Microstructure of directionally solidified Cu-Cr composites

Cu-Cr composites were prepared by self-made directional solidification equipment with the high temperature gradient and double-zone heating. The microstructural evolution was investigated during the directional solidification with the different solidification rate for Cu-1.0%Cr, Cu-1.7%Cr and Cu-5.6%Cr alloy, respectively. It is shown that for the hypoeutectic Cu-1.0%Cr alloy, the general microstructure consists of primary α(Cu) phase and the rod-like or needle-like (α-β) eutectics, and for the hypereutectic Cu-1.7%Cr and Cu-5.6%Cr alloys, α(Cu) phase, primary β(Cr) phase and (α+β) eutectics coexist. With the increase of the solidification rate, the morphology evolution of every phase is that first cellular (dendrite) of α(Cu) phase thins and cellular (dendrite) spacing shortens gradually, (α+β) eutectics set in α(Cu) cellular or dendrite, and primary β(Cr) phase distributes unevenly on α(Cu) matrix, whose morphology undergoes the change from dendrite to particle.