Influence of Solidification Thermal Parameters on the Columnar-to-Equiaxed Transition of Aluminum-Zinc and Zinc-Aluminum Alloys |
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Authors: | AE Ares CE Schvezov |
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Affiliation: | (1) Consejo Nacional de Investigaciones Científicas y Técnicas, (CONICET)/Faculty of Sciences, Misiones State University, (3300) Posadas, Misiones, Argentina |
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Abstract: | Understanding the interaction between the parameters involved in the columnar-to-equiaxed transition (CET) has gained considerable
attention over the last two decades in the study of the structure of ingot castings. The present investigation was undertaken
to investigate experimentally the directional solidification of Al-Zn and Zn-Al (ZA) alloys under different conditions of
superheat and heat-transfer efficiencies at the metal/mold interface. The CET is observed; grain sizes are measured and the
observations are related to the solidification thermal parameters: cooling rates, growth rates, thermal gradients, and recalescence
determined from the temperature vs time curves. The temperature gradient in the melt, measured during the transition, is between –0.338 °C/mm and 0.167 °C/mm.
In addition, there is an increase in the velocity of the liquidus front faster than the solidus front, which increases the
size of the mushy zone. The size of the equiaxed grains increases with distance from the transition, an observation that was
independent of alloy composition. The observations indicate that the transition is the result of a competition between coarse
columnar dendrites and finer equiaxed dendrites. The results are compared with those previously obtained in lead-tin alloys.
This article is based on a presentation made in the symposium entitled “Solidification Modeling and Microstructure Formation:
in Honor of Prof. John Hunt,” which occurred March 13–15, 2006 during the TMS Spring Meeting in San Antonio, Texas, under
the auspices of the TMS Materials Processing and Manufacturing Division, Solidification Committee. |
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Keywords: | |
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