Activity Measurement of the Constituents in Liquid Cu-Al, Cu-Mg and Cu-Ca Alloys with Mass-Spectrometry

摘要

The activities of the constituents in liquid Cu-Mg and Cu-Ca alloys have been determined by mass spectrometry in the temperature range from 790 to 1305K for Cu-Mg and 520 to 1250K for Cu-Ca system. The following conclusions can be obtained. 1) The activities exhibit negative deviation from ideality and this deviation becomes slightly smaller at higher temperature in both of Cu-Mg and Cu-Ca systems. 2) The activities observed in Cu-Mg alloy are in good agreement with the measured by Garg et al. The activities determined in Cu-Ca system show excellent agreement with the assessed by Risold et al. 3) The partial molar heats of mixing of constituents, and the integral heats of solution in Cu-Mg and Cu-Ca alloys are determined. The integral heats of solution shows the maximum exothermic value of approximately -9.7 kJ/mol at around X_(Cu)=0.5 in Cu-Mg and -7.2 kJ/mol at X_(Cu)=0.6 in Cu-Ca system. 4) RTln_γ(Mg) and RTlnγ_(Cu) in Cu-Mg system depend on temperature slightly and the alloy composition. On the other hand, RTlnγ_(Ca) and RTlnγ_(Cu) are identical with ΔH_(Ca) and ΔH_(Cu) in liquid Cu-Ca system and RTlnγ_(Ca) and RTlnγ_(Cu) are independent of temperature and depend only on the alloy composition.