O crescimento significativo da capacidade instalada de produção de laminados de alumínio no País deve-se ao crescente consumo de latas para bebidas, um sinal de confiança dos consumidores e de sucesso sem precedentes em termos de solução para o mercado de embalagens. A lata de alumínio pode ser reciclada infinitas vezes. Por isso, consagrou também sua unanimidade, devido ao enorme benefício da reciclagem, que reduz o consumo de energia para a produção do alumínio, preserva o meio ambiente, movimenta a economia, gerando empregos e fonte de renda na coleta, e promove a educação dos cidadãos para o desenvolvimento sustentado. O foco deste trabalho é o estudo da alteração da textura de uma liga de alumínio 3104-H19 nas várias etapas do processo de estampagem das latas de alumínio para bebidas através da análise dos resultados de mesotextura obtidos pelos método MEV( Microscópio eletrônico de Varredura)- EBSD (Electron Backscatter Diffraction), bem como a compreensão dos mecanismos da formação da textura e sua influência na conformação das latas de alumínio. A composição química da liga de alumínio foi avaliada através de espectroscopia de dispersão de energia (EDS-MEV) e espectrometria de emissão ótica. Analisou-se sua microestrutura através de microscopia ótica e microscopia eletrônica de varredura (MEV). Realizou-se o ensaio de textura cristalográfica pelo método (SEM- EBSD) nas etapas de estampagem do corpo da lata e em ângulos de zero, 45 e 90 graus em relação a direção de laminação. Avaliou-se o resultado da textura cristalográfica através de Figuras de Polo. A análise microestrutural do laminado revelou dois tipos de compostos intermetálicos com morfologia distinta, Al6(Fe,Mn) e Al12(Fe,Mn)3Si, espalhados não homogeneamente, junto a dispersoides bem distribuídos na matriz de alumínio. Observou-se que na chapa laminada a textura a zero 45 e 90 graus são diferentes e à medida que os estágios de conformação do corpo da lata vão avançando as texturas a 45 e 90 graus vão se modificando e ficando semelhantes a da textura a zero grau (direção de laminação). A textura típica de deformação para ligas de alumínio, latão {110} e cobre {112}, junto a textura Goss {110}, estavam balanceadas pela textura cubo {001}, típica de recristalização. / The significant growth in the installed capacity of aluminum rolled products in Brazil is due to the increasing consumption of beverage cans, a sign of consumer confidence and unprecedented success in terms of solution for the packaging market. The aluminum can be recycled endlessly. Therefore, it also consecrated its unanimity, due to the enormous benefit of recycling, which reduces energy consumption for the production of aluminum, preserves the environment, moves the economy, generates jobs and sources of income in the collection, and promotes the education of citizens for sustainable development. The focus of this work is the study of the alteration of the texture of a 3104-H19 aluminum alloy in the various stages of the process of stamping aluminum cans for beverages by comparing the mesotexture results obtained by SEM (Scanning Electron Microscope) EBSD (Electron Backscattered Diffraction), as well as the understanding of the mechanisms of texture formation and its influence on the conformation of aluminum cans. The chemical composition of the aluminum alloy was evaluated using energy dispersive spectroscopy (EDS-MEV) and optical emission spectrometry. Its microstructure was analyzed by optical microscopy and scanning electron microscopy (SEM). The crystallographic texture test (SEM-EBSD) was carried out in the stamping stages of the can body and at angles of zero, 45 and 90 degrees with respect to the rolling direction. The result of the crystallographic texture was evaluated through Polo Figures. Microstructural analysis of the laminate revealed two types of intermetallic compounds with distinct morphology, Al6 (Fe, Mn) and Al12(Fe, Mn)3Si, dispersed in a homogeneous manner, together with dispersoides well distributed in the aluminum matrix. It was observed that in the laminated plate the texture at zero 45, 90 degrees are different, and as the stages of conformation of the body of the can advance the textures at 45 and 90 degrees, they are changing and being similar to the texture at zero degree (direction of rolling). The typical deformation texture for aluminum alloys, brass {110} and copper , together with Goss texture , were balanced by the cube texture {001}, typical of recrystallization.

In this study, we have investigated the relationship between the process-microstructure to predict and modify the material's properties. Understanding these relationships allows the identification and correction of processing deficiencies when the desired properties are not achieved, depending on the microstructure. Hence, the co-relation between process-microstructure-properties helped reduce the number of experiments, materials & tool costs and saved much time. In the case of high entropy alloys, friction stir welding (FSW) causes improved strength due to the formation of fine grain structure and phase transformation from f.c.c to h.c.p. The phase transformation is temperature sensitive and is studied with the help of differential scanning calorimetry (DSC) to calculate the enthalpy experimentally to obtain ΔGγ→ε. The second process discussed is heat treatment causing precipitation evolution. Fundamental investigations aided in understanding the influence of strengthening precipitates on mechanical properties due to the aging kinetics – solid solution and variable artificial aging temperature and time. Finally, in the third case, the effect of FSW parameters causes the thermal profile to be generated, which significantly influences the final microstructure and weld properties. Therefore, a computational model using COMSOL Multiphysics and TC-Prisma is developed to generate the thermal profile for different weld parameters to understand its effect on the microstructure, which would eventually affect and predict the final properties of the weld. The model's validation is done via DSC, TEM, and mechanical testing.

In the present study both fusion based - laser powder bed fusion (LPBF), and solid state - additive friction stir deposition (AFSD) additive manufacturing processes were employed for the manufacturing of a metastable high entropy alloy (HEA), Fe40Mn20Co20Cr15Si5 (CS-HEA). A processing window was developed for the LPBF and AFSD processings of CS-HEA. In case of LPBF, formation of solidification related defects such as lack of fusion pores (for energy density ≤ 31.24 J/mm3) and keyhole pores (for energy density ≥ 75 J/mm3) were observed. Variation in processing conditions affected the microstructural evolution of the metastable CS-HEA; correlation between processing conditions and microstructure of the alloy is developed in the current study. The tendency to transform and twin near stress concentration sites provided excellent tensile and fatigue properties of the material despite the presence of defects in the material. Moreover, solid state nature of AFSD process avoids formation of solidification related defects. Defect free builds of CS-HEA using AFSD resulted in higher work hardening in the material. In summary, the multi-processing techniques used for CS-HEA in the present study showcase the capability of the AM process in tailoring the microstructure, i.e., grain size and phase fractions, both of which are extremely critical for the mechanical property enhancement of the alloy.

The microstructure-property relationship for interpenetrating phase composites (IPCs) is currently poorly understood. In an attempt to improve this understanding this study focused on one particular part of this relationship: the effect of phase shape on the elastic and plastic behaviour. A review of previous research showed that investigations had linked phase shape to the elastic and plastic behaviour of various inclusion reinforced composites, but that no similar work had been completed for IPCs. <p> To study the complex response of the IPC microstructure under load, a numerical modelling analysis using the finite element method (FEM) was undertaken. Two three-dimensional models of IPCs were created, the first consisting of an interconnected spherical phase with the interstitial space forming the other interconnected phase, and the second replacing the spherical phase with an interconnected cylindrical phase. With the simulation of a uniaxial tension test under elastic and plastic conditions, these two models exhibited different responses based on the shape of the phases. <p> Results from an analysis of the macroscopic behaviour identified that the cylindrical model produced greater effective properties than the spherical model at the same volume fraction. The influence of phase shape was connected to the increased contiguity of the superior phase within the IPC for the cylindrical model, which allowed similar levels of long-range continuity with smaller amounts of the superior phase (compared to the spherical model). <p> An examination of microstructural stress distributions showed that preferential stress transfer occurred along paths of low compliance. This provided an explanation of how the improved contiguity of the stiffer (or stronger) phase could enhance the macroscopic effective properties of an IPC. Contiguity of the stronger phase was particularly important for plastic behaviour, where early yielding of the weaker phase requires the stronger phase to carry nearly all the load within itself.

The microstructure-property relationship for interpenetrating phase composites (IPCs) is currently poorly understood. In an attempt to improve this understanding this study focused on one particular part of this relationship: the effect of phase shape on the elastic and plastic behaviour. A review of previous research showed that investigations had linked phase shape to the elastic and plastic behaviour of various inclusion reinforced composites, but that no similar work had been completed for IPCs. <p> To study the complex response of the IPC microstructure under load, a numerical modelling analysis using the finite element method (FEM) was undertaken. Two three-dimensional models of IPCs were created, the first consisting of an interconnected spherical phase with the interstitial space forming the other interconnected phase, and the second replacing the spherical phase with an interconnected cylindrical phase. With the simulation of a uniaxial tension test under elastic and plastic conditions, these two models exhibited different responses based on the shape of the phases. <p> Results from an analysis of the macroscopic behaviour identified that the cylindrical model produced greater effective properties than the spherical model at the same volume fraction. The influence of phase shape was connected to the increased contiguity of the superior phase within the IPC for the cylindrical model, which allowed similar levels of long-range continuity with smaller amounts of the superior phase (compared to the spherical model). <p> An examination of microstructural stress distributions showed that preferential stress transfer occurred along paths of low compliance. This provided an explanation of how the improved contiguity of the stiffer (or stronger) phase could enhance the macroscopic effective properties of an IPC. Contiguity of the stronger phase was particularly important for plastic behaviour, where early yielding of the weaker phase requires the stronger phase to carry nearly all the load within itself.

Many technologically important alloys such as Ni base superalloys and Ti-Al base alloys benefit from the precipitation of an ordered β phase from a disordered α matrix. When the crystallographic symmetry of the β phase is a subgroup of that of the disordered α phase, the microstructure may contain multiple orientational variants of the β phase, each with its own (anisotropic, crystallographically equivalent) misfit (lattice parameter mismatch) with the matrix phase. Examples include orthorhombic precipitates in a hexagonal matrix in Ti-Al-Nb alloys, and tetragonal precipitates in a cubic matrix in ZrO2-Y2O3. We have studied two-phase microstructures containing multiple variants of the precipitate phase. In particular, we have used phase field simulations to study the effect of elastic stresses in a two dimensional system containing a disordered matrix and three different orientational variants of the precipitate phase, with a view to elucidate the effect of different levels of anisotropy in misfit. We consider a two dimensional, elastically homogeneous and isotropic model system in which the matrix (α) and precipitate (β) phases have hexagonal and rectangular symmetries, respectively, giving rise to three orientational variants of the β phase. Therefore, our phase field model has composition (c) and three order parameters (η1, η2, η3) as the field variables.Due to the difference in crystallographic symmetry, the precipitate-matrix misfit strain tensor, ε*, can be anisotropic. ε*maybe represented in its principal form as ε *= (ε xx 0 ) 0 εyy where ε xx and ε yy are the principal components of the misfit tensor. We define t= εyy/εxx as the parameter representing anisotropy in the misfit. In this thesis, we report the results of our systematic study of microstructural evolution in systems with different values of t, representing different levels of anisotropy in misfit: •Case A: t=1 (dilatational or isotropic misfit) • Case B: 0 <t<1 (principal misfit components are unequal but have the same sign) • Case C: t=0 (the principal misfit along the y direction is zero) • Case D: -1 <t<0 (principal misfit components have opposite signs and unequal magnitudes) • Case E: t= -1 (principal misfit components are equal, but with opposite signs; pure shear) In Cases D and E, there is an invariant line along which the normal misfit is zero. In Case D, this invariant line is at ±54.72◦, and in Case E, it is at ±45◦, with respect to the x-axis. Our simulations of microstructural evolution in this system are based on numerical integration of the Cahn-Hilliard and Cahn-Allen equations which govern the evolution of composition and order parameter fields, respectively. In each case, we have studied two different situations: isolated particle (single variant) and many interacting particles (multivariant). Dynamical growth shape of an isolated precipitate In systems with an isotropic misfit (Case A), the precipitate shape remains circular at all sizes. In Cases B and C, the precipitate shape is elongated along the y-axis, which is also the direction in which the magnitude of the misfit strain is lower. In all these cases, the symmetry of the particle shape remains unaltered at all sizes. In contrast, in Cases D and E, the particle shape exhibits a symmetry-breaking transition. In Case D, the precipitate elongates initially along the y direction (i.e. the direction of lower absolute misfit), before undergoing a transition in which the mirror symmetry normal to x and yaxes is lost. In Case E, the particle has an initial square-like shape (with its sides normal to the 11directions) before losing its four-fold rotation axis to become rectangle-like with its long axis along one of the the 11directions. The critical precipitate size at which the symmetry-breaking shape transition occurs is obtained using bifurcation diagrams. In both Cases D and E, the critical size for the dynamical growth shapes is larger than those for equilibrium shapes[1].This critical size is larger when the matrix supersaturation is higher or shear modulus is lower. Microstructural Evolution In all the five cases, the elastic stresses have a common effect: they lead to microstructures in which the precipitate volume fraction is lower than that in a system with no misfit. This observation is consistent with the results from the thermodynamics of stressed solids that show that a precipitate-matrix misfit increases the interfacial composition in both the matrix and the precipitate phase. In systems with isotropic misfit (Case A), the microstructure consists of isolated circular domains of the precipitate phase that retain their circular shape during growth and subsequent coarsening. In Cases B and C with anisotropic misfit with t≥0, the three orientational variants of the precipitate phase are elongated along the directions of lower misfit (y-axis and ±120◦to y-axis). At a given size, particles in Case C (in which one of the principal misfits is zero) are more elongated than those in Case B. Systems with a higher shear modulus enhance the effect of misfit stresses, and therefore, lead to thinner and longer precipitates. When the precipitate volume fraction is increased, these elongated precipitates interact with (and impinge against) one another to a greater extent, and acquire a more jagged appearance. For Cases D and E, each orientation domain is associated with an invariant line along which the normal misfit is zero. Thus, in Case D, early stage microstructures show particles elongated along directions of lower absolute misfit (y-axis and ±120°to y-axis). At the later stages, the domains of the precipitate phase tend to orient along the invariant lines; this leads some of the particles to acquire a ‘Z’ shape before they completely re-orient themselves along the invariant line. In Case E, each variant grows as a thin plate elongating along the invariant line. The growth and impingement of these thin plates leads to a microstructure exhibiting complex multi-domain patterns such as stars, wedges, triangles, and checkerboard. These patterns have been compared (and are in good agreement) with experimental observations in Ti-Al-Nb alloys containing the precipitate (O) and matrix (α2)phases[2]. Since in Case E the sum of misfit strains of the three variants is zero, elastic energy considerations point to the possibility of compact, self-accommodating clusters of the three variants, sharing antiphase boundaries (APBs). Thus, if the APB energy is sufficiently low, the microstructure may consist of such compact clusters. Our simulations with such low APB energy do show triangle shaped clusters with six separate particles (two of each variant)in a self-accommodating pattern. (Refer PDF file)

Aluminium alloys with Si as the major alloying element form a class of material providing the most significant part of all casting manufactured materials. These alloys have a wide range of applications in the automotive and aerospace industries due to an excellent combination of castability and mechanical properties, as well as good corrosion resistance and wear resistivity. Additions of minor alloying elements such as Cu and Mg improve the mechanical properties and make the alloy responsive to heat treatment. The aim of this work is studying the role of size and morphology of microstructural constituents (e.g SDAS, Si-particles and intermetalics) on mechanical properties of Al-Si based casting alloy at room temperatures up to 500 ºC. The cooling rate controls the secondary dendrite arm spacing (SDAS), size and distribution of secondary phases. As SDAS becomes smaller, porosity and second phase constituents are dispersed more finely and evenly. This refinement of the microstructure leads to substantial improvement in tensile properties (e.g. Rm and εF). Addition of about 280 ppm Sr to EN AC- 46000 alloy yields fully modified Si-particles (from coarse plates to fine fibres) regardless of the cooling conditions. Depression in eutectic growth temperature as a result of Sr addition was found to be strongly correlated to the level of modification irrespective of coarseness of microstructure. Modification treatment can improve elongation to failure to a great extent as long as the intermetallic compounds are refined in size. Above 300 ºC, tensile strength, Rp0.2 and Rm, of EN AC-46000 alloys are dramatically degraded while the ductility was increased. The fine microstructure (SDAS 10 μm) has superior Rm and ductility compared to the coarse microstructure (SDAS 25 μm) at all test temperature (from room to 500 ºC). Concentration of solutes (e.g. Cu and Mg) in the dendrites increases at 300 ºC and above where Rp0.2 monotonically decreased. The brittleness of the alloy below 300 ºC was related to accumulation of a high volume fraction damaged particles such as Cu- Fe-bearing phases and Si-particles. The initiation rate of damage in the coarse particles was significantly higher, which enhances the probability of failure and decreasing both Rm and εF compared to the fine microstructure. A physically-based model was adapted, improved and validated in order to predict the flow stress behaviour of EN AC- 46000 cast alloys at room temperature up to 400 ºC for various microstructures. The temperature dependant variables of the model were quite well correlated to the underlying physics of the material

The heat-affected zone (HAZ) is the most common region of weld failures. The weld failures are directly related to the microstructure. Microstructure control of the HAZ is crucial to weld quality and prevention of weld failures. However, publications on modeling the development of the HAZ are relatively limited. Moreover, no efforts have been made to predict the HAZ microstructures in real-time. The primary goal of this research is to present a methodology to enable real-time predictions of microstructure evolution in the HAZ and its mechanical properties. This goal was achieved by an approach based on materials science principles and real-time sensing techniques. In this study, the entire welding process was divided into a series of sub-processes. Real-time multiple measurements from multiple sensors were incorporated into the sub-processes. This resulted in an integrated welding system upon which the predictions for the final HAZ microstructure are based. As part of the integrated system, the microstructural model was used to predict the TTT curves, volume fractions of the decomposition products, and hardness numbers of the heat-affected zones of steel alloys. Actual welds were performed under two different sets of conditions, and the resulting experimental data were compared with predictions made using the microstructural model. The predicted and experimental microstructure and hardness are found to be in good agreement, indicating that the microstructural model can be used in real applications. This research can act as an important component of future research to enable physics-based flexible control of welding. / text

Superplastic forming (SPF) is a near net-shape forming process which offers many advantages over conventional forming operations including low forming pressure due to low flow stress, low die cost, greater design flexibility, and the ability to shape hard metals and form complex shapes. However, low production rate due to slow forming process and limited predictive capabilities due to lack of accurate constitutive models for superplastic deformation, are the main obstacles to the widespread use of SPF. Recent advancements in finite element tools have helped in the analysis of complex superplastic forming operations. These tools can be utilized successfully in order to develop optimized superplastic forming techniques. In this work, an optimum variable strain rate scheme developed using a combined micromacro stability criterion is integrated with ABAQUS for the optimization of superplastic forming process. Finite element simulations of superplastic forming of Ti-6Al-4V sheet into a hemisphere and a box are carried out using two different forming approaches. The first approach is based on a constant strain rate scheme. The second one is based on the optimum variable strain rate scheme. It is shown that the forming time can be significantly reduced without compromising the uniformity of thickness distribution when using the proposed optimum approach. Further analysis is carried out to study the effects of strain rate, microstructural evolution and friction on the formed product. Finally the constitutive equations and stability criterion mentioned above are used to analyze the forming of dental implant superstructure, a modern industrial application of superplastic forming.

Magnesium and magnesium alloys are used in a wide variety of structural applications including automotive, aerospace, hand tools and electronic industries thanks to their light weight, high specific strength, adequate corrosion resistance and good castability. Al and Zn are the primary alloying elements in commercial Mg alloys and commonly used in automotive industries. AZ91 is one of the most popular Mg alloys containing 9% Al and 1% Zn. Hence, lots of research have been done during last decades on AZ91D. However, the existing data concerning mechanical properties and microstructural features showed large scatter and is even contradictory. This work focused on the correlation between the microstructure and the mechanical properties of as-cast AZ91 alloy. An exhaustive characterization of the grain size, secondary dendrite arm spacing (SDAS) distribution, and fraction of Mg17Al12 using optical and electron backscattered diffraction (EBSD) was performed. These microstructural parameters were correlated to offset yield point (Rp0.2), fracture strength and elongation to fracture. It was understood that the intermetallic phase, Mg17Al12, plays an important role in determining the mechanical and physical properties of the alloy at temperature range from room temperature up to 190oC. It was realized that by increasing the Mg17Al12 content above 11% a network of intermetallic may form. During deformation this rigid network should break before any plastic deformation happen. Hence, increase in Mg17Al12 content resulted in an increase in offset yield point. The presence of this network was supported by study of thermal expansion behaviour of the alloy containing different amount of Mg17Al12. A physically-based model was adapted and validated in order to predict the flow stress behaviour of as-cast AZ91D at room temperature up to 190ºC for various microstructures. The model was based on dislocation glide and climb in a single-phase (matrix) material containing reinforcing particles. The temperature dependant variables of the model were quite well correlated to the underlying physics of the material.