Solidificação unidirecional transitória de ligas peritéticas do sistema Pb-Bi

TL;DRAbstract

are proposed. Power laws with -0,5 and -1,0 exponents for 1 and 2 as a function of T and V L xvii respectively, were found to better represent the dendritic growth under transient heat flow conditions for all alloys and cooling conditions investigated. The laws obtained experimentally were compared with theoretical predictions furnished by both unsteady-state growth models (Bouchard-Kirkaldy and Hunt-Lu) and steady-state models (Hunt, Trivedi and Kurz-Fisher). Some experiments were also carried out in a vertical tube furnace for Pb-9,5wt%Bi, Pb-25wt%Bi and Pb-32wt%Bi alloys, under cooling rates closer to equilibrium during solidification. The proposed experimental growth laws have also been checked against experimental results from the literature concerning the growth of Pb-Bi peritectic alloys under steady-state conditions. It is shown that the proposed growth laws are able to encompass also the growth primary dendritic branches during steady-state solidification.

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