Thermodynamic Reassessment of the Binary Cu-Sn, Cu-P, and Sn-P and Ternary Cu-Sn-P Systems

The Cu-Sn-P phase diagram is essential for understanding the metallurgical phenomena of Cu-Sn bronze, brazing filler metals, and Sn-Cu lead-free solder. In this study, the solidus, liquidus temperatures and solubilities of P in the Cu-rich of the Cu-P system were determined using the electron probe micro-analyzer and differential scanning calorimetry. In addition, the thermodynamic assessment of the Cu-Sn, Cu-P, Sn-P, and Cu-Sn-P systems was carried out based on the results of previous studies and experiments of the current study. An associate-solution model was employed for the liquid phase, and an order/disorder model was employed for the bcc-based phase. The calculated phase diagrams and thermodynamic properties were in good agreement with the experimental data. The parameter set reproduced the Cu-Sn-P ternary phase diagrams without introducing ternary parameters into the liquid phase. Thus, the proposed model can reproduce the full-range of the compositional phase diagram of the Cu-Sn-P system.