Variations of microhardness with the solidification processing parameters and thermo-electrical properties with the temperature in the Sn-Cu alloy
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Sn-1.2wt.%Cu eutectic alloy was directionally solidified upward with different growth rates (2-78-136.36 mu m s(-1)) at a constant temperature gradient (2.69 K mm(-1)) and with different temperature gradients (2.69-8.88 K mm(-1)) at a constant growth rate (6.80 mu m s(-1)) 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 analysed. According to these results, it has been found that with the increasing values of V and G, the values of HV increase. Variations of electrical resistivity (p) and electrical conductivity (a) for Sn-1.2wt.%Cu cast alloy with the temperature in the range of 300-500 K were also measured by using a standard d.c. four-point probe technique. The variation of Lorenz coefficient with the temperature for Sn-1.2wt.%Cu eutectic alloy was determined by using the measured values of electrical conductivity and thermal conductivity. The enthalpy of fusion for the same alloy was determined by means of differential scanning calorimeter (DSC) from heating trace during the transformation from eutectic liquid to eutectic solid.