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|Type:||Artigo de periódico|
|Title:||Cellular growth during the transient directional solidification of Zn-rich Zn-Cu monophasic and peritectic alloys|
|Abstract:||Zn-Cu alloys located in the monophasic and hypoperitectic ranges of compositions of Zn-rich Zn-Cu alloys were directionally solidified under unsteady-state heat flow conditions. The experimental cooling curves allow solidification thermal parameters: tip cooling rate ((T) over dot), tip growth rate (V-L) and temperature gradient (G(L)) to be experimentally determined. The observed microstructural evolution of both alloys has shown that a regular cellular morphology prevails along the whole castings lengths. Only the regions very close to the cooled casting surface showed the presence of plate-like cells due to very high cooling rates (higher than 25 K/s). The cell spacing (lambda(c)) was measured along the castings lengths, and experimental correlations between lambda(c) and experimental solidification thermal parameters have been established. Power laws with -0.55 and -1.1 exponents expressing lambda(c) as a function of (T) over dot and V-L, respectively, were found to better represent the growth of cells under transient heat flow conditions for both alloys experimentally examined. The predictions furnished by the Hunt-Lu model underestimate the experimental cell spacings found for both alloys examined. It was shown that the proposed equations relating lambda(c) as a function of (T) over dot are able to represent both the steady-state and unsteady-state cellular growth of monophasic and peritectic Zn-rich Zn-Cu alloys. (C) 2012 Elsevier Ltd. All rights reserved.|
|Editor:||Pergamon-elsevier Science Ltd|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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