Activity measurement of silicon in molten Cu-Si binary alloy

Abstract

The activity of Si in molten Cu-Si alloy was determined by a new experimental technique, that is, the combination of chemical equilibration technique and mass spectrometry. The ion current ratio of SiO to Cu at 1 600-1 700 K was measured for Cu-Si alloy equilibrated with SiO2 by mass spectrometry. Since the vapor pressure of Si is relatively low, the formation reaction of volatile sub-oxide, SiO, was utilized in the present work. The activity coefficient of Si in liquid copper at 1 623 K was also determined by equilibrating a Cu-Si alloy with SiO2 saturated CaO-Al2O3-SiO2 slag in a graphite crucible under CO atmosphere. From these results, the activity coefficient of Si in copper at 1 600-1 700 K was determined. The thermodynamic property of Cu-Si alloy was assessed and it was confirmed that the present work agreed with the reported phase diagram of Cu-Si binary system.