Microstructural evolution of a heavily cold-rolled CuCr in situ metal matrix composite

The microstructural evolution of a Cu-15wt.%Cr in situ metal matrix composite has been investigated by means of scanning electron microscopy, analytical transmission electron microscopy, high resolution electron microscopy and energy-dispersive X-ray spectrometry. It is found that the dendritic Cr and equiaxed Cr in the as-cast state are mostly deformed into Cr ribbons after cold rolling to 89.8% reduction in thickness. In these heavily deformed Cr ribbons, ellipsoidal Cu-rich clusters with size around 1 nm were observed which have the same lattice as the Cr ribbons but different Cu concentrations from each other. Lattice distortion also exists around these Cu-rich clusters, though its extent varies depending on the Cu concentration in each cluster.