Peritectic transformation and primary α-dendrite dissolution in directionally solidified Pb–26%Bi alloy

Peritectic transformation is one of the main mechanisms during solidification of peritectic alloys, and accompanied with dissolution of primary phase. In the present work, the effect of solidification temperature on the peritectic transformation and dissolution of primary α-dendrite was investigated during directional solidification of Pb–26wt%Bi peritectic alloy. The resulting microstructures of the alloy in consideration of different solidification temperature have been investigated using optical microscopy. The volume fraction of peritectic β-phase and the average size of α-dendrite core were measured using image analyzing software SISC IAS V8.0. These results show that the increment in β-phase volume fraction and decrement in size of α-dendrite core first increase, then decrease with falling solidification temperature. These results can be explained from the viewpoint of a reduced solidification temperature leading to the rate of peritectic transformation first increases to a maximum, and then decreases.