Physical properties of some Sn-Cu melts at high temperatures

Abstract

Several physical properties (density, viscosity, ultrasound velocity, electroresistivity and magnetic susceptibility) of pure tin, copper, silver and their alloys with near eutectic compositions are investigated in the wide temperature range up to 1600 degrees C. In cases of copper and silver the temperature dependences of properties are found to be smooth. As for liquid tin, three temperature ranges with abnormal behaviour of properties were discovered: t(1) near 400 degrees C (anomalies in density and electroresistivity); t(2) = 1000-1050 degrees C (anomalies in viscosity and electroresistivity); t(3) approx. 1400 degrees C (anomalies in density, electroresistivity and magnetic susceptibility). The decrease in heating rate from 4 to 1 degrees C/min shifts t2 down to 800 degrees C, and the purification of samples from 99.9 to 99.999% provides the incoincidence of viscosity heating and cooling curves for all the temperatures below 800 degrees C. The introduction of copper into liquid tin (99.9% purity) shifts the temperature of anomaly t(2) from 1000-1050 degrees C to 790 degrees C. We connect this abnormal behaviour of physical properties at t(an) with beta-gamma structural transformation. Hence, by warring regimes of melts heat treatment before solidification it becomes possible to obtain samples with different properties in solid state.