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A Study of Microsegregation in Al-Cu Using a Novel Single-Pan Scanning Calorimeter

By Hongbiao Dong, M. R. M. Shin, E. C. Kurum, J. D. Hunt and H. Cama

Abstract

This paper was published in Metallurgical and Materials Transactions A, 2003, Volume 34. Issue 3, pp.441-447 and is made\ud available as an electronic reprint with the permission of ASM International. One print or electronic copy may\ud be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via\ud electronic or other means, duplications of any material in this paper for a fee or for commercial purposes, or\ud modification of the content of this paper are prohibited.A single-pan scanning calorimeter has been developed that eliminates the smearing of latent heat that occurs in a conventional two-pan heat-flux differential scanning calorimeter (DSC). In the new calorimeter, accurate enthalpy/temperature data was obtained in pure Al without smearing, and excellent sensitivity to new phases was obtained in a multicomponent Al alloy (LM25). The calorimeter has been used to investigate microsegregation in an Al-4.45 wt pct Cu alloy. The enthalpy/temperature data fell between that calculated, assuming no mixing in the solid (Scheil) and complete mixing in the solid (equilibrium solidification). The amount of segregation agreed well with that calculated using a diffusion-based model of microsegregation. The difficulty of getting the fraction solid from the enthalpy data is discussed, and it is concluded that it is not possible to do so without using a microsegregation model. In addition, it is concluded that it is wrong to assume that the enthalpy of an alloy can be given by a specific heat term and a constant latent heat term that depend on fraction liquid as is assumed in most casting models. [This article is based on a presentation given in the symposium “Fundamentals\ud of Solidification,” which occurred at the TMS Fall meeting in\ud Indianapolis, Indiana, November 4–8, 2001, under the auspices of the TMS\ud Solidification Committee.]Peer-reviewedPublisher Versio

Publisher: Springer Verlag on behalf of ASM International
Year: 2003
DOI identifier: 10.1007/s11661-003-0080-6
OAI identifier: oai:lra.le.ac.uk:2381/1908
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Citations

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