Activity Measurement of the Constituents in Liquid Cu–Al Alloy with Mass-Spectrometry

A mass spectrometer has been used to study activities of the constituents in liquid Cu–Al alloy. According to Belton-Fruehan’s treatment, activities and heats of mixing have been able to be determined from a series of measurements of the ratio of the ion current intensities of the solution components. The activities in the Cu–Al system were found to be in excellent agreement with the values recommended by Hultgren et al. The activities exhibited negative deviation from ideality and the terms of RTlnγAl and RTlnγCu were almost independent of the temperature within the present experimental range. Partial molar and integral heats of mixing of the liquid Cu–Al system were also estimated.