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° 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: t1 near 400° C (anomalies in density and electroresistivity); t2 = 1000–10500 °C (anomalies in viscosity and electroresistivity); t3 approx. 1400° C (anomalies in density, electroresistivity and magnetic susceptibility). The decrease in heating rate from 4 to 1 °C/min shifts t2 down to 800° 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° C. The introduction of copper into liquid tin (99.9 % purity) shifts the temperature of anomaly t2 from 1000–1050° C to 790° C. We connect this abnormal behaviour of physical properties at tan with β-γ structural transformation. Hence, by warring regimes of melts heat treatment before solidification it becomes possible to obtain samples with different properties in solid state.