Influence of Cooling Rate on Solidification and Segregation Characteristics of Cu-Ni-Si Alloy.

Differential scanning calorimetry (DSC) and confocal scanning laser microscopy (CSLM) were used to investigate the effects of different cooling rates on the solidification and segregation characteristics of Cu-Ni-Si alloy. The microstructures were characterized by electron probe microanalysis and scanning electron microscope. The effects of cooling rate on segregation degree, grain size, solidification temperature and secondary dendrite spacing (λ₂) were analyzed, and the correlation function was established. The results show that the characteristic temperature of DSC phase transformation is similar to the characteristic temperature of CSLM in situ microstructure evolution. Increasing cooling rate can reduce segregation degree and refine grains. The relationships between cooling rate and crystallization temperature (T_L→S) and secondary dendrite spacing (λ₂) with cooling rate are as follows: T_L→S = 176 × exp(− v/17.6) + 891 and λ₂ = 63 × v^−0.236, respectively. The above relations were applied to predict the solidification microstructure characteristics produced by twin-roll strip casting and ingot casting processes, and the predicted results are in good agreement with the experimental values. The advantages of grain refinement and segregation improvement and its optimization mechanism of twin-roll strip casting have been clarified. [ABSTRACT FROM AUTHOR]