采用熔融玻璃净化与循环过热相结合的方法研究Cu-20%Pb亚偏晶合金的凝固组织，用BCT-LKT枝晶生长模型对深过冷凝固过程的热力学参数进行了计算，分析了过冷Cu-20%Pb亚偏晶合金的凝固机制。结果表明，在低过冷度下，Cu-20%Pb亚偏晶合金凝固组织由粗大的Cu枝晶和分布于枝晶间的Pb相组成。随着过冷度的增大，枝晶细化，Pb相分布均匀。但在不同的过冷度范围，凝固组织细化机制不同。当过冷度小于200K时，快速凝固阶段结晶潜热集中释放造成的温度回升引起枝晶大量重熔是枝晶细化的主要因素。过冷度大于200K时，枝晶高速生长导致枝晶各部位的不均匀收缩及枝晶骨架间液相的高速流动会使枝晶受力产生碎断。在此阶段，枝晶重熔和枝晶碎断共同作用使得枝晶发生细化。
The solidification microstructure of Cu-20%Pb hypomonotectic alloy was investigated by means of combination of melted glass denucleation and cyclical superheating. The variation of thermomechanical parameters related to solidification of undercooled Cu-20%Pb hypomonotectic alloy was calculated based on the BCT-LKT dendritic growth model, thus the solidification mechanism of the alloy was discussed. The experimental results shows that the microstructure of Cu-20%Pb hypomonotectic alloy combines α(Cu) dendrites with Pb phases distributed between them at little undercooling solidification. Dendrites get refined and uniformed as undercooling increases. It can be concluded that the reason of dendrite refinement at different undercooling is not same. The melt can be heated above the solidus temperature due to release of latent heat during rapid solidification of the undercooled melt, thus part of solidified dendrites can be melted and refined when the undercooling is smaller than 200K. When undercooling is high, the contraction of different parts of dentrites and flow velocity of the melt are so high that the dendrites are impacted and become fragmented. Thus when undercooling is above 200K, dentrites will be refined by dendrite remelting and dendrite fragmentation together.
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