In numerous Gram-negative and Gram-positive bacteria as well as in Archaea SL proteins form the outermost layer of the cell envelope. SL (glyco)monomers self-assemble with oblique (p2), tetragonal (p4), or hexagonal (p3, p6) symmetries [12]. SL subunits interact with each other and with the underlying cell surface by relatively weak non-covalent forces such as hydrogen-bonds, ionic bonds, salt-bridges or hydrophobic interactions. This makes them easy to isolate by applying chaotropic agents like urea and guanidine hydrochloride (GuHCl), chelating chemicals, or by changing the pH of the environment [10]. Upon dialysis in an ambient buffer monomers recrystallize into regular arrays that possess the forms of flat sheets, open ended cylinders, or spheres on solid substrates, at air-water intefaces and on lipid films, making them appealing for nanobiotechnological applications [3, 18]. The aim of this study was to investigate the structure, thermal stability, in vivo self-assembly process, recrystallization and metallization of three different recombinant SL proteins (SslA-eGFP, mSbsC-eGFP and S13240-eGFP) expressed in yeast S. cerevisiae BY4741 which could be further used in nanobiotechnological applications. In order to fulfill this aim, I investigated the in vivo expression of SL proteins (SslA, SbsC, S13240) tagged with eGFP (SL-eGFP) in the yeast S. cerevisiae BY4141. First, I characterized the heterologous expression of SL fusion constructs with growth and fluorescence measurements combined with Western blot analyses. Fluorescence microscopy investigations of overnight grown cultures showed that SslA-eGFP fusion protein was expressed as fluorescent patches, mSbsC-eGFP as tubular networks, and S13240-eGFP as hollow-like fibrillar network structures, while eGFP did not show any distinct structure Thermal stability of in vivo expressed SL-eGFP fusion proteins were investigated by fluorescence microscopy and immunodetection. In vivo self-assembly kinetics during mitosis and meiosis was the second main issue. In parallel, association of in vivo mSbsC-eGFP structures with the cellular components was of interest. A network of tubular structures in the cytosol of the transformed yeast cells that did not colocalize with microtubules or the actin cytoskeleton was observed. Time-resolved analysis of the formation of these structures during vegetative growth and sporulation was investigated by live fluorescence microscopy. While in meiosis ascospores seemed to receive assembled structures from the diploid cells, during mitosis surface layer structures were formed de novo in the buds. Surface layer assembly always started with the appearance of a dot-like structure in the cytoplasm, suggesting a single nucleation point. In order to get these in vivo SL assemblies stably outside the cells (in situ), cell distruption experiments were conducted. The tubular structures formed by the protein in vivo were retained upon bursting the cells by osmotic shock; however their average length was decreased. During dialysis, monomers obtained by treatment with chaotropic agents recrystallized again to form tube-like structures. This process was strictly dependent on calcium ions, with an optimal concentration of 10 mM. Further increase of the Ca2+ concentration resulted in multiple non-productive nucleation points. It was further shown that the lengths of the S-layer assemblies increased with time and could be controlled by pH. After 48 hours the average length at pH 9.0 was 4.13 µm compared to 2.69 µm at pH 5.5. Successful chemical deposition of platinum indicates the potential of recrystallized mSbsC-eGFP structures for nanobiotechnological applications. For example, such metalized protein nanotubes could be used in conductive nanocircuit technologies as nanowires.

D. Tech. Chemical, Metallurgical and Materials Engineering / Discusses the objective of this present study is to manufacture particulate-strengthening Zn-Al-SnO2-TiO2 composite alloy on mild steel from chloride and sulphate baths with the target of improving mechanical and anti-corrosion, wear properties for automotive and decorative applications. Sub-Objectives:To study the effect of Zn-Al-SnO2-TiO2 composite properties on mild steel substrate To investigate the novel multifunctional thin films evolution formed on mild steel and their tribological properties. To investigate thermo-mechanical recrystallization behaviour and its thermal instability.To study the anti-corrosion resistance performance of the electrofabricated quaternary Zn-Al-SnO2-TiO2 coatings.To draw attention to the functional processing parameters of Zn-Al-SnO2-TiO2 produced coatings for high durability.

The purpose of this report is to evaluate the hardness and microstructure in bent and welded samples of Alloy 718. The results will be used by GKN aerospace to evaluate the simulated values of the production process of vines in a jet engine. In total, eleven samples from three different production chains are evaluated. All samples are bent and go through different stages within the production including bending, solution treatment and welding. The samples are cut and mounted in bakelite then polished and etched in order for the microstructure to be seen and evaluated. Hardness tests were made on the mounts to evaluate how bending, solution treatment and welding affects the hardness. The bent samples without the solution treatment became harder depending on the amount of cold deformation. The amount of cold deformation controls how fast the material recrystallizes during subsequent solution treatment. During the solution treatment, the δ-phase (Ni3Nb) is precipitated in the grain boundaries which prevents a coarser grain size and therefore promotes a smaller grain size.  The laser weld creates a small HAZ (heat affected zone) that becomes softer because the heat dissolves the δ-phase which therefore triggers the grains to grow. The weld consists of eutectic γ-dendrites with interdendritic pools of alloying elements. After the solution treatment, many needle shaped δ-phases arise from the pools and HAZ. The hardness measurements were tested on a manual machine which makes potential human error important to consider when the measurements are evaluated. When the grain size measurements are done on the solution treated samples, the grain boundaries can be difficult to determine because the δ-phases and twins create wide and incorrect boundaries. The results will be used by GKN Aerospace in order to verify their simulations. The heterogenic material after solution treatment will probably be studied further. / Syftet med projektet är att undersöka hårdhet och mikrostruktur i bockade och svetsade prover tillverkade av Alloy 718. Totalt undersöks elva stycken prover som är tillverkade på olika sätt enligt tre tillverkningskedjor. Alla provbitar är bockade och har sedan genomgått olika många steg i tillverkningen som består utav bockning, upplösningsbehandling och svets. Genom att kapa upp provbitarna i mindre bitar, baka in de i bakelit och etsa de studerades mikrostrukturen och hur den påverkas av bockning, upplösningsbehandling och svets. Vidare gjordes hårdhetsmätningar över olika delar av proven för att undersöka hur mycket hårdare materialet blir vid kalldeformation och hur upplösningsbehandling och svets påverkar hårdheten i Alloy 718. Endast bockade prov blir hårdare beroende på hur mycket kalldeformation provbiten har utsatts för. Hur mycket provet har deformerats styr hur snabbt rekristallisationen sker vid en efterföljande upplösningsbehandling. Under upplösningsbehandlingen utskiljs även δ-fas (Ni3Nb) i korngränser vilket främjar en mindre kornstorlek. Lasersvetsen ger ett litet värmepåverkat område men värmen från svetsen bidrar till att δ-fasen löses upp och större korn bildas. Svetsen består av långa eutektiska γ-dendriter med interdendritiska poler av mycket legeringsämnen. Vid upplösningsbehandling efter utförd svets bildas det δ-fas i de värmepåverkade och i svetsen. Hårdhetsmätningarna har utförts på en manuell hårdhetsmaskin vilket innebär att felmarginalen blir större då den mänskliga felfaktorn spelar en stor roll. Vid beräkning av kornstorlek har det varit svårt att utskilja vad som är en korngräns i upplösningsbehandlade prov då mängden δ-fas efter upplösningsbehandling ger tjocka korngränser.  Resultaten kommer användas av GKN Aerospace för att verifiera sina simulationer. Det heterogena materialet efter upplösningsbehandlingen kommer troligtvis studeras vidare.

Co-20Cr-15W-10Ni alloy (L-605) is a cobalt-based superalloy combining high strength with keeping high ductility, biocompatible and corrosion resistant. It has been used successfully for heart valves for its chemical inertia, and this alloy is a good candidate for stent elaboration. Control of grain size distribution can lead to significant improvement of mechanical properties: in one hand grain refinement enhance the material strength, and on the other hand large grains provide the ductility necessary to avoid the rupture in use. Therefore, tailoring the grain size distribution is a promising way to adapt the mechanical properties to the targeted applications. The grain size can be properly controlled by dynamic recrystallization during the forging process. Therefore, the comprehension of the recrystallization mechanism and its dependence on forging parameters is a key point of microstructure design approach. The optimal conditions for the occurrence of dynamic recrystallization are determined, and correlation between microstructure evolution and mechanical behavior is investigated. Compression tests are carried out at high-temperature on Thermec-master Z and Gleeble forging devices, followed by gas or water quench. Mechanical behavior of the material at high temperature is analyzed in detail, and innovative methods are proposed to determine the metallurgical mechanisms at stake during the deformation process. Mechanical properties of the material after hot-working and annealing treatments are investigated. The grain growth kinetics of L-605 alloy is determined, and experimental results are compared with the static recrystallization process. Microstructures after hot deformation are evaluated using SEM-EBSD and TEM. Significant grain refinement occurs by dynamic recrystallization for high temperature and low strain rate (T≥1100 ◦ C, strain rate < 0.1s−1), and at high strain rate (strain rate > 10s−1). Dynamic recrystallization is discontinuous and takes place from the grain boundaries, leading to a necklace structure. The nucleation mechanism is most likely to be bulging from grain boundaries and twin boundaries. A new insight of the modeling of dynamic recrystallization taking as a starting point the experimental data is proposed. By combining the results from the mechanical behavior study and microstructure observation, the recrystallization at steady-state is thoroughly analyzed and provides the mobility of grain boundaries. The nucleation criterion for the bulging from grain boundaries is reformulated to a more general expression suitable for any initial grain size. Nucleation frequency can be deduced from experimental data at steady-state through modeling, and is extrapolated to any deformation condition. From this point, a complete analytical model of the dynamic recrystallization is established, and provides a fair prediction on the mechanical behavior and the microstructure evolution during the hot-working process.

The effect of deformation on microstructural changes in metals and alloys is the subject of considerable practical interest. The ultimate goal is to control, improve and optimize the microstructure and texture of the finished products produced by metal forming operations. The development in the subject field is remarkable but a more in-depth study could lead us to the better understanding of the phenomena.   In the present work microstructural evolution during the plastic deformation of as-cast pure metals and alloys is studied. An experimental method was developed to study the material behavior under the hot compression testing. This method was applied on the as-cast structure of copper, bearing steel, Incoloy 825 and β brass at different temperatures and strain rates. The temperature of the samples was measured during and after the deformation process. The microstructure of the samples was examined by optical microscopy and scanning electron microscopy (SEM). The microstructural evolution during deformation process was investigated by transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD). The samples were subsequently subjected to electron microprobe analysis (EMPA) to investigate the effect of the deformation on the microsegregation of Mo, Cr, Si, and Mn.   It was observed that the temperature of the samples deformed at strain rates of 5 and 10 s-1 increases abruptly after the deformation stops. However, compression test at the lower strain rates of 1 and 0.5 s-1 revealed that a constant temperature was maintained in the early stage of deformation, followed by an increase until the maximum temperature was obtained. This temperature behavior can be explained by the microstructural evolution during the deformation process. Micrograph analysis revealed the formation of deformation bands (DBs) in highly strained regions. The DBs are highly effective sites for recrystallization. The interdendritic regions are suitable sites for the formation of DBs due to the high internal energy in these regions. EMPA indicated a tendency towards uphill diffusion of Mo in the DBs with increasing strain. The effect of strain on the dissolution of carbides in the band structure of bearing steel was investigated by measuring the volume fraction of carbides inside the band structure at different strain levels. The results indicate that carbide dissolution is influenced by strain.    The microstructural evolution inside the DBs was studied as a function of several properties: temperature, internal energy, and microsegregation. Compression of β brass revealed that twinning is the most prominent feature in the microstructure. EBSD analysis and energy calculations demonstrated that the twinning is not due to a martensitic process but rather the order/disorder transition during the deformation process. The effect of heat treatment at Tc (650°C) prior to deformation on the microstructure of β brass was also investigated, which revealed a relationship between twin formation and the anti-phase domain boundaries / <p>QC 20131104</p>

Les zéolithes sont largement utilisées en catalyse acide, particulièrement en pétrochimie. Toutefois, leur activité n'est pas optimale à cause des limitations diffusionnelles imposées par leur structure microporeuse. Diverses approches ont été proposées pour contourner ces limitations et notamment la préparation des zéolithes mésoporeuses. Après une évaluation industrielle des différentes méthodes rapportées dans la littérature, la première partie de la thèse a été consacrée à la mise au point, la compréhension et l'optimisation d'une procédure de préparation de zéolithes à mésoporosité contrôlée à l'aide d'un agent structurant organique. Nous nous sommes intéressés à la recristallisation de la zéolithe Y qui permet de créer un volume mésoporeux important au sein des cristaux de zéolithe par transformation pseudomorphique. Dans une seconde partie, nous rapportons la première synthèse de zéolithes mésoporeuses à partir d'un agent structurant récupérable et recyclable en conditions douces dans l'eau. En synthétisant un agent structurant thermosensible adapté aux conditions de recristallisation, une mésostructure contrôlée a pu être obtenue au sein de la zéolithe. L'extraction du polymère en solution aqueuse a été optimisée et son recyclage sur quatre cycles de recristallisation a été démontré. / Zeolites are widely used in acid catalysis, especially in petrochemistry. However, their activity is not optimal because of diffusional limitations imposed by their microporous structure. Various approaches have been proposed to circumvent these limitations, including the preparation of mesoporous zeolites. After an industrial assessment of the different methods reported in the literature, the first part of the thesis was devoted to the development, understanding and optimization of a procedure for preparation of zeolites with controlled mesoporosity using an organic structuring agent. We studied the recrystallization of the zeolite Y, which creates a large mesoporous volume in the zeolite crystals by pseudomorphic transformation. In the second part, we report the first synthesis of mesoporous zeolites using a structuring agent recoverable and recyclable under mild conditions in water. By synthesizing a structuring agent adapted to the conditions of thermal recrystallization, controlled mesostructure could be obtained within the zeolite. The extraction of the polymer in aqueous solution has been optimized and recycling of four cycles of recrystallization has been demonstrated.

O tungstato de zircônio (ZrW2O8) é um material cerâmico que exibe diversos compor-tamentos incomuns: expansão térmica negativa, amorfização induzida por altas pressões (entre 1,5 GPa e 2,0 GPa) e recristalização endotérmica quando aquecido a temperaturas superiores a 600 C. A relaxação estrutural exotérmica e irreversível é o fenômeno que precede a recristalização da fase amorfa do composto e é caracterizada por um espectro contínuo de energia de ativação. Este trabalho tem como objetivo principal explorar o mecanismo de relaxação estrutural da fase amorfa do tugnstato de zircônio, em particular, determinar se este fenômeno envolve a quebra das ligações W-O formadas durante a amorfização. Com esta finalidade, foram utilizadas as técnicas de ressonância magnética nuclear de estado sólido do núcleo 17O (RMN), espectroscopia Raman e espectroscopia na região do infravermelho longínquo (FT-FAR-IR). Além disso, como objetivo secundário, foi calculado, por meio de medidas de calorimetria exploratória diferencial modulada (MDSC) o espectro de energia de ativação deste processo. Esse cálculo envolveu a resolução do problema inverso originado do modelo cinético utilizado, que resulta em uma equação integral de Fredholm do primeiro tipo. O espectro obtido apresenta uma distribuição assimétrica de probabilidade de que processos cinéticos ocorram como função da energia com dois máximos em aproximadamente 1.4 eV e 2.7 eV, indício de que dois processos com mecanismos distintos ocorrem durante a relaxação. A evolução da estrutura amorfa durante a relaxação foi acompanhada por RMN do estado sólido do núcleo 17O e por meio das técnicas de espectroscopias vibracionais. Os resultados indicam que durante a relaxação estrutural da fase amorfa do ZrW2O8 não ocorre quebra das ligações W-O formadas durante a amorfização, mas apenas um rearranjo local dos átomos de oxigênio. Somente na temperatura de recristalização é fornecida energia suficiente para que ocorra o rompimento destas ligações. / Submitted by Ana Guimarães Pereira (agpereir@ucs.br) on 2016-12-19T16:39:57Z No. of bitstreams: 1 Tese Fernanda Miotto.pdf: 6599930 bytes, checksum: 758989ba90137070ed1f00a6452fd4f6 (MD5) / Made available in DSpace on 2016-12-19T16:39:57Z (GMT). No. of bitstreams: 1 Tese Fernanda Miotto.pdf: 6599930 bytes, checksum: 758989ba90137070ed1f00a6452fd4f6 (MD5) Previous issue date: 2016-12-19 / Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul, FAPERGS. / Zirconium tungstate (ZrW2O8) is a ceramic material which exhibits several unusual properties such as negative thermal expansion, amorphization induced by high pressures ( 1.5 GPa and 2.0 GPa) and endothermic recrystallization when heated to temperatures above 600 C. The irreversible exothermic structural relaxation is the phenomenon that precedes the recrystallization of the amorphous phase and is characterized by a continuous activation energy spectrum. This work aims to explore the structural relaxation mechanism of the amorphous phase of zirconium tungstate, in particular, determine whether this phenomenon involves the breakdown of W-O bonds formed during amorphization. To this end, the techniques of 17O solid-state nuclear magnetic resonance (NMR), Raman spectroscopy and far infrared spectrocopy (FT-FAR-IR) were used. As secondary objective, the activation energy spectrum of this process is calculated using modulated di˙erential scanning calorimetry measurements (MDSC). This calculation involved the resolution of the inverse problem originated from the kinetic model used, which results in a Fredholm integral equation of the first kind. The spectrum obtained shows an asymmetric distribution of probability that kinetic processes occur as a function of energy with two maxima at about 1.4 eV and 2.7 eV, evidence that two processes with distinct mechanisms occur during relaxation. The evolution of the amorphous structure during relaxation was monitored by 17O solid-state NMR and vibrational spectroscopy. The results indicate that during structural relaxation of the amorphous phase of ZrW2O8 ther is not breaking of bonds but only a re-arrangement of oxygen atoms. Only at recrystallization temperature enough energy is available to promote the breaking of the W-O bonds formed during amorphization.

O tungstato de zircônio (ZrW2O8) é um material cerâmico que exibe diversos compor-tamentos incomuns: expansão térmica negativa, amorfização induzida por altas pressões (entre 1,5 GPa e 2,0 GPa) e recristalização endotérmica quando aquecido a temperaturas superiores a 600 C. A relaxação estrutural exotérmica e irreversível é o fenômeno que precede a recristalização da fase amorfa do composto e é caracterizada por um espectro contínuo de energia de ativação. Este trabalho tem como objetivo principal explorar o mecanismo de relaxação estrutural da fase amorfa do tugnstato de zircônio, em particular, determinar se este fenômeno envolve a quebra das ligações W-O formadas durante a amorfização. Com esta finalidade, foram utilizadas as técnicas de ressonância magnética nuclear de estado sólido do núcleo 17O (RMN), espectroscopia Raman e espectroscopia na região do infravermelho longínquo (FT-FAR-IR). Além disso, como objetivo secundário, foi calculado, por meio de medidas de calorimetria exploratória diferencial modulada (MDSC) o espectro de energia de ativação deste processo. Esse cálculo envolveu a resolução do problema inverso originado do modelo cinético utilizado, que resulta em uma equação integral de Fredholm do primeiro tipo. O espectro obtido apresenta uma distribuição assimétrica de probabilidade de que processos cinéticos ocorram como função da energia com dois máximos em aproximadamente 1.4 eV e 2.7 eV, indício de que dois processos com mecanismos distintos ocorrem durante a relaxação. A evolução da estrutura amorfa durante a relaxação foi acompanhada por RMN do estado sólido do núcleo 17O e por meio das técnicas de espectroscopias vibracionais. Os resultados indicam que durante a relaxação estrutural da fase amorfa do ZrW2O8 não ocorre quebra das ligações W-O formadas durante a amorfização, mas apenas um rearranjo local dos átomos de oxigênio. Somente na temperatura de recristalização é fornecida energia suficiente para que ocorra o rompimento destas ligações. / Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul, FAPERGS. / Zirconium tungstate (ZrW2O8) is a ceramic material which exhibits several unusual properties such as negative thermal expansion, amorphization induced by high pressures ( 1.5 GPa and 2.0 GPa) and endothermic recrystallization when heated to temperatures above 600 C. The irreversible exothermic structural relaxation is the phenomenon that precedes the recrystallization of the amorphous phase and is characterized by a continuous activation energy spectrum. This work aims to explore the structural relaxation mechanism of the amorphous phase of zirconium tungstate, in particular, determine whether this phenomenon involves the breakdown of W-O bonds formed during amorphization. To this end, the techniques of 17O solid-state nuclear magnetic resonance (NMR), Raman spectroscopy and far infrared spectrocopy (FT-FAR-IR) were used. As secondary objective, the activation energy spectrum of this process is calculated using modulated di˙erential scanning calorimetry measurements (MDSC). This calculation involved the resolution of the inverse problem originated from the kinetic model used, which results in a Fredholm integral equation of the first kind. The spectrum obtained shows an asymmetric distribution of probability that kinetic processes occur as a function of energy with two maxima at about 1.4 eV and 2.7 eV, evidence that two processes with distinct mechanisms occur during relaxation. The evolution of the amorphous structure during relaxation was monitored by 17O solid-state NMR and vibrational spectroscopy. The results indicate that during structural relaxation of the amorphous phase of ZrW2O8 ther is not breaking of bonds but only a re-arrangement of oxygen atoms. Only at recrystallization temperature enough energy is available to promote the breaking of the W-O bonds formed during amorphization.

This work studied the deformation and recrystallization in Ti-35Nb-0,15Si alloy. Were produced alloys with four different compositions in arc melting furnace under controlled argon atmosphere. The amount of Nb was kept constant at 35 wt% and the amount of Si ranging between 0.15 and 0.55% wt%. The amount of Ti ranging according amount of Si. The alloys were homogenized at 1000 ° C for 8 hours, and then cold-deformed by compression in a matrix. Deformed alloys were recrystallized at the temperatures of 500, 600 and 700 ° C for 1 hour in the differential thermal analysis equipment (DTA). Were used techniques of the optical microscopy, X-ray diffraction and microhardness to evaluate the changes caused by the deformation and the recrystallization. The alloy with the composition Ti-35Nb-0, 15Si showed the highest level of deformation, resulting in increased hardness and formation of a martensitic phase. DTA curves provide information about the ß transus temperature, recovery and recrystallization of the alloys. The recrystallization at 500, 600 and 700 ° C propitiated stress relief, decreasing in the amount of a" and hardness reduction. / Este trabalho estudou a deformação e recristalização em ligas de Ti-Nb-Si. Foram produzidas ligas com quatro composições diferentes em forno de fusão a arco sob atmosfera controlada de argônio. A quantidade de Nb foi mantida constante em 35% em peso e a quantidade de Si variou entre 0,15 e 0,55% em peso. A quantidade de Ti variou de acordo com a quantidade de Si. As ligas produzidas foram homogeneizadas a 1000 °C por 8 horas e posteriormente deformadas a frio em uma matriz via compressão. As ligas deformadas foram recristalizadas nas temperaturas de 500, 600 e 700 °C por 1 hora no equipamento de análise térmica diferencial (DTA). Foram utilizadas as técnicas de microscopia óptica, difração de raios-X e microdureza Vickers para avaliar as mudanças ocasionadas pela deformação e pela recristalização. A liga com composição Ti-35Nb-0,15Si foi a que apresentou maior nível de deformação, gerando aumento na microdureza e formação da fase martensítica a . As curvas de DTA forneceram informações a respeito das temperaturas ß transus, recuperação e recristalização das ligas As recristalizações a 500, 600 e 700 oC propiciaram alívio das tensões, diminuição da quantidade de a e redução da microdureza.

Este trabalho tem como objetivo caracterizar as mudanças microestruturais durante o recozimento isotérmico de um fio de ferro trefilado a frio e de pureza comercial com ênfase no crescimento de grão. Os recozimentos foram realizados no intervalo de 823-1173 K por diversos tempos. As informações estatísticas do tamanho de grão foram obtidas por meio do método dos interceptos lineares. O mapeamento das orientações foi obtido por meio de difração de elétrons retroespalhados (EBSD). O material apresenta uma microestrutura ferrítica e totalmente recristalizada a partir de 873 K. Foram encontrados indícios de crescimento normal de grão a partir de 1023 K, porém este crescimento não evoluiu consideravelmente ao longo do tempo de tratamento. Os resultados obtidos a partir do método dos interceptos lineares demonstram que a distribuição de tamanho de grão segue uma curva próxima à log-normal. Nas amostras recozidas a partir de 1123 K, verificou-se a ocorrência de crescimento anormal de grão. O crescimento anormal de alguns grãos inicia-se na região central do fio, estendendo-se até uma região próxima à superfície do fio. Algumas modificações na dimensão da amostra e na atmosfera de recozimento foram realizadas a fim de se estudar a interação destas variáveis no desenvolvimento dos grãos anormais. Foram identificados indícios morfológicos de que o mecanismo para ocorrência de crescimento anormal foi o molhamento de contornos no estado sólido (solid-state wetting) que depois foram confirmados pelas análises de micro e mesotexturas. A análise de microtextura também revela que o material apresenta duas componentes preferenciais, as fibras || DT e || DT, onde DT é a direção axial de trefilação. A primeira orientação é a mais intensa, sendo que seu fortalecimento parece ser impulsionado pelo crescimento anormal de grão. A segunda é menos intensa e parece estar relacionada com as orientações dos grãos oriundos da recristalização primária. Aspectos teóricos e analíticos sobre o crescimento de grão são apresentados e associados aos resultados experimentais e à literatura. / This Dissertation aims follow the microstructural changes occurring during isothermal annealing of commercially-pure cold-drawn iron wire, with emphasys on grain growth phenomena. The grain size data were obtained by means of the linear intercept method. The orientations scanning were done by means of electron backscatter diffraction patterns (EBSD). Isothermal annealing was performed within the temperature range 823 - 1173 K for several times. The material displays full recrystallization at temperatures above 873 K. Normal grain growth was observed above 1023 K, although this growth did not evolve through longer annealing times. The results of the linear intercept method show the grain size distribution has a log-normal shape. For samples annealed above 1123 K, abnormal grain growth occurs. The first signs of secondary recrystallization appear close to the center of the wire, growing towards the surface. Changes in the wire diameter and annealing atmosphere were performed to assess the effect of these variables on abnormal grain growth. Results point out that abnormal grain growth is driven by solid-state wetting. These morphological observations were also confirmed by micro and mesotexture analyses. The microtexture also shows the presence of two major fiber texture components || WD and || WD, were WD is the axial wire-drawn direction. The first one is the most intense and its strengthening seems to be related with abnormal grain growth. The second one is weaker and it seems to be most related with small primary recrystallized grains. Theoretical and analytical features about grain growth are presented and discussed in light of literature and experimental results.