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 SiO_² by mass spectrometry. Since the vapor pressure of Si is relatively low, the formation reaction of volatile suboxide, 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 SiO_² saturated CaO-Al_²O_³-SiO_² 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.