Influence of a liquid structural change on the solidification of the alloy CuSn30

The effect of a liquid structural change on the solidification of the alloy CuSn30 is discussed. The temperature dependence of the electrical resistivity (ρ-T) of a CuSn30 (wt.%) melt was measured, and an abnormal change was found on the ρ-T curve within a range of 855°C to 1040°C, which suggests that the melt may have undergone a temperature-induced liquid-liquid structural transition (TI-LLST). The existence of the TI-LLST was verified by means of differential scanning calorimetry. Furthermore, the melt that experienced the TI-LLST needed higher undercooling to nucleate, and the eventual grain size was evidently refined. Analysis of the atomic bonding mechanism of the CuSn30 melt at temperatures above melting point suggest that the structural transition can be attributed to the destruction of the inherited chemical short-range orders or clusters, and that this destruction alone results in the homogeneity of the melt. In turn, the homogeneity of the melt inhibits the nucleation and growth of the primary phase, promotes a peritectic reaction, and eventually refines the solidification microstructures.