An alternative method to identify critical temperatures for semisolid materials process applications using differentiation
Gabriela Lujan Brollo, Cecília Tereza Weishaupt Proni, Leandro Cássio de Paula, Eugênio José Zoqui
ARTIGO
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Agradecimentos: The authors would like to thank the Brazilian research funding agencies FAPESP (São Paulo Research Foundation – Projects 2013/09961-3 and 2015/22143-3), CNPq (National Council for Scientific and Technological Development – Project 470572/2011-6) and CAPES (Federal Agency for the...
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Agradecimentos: The authors would like to thank the Brazilian research funding agencies FAPESP (São Paulo Research Foundation – Projects 2013/09961-3 and 2015/22143-3), CNPq (National Council for Scientific and Technological Development – Project 470572/2011-6) and CAPES (Federal Agency for the Support and Improvement of Higher Education) for providing financial support for this study. The authors are also indebted to the Faculty of Mechanical Engineering at the University of Campinas for the practical support very kindly provided
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A novel method is proposed for identifying critical temperatures in thixoformability analysis. The proposed method applies the principles of differential calculus to semisolid transformation curves. The method is compared with the conventional tangent method for determining the solidus and liquidus...
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A novel method is proposed for identifying critical temperatures in thixoformability analysis. The proposed method applies the principles of differential calculus to semisolid transformation curves. The method is compared with the conventional tangent method for determining the solidus and liquidus temperatures using DSC curves and with the visual recognition method for identifying the “knee”, or unstable main eutectic transformation temperature. Numerical simulation is performed with Thermo-Calc® (under the Scheil condition) for A356 alloy, and the same alloy is used to generate experimental DSC data for cooling and heating cycles under different kinetic conditions (5, 10, 15, 20 and 25 °C/min) in order to compare the conventional methods for identifying critical temperatures and the novel method described here. The findings indicate that the proposed method, referred to here as the differentiation method, is an efficient tool for identifying critical points such as the solidus, liquidus and knee temperatures and that the results obtained using the method are in good agreement with results obtained with traditional methods. The method also proved to be operator-independent, as it uses well-defined mathematical/graphical criteria to identify critical points. Furthermore, the new method is easy to use, as after differentiation the critical points become easily recognizable visual and numerical features such as valleys and peaks (for the knee temperature) and zeros (for the solidus and liquidus) on the curve being analyzed. The following formal definition for the eutectic knee, the first of its kind in the literature, is proposed: “the peak/valley in the expected eutectic range of the differentiated DSC curve of the solidification/melting transformation”. Application of the proposed definition yields results that agree well with results obtained by the traditional visual recognition method, indicating its suitability for identification of the eutectic knee, especially when a comparative study of different shaped curves is being performed. A definition that allows suitable lower and upper limits for the SSM processing window to be identified is also proposed
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FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP
2013/09961-3; 2015/22143-3
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ
470572/2011-6
COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES
Fechado
An alternative method to identify critical temperatures for semisolid materials process applications using differentiation
Gabriela Lujan Brollo, Cecília Tereza Weishaupt Proni, Leandro Cássio de Paula, Eugênio José Zoqui
An alternative method to identify critical temperatures for semisolid materials process applications using differentiation
Gabriela Lujan Brollo, Cecília Tereza Weishaupt Proni, Leandro Cássio de Paula, Eugênio José Zoqui
Fontes
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Thermochimica acta Vol. 651 (May, 2017), p. 22-33 |