Influência da convecção termossolutal nos espaçamentos dendríticos primários durante a solidificação direcional horizontal de ligas Sn-Pb

Abstract

In order to investigate the effect of thermosolutal convection on the primary dendritic spacings of Pb–Sn hypoeutectic alloys, horizontal directional solidification experiments have been carried out. For this purpose, a water-cooled solidification experimental apparatus was developed and specimens were solidified in unsteady state heat flow conditions. A combined theoretical and experimental approach is developed to quantitatively determine the solidification thermal parameters: tip growth rates, thermal gradients and cooling rates. The results also include transient metal/mold heat transfer coefficients, determined from comparisons between the experimental thermal profiles in castings and the simulations provided by a finite difference heat flow program. A comparison between theoretical models that predict primary dendritic spacings with the experimental results generated in this study is conducted. A comparative study between some experimental data of this work and those from the literature proposed to predict the primary dendritic spacings during upward and downward vertical unsteady-state directional solidification of Sn–Pb alloys have is presented. The observation of the microstructures has indicated that the primary dendritic spacings have been affected by the direction of growth, increasing in conditions of horizontal solidification when compared with those obtained during upward and downward vertical solidification of Sn–Pb hypoeutectic alloys analyzed.