Investigation of two-phase microstructure during directional solidification of Pb-30wt%Bi peritectic alloy

Directional solidification experiments were conducted on Pb-30 wt%Bi peritectic alloy to investigate the two-phase microstructure at various growth rates and diameters of samples, and the formation of two-phase microstructure and the micro-scale were also studied. The experiment results show that the transition of the structure from cellular primary α phase and inter-cellular peritectic β phase to dendritic primary α phase and inter-dendritic peritectic β phase was presented with increasing the growth velocity from 1 μm/s to 100 μm/s. Whereas the incomplete banded structure and the oscillatory structure were observed in sample with diameter of 1.8 mm and 7 mm as the growth rate V ≤ 0.5 μm/s, respectively. It is also demonstrated that the primary dendrite arm spacing of α phase coincides with the equation of λV ^0.16= 241.0μmV ^1.16sV ^-0.16, which shows a good agreement with Hunt model and Trivedi model.