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Type: Artigo de periódico
Title: Solidification thermal parameters affecting the columnar-to-equiaxed transition
Author: Siqueira, CA
Cheung, N
Garcia, A
Abstract: Experiments were conducted to analyze the columnar-to-equiaxed transition (CET) during the upward unsteady-state directional solidification of Al-Cu and Sn-Pb alloys, under different conditions of superheat and heat-transfer efficiencies at the metal/mold interface. A combined theoretical and experimental approach is developed to quantitatively determine the solidification thermal parameters: transient heat-transfer coefficients, tip growth rates, thermal gradients, and cooling rates. The observed results do not give support to CET criteria based individually either on tip growth rate or temperature gradients ahead of the liquidus isotherm. Rather, the analysis has indicated that a more convenient criterion should encompass both thermal parameters through the tip cooling rate. The columnar growth is expected to prevail throughout the casting for a tip cooling rate higher than a critical value, which depends only on the alloy system and was observed to be about 0.2 K/s for Al-Cu alloys and 0.01 K/s for Sn-Pb alloys in the present investigation.
Country: EUA
Editor: Minerals Metals Materials Soc
Rights: aberto
Identifier DOI: 10.1007/s11661-002-0042-4
Date Issue: 2002
Appears in Collections:Unicamp - Artigos e Outros Documentos

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