Formation of Cu-rich Nanoprecipitates in Cu Containing Pearlitic SGI
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Laura N. Garcı´a Instituto de Meca´nica Aplicada, Universidad Nacional de San Juan, San Juan, Argentina Rodrigo Magnabosco Departamento de Engenharia de Materiais, Centro Universita´rio FEI, Sa˜o Bernardo do Campo, Brasil Roberto E. Boeri Instituto de Investigaciones en Ciencia y Tecnologı´a de Materiales, Universidad Nacional de Mar del Plata-CONICET, Mar del Plata, Argentina CONICET, Ciudad Auto´noma de Buenos Aires, Argentina Alfredo J. Tolley Centro Ato´mico Bariloche, Comisio´n Nacional de Energı´a Ato´mica, San Carlos de Bariloche, Argentina CONICET, Ciudad Auto´noma de Buenos Aires, Argentina Marcela E. Saavedra ICATE-CONICET, San Juan, Argentina CONICET, Ciudad Auto´noma de Buenos Aires, Argentina Copyright Ó 2020 American Foundry Society https://doi.org/10.1007/s40962-020-00543-x
Abstract The presence of Cu-rich nanoprecipitates in a pearlitic spheroidal graphite (ductile) cast iron alloyed with 0.82 wt%Cu was studied. The size and distribution of the precipitates were examined by transmission electron microscopy at different locations of the pearlitic matrix. Some areas were nearly free from precipitates, while other regions showed precipitates at the cementite and ferrite lamellae and at the ferrite/cementite interface. Calculation of the thermodynamic equilibrium under stable and metastable conditions using Thermo-Calc led to the identification of the conditions controlling the formation of Curich nanoprecipitates along three different stages depending on the Cu concentration. Together with a differential scanning calorimetry test and elemental diffusional
calculations, thermodynamic predictions supported the observation of Cu-rich precipitates despite the low concentration of Cu of the alloy investigated and allowed the authors to explain the observed heterogeneity in the distribution of precipitates as resulting from the heterogeneous distribution of Cu in the alloy caused by microsegregation during solidification. The knowledge gained is relevant for the design of strengthening strategies in SGI based on the dispersion of Cu-rich nanoprecipitates.
Introduction
increasing the mechanical resistance of materials for structural use, with the consequent reduction in the volumes required in different applications, contributing to a more sustainable future.1 In this regard, the fine dispersion of nanoparticles has proven to be one of the most effective methods for improving the strength of ferrous alloys.2 In particular, the formation of Cu-rich nanoprecipitates in
Nanostructured materials are essential for the modern world, as their continuous innovation is critical for
Received: 09 September 2020 / Accepted: 26 October 2020
International Journal of Metalcasting
Keywords: spheroidal graphite cast irons, Cu-rich nanoprecipitates, nanostructured materials, Thermo-Calc, microsegregations, transmission electron microscopy
steels has become an attractive method to increase strength without causing a significant reduction in ductility at a relatively low cost.3,4 As a result, steels containing Cu-rich
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