo da tese digital / Abstract: Aluminum casting alloys have properties which are of great industrial interest, such as low density, good corrosion resistance, high thermal and electrical conductivities, good combination of mechanical properties, good workability in machining processes and mechanical forming. Currently, these alloys are produced in various systems and dozens of compositions. The literature presents several studies, both theoretical and experimental, focusing on the microstructural evolution of binary aluminum base alloys. Theoretical and experimental cellular and dendritic growth laws have been proposed and validated. Macrosegregation and pore formation during solidification of binary alloys of aluminum have been the focus of several recent studies. However, there are few studies in the literature addressing important families of multicomponent aluminum base alloys. Accordingly, this study aims to analyze Aluminum- Silicon-Copper alloys (series: A319.1 and A333.1) [Al-5.5wt%Si-3.0wt%Cu and Al-9.0wt%Si- 3.0wt%Cu] with respect to the evolution of the dendritic microstructure, porosity formation and macrosegregation during solidification. For the production of the ternary alloys commercially pure aluminum and silicon and electrolytic copper have been used. Solute macrosegregation and microporosity formation are investigated both experimentally and through numerical simulations. The dendritic microstructure is quantified by their primary, secondary and tertiary arm spacings, which are correlated with solidification thermal parameters. The solute macrosegregation profiles, theoretical and apparent densities have been determined along the castings lengths. The solute segregation profiles were obtained by X-ray fluorescence spectrometry and the simulations were performed taking into account secondary phase transformations that occur during solidification. Microporosity measurements were carried out by the picnometry technique...Note: The complete abstract is available with the full electronic document / Doutorado / Materiais e Processos de Fabricação / Doutor em Engenharia Mecânica

Les culasses de moteur diesel PSA sont réalisées en alliages d'aluminium de fonderie durcis par précipitation. La culasse atteint une température stable lors de l'utilisation du véhicule mais la succession de démarrages et d'arrêts engendre un phénomène de fatigue thermique au niveau du pontet inter-soupapes. L'exposition à des températures élevées modifie la microstructure de précipitation provoquant une diminution des propriétés mécaniques et donc un vieillissement de l'alliage. Il est donc nécessaire de prendre en compte le vieillissement thermique dans le dimensionnement. Pour y parvenir, nous avons d'abord analysé la microstructure de précipitation (nature des phases précipitées, morphologie et taille) en Microscopie Electronique en Transmission (MET) et le comportement cyclique viscoplastique pour différents vieillissement isothermes. Des essais thermomécaniques anisothermes, simulant le chargement en service, ont été réalisés afin d'analyser les relations entre la déformation plastique et la précipitation. Les paramètres géométriques de la précipitation ont été déterminés en MET pour différents nombres de cales thermomécaniques et ont été comparés à ceux de la précipitation résultant de l'exposition de l'alliage au seul cycle thermique pendant le même nombre de cycles.La microdureté étant un bon indicateur du vieillissement des alliages d'aluminium durcis par précipitation, des modèles d'évolution de microdureté ont été développés afin de simuler sa décroissance dans la structure lors d'un essai représentatif des conditions en service. Ces simulations permettent d'améliorer l'estimation du vieillissement de ces alliages lors de l'utilisation de la culasse. / Cylinder heads of automotive engines are produced by casting of precipitation strengthened Al-Si alloys.The cylinder head quickly reaches a steady state temperature but the succession of starts and stops generates thermomechanical fatigue in the area between the valve seats. At service temperature, the precipitation microstructures evolve from their state after precipitation hardening heat treatment to an aged state, which results in the reduction of their mechanical properties. The increase of thermomechanical stresses in new engines requires taking thermal aging into account for sizing. To that end, the precipitation microstructures (precipitates crystal structures, composition, morphology, and distribution) have been analyzed by Transmission Electron Microscopy (TEM) for various aging conditions and the corresponding cyclic least-viscoplastic behavior has been determined. The effect of plastic deformation on the kinetics of precipitate growth has been studied throughout loadings representative of engine operation. The morphological characteristics of the precipitation microstructure resulting from the thermomechanical aging were determined by TEM for different numbers of cycles and compared with those resulting from the mere thermal aging in order to assess the effect of plastic deformation on the kinetics of precipitate growth. As micro hardness is a good indicator of the aging of precipitation strengthened aluminium alloys, micro hardness evolution models have been developed to calculate its decrease in the cylinder head during a test simulating in service conditions. The simulations give us a better understanding of the in-service aging of these alloys.

The mechanical properties achieved with high performance wrought aluminium alloys are superior to cast aluminum alloys. To obtain an intricate shaped component, wrought alloys are commonly subjected to forging followed by subsequent machining operation in the automobile industry. As machining of such high strength wrought aluminium alloys adds to cost, productivity gets affected. Shortening the process by near net shaped casting would tremendously enhance productivity. However, casting of such alloys frequently encounter hot tear defect. Therefore, circumventing hot tear to successfully die cast near net shaped wrought alloy components is industrially relevant. A recent advanced casting process, namely ‘Semisolid Die casting’, is proposed as a likely solution. Hot tearing originates due to lack of liquid flow in the inter-dendritic region. To reduce hot tear susceptibility, fine and non-dendritic grain structure is targeted, amenable for processing by semisolid route. For semisolid processing an adequate freezing range for processing is required. Accordingly A6061 wrought alloy whose composition is tuned with higher silicon and magnesium content within the grade limits, is chosen for the study. With the objective of obtaining fine and non-dendritic microstructured billets, electromagnetic stirring (EMS) and cooling slope (CS) methods are employed. On conducting a parametric study with EMS, a finest possible primary α-Al grain size of about 70 μm is obtained at low stirring time at stirring current levels of 175 A and 350 A, with the addition of grain refiner. CS, on the other hand, rendered a grain of 60 μm at a slope length of 300 mm at a slope angle of 45° with grain refiner addition. Of the two methods, CS billets are chosen for subsequent induction heating. A 3-step induction heating cycle has been devised to attain a temperature of 641°C in the billet on the basis of factors including coherency point, viscosity of the slurry and solid fraction sensitivity with temperature. The billet microstructure is found to be homogenous throughout after quenching in water. The characterization of phase along primary α-Al grain boundary and its composition analysis is done by SEM and EPMA respectively, after billet casting as well as induction heating. In addition, the bulk hardness is determined in BHN. The induction heated billets are semisolid die cast to produce an engine connecting rod used in automobiles. The microstructure is characterized at various locations, and is found to consist of smooth α-Al grains in a background matrix of fine grains formed due to secondary solidification. The component hardness is found to be 66 BHN comparable with A6061 alloy under T4 heat treated condition. X-ray radiography does not confirm presence of surface hot tear, which is the normal defect associated with casting of wrought aluminium alloys. No defects are observed along the constant cross-sectional area of the connecting rod, suggesting that the processing could be suitable for semisolid extrusion.

Aluminium alloys are frequently pre-treated by a conversion coating before application of an organic coating in order to improve the corrosion resistance and adhesive properties of the surface and the corrosion resistance provided by the system. Chromate-containing conversion coatings are commonly used for this purpose. However, legislation limits future use of hexavalent chromium compounds due to their toxic and carcinogenic nature. Therefore, alternative, so-called chromium-free conversion coatings are being developed that are more environmentally-compliant.The purpose of the present work has therefore been to contribute to a better understanding of how the aluminium substrate affects the formation and properties of conversion coatings for adhesive bonding. In particular, a chrome-free zirconium-based conversion treatment process has been investigated as a possible replacement for conventional chromate conversion treatment. The influence of the conversion time on the thickness of the formed layer on pure aluminium was investigated using complementary surface analytical techniques. The conversion time was varied between 30 and 600 seconds.In this study, the structure and composition of zirconium-based chromium-free conversion coatings on magnetron sputtered superpure aluminium and a range of aluminium-copper alloys were characterised as a function of immersion time in the aqueous conversion bath to understand the mechanism of coating formation and protection. However, the presence of copper significantly influences the coating development and ultimately the performance of the conversion coatings formed on binary copper-containing aluminium alloys.The morphology and composition of the coatings have been probed using transmission electron microscopy, Rutherford backscattering spectroscopy and glow discharge optical emission spectroscopy, with loss of substrate through growth of the conversion coating also quantified. A comparison of the RBS spectra obtained for the superpure aluminium specimens after different immersion times revealed that zirconium (Zr) and oxygen (O) peaks were wider for longer immersion times, indicating thickening of the coating with increased immersion times. Thus, increasing the immersion time resulted in an increase in coating thickness but little change in coating composition occurred as determined by the RBS RUMP simulations. Alloying decreases the coating thickness, as well as metal consumption. Here, aspects of the corrosion behaviour of superpure aluminium and aluminium-copper alloys were also considered using electronoptical, electrochemical and surface analytical probing. The influence that short and prolonged treatment times exert on the performances of such conversion coating is discussed. The conversion coating formed after 60 s and 180 s of immersion in the zirconium-based conversion coating bath provide good corrosion resistance which can be attributed to the high stability of the compounds that constitute the surface oxide layer, and good adhesion properties.

Orientador: Amauri Garcia / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-18T19:08:04Z (GMT). No. of bitstreams: 1 Silva_MariaAdrinaPaixaodeSouzada_D.pdf: 5780858 bytes, checksum: b602bf47a710b2fb6f161a596020054f (MD5) Previous issue date: 2011 / Resumo: Ligas de alumínio dispersas com bismuto, chumbo e índio apresentam aplicações promissoras em componentes automotivos resistentes ao desgaste. Essas dispersões de elementos de baixa temperatura de fusão diminuem a dureza e escoam facilmente em condições de deslizamento, resultando em um comportamento tribológico favorável. Muitos estudos têm sido realizados a fim de melhor compreender as distintas morfologias obtidas pela reação monotética Algumas pesquisas assumem que a evolução do espaçamento interfásico (?) nas Iigas monotéticas ou obedece à clássica relação utilizada para eutéticos: ?2v = C, ou ainda a relação de crescimento dentrítico ?.va.Gb = C, onde v é a velocidade de solidificação e C uma constante para ambos os casos, G é o gradiente de temperatura e a e b são constantes. Tais estudos utilizaram fornos de aquecimento à resistência do tipo Bridgman para produzir a solidificação direcional de ligas monotéticas. Existe uma falta de estudos consistentes no desenvolvimento microestrutural de ligas monotéticas durante condições de fluxo de calor transitório, que são de importância primordial, uma vez que esse tipo de fluxo de calor engloba a maioria dos processes industriais e de solidificação. No presente estudo, foram realizados experimentos de solidificação unidirecional em regime não-estacionário com as Iigas hipomonotéticas Al-0,9%Pb e Al-5,5%In, com a liga monotética Al-1,2% Pb e com as Iigas hipermonotéticas Al-5,0%Bi, Al-7,0%Bi e Al- 2,1%Pb, além da análise da rnacrossegregação da liga monotética Al-3,2%Bi. Os parâmetros térmicos como velocidades de crescimento, taxas de resfriamento e gradientes térmicos foram determinados experimentalmente por curvas de resfriamento adquiridas ao longo do comprimento do lingote. A evolução microestrutural foi caracterizada por técnicas metalográficas e os espaçamentos foram correlacionados com os parâmetros térmicos de solidificação. Verificou-se que a lei de crescimento ?2v= C é válida apenas para os casos onde há ocorrência de partículas de soluto dispersas irregularmente na matriz e que esta lei não se aplicou nos casos onde foi observado uma frente monotética celular e morfologia de fibras e cordões de pérolas. Já a lei ?.va.Gb = C se mostrou aplicável em todos os casos ascendentes. O aumento do teor de soluto das ligas e o fluxo convectivo induzido provocaram mudanças nas morfologias das fases, na magnitude dos espaçamentos interfásicos e nos diâmetros das partículas / Abstract: Aluminum alloys dispersed with bismuth, lead and indium show promising applications in wear­resistant automotive components. Such dispersions of low melting temperature elements decrease hardness and flow easily under sliding conditions, resulting in favorable tribological behavior. Much research has been devoted in order to better comprehend the distinct morphologies obtained by monotectic reactions. Some researches assume that the interphase spacing evolution in monotectic alloys follows the classical relationship used for eutectics: ?2v = C, or the dendritic growth relationship ?.va.Gb = C, where v is the solidification velocity and C a constant value for both cases, G is the thermal gradient and a and b are constants. Such studies have used Bridgman type het resistance furnaces to produce the directionally solidified monotectic samples. There is a lack of consistent studies on the microstructural development of monotectic alloys during transient heat flowconditions, which are of prime importance since this class of heat flow encompasses the majority of solidification industrial processes. In the present study, directional unsteady-state solidification experiments were carried out with hypomonotectic Al-0.9wt%Pb and Al-5.5wt%In, monotectic Al-1.2wt%Pb and hypermonotectic Al-5.0wt%Bi, Al-7.0wt%Bi and Al-2.1wt%Pb alloys, besides the macrosegregation analysis of the monotectic Al-3.2wt%Bi alloy. Thermal parameters such as the growth rate, cooling rate and thermal gradient were experimentally determined by cooling curves recorded along the casting length. The microstructural evolution was characterized by metallography and the spacings were correlated with the thermal parameters. It is show that the ?2v = C growth law is valid only for the cases where there is a morphology of solute particles irregularly arranged in the matrix and it is not applied on the cases where a cellular monotectic front or fibers and strings of pearls morphologies were observed. On the other hand, ?.va.Gb = C law seems to be able to characterize all the upward cases. The increase in the alloy solute content and induced convective flow affected the morphologies of the resulting phases, the magnitude of the interphase spacing and the diameters of the solute-rich particles / Doutorado / Materiais e Processos de Fabricação / Doutor em Engenharia Mecânica