Nucleation transitions in undercooled Cu70Co30 immiscible alloy

High temperature differential scanning calorimetry (DSC) is applied to undercool and crystallize melts of a Cu70Co30 alloy into the metastable miscibility gap. The kinetic prefactor Γ and the activation energy ΔG* of the nucleation rate are determined based on the statistical analysis within classical nucleation theory. The value of Γ reaches 2.64 (0.21) × 1037 m−3 s−1, which is close to that of the value for homogenous nucleation and much larger than that of undercooled pure Co melts. The value of ΔG* is estimated to be 67 (2.5) kBT which is also higher than that of undercooled pure Co melts. The nucleation of the crystallization of the Co-rich phase is governed by homogeneous nucleation or conditions that are indistinguishable from homogeneous nucleation and the Cu-rich liquid phase effectively prevents the occurrence of heterogeneous nucleation for the nucleation of the Co-rich phase in the liquid-phase separated Cu70Co30 alloy. The results indicate that nucleation of the crystalline phase is sensitive...