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Volta Redonda, Brazil

Costa E Silva A.,EEIMVR UFF | Goulart L.,VSBM | Araujo E.,VSBM | Batista R.,CSN | Martins A.,CSN
TMS Annual Meeting | Year: 2015

Steel cleanness is of great importance to the performance of almost all steel products. From very clean steel for bearings to long products used in civil construction, processing variables - in special those in steelmaking operations- must be properly balanced to achieve adequate cleanness for the desired performance. With the present complexity of steels as alloy systems, it is not efficient nor appropriate to develop these processes on empirical basis alone. Computational thermodynamics can greatly improve process development to achieve the desired cleanness level at reasonable costs. In this work, examples of these calculations and their applications to real steel processing are presented and discussed. The advantages, limitations and areas in which improvement in these calculations is desired are highlighted and discussed. Copyright © 2015 by The Minerals, Metals & Materials Society. All rights reserved.

Palumbo M.,Ruhr University Bochum | Burton B.,U.S. National Institute of Standards and Technology | Costa e silva A.,EEIMVR UFF | Fultz B.,California Institute of Technology | And 8 more authors.
Physica Status Solidi (B) Basic Research | Year: 2014

Progress in materials science through thermodynamic modelling may rest crucially on access to a database, such as that developed by Scientific Group Thermodata Europe (SGTE) around 1990. It gives the Gibbs energy G(T) of the elements in the form of series as a function of temperature, i.e. essentially a curve fitting to experimental data. In the light of progress in theoretical understanding and first-principles calculation methods, the possibility for an improved database description of the thermodynamics of the elements has become evident. It is the purpose of this paper to provide a framework for such work. Lattice vibrations, which usually give the major contribution to G(T), are treated in some detail with a discussion of neutron scattering studies of anharmonicity in aluminium, first-principles calculations including ab initio molecular dynamics (AIMD), and the strength and weakness of analytic model representations of data. Similarly, electronic contributions to G(T) are treated on the basis of the density of states N(E) for metals, with emphasis on effects at high T. Further, we consider G(T) below 300K, which is not covered by SGTE. Other parts in the paper discuss metastable and dynamically unstable lattices, G(T) in the region of superheated solids and the requirement on a database in the calculation of phase diagrams. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Costa e Silva A.,EEIMVR UFF | Nakamura L.,Aperam S.A | Rizzoc F.,DEMa PUC RJ
Journal of Mining and Metallurgy, Section B: Metallurgy | Year: 2012

In previous works the possibilities and limitations of the application of calculations in the Al-Fe-N system to describe the precipitation of AlN in steel, both in the solid state and during the solidification were discussed and some difficulties related to the extension of these calculations to more complex steel systems, due to limitations in the thermodynamic data were also presented. Presently, the precipitation kinetics of AlN in ferrite (BCC) and austenite (FCC) is discussed. The correct description of the precipitation of AlN in both phases is relevant to: (a) the precipitation at higher temperatures, in the austenite field, that occurs in some steels, (b) the concurrent precipitation of this nitride with the annealing treatment, when the steel is mostly ferritic, used in the processing of some types of deep drawing steels (c) the precipitation of this nitride in some silicon alloyed electric steels at relatively high temperatures, when these steels can have significant fractions of BCC and FCC in their microstructure. The precise knowledge of the precipitation-dissolution behavior of AlN in special in these two latter classes of steels is of great importance to their correct processing. In this work, a computational tool for simulating multiparticle precipitation kinetics of diffusion-controlled processes in multi-component and multi-phase alloy systems is employed in an attempt to describe these precipitation processes. The results are compared with experimental data on precipitation. The assumptions necessary for the application of the multi-particle modeling tool are discussed, agreements and discrepancies are identified and some possible reasons for these are indicated. Furthermore, the impact of the use of different sources of data on steel processing development is discussed and the need for further studies highlighted.

Costa e Silva A.,EEIMVR UFF | Rizzo F.,EEIMVR UFF
Calphad: Computer Coupling of Phase Diagrams and Thermochemistry | Year: 2012

XL CALPHAD-Computer Coupling of Phase Diagrams and Thermochemistry conference was held in Rio de Janeiro, Brazil, May 22-27, 2011. The conference had an audience of 192 persons. There were 88 oral and 100 poster presentations. Presentations were divided according to themes: ab initio; the CALPHAD method, and assessments; applications - energy; applications - steel, superalloys, oxides and experiments and databases. A total of 90 companies were represented among authors and audience. In this summary, a brief description of the highlights of the conference is presented as well as the abstracts for the contributed papers.

de Oliveira E.M.,EEIMVR UFF | ValadaO I.C.R.P.,EEIMVR UFF | de Souza Forster ArauJo A.,EEIMVR UFF | de Castro J.A.,EEIMVR UFF
Materials Science Forum | Year: 2014

The study of nanoparticles involves a new field of research in various areas of technology, whose production and use have been recognized as multiple benefits to the society. However, the uncontrolled emission to the environment of nanoparticles is growing exponentially over the last decade. Thus, knowledge of the influence of nanoparticles and how they can modify the ecosystem is extremely importantand demand specific studies. Therefore, it is of fundamental importance to increase the knowledge of the interactions and transport of nanoparticles in soil, in particular this research will study the TiO2 nanoparticles (TiNPs). Aiming to improve such knowledge, this paper addressed tests on columns with soil collected in the landfill Volta Redonda located in the state of Rio de Janeiro, Brazil. Aliquots of TiO-nanoparticle suspensions in soil were collected periodically after their preparation, and analyzed the aggregate of particles distribution and Ti concentration. Experimental results suggest that the higher stability of TiO2 suspensions resulted in a higher mobility of TiO2 through soil layers with lower retention rate. © (2014) Trans Tech Publications, Switzerland.

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