Research on lamellar structure and micro-hardness of directionally solidified Sn-58Bi eutectic alloy

In this work, the Sn-58Bi (weight percent) eutectic alloy was directionally solidified at a constant temperature gradient (G = 12 K·mm-1) with different growth rates using a Bridgman type directional solidification furnace. A lamellar microstructure was observed in the Sn-58Bi samples. The lamellar spacing and micro-hardness of longitudinal and transversal sections were measured. The values of lamellar spacing of both longitudinal and transversal sections decrease with an increase in growth rate. The microhardness increases with an increase in the growth rate and decreases with an increase in the lamellar spacing. The dependence of lamellar spacing on growth rate, and micro-hardness on both growth rate and lamellar spacing were obtained by linear regression analysis. The relationships between the lamellar spacing and growth rate, microhardness and growth rate, and micro-hardness and lamellar spacing for transversal and longitudinal sections of Sn-58Bi eutectic alloy were given. The fitted exponent values obtained in this work were compared with the previous similar experimental results and a good agreement was obtained.