Effect of growth rates and temperature gradients on the lamellar spacing and the undercooling in the directionally solidified Pb-Cd eutectic alloy
Lead-cadmium of high (99.99%) purity eutectic alloy was melted in a graphite crucible under vacuum atmosphere. These regular eutectic alloys were directionally solidified upward with a constant growth rate of 8.3 mum/s, and different temperature gradients G (similar to1.6-6.4 K/mm range), and also with a constant temperature gradient (similar to6.4 K/mm) and different growth rates V (8.3-165.5 mum/s range) in the Bridgman-type directional solidification furnace. The lamellar spacings lambda were measured from both transverse section and longitudinal section of the specimen. The variations of lambda with respect to G and V were determined by using linear regression analysis. The dependence of lambda on DeltaT(e) (the extremum undercooling) was also analysed. The variation of DeltaT(e) with Vat constant G and with G at constant V were investigated. According to these results, it has been found that lambda decreases with the increasing values of G and V Also DeltaT(e) increases with increasing V for a constant G and with the increasing G for a given V, respectively. The results obtained in this work have been compared with the Jackson-Hunt eutectic theory and the previous experimental results. (C) 2003 Elsevier Ltd. All rights reserved.