Microstructural Evolution

The tailoring of cold-deformation to promote recovery and recrystallization processes upon subsequent heat-treatment is well understood in rolled monolithic alloys. In contrast, clad aluminum systems, which feature two or more different alloy systems bonded to a core alloy, contain an inter-alloy region with recovery and recrystallization behaviours which could be different from the individual clad and core alloys. Understanding these behaviours is important in optimizing the final properties of the clad product. This study examines the static recovery behaviour of a clad aluminum alloy manufactured by Novelis Fusion TM technology after 72% cold rolling. The clad alloy system studied consisted of a core AA6XXX alloy clad on one side with AA3003. The Recovery at the inter-alloy region is compared with the recovery of core AA6XXX at the same depth from the rolling surface. Sample coupons from the inter-alloy region and core AA6XXX were heated isochronally and isothermally, at different temperatures and times, respectively, to probe the recovery kinetics of the X-ray peak broadening, Xray macro-texture and micro-hardness from the cold rolled state. The recovery of the {220} and {311} X-ray line profiles were observed between the anneals. A pseudo-Voigt fit function was fit to the profile to obtain the defect related information. Recovery in the peak broadening began by 100°C and correlated to a decrease in the hardness. Sharpening of X-ray profiles during recovery is attributed to the microstructural evolution resulting from preferred release of the stored energy due to dislocation rearrangement and annihilation. Kinetic behaviour of the recovery is measured by observing the evolution of X-ray profiles and hardness during isothermal annealing at two different temperatures. Recovery behaviour in the inter-alloy region is measured to be relatively iii slower than the recovery of the core AA6XXX after same macroscopic pre-strain. Activation energy for recovery is calculated from the isothermal data to deduce a recovery mechanism. The activation energy calculated in core AA6XXX, 1.7eV, is close to the activation energy value for diffusion of Mg in Al (1.3-1.7eV). This indicates a possible role of Mg diffusion in the recovery of AA6XXX. The relatively higher activation energy for recovery of 2.9eV measured in the inter-alloy region may be due to pinning by nano-scale Al-Mn precipitates. The X-ray broadening data is deconvoluted to determine the apparent dislocation content using a modified Williamson-Hall model. The dislocation density measured in the AA6XXX and inter-alloy regions in the deformed and recovered conditions indicates that dislocation density is a suitable parameter that represents the stored energy that drives subsequent structural evolution during recovery. Firstly I express my cordial thanks and gratitude to my research advisor Dr. Bradley. J. Diak for his constant support, guidance and many earnest gestures throughout my stay in Queen`s. I also thank the entire Materials faculty and graduate students community in Nicol Hall with whom I have shared a stimulating as well as friendly atmosphere during courses, seminars and conference. It is with much pleasure that I thank Dr. Haiou Jin from Novelis Global Technology Center, Kingston, for providing me with clad aluminum metal sheet, for carrying out the chemical analysis experiments for me and also for many fruitful discussions that I have had with him along with my supervisor. I also thank Novelis Inc, Kingston, Queen`s University and NSERC for providing the financial support for this project. I would also like to thank Chris Cuoppolo for writing the MATLAB ® fitting routine used in this thesis, and Alex Penlington for helpful discussions about the Fusion alloy sheet. I would like to thank all my friends in Queen`s and in Kingston, and especially my friends in An clachan community housing, Arnab, Avik and Agnita who made my life in Kingston enjoyable and memorable. Finally, I would like to thank my parents and family for their unending emotional support, encouragement and blessings, without which I could never finish writing this thesis. I would like to dedicate this thesis to my mother. v

MASTER OF SCIENCE UNIVERSITY OF NORTH TEXAS August 2017 Mikler, Calvin Vijay. Laser Additive Manufacturing of Magnetic Materials. Master of Science (Materials Science and Engineering), August 2017, 64 pp., 2 tables, 21 figures, chapter references. A matrix of variably processed Fe-30at%Ni was deposited with variations in laser travel speeds as well and laser powers. A complete shift in phase stability occurred as a function of varying laser travel speed. At slow travel speeds, the microstructure was dominated by a columnar fcc phase. Intermediate travel speeds yielded a mixed microstructure comprised of both the columnar fcc and a martensite-like bcc phase. At the fastest travel speed, the microstructure was dominated by the bcc phase. This shift in phase stability subsequently affected the magnetic properties, specifically saturation magnetization. Ni-Fe-Mo and Ni-Fe-V permalloys were deposited from an elemental blend of powders as well. Both systems exhibited featureless microstructures dominated by an fcc phase. Magnetic measurements yielded saturation magnetizations on par with conventionally processed permalloys, however coercivities were significantly larger; this difference is attributed to microstructural defects that occur during the additive manufacturing process. Finally, a compositionally graded AlCoxCr1-xFeNi (0.0<x<1.0) complex concentrated alloy was deposited with six distinct compositional steps. As a function of composition, the microstructure varied from single phase B2 (ordered) to a mixture of B2 + bcc (disordered). Increasing chromium content results in a spinodal decomposition within the matrix, forming a B2+bcc microstructure. Saturation magnetizations are highest at x=1.0 (AlCoFeNi), and lowest at x=0.0 (AlCrFeNi). The coercivity reached a maximum at x=0.4.

The artificial aging of Aluminum 2024, a critical aerospace alloy, represents a complex metallurgical process with significant implications for material performance. This study systematically investigates the precipitation hardening mechanisms through comprehensive thermal treatments at varying temperatures (178°C, 190°C, and 200°C) and durations, alongside natural aging. By analyzing hardness variations, microstructural transformations, and precipitate evolution, we reveal the intricate relationships between aging conditions and mechanical properties. Our research demonstrates that the precipitation sequence involving-Guinier-Preston zones, θ" and θ' phases, and and S phases evolution-plays a pivotal role in material strengthening. The 190°C treatment emerged as optimal, providing a stable hardening window with peak hardness maintained for up to 12 hours. Comparative analyses between artificial and natural aging processes highlight the superiority of controlled thermal treatments in accelerating precipitate formation and improving mechanical properties. The study provides an understanding of how temperature, time, and microstructural evolution interact to optimize the alloy's performance.

The effect of hot rolling and austenite revert transformation (ART) on the microstructure development and mechanical properties for a series of newly developed manganese steels with small carbon and/or boron content was investigated in this study. The cast steels were hot rolled, ART annealed and subjected to tensile testings after each step. The carbon-bearing alloy revealed a significant combination of ultimate tensile strength (UTS) and elongation (El. pct) with 1.1 GPa and 42 pct values, respectively. The boron-bearing alloy exhibited a UTS of 760 MPa having 30 pct elongation. Moreover, the carbon and boron alloyed steel had a fully martensitic structure with a UTS of 1.4 GPa and a negligible elongation. X-ray diffraction, SEM and electron backscatter diffraction analyses were used to rationalize the mechanical behaviour of the developed alloys. The higher ductility values for the boron alloyed and carbon alloyed steels were attributed to the presence of the austenite phase in conjunction with a¢-and e-martensite and the transformation-induced martensite during the tensile loadings. The ART annealing at 290 °C, 450 °C and 510 °C increased the austenite fraction in the final microstructure of the boron alloyed and carbon alloyed steels but had an insignificant influence on the boron and carbon alloyed steels. It was concluded that the a¢ fi c transformation occurring at higher ART annealing temperature is the dominant factor for the improved mechanical properties in the developed alloys.

The work-hardening mechanisms of two novel advanced high-strength steels (Fe 67.4−x Cr 15.5 Ni 14.1 Si 3.0 B x [x = 0 (0B), 2 (2B)] wt%) were investigated by means of field emission gun scanning electron microscopy coupled with angle-selective backscattered detection, transmission electron microscopy, and electron backscattered diffraction. The 0B and 2B specimens combined low yield stresses and high ultimate tensile strengths with good total elongation percentages, with results of 219 MPa, 568 MPa, and 83% and 357 MPa, 703 MPa, and 42%, respectively. The 0B and 2B alloys were characterized by a decreasing work hardening rate, followed by a constant and finally a steep decreasing change tendency. Detailed angle-selective backscattered and electron backscattered diffraction microscopy observations on interrupted tensile test specimens revealed that the work hardening rate in these alloys was facilitated by planar (extended stacking faults) and wavy (dislocation cell and wavy microbands) characteristics and mechanical nano-twins. The total flow stresses of the 0B and 2B specimens were calculated from the dislocation density and twin spacing. This indicated that the work hardening contribution of the microband mechanism can be estimated via a dislocation hardening formula. The rule of mixture was also used to evaluate the effect of a boron addition on the total flow stress of the 2B specimen; this illustrated that, in addition to the strengthening contribution of the second hard phase to the yield stress, the rule of mixture must also be considered. The calculated values of the contribution of the mechanical nano-twins and dislocations on the work-hardening for 0B and 2B specimens were about 62% and 18.6% and 52% and 31.8%, respectively.

In this study butt joining of 7020-T6 alloy was performed using tungsten inert gas (TIG) welding with continuous (constant) and pulsed current. Effect of heat input on microstructure and mechanical properties of the joints was investigated. Microstructural examinations were conducted using optical and scanning electron microscopy. Differential scanning calorimetry (DSC) was used to identify the precipitates phase evolution. Temperature at the welding region was recorded by inserting thermocouples. Hardness and tensile strength of the joints was evaluated. Results showed that current pulsing leads to relatively finer grain size in weld metal compare to the one welded by constant current. In either cases of constant and pulsed current, the grain size and the width of heat affected zone increased with increasing heat input. Unlike earlier studies in precipitation hardening aluminum alloys, strength of the weld metal were increased as compare to base metal in T6 condition. The enhancement in mechanical properties of weld metal was attributed to the solution annealing and re-formation of strengthening precipitates on cooling from welding temperature.

Se estudió la evolución microestructural en dos aleaciones resistentes al calor envejecidas a 750°C por periodos de hasta 1000 h mediante microscopía óptica y electrónica de barrido. La transformación de NbC a Nb 3 Ni 2 Si se describe por medio de la técnica de electrones retrodispersados, así como análisis de la espectrometría de rayos X en el microscopio electrónico de barrido. La microstructura de las aleaciones en su condición de vaciado consiste en una matriz de austenita con una red de carburos primarios de los tipos NbC y M 7 C 3 . El envejecimiento promueve la precipitación de carburos secundarios M 23 C 6 y la transformación de NbC a Nb 3 Ni 2 Si. Los resultados muestran que esta última transformación se inicia en los límites del carburo hacia su centro, enriqueciéndolo con silicio y níquel, a la vez que el carbono migra a la matriz promoviendo la precipitación de carburos ricos en cromo. Aleaciones resistentes al calor, envejecimiento, evolución microestructural.

In this study, the formation of super saturated solid solution in the binary Cu-Fe system was investigated. Three powder blends with 30, 50 and 70 wt.% of Fe were milled for different times to 96 h. The variations of lattice parameter and inter-planar spacing were calculated and analyzed using X-ray diffraction analysis (XDA). The anisotropy of lattice deformation in the FCC phase was studied and the obtained results were compared to milled pure Cu powder. Furthermore, crystallite size was calculated using Scherer formula in comparison with Rietveld full profile refinement method. Considering the previous studies about the formation of non-equilibrium FCC and BCC phases, the phase evolution has been discussed and the proportion of each phase was calculated using Rietveld refinement method. Supplementary studies on the evolution of microstructure and formation of solid solution were carried out using high resolution transmission electron microscopy (HRTEM). Finally, high angle annular dark field (HAADF) imaging was utilized to find out the level of homogeneity in the resulting phases. While true alloying takes place in each phase, the final structure consists of both FCC and BCC nano-crystallites.

India's cement industry is the second largest in the world, generating 6.9% of the global cement output. Polycarbonate waste ash is a major problem in India and around the globe. Approximately 370,000 tons of scientific waste are generated annually from fitness care facilities in India. Polycarbonate waste helps reduce the environmental burden associated with disposal and decreases the need for new raw materials. The primary variable in this study is the quantity of polycarbonate waste ash (5, 10, 15, 20 and 25% of the weight of cement), partial replacement of cement, watercement ratio and aggregates. The mechanical properties, such as compressive strength, split tensile strength and flexural test results, of the mixtures with the polycarbonate waste ash were superior at 7, 14 and 28 days compared to those of the control mix. The water absorption rate is less than that of standard concrete. Compared with those of conventional concrete, polycarbonate waste concrete mixtures undergo minimal weight loss under acid curing conditions. Polycarbonate waste is utilized in the construction industry to reduce pollution and improve the economy. This study further simulated the strength characteristics of concrete made with waste polycarbonate ash using least absolute shrinkage and selection operator regression and decision trees. Cement, polycarbonate waste, slump, water absorption, and the ratio of water to cement were the main components that were considered input variables. The suggested decision tree model was successful with unparalleled predictive accuracy across important metrics. Its outstanding predictive ability for split tensile strength (R 2 = 0.879403), flexural strength (R 2 = 0.91197), and compressive strength (R 2 = 0.853683) confirmed that this method was the preferred choice for these strength predictions.

India's cement industry is the second largest in the world, generating 6.9% of the global cement output. Polycarbonate waste ash is a major problem in India and around the globe. Approximately 370,000 tons of scientific waste are generated annually from fitness care facilities in India. Polycarbonate waste helps reduce the environmental burden associated with disposal and decreases the need for new raw materials. The primary variable in this study is the quantity of polycarbonate waste ash (5, 10, 15, 20 and 25% of the weight of cement), partial replacement of cement, watercement ratio and aggregates. The mechanical properties, such as compressive strength, split tensile strength and flexural test results, of the mixtures with the polycarbonate waste ash were superior at 7, 14 and 28 days compared to those of the control mix. The water absorption rate is less than that of standard concrete. Compared with those of conventional concrete, polycarbonate waste concrete mixtures undergo minimal weight loss under acid curing conditions. Polycarbonate waste is utilized in the construction industry to reduce pollution and improve the economy. This study further simulated the strength characteristics of concrete made with waste polycarbonate ash using least absolute shrinkage and selection operator regression and decision trees. Cement, polycarbonate waste, slump, water absorption, and the ratio of water to cement were the main components that were considered input variables. The suggested decision tree model was successful with unparalleled predictive accuracy across important metrics. Its outstanding predictive ability for split tensile strength (R 2 = 0.879403), flexural strength (R 2 = 0.91197), and compressive strength (R 2 = 0.853683) confirmed that this method was the preferred choice for these strength predictions.

Pulse-echo ultrasonic method was carried out to investigate possible anisotropy in selective laser melting additively manufactured (AM) AlSi10Mg samples. Three types of ultrasonic analyses were employed: time of flight (TOF) sound velocity measurement, frequency depended attenuation and exponential fitted attenuation. Analysis of the transverse waves TOF sound velocity as a function the oscillation angle relative to the build direction reveals that the AM AlSi10Mg material has anisotropy in both transverse wave velocity and attenuation with respect to the build direction. Such an anisotropy is with symmetry around the build direction. Three transverse wave velocity zones were identified, low-velocity zone, where the transverse oscillation direction perpendicular to the build direction, high-velocity zone where the transverse oscillation direction parallel to the build direction and a transition zone. This behavior held even after heat treatments. The transverse velocity and the frequency depended attenuation seems to be sensitive tools that enable detection of subtle changes in AM products.

Four titanium alloys (Ti-Ta, Ti-Ta-Sn, Ti-Ta-Mn, and Ti-Nb-Sn) were synthesized by mechanical alloying (MA) in a planetary mill in different times between 2 h and 100 h. The microstructure characterization was made by X-ray diffraction (XRD), in which the Rietveld method was applied to analyze the diffraction patterns. The study demonstrated that after short milling times between 2 h and 30 h, the fraction of hexagonal close-packed (hcp) phase decreases; at the same time, the formation of body-centered cubic (bcc) and face-centered cubic (fcc) Ti phases are promoted. Additionally, after 30 h of MA, the full transformation of hcp-Ti was observed, and the bcc-Ti to fcc-Ti phase transformation took place until 50 h. The results suggest that the addition of Ta and Sn promotes the fcc-Ti phase formation, obtaining 100% of this phase at 50 h onwards, whereas Nb and Mn show the opposite effect.

Heterogeneous grain growth during austenitization in ASTM A213-T91 steel has been studied using a Gleeble 3500 thermomechanical simulator. Starting from a uniform, fine austenite grain size distribution after 1 min austenite holding time, a heterogeneous austenite grain size distribution was observed after 15 min austenite holding time at 1 060°C and 1 080°C. The state of precipitation of second phase particles was studied in detail as a function of austenitization time. The particle size distribution changed towards a bimodal feature as a function of time whereas the count frequency of the coarse precipitates increased and the count frequency of fine precipitates diminished with time. V-rich precipitates were dissolved during austenitization and only Nb-rich particles remained after 15 min austenitizing time. The experimental observations on the evolution of the austenite grain size distribution are rationalized on the basis of the Gladman's approach to abnormal grain growth.

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

This work focuses on the modeling of the evolution of anisotropy induced by the development of the dislocation microstructure. A model formulated at the engineering scale in the context of classical metal plasticity and a model formulated in the

Stacking fault energy (SFE) changes the restoration mechanisms during friction stir welding (FSW) of copper alloys. • At higher SFE (N80 mj m-2), the continuous dynamic recrystallization (CDRX) and static recovery (SRX) are active mechanisms. • At lower SFE (b80 mj m-2), in addition to CDRX, the discontinuous dynamic recrystallization (DDRX) happens during FSW. • By decreasing SFE from 80 to 12 mj m-2 , the amount of DDRX increases. • More DDRX results in higher yield strength of the joints.

Niobium single crystals were deformed by equal channel angular extrusion (ECAE) with one, four, and eight passes at room temperature. Microstructural characterization was performed using scanning electron microscopy (SEM) and electron-backscattered diffraction (EBSD). The microstructure of the sample deformed after one ECAE pass displays uniformly spaced coarse parallel sets of shear bands. After four passes, the shear bands intersect each other throughout the sample giving rise to the development of fine-grained crystallites at their intersections. In the most deformed specimen (eight ECAE passes), the microstructure becomes more uniform and consists of fine grains with sizes of about 1 m and elongated subgrains lying nearly parallel to the extrusion direction. The fraction of high angle boundaries is about 48%.

Micro-Fabric Analyzer (MFA) is a new GIS-based tool for the quantitative extrapolation of rock microstructural features that takes advantage both of the characteristics of the X-ray images and the optical image features. Most of the previously developed edge mineral grain detectors are uniquely based on the physical properties of the X-ray-, electron-, or optical-derived images; not permitting the exploitation of the specific physical properties of each image type at the same time. More advanced techniques, such as 3D microtomography, permit the reconstruction of tridimensional models of mineral fabric arrays, even though adjacent mineral grain boundaries with the same atomic density are often not detectable. Only electron backscatter diffraction (EBSD) allows providing high-performing grain boundary detection that is crystallographically differentiated per mineral phase, even though it is relatively expensive and can be executed only in duly equipped microanalytical laboratories by...

In this paper, we aim at characterizing three different cast iron alloys and their microstructural features, namely lamellar, compacted and nodular graphite iron. The characterization of microscopic features is essential for the development of methods to optimize the behavior of cast iron alloys; e.g. maximize thermal dissipation and/or maximize ductility while maintaining strength. The variation of these properties is commonly analyzed by metallography on two-dimensional representations of the alloy. However, more precise estimates of the morphologies and material characteristics are obtained by three-dimensional reconstruction of microstructures. The use of X-ray microtomography provides an excellent tool to generate high resolution threedimensional microstructure images. The characteristics of the graphite constituent in the microstructure, including the size, shape and connectivity, were analyzed for the different cast iron alloys. It was observed that the lamellar and compacted graphite iron alloys have relatively large connected graphite morphologies, as opposed to ductile iron where the graphite is present as nodules. The results of the characterization for the different alloys were ultimately used to generate finite element models.

This paper focuses on local strain distribution in the microstructure of high silicon ductile iron during cyclic loading. In-situ cyclic test was performed on compact-tension (CT) samples inside the scanning electron microscope (SEM) to record the whole deformation and obtain micrographs for microstructural strain measurement by means of digital image correlation (DIC) technique. Focused ion beam (FIB) milling was used to generate speckle patterns necessary for DIC measurement. The equivalent Von Mises strain distribution was measured in the microstructure at the maximum applied load. The results revealed a heterogeneous strain distribution at the microstructural level with higher strain gradients close to the notch of the CT sample and accumulated strain bands between graphite particles. Local strain ahead of the early initiated micro-cracks was quantitatively measured, showing high strain localization, which decreased by moving away from the micro-crack tip. It could be observed that the peak of strain in the field of view was not necessarily located ahead of the microcracks tip which could be because of the (i) strain relaxation due to the presence of other micro-cracks and/or (ii) presence of subsurface microstructural features such as graphite particles that influenced the strain concentration on the surface.

Knowledge of radiation-induced helium bubble nucleation and growth in SiC is essential for applications in fusion and fission environments. Here we report the evolution of microstructure in nanoengineered (NE) 3C SiC, pre-implanted with helium, under heavy ion irradiation at 700 °C up to doses of 30 displacements per atom (dpa). Elastic recoil detection analysis confirms that the as-implanted helium depth profile does not change under irradiation to 30 dpa at 700 °C. While the helium bubble size distribution becomes narrower with increasing dose, the average size of bubbles remains unchanged and the density of bubbles increases somewhat with dose. These results are consistent with a long helium bubble incubation process under continued irradiation at 700 °C up to 30 dpa, similar to that reported under dual and triple beam irradiation at much higher temperatures. The formation of bubbles at this low temperature is enhanced by the nano-layered stacking fault structure in the NE SiC, which enhances point defect mobility parallel to the stacking faults. This stacking fault structure is stable at 700 °C up to 30 dpa and suppresses the formation of dislocation loops normally observed under these irradiation conditions.

The present contribution deals with quantitative microstructural analysis, which was performed on granodiorites of the syn-tectonic Symvolon pluton (Punturo et al., 2014) at the south-western boundary of the Rhodope Core Complex (Greece). Our purpose is the quantification of ductile strain rate achieved across the pluton, by considering its cooling gradient from the centre to the periphery, using the combination of a paleopiezometer (Shimizu, 2008) and a quartz flow law (Hirth et al., 2001). Obtained results, associated with a detailed cooling history (Dinter et al., 1995), allowed us to reconstruct the joined cooling and strain gradient evolution of the pluton from its emplacement during early Miocene (ca. 700◦C at 22 Ma) to its following cooling stage (ca. 500-300◦C at 15 Ma). Shearing temperature values were constrained by means of a thermodynamic approach based on the recognition of syn-shear assemblages at incremental strain; to this aim, statistical handling of mineral chemist...

A homogenized Mg-10Gd-4.8Y-0.6Zr (wt.%) alloy was subjected to multidirectional forging (MDF) at 773 K. It was shown that the average grain size decreased with increasing cumulative strain till 6 passes. Uniform fine-grained structure with an average grain size of 9.3 lm was achieved after 6 passes, i.e., cumulative strain of 1.8. Results revealed that grain refinement was induced by a complicated combination of discontinuous dynamic recrystallization at low strain regions and continuous dynamic recrystallization or rotation recrystallization at medium-to-high strain regions. The alloy multi-directionally forged (MDFed) for 6 passes exhibited an excellent balance of strength and ductility at room temperature with ultimate tensile strength (UTS) of 336 MPa and elongation to fracture of 21.0%.

The present paper reports the results of the relationship between the surface topography, microstructure and the in vitro bioactivity of samples with and without fluorapatite content in simulated body fluid. Glasses and glass ceramics belonging to the Li2O-SiO2-CaO-P2O5-CaF2 system were prepared by using conventional melting technique following by heat treatment to obtain glass ceramics. This current study demonstrates the benefits of combining two microscopic methods for better investigation of the surface structure. The formation of apatite layer on the surface and the increase in surface roughness proved that the glasses and glass ceramics with bioactive fluorapatite content could satisfy to the requirements for biomaterial applications. The results also showed that the roughness of apatite layer formed after immersion in body fluid on the surface of glasses with fluorapatite was more pronounced than that of equivalent glass ceramic samples cured under the same conditions.

Este trabalho se compreende na criação de um conjunto de obras que proporcionam uma reflexão encima do desenvolvimento da tecnologia como um traço inerente a raça humana, bem como suas falhas. Estas obras realizadas em diversos meios e materiais, durante os anos de 2017 à 2019 visam constituir-se como elemento perturbador para desestabilizar noções científicas e arqueológicas reestruturando ligações entre estes campos. Estas ligações revelam um espaço não linear e produzem novas relações formais e conceptuais. Este espaço totalmente caótico e mutável é por outro lado tangível de compreensão. Ao entrar neste paralelo podemos situar o ser humano como um gerador de informação no seu espaço exploratório e trazer à superfície a potencialidade da existência de um universo de dados ainda por desvendar ou decifrar. Ao refletir sobre estas questões várias relações emergem. A primeira delas fora projeções sob o avanço tecnológico, onde pontuo sintomas da evolução desenfreada das medias digitais. A segunda se desenvolveu em projeções sob o erro digital, relacionando a integração humana com a máquina. A Terceira relação se encontra no desvio, onde uma nova forma de criação surge encima do tema, desencadeando a quarta relação que se compõe na cristalização do tempo como fator essencial capaz de transmutar informação. Por fim, ao tratar de uma obra de caráter ficcional, um projeto de criação de um ambiente "desviante" da realidade, o estudo propõe a discussão da experiência do sujeito como viajante explorador, baseada na análise crítica dos desvios da ciência, utilizando a tecnologia como seu reflexo na sociedade e na criação artística .

Additive manufacturing has been recognized as an alternative manufacturing technique for industrial sustainability by obtaining components with geometry close to the final shape, on-demand production and synthesis of post-processing steps, reducing material waste, manufacturing costs and CO2 emissions. In this sense, the objective of this work was to develop an additive manufacturing component with wire and arc for application in the context of the oil and gas industries. Studies of process parameters and deposition trajectories were carried out, followed by computational simulation, microstructural, mechanical and corrosive characterization. It was concluded that the printed materials presented properties within the standards requirements and properties equivalent or superior to their counterpart manufactured via forging.

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

In the present work, PTA welding process was used to investigate the influence of welding parameters on the dilution, microhardness and corrosion resistance of Inconel 625 alloy coatings on the API 5L X70 grade steel. The electrochemical impedance spectroscopy (EIS) and linear potentiodynamic polarization (LPP) measurements were used to study the protection properties of the deposited layer when immersed in a 3.5% NaCl solution. The results of EIS and LPP have shown that the corrosion resistance results were more satisfactory for coatings with higher dilution index. The results also showed that the dilution values D (%)varied from 15.33% to 4.39% at the maximum (18.99 kJ/cm) and the minimum (8.34 kJ/cm) welding energy levels. The most relevant dilution value obtained was 4.39%.

La secuencia de solidificación influye sobre la formación y crecimiento de las fases en una aleación metálica. En las aleaciones Zn-(3-4)Al-(5-10)Cu, la fase épsilon determina sus propiedades mecánicas. Investigaciones previas han analizado el efecto sobre esta fase del contenido de Cu y de la cinética de solidificación. En este estudio, utilizando técnicas de análisis térmico y microscopia óptica, se observó el efecto sobre la microestructura de las velocidades de enfriamiento en diferentes posiciones respecto al frente de solidificación templando la aleación desde la temperatura de formación de la fase primaria después de aplicar diferentes ciclos térmicos.

The current research was undertaken to study the improvement of the tribological behavior of nanocrystalline bioceramic, α-alumina sample, produced by the calculations of gibbsite at different temperatures (300 to 1200°C), followed by uniaxial pressing, sintering and HIP treatment. The improved friction and wear resistance is attributed to the fine microstructure of the sample calcined at 1400 °C. 1. MATERIALS AND METHODS The calcined alunminas powders were uniaxially pressed at 150 MPa into discs of 17 mm in diameter and 4 mm thickness. The compaction was carried out at a constant strain rate. After ejecting from the die, the samples were measured and weighed to calculate the density. Green compacts were placed into an alumina crucible with Al2O3 powder and sintered at different temperatures of 1250, 1300, 1350, 1400 and 1450 °C for 2 h at a heating rate of 30 K min in order to obtain a closed porosity (high density) as observed by M.H. Bocangera [1, 2]. The sintered samples were t...

This paper presents an experimental examination of AA2024 aluminium alloy through Equal Channel Angular Pressing (ECAP), annealing, and ECAPed plus aging applications. The aim of this study is to compare and observe the effects of the a forecited processes in terms of hardness and electrical conductivity. ECAP is one of the frequently used methods for Severe Plastic Deformation (SPD). SPD give rises to obtain stronger mechanical properties of materials as an improvement technique in material science. Four AA2024 specimens are prepared. One is as received sample, second is annealed AA2024, third one is ECAP processed and the last one is ECAP and then aging processed form. Hardness measurement is done as mechanical properties investigation. In addition, microstructure behaviour with SEM is studied. Once again, electrical conductivity of all four specimens are examined. All parameters are compared with each other. After annealing process the hardness of AA2024 is reduced according to as received form. ECAP increased the hardness, despite this, the highest hardness value is observed on ECAPed plus aging processed sample. The electrical conductivity of AA2024 is increased after annealing process according to as received form. However, it reduced after ECAPed plus aging process. Nevertheless, ECAPed sample gained more conductivity and has the least resistivity.

A practical approach to predict the yield strength and work-hardening exponent (n value) to evaluate the deep-drawing performance of annealed 3104 aluminum sheets is presented in the present work by only measuring and analyzing the grain size of the sheet. The various grain sizes were obtained through the different annealing treatment and then the evolution of the n value under different strains and the yield strength of annealed 3104 aluminum sheet were evaluated. Results showed that the n value and yield strength vary greatly with the grain size. A mathematical model relating grain size d, work-hardening exponent n, target strain ε, and yield strength Rp0.2 was developed in the present work. Within the studied grain size range d (12–29 μm), the n value generally increased with d in a strain-dependent manner, such that n = 0.1875 − 85.03   ×   exp [ − d / 1.94 ] when the ε was less than 0.5%, but n = 0.3 − 0.15 d − 1 / 2 when the ε was greater than 2%. On the other hand, the n valu...

Welding of annealed plates with thickness 8.5 mm of metastable β Ti-55511 alloys has been carried out through Electron beam Welding (EBW) technique in this research effort. Weldment has been characterized by microscopy, microhardness and tensile test at room temperature with controlled strain rates (i.e. 0.01s-1 , 0.001s-1 and 0.0001s-1). The Fusion zone (FZ) found is 'crown shaped' or 'hour-glass shaped'. The microstructure of FZ, Heat Affected Zone (HAZ) and Parent Material (PM) consists of long columnar β-grains, coarse equiaxed β-grains and near globular/equiaxed α in transformed β matrix respectively. Lower UTS, lower percentage elongation and lower microhardness are observed in EB weldments as compared to PM (annealed). Minimum 80% weld efficiency has been noticed in welded condition. The fracture surface of PM shows flute as well as fine dimples which confirm the ductile fracture while 'as-welded' fracture shows facets and ridges with very fine dimples and micro-pores indicating relatively brittle nature.

The bioactivity of glass ceramics from Li 2 O-SiO 2-CaO-P 2 O 5-CaF 2 system, with different amount of fluorapatite expressed as P 2 O 5 content, has been tested in vitro under static and dynamic regime. The paper reports the results of bioactivity test of glass ceramics in static and dynamic regime. XRD, SEM and EPMA analysis were used to characterise the sample as well as to detect the presence of new phase onto the surface of glass ceramics. The bioactivity, as demonstrated by the formation of new apatite layer, depends on P 2 O 5 content and testing regime. In static regime, one can observe a fine microstructure of hydroxyapatite layer on the surface on glass ceramics samples. In dynamic regime, the formation rate of this layer seems to be retarded in comparison with that of static regime.

This text describes the plasma nitriding of a ductile iron, to increase the surface hardness and improve its wear behavior. A ferritic ductile iron was used and processed with gases (N2 + H2) for 5 hours in a treatment chamber built at the UNAM Physics Institute. The treated samples were characterized using scanning electron microscopy, atomic force microscopy, microhardness and X-ray diffraction. The presence of Fe-N compounds was corroborated on the surface of the material. Modifications in surface morphology and a 30% increase in microhardness were also obtained.

This paper comprises an investigation using finite element analysis to study the behaviour of nanocrystalline grain structures during Equal Channel Angular Press (ECAP) processing of metals. The effects of average grain size and misorientation angle on the deformation are examined in order to see how microstructural features might explain the observed increase in strength of nanocrsytalline metals. While this approach forms a convenient starting as it offers a simple way of including grain size effects and grain misorientation to which we could add additional phenomena through developing the material model used to describe the anisotropy and techniques that would automatically re-mesh the refined grain structure produced under severe plastic deformation. From this, it can be concluded that these additional techniques incorporated into the finite element model produced effects that correspond to observed behaviour in real polycrystals.

Flat-top cylinder indenter for mechanical characterization (FIMEC) is an indentation technique employing cylindrical punches with diameters ranging from 0.5 to 2 mm. The test gives pressure-penetration curves from which the yield stress can be determined. The FIMEC apparatus was developed to test materials in the temperature range from À180 to +200°C. Recently, the heating system of FIMEC apparatus has been modified to operate up to 500°C. So, in addition to providing yield stress over a more extended temperature range, it is possible to perform stress-relaxation tests at temperatures of great interest for several nuclear fusion reactor (NFR) alloys. Data on MANET-II, F82H mod., Eurofer-97, EM-10, AISI 316 L, Ti6Al4V and CuCrZr are presented and compared with those obtained by mechanical tests with standard methods.

Autor para quem deverá ser enviada a correspondência Resumo: O sistema Cu-Li-Mg só foi, até ao momento, alvo de estudos por Mel'nik et al. que, com base nos resultados de ensaios de DRX, definiram a secção isotérmica a 643 K; a única fase ternária detectada corresponde à estequiometria Cu 8 Li 2 Mg 15. No presente trabalho, começou por se desenvolver um estudo, em DRX e MEV/EDS, que permitiu confirmar a existência daquela fase ternária à temperatura ambiente. Além disso, foi desenvolvida uma primeira modelização que relaciona os valores experimentais obtidos e os de Mel'nik et al. com a energia de Gibbs das fases que constituem o sistema. Reconhecido o facto dos valores experimentais serem manifestamente escassos e não cobrirem temperaturas próximas da curva de liquidus, afigurou-se necessário desenvolver estudos em CDV/ATD. Assim, foram feitas experiências em ATD de "fluxo contínuo" com amostras correspondentes a três secções verticais. Os resultados obtidos para a secção vertical relativa a x Li  0.05 foram comparados com a modelização dessa mesma secção.

Al-Cu-Li alloy with the thickness of 4 mm is welded by electron beam welding (EBW). Microstructure and mechanical properties of welded joint are systematically investigated. The formation mechanism of weld porosity is fully discussed. Orthogonal experiment results show that welding parameters have great effect on the generation of weld gas pore, and welding speed is the main factor affecting the porosity, followed by electron beam scanning mode, electron beam current is the minimal one. Microstructure analysis demonstrates that weldment is mainly equiaxed grains, and some dendrites exist too. Mechanical properties of welded joints indicate that, under the following welding parameters, electron beam current 13 mA, welding speed 600 mm/min, circular electron beam scanning, a welded joint with good mechanical performance can be obtained. Tensile strength of welded joint is 368.4 MPa, which is about 68% of that of the base metal (BM). SEM analysis shows that there are many fine dimples distributed on the fracture surface of welded joint, and it obviously presents the characteristic of ductile fracture.

The quenched and tempered reduced-activation ferritic/martensitic steel EUROFER 97 is one of the candidates for structural components of fusion reactors. The cyclic behaviour of this steel during isothermal plastic strain-controlled tests is investigated at room temperature. Under Low-Cycle Fatigue (LCF) tests this steel shows, after the first few cycles, a pronounced cyclic softening accompanied by microstructural changes such as the decrease of the dislocation density inside the subgrain and the vanishing of low-angle boundaries. Based on the identified mechanisms of softening a mean-field polycrystalline model is proposed.

An experimental investigation was carried out to determine the corrosive impact of oxidizing and non-oxidizing environments on sensitized welded and unwelded samples of AISI 304. The selected samples were cut into several sizes. To induce sensitization, the samples were heated and soaked at 750oC at different soaking time intervals such as 30 minutes, 60 minutes, 180minutes, 300 minutes and 600 minutes  followed by water quenching [1]. The resultant sensitized weldment and unwelded samples were subjected to immersion duration test each in oxidizing (H2SO4) and non-oxidizing (HCL) media for 5, 10, 15, 20, 25, 30, 35, 40, 45, & 50 minutes respectively. From the results obtained, it was concluded that corrosion rate decreases as soaking time/immersion duration increases, at constant soaking temperature in non-oxidizing medium of hydrochloric acid (HCL). However, the corrosion rate decrease of the unwelded samples of AISI 304 in non-oxidizing medium is greater than that of their welded ...