Preparation of gradient material in Sn–Cd peritectic alloy using rotating magnetic field

•Gradient material was obtained by using RMF in Sn–0.75 wt%Cd alloy.•Gradient material was obtained by using RMF in Sn–1.6 wt%Cd alloy.•Formation conditions of gradient material in peritectic alloy are presented.

Directional solidification experiments have been conducted in Sn–0.75 wt%Cd and Sn–1.6 wt%Cd peritectic alloys with and without rotating magnetic field (RMF) to study the preparation of gradient material in peritectic alloy at low growth velocity. Under the influence of RMF, a gradient material in which the microstructure changes from cellular primary phase to planar primary phase along the radial direction was obtained when Sn–0.75 wt%Cd alloy was solidified with a temperature gradient of 8.3 K/mm and a growth velocity of 4 μm/s. Another type of gradient material in which the microstructure changes from cellular peritectic phase to cellular primary phase along the radial direction was obtained under the influence of RMF when Sn–1.6 wt%Cd alloy was solidified with a temperature gradient of 7.2 K/mm and a growth velocity of 5 μm/s. On the other hand, no gradient material was obtained when Sn–1.6 wt%Cd alloy was solidified with a temperature gradient of 6.7 K/mm and a growth velocity of 2.5 μm/s under the influence of RMF. Based on the constitutional undercooling criterion and formation conditions of banded structure, the formation mechanism of those gradient materials is discussed and a simple formation condition of gradient material is presented.