Phase Equilibria in the Al-Sn-Co Ternary System

The isothermal sections of the Al-Sn-Co ternary system at 800 °C and 1000 °C were constructed by twenty-nine key samples and two solid–liquid diffusion couples using electron probe microanalysis and x-ray diffraction analysis. The results show that: (1) No ternary intermetallic compound was found in this ternary system at 800 °C and 1000 °C. (2) The solid solubility of Sn in the Al-Co binary compounds is very small. (3) As-cast Al₄₇Sn₄₇Co₆, Al₄₆Sn₄₆Co₈ and Al₄₅Sn₄₅Co₁₀ (at.%) alloys exhibit the separated macroscopic morphologies. The reason is that the addition of Co can significantly promote the metastable liquid-phase separation in Al-Sn binary system. The newly determined phase equilibria may contribute to thermodynamic assessment and development of Al-based alloys.