Fig. 13: Miscibility gap in the Cu-Co system. Left: The Co-Cu phase diagram optimized by CALPHAD; the metastable miscibility gap in the liquid is given by the binodal (dashed line), which separates the regions of homogeneous liquid L and metastable liquids L1 and L2.

When the homogeneous liquid L is undercooled into the metastable miscibility gap, L demixes into the metastable liquids L1 and L2 with their concentrations given by the binodal and the actual temperature. Solid lines indicate stable phase boundaries. Data points are experimental points from the literature, the sources are given in ref. ⁶⁸. L, αCo, and Cu indicate the respective phases of the stable phase diagram. The dotted line in the αCo-region indicates the magnetic phase transition. Right: Cross section of a Cu₆₀Co₄₀ sample processed using differential scanning calorimetry (DSC). Backscattered electron image where dark regions are Co-rich and bright regions are Cu-rich representing the metastable L1 and L2 liquids. The arrow indicates a Cu-rich droplet within the solidified L1 phase.