250 °C isothermal section of ternary Sn-In-Cu phase equilibria

Ternary Sn-In-Cu alloys are prepared and equilibrated at 250 °C for 2 to 20 weeks. The phases formed in these alloys are experimentally determined. The 250 °C Sn-In-Cu isothermal section is established according to the phase equilibrium information obtained in this study and that of the three constituent binary systems. It has eight single-phase regions, namely liquid, δ₁-Cu₄₁Sn₁₁, ε-Cu₃Sn, δ₂-Cu₇In₃, η-(Cu₆Sn_5, Cu₂In), Cu₁₁In₉, Cu₂In₃Sn, and α-(Cu) phases, 14 two-phase regions, and seven three-phase regions. In the Sn-In-Cu system at 250 °C, the η-Cu₆Sn₅ and η-Cu₂In phases form a continuous solid solution and the ternary Cu₂In₃Sn compound is observed. The δ₁-Cu₄₁Sn₁₁ phase is stabilized at 250 °C with the introduction of indium although it transforms into α-(Cu) and ε-Cu₃Sn phases via a eutectoid reaction around 350 °C in the binary Sn-Cu system. Except for the Cu₁₁In₉ phase and the Cu₂In₃Sn ternary compound, the other binary compounds all have significant indium and tin mutual solubilities.