Band-like microstructures and formation mechanism in directionally solidified Cu-1.0%Cr alloy

Three band-like microstructures, the α-Cu phase plane front plus eutectic structure, cellular α-Cu and coupled eutectic plus the α-Cu phase plane front, and cellular α-Cu plus eutectic structure, were observed in directionally solidified Cu-1.0%Cr hypoeutectic alloy at the growth rate ranging from 2 to 10 μm/s and the temperature gradient of 200 K/cm in liquid. The formation of band-like microstructures is related to the solute distribution ahead of solid-liquid interface, and the changes of the growth rate and alloy composition during directional solidification. In addition, with the increase of the liquid concentration ahead of the planar interface of α-Cu phase, the growth rate of the α-Cu phase plane front increased, but in the growth of coupled eutectic the growth rate decreased.