Microstructural evolution of the directionally solidified Cu-Cr in-situ composites

The microstructure and its evolution of directionally solidified Cu-Cr in-situ composites are investigated under the condition of the different solidification rates. The Cu-1.0 wt% Cr and Cu-1.7 wt% Cr in-situ composites respectively were prepared by the high temperature gradient directional solidification equipment. The microstructure is observed with metalloscope and SEM, and its component is analyzed by EDS. The results show that, the microstructures of the hypoeutectic Cu-1.0 wt% Cr alloy consists of primary α(Cu) phase and the rod-like or needle-like(α + β) eutectics, and the one of the hypereutectic Cu-1.7% Cr alloy is of α(Cu) phase, primary β(Cr) phase and (α + β) eutectics. The 1st cellular (dendrite) of α(Cu) phase thins gently and cellular (dendrite) spacing shortens gradually with the increase of the solidification rates. The (α + β) eutectics as the reinforce phase set in α(Cu) cellular or dendrite, and primary β(Cr) phase as particle distribute unevenly on α(Cu) matrix.