EBSD analysis of orientation gradients developed near grain boundaries

The local misorientation and orientation gradient development near grain boundaries (GBs) are analyzed in a deep drawing quality steel sheet (AKDQ) subjected to interrupted tensile tests in a notched sample. The microstructure is studied using electron backscatter diffraction (EBSD) with subgrain-level spatial resolution. The evolution of misorientation accumulation for particular GBs was traced in grains located in different zones inside the notch, identifying the effective area of influence of GBs inside the neighboring grains. A local study was performed, and the evolution in misorientation development near GB was investigated. The results show a low correlation between GB width and sharpness of the orientation gradient with the mesoscopic strain, but instead orientation gradients between GB zones and the interior of the grains were observed with increasing strain. The increase in severity observed in some GBs can be related to dislocation pile up development, which reduces the permeability of a boundary to dislocation transmission.Fil: de Vincentis, Natalia Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Roatta, Analía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Bolmaro, Raul Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Signorelli, Javier Walter. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; Argentin

Orientation gradients in grain boundary proximity studied by EBSD

El objetivo de este estudio es evaluar la desorientación local, su distribución y el gradiente de orientación en el desarrollo de la microestructura de una chapa de acero de calidad de embutido profundo (AKDQ). La microestructura se caracteriza con una resolución espacial a nivel de sub-grano usando difracción de electrones retrodifundidos (EBSD) en muestras sometidas a tensión uniaxial interrumpida en una probeta entallada y a solicitaciones típicas de procesos de conformado a través de ensayos Nakajima con diferentes geometrías de probeta. El empleo de la probeta entallada permite el estudio local de la evolución de la microestructura sobre un conjunto de granos identificables a medida que el material deforma, mientras las muestras correspondientes a los ensayos Nakajima se emplean para estudiar el comportamiento del gradiente de orientación con la distancia a los bordes de grano, bajo un enfoque estadístico. A partir de este último análisis se introducen dos nuevos parámetros basados en EBSD, llamados severidad promedio del gradiente (GAS) y espesor efectivo del borde (BET). En láminas de acero AKDQ de 0.67 mm de espesor, el valor del BET como indicador de la zona de influencia del BG resulta, en un sentido promedio, independiente del tamaño del grano y la condición de carga, sin superar los 3 μm. La severidad del gradiente muestra una buena correlación con la deformación plástica mesoscópica. Se observa además que la desorientación local se acumula en las proximidades de los bordes de grano mostrando diferencias en cada condición de carga.The goal of this study is the evaluation of local misorientation, its distribution and orientation gradient in the microstructural development of a deep drawing quality steel sheet (AKDQ). The microstructure is characterized at sub-grain level spatial resolution using Electron Backscatter Diffraction (EBSD) in samples submitted to interrupted uniaxial tension in a notched sample and to typical solicitations in forming process through Nakajima tests with different sample geometries. The use of a notched sample allows performing a local study of the microstructural evolution in a set of identifiable grains as the material deforms, while the samples corresponding to Nakajima tests are used to study the behavior of the orientation gradient with the distance to the grain boundary under a statistical approach. From the latter analysis, two new EBSD-based parameters are introduced, named Gradient Average Severity (GAS) and Boundary Effective Thickness (BET). In 0.67 mm thick AKDQ steel sheets, the BET value as an indicator of GB influence zone is, in an average sense, independent on the grain size and the loading condition, below 3 ìm. The gradient severity shows a good correlation with the mesoscopic plastic deformation. It is also observed that local misorientation accumulates in the grain boundary proximity, showing differences for each loading condition.Fil: Roatta, Analía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Schwindt, Claudio Daniel. Universidad Nacional del Sur. Departamento de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: de Vincentis, Natalia Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Signorelli, Javier Walter. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; Argentin

Anisotropic and Heterogeneous Development of Microstructures. Combining Laboratory/Synchrotron X-rays and EBSD on a few SPD Metallic Systems

The onset of Severe Plastic Deformation (SPD) regime is quite instructive on the possible origins of the nano-microstructures developed in metals and alloys. It is known that grain fragmentation and dislocation accumulation, among other defects, proceed at different paces depending fundamentally on grain orientations and active deformation mechanisms. There have been many attempts to characterize nano-microstructure anisotropy, leading all of them to sometimes contradictory conclusions. Moreover, the characterizations rely on different measurements techniques and pos-processing approaches, which can be observing different manifestations of the same phenomena. On the current presentation we show a few experimental and computer pos-processing and simulation approaches, applied to some SPD/alloy systems. Williamson-Hall and Convolutional Multiple Whole Profile (CMWP) techniques will be applied to peak broadening analysis on experimental results stemming from laboratory Cu Ka X-rays, and synchrotron radiation from LNLS (Laboratório Nacional de Luz Síncrotron, Campinas, Brazil) and Petra III line (HEMS station, at DESY, Hamburg, Germany). Taking advantage of the EBSD capability of giving information on orientational and topological characteristics of grain boundaries, microstructures, grain sizes, etc., we also performed investigations on dislocation density and Geometrically Necessary Dislocation Boundaries (GNDB) and their correlation with texture components. Orientation dependent nano-microstructures and domain sizes are shown on the scheme of generalized pole figures and discussions provide some hints on nano-microstructure anisotropy.Fil: Bolmaro, Raul Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Física de Rosario (i); ArgentinaFil: de Vincentis, Natalia Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Física de Rosario (i); ArgentinaFil: Benatti, Emanuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Física de Rosario (i); ArgentinaFil: Kliauga, Andrea M.. Universidade Federal Do Sao Carlos. Departamento de Engenharia de Mteriales; BrasilFil: Avalos, Martina Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Física de Rosario (i); ArgentinaFil: Schell, Norbert. Helmholtz-Zentrum Geesthacht; AlemaniaFil: Brokmeier, Heinz Günter. Institut für Werkstoffkunde und Werkstofftechnik; Alemani

Factors affecting Confidence Index in EBSD analysis

Automated EBSD analysis systems have been used for over two decades relying on the fact that the correctness ofa particular orientation solution could be assessed through the calculation of a Confidence Index. However, suchan index only reports whether a particular solution stands out among any other possible solutions, by receiving alarger number of votes than others, and does not necessarily imply that the corresponding orientation is correct.This issue is addressed in the present paper, where the correctness of solutions and the factors that might affect ithave been studied for single crystal Si and polycrystalline Zn. The results were compared to those presented inprevious papers where this matter was studied in particular for an FCC material. It was observed that about 90%of the solutions were correct if they were obtained using a confidence index of 0.1 using at least 8 Hough bandsregardless of the crystallographic structure or orientation.Fil: de Vincentis, Natalia Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Field, D. P.. Washington State University Pullman; Estados Unido

Strain path dependence of anisotropic microstructure evolution on low Stacking Fault Energy F138 steel

Severe Plastic Deformation (SPD) techniques are widely used nowadays because of the mechanical properties improvements caused by grain refinement and development of dislocation arrays. Diffraction techniques can be used to assess the changes registered in the microstructure through these methods. Two sets of samples of F138 austenitic stainless steel were analyzed in this paper: one set was deformed by ECAE up to two pressings at room temperature, and the other set was cold rolled to 70% reduction and annealed at 600, 700, 800 and 900 °C for 1 h. The microstructural changes were determined using X-Ray diffraction and EBSD, combining both, global and local information and characterizing domain sizes, dislocation and stacking fault densities and misorientation degree and distribution caused by the different thermomechanical processing. It was observed that, despite cold rolling and 2 ECAE passes rendered rather similar von Mises deformations, the microstructure through each deformation method was different: 2 ECAE passes seem to be more effective for grain refinement and generation of equiaxed domains than cold rolling. The more significant twin activation observed in the former sample, because of continuous strain path change, may explain the difference, although dislocation densities and mechanical properties did not differ substantially for both deformation methods.Fil: de Vincentis, Natalia Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Avalos, Martina Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Kliauga, A.. Universidade Federal do São Carlos; BrasilFil: Brokmeier, H. G.. Institut für Werkstoffkunde und Werkstofftechnik; Alemania. Helmholtz Zentrum Geesthacht; AlemaniaFil: Bolmaro, Raul Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; Argentin

Creation of heterogeneous microstructures in copper using high-pressure torsion to enhance mechanical properties

This paper studies the effects of high-pressure torsion (HPT) at ambient temperature on microstructural evolution and mechanical properties enhancement in pure copper. The aim is to introduce gradient microstructure, with various statistical distributions of grain size and grain orientations to examine their effect on strength and ductility. To this end, extruded cylindrical pure copper subjected to HPT for 1, 2, and 3-turns resulted in grain refinement down to the grain size of 500 nm. Combination of microhardness test and EBSD scans through the radial direction confirm the creation of a heterogeneous structure through the thickness and radial directions. The results demonstrate that increasing the shear strain leads to (1) ultra-fine grain (UFG) generation at deformed coarse-grain boundaries, (2) an increase in the fraction of recrystallized grains and high angle grain boundaries, and (3) a homogenous structure in the last step. A unique mixture has been obtained due to the particular shape of the anvils. The mixture included a chain of UFGs and coarse grains contain dislocations and subgrains. The highest level of gradient structure through the thickness was observed after 1-turn, which leads to the best combination of strength and ductility.Fil: Jamalian, Maryam. Washington State University; Estados UnidosFil: Hamid, Mehdi. Washington State University; Estados UnidosFil: de Vincentis, Natalia Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; Argentina. Washington State University; Estados UnidosFil: Buck, Quentin. Washington State University; Estados UnidosFil: Field, David P.. Washington State University; Estados UnidosFil: Zbib, Hussein M.. Washington State University; Estados Unido

Cryptic Diagenetic Changes in Quaternary Aragonitic Shells: A Textural, Crystallographic, and Trace-Element Study on Amiantis Purpurata (Bivalvia) From Patagonia, Argentina

Modern to Pleistocene Amiantis purpurata shells collected in Bahı´a San Antonio (Patagonia, Argentina) were studied by X-ray diffraction (XRD), optical and electron microscopy, electron microprobe analyses, and microindentation, in order to characterize early diagenetic changes and mechanical resistance. The sole crystalline phase is twinned aragonite showing pseudohexagonal symmetry. The regularity of the crystallographic texture decreases in older samples, but average crystallite size does not increase. The microstructure, which is dominantly crossed lamellar, is progressively replaced by a more randomly oriented grain aggregate. Compositional profiles across the shell show gradients in Sr, Na, S, and Cl, whereas Mg and P are more evenly distributed. Each shell layer has a distinct chemical signature. A marked decrease in the concentration of all of these elements, along with flattening of profiles, is evident as age increases. Vickers microhardness is lowest in modern specimens, showing at the same time the least chipped regions; older shells become harder and more fragile. All of these changes are attributed to postdepositional modifications by dissolution-recrystallization processes mediated by a thin film of water in a vadose environment. Microstructural adjustments are more sluggish than chemical modifications produced by diagenetic processes, whereas microhardness rapidly reaches high values,probably due to the early degradation of organic compounds from the shell. Our study shows that aragonitic shells that retain their primary mineralogical composition have undergone subtle chemical and microstructural changes. A very small amount of calcite was produced during grinding for XRD. Care should therefore be taken when seeking calcite as evidence of diagenetic changes.Fil: Bayer, María Sol. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Centro de Investigaciones En Ciencias de la Tierra; ArgentinaFil: Colombo, Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Centro de Investigaciones En Ciencias de la Tierra; ArgentinaFil: de Vincentis, Natalia Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Física de Rosario (i); ArgentinaFil: Duarte, Gonzalo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Física de Rosario (i); ArgentinaFil: Bolmaro, Raul Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Física de Rosario (i); ArgentinaFil: Gordillo, Sandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Centro de Investigaciones En Ciencias de la Tierra; Argentin

Assessing the Power of Electron Back Scattering Diffraction Characterization of Deformed F-138 Steel from the View Point of Crystal Diffraction

Microstructural characterization by combined EBSD and X-ray diffraction analysis is shown for an FCC material deformed by rolling and further heat treatment on air. The wide variety of x-rays sources combined with EBSD allows some correlations between microstructural parameters to be withdrawn by carefully analyzing x-ray peak broadening. The combination of both techniques provides a deeper understanding of anisotropic accumulation of dislocation arrays on a deformed F 138 stainless steel. The anisotropy results in a smaller peak breadth for crystal orientations with [110] planes contained on the rolling plane, further explained as resulting from a lower storage of dislocations. After heat treatment the effect is reverted and the formerly less misoriented orientations become more uniformly oriented revealing a faster dislocation migration and annihilation and/or trappingBehandelt wird die mikrostrukturelle Charakterisierung mittels kombinierter EBSD- und Röntgenbeugungsanalyse für einen durch Walzen und Wärmebehandlung an Luft verformten kfz-Werkstoff. Die Kombination eines breiten Spektrums an Röntgenquellen und EBSD ermöglicht auf der Grundlage einer sorgfältigen Analyse der Röntgenpeakverbreiterung die Ableitung einiger zwischen mikrostrukturellen Parametern bestehenden Korrelationen. Die Kombination beider Techniken sorgt für ein tieferes Verständnis der anisotropen Ansammlung von Versetzungsanordnungen in rostfreiem Stahl F 138. Aus der Anisotropie ergibt sich eine geringere Peakbreite für in der Walzebene enthaltene Kristallorientierungen mit [110]-Ebenen, die auch als Folge einer geringeren Einlagerung an Versetzungen erklärt werden kann. Nach der Wärmebehandlung kommt es zu einer Umkehrung des Effekts und die zuvor wenig fehlorientierten Ausrichtungen richten sich einheitlicher aus und weisen eine schnellere Versetzungswanderung und -annihilation und/oder Trapping (etwa: „Einfangen“) aufFil: Bolmaro, Raul Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Avalos, Martina Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: de Vincentis, Natalia Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Kliauga, Andrea M.. Federal University of São Carlos; BrasilFil: Brokmeier, Heinz Günter. Institut für Werkstoffkunde und Werkstofftechnik; Alemani

Evaluation of microstructure anisotropy on room and medium temperature ECAP deformed F138 steel

Abstract The microstructure developed during severe plastic deformation results in improved mechanical properties because of the decrease in domain sizes and accumulation of defects, mainly dislocation arrays. The characteristic deformation stages observed in low stacking fault energy (SFE) face centered cubic (FCC) materials are highly influenced by the development of the primary and secondary twinning that compete with dislocation glide. In this paper, a low SFE F138 stainless steel is deformed by equal channel angular pressing (ECAP) up to 4 passes at room temperature (RT) and at 300°C to compare the grain refinement and twin boundary development with increasing deformation. Tensile tests were performed to determine the deformation stages reached by the material before and after ECAP deformation, and the resulting microstructure was observed by TEM. X-ray diffraction and EBSD, average technique the first and local the second one, were used to quantify the microstructural changes, allowing the determination of diffraction domain sizes, dislocation and stacking fault densities and misorientation indices, which lead to a complete analysis of the deformation introduced in the material, with comparative correlations between various microstructural parameters.Fil: de Vincentis, Natalia Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Kliauga, A.. Universidade Federal do São Carlos; BrasilFil: Ferrante, M.. Universidade Federal do São Carlos; BrasilFil: Avalos, Martina Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Brokmeier, H. G.. Institut für Werkstoffkunde und Werkstofftechnik; AlemaniaFil: Bolmaro, Raul Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; Argentin