Investigation of microhardness and thermo-electrical properties in the Sn-Cu hypereutectic alloy

Sn-3 wt% Cu hypereutectic alloy was directionally solidified upward with different growth rates (2.24-133.33 mu m/s) at a constant temperature gradient (4.24 K/mm) and with different temperature gradients (4.24-8.09 K/mm) at a constant growth rate (7.64 mu m/s) in the Bridgman-type growth apparatus. The measurements of microhardness of directionally solidified samples were obtained by using a microhardness test device. The dependence of microhardness HV on the growth rate (V) and temperature gradient (G) were analyzed. According to these results, it has been found that with the increasing the values of V and G the value of HV increases. Variations of electrical resistivity (rho) and electrical conductivity (sigma) for casting samples with the temperature in the range of 300-500 K were also measured by using a standard dc four-point probe technique. The variation of Lorenz coefficient with the temperature for Sn-3 wt% Cu hypereutectic alloy was determined by using the measured values of electrical and thermal conductivities. The enthalpy of fusion for same alloy was determined by means of differential scanning calorimeter from heating trace during the transformation from eutectic liquid to eutectic solid.