Microstructures of 3%C-Cu composite powders prepared by mechanical milling

To obtain C-Cu composite powders with excellent microstructures, which are beneficial to such subsequent processes as pressing, sintering and extrusion, 3%C-Cu (mass percent) composite powders were prepared by mechanical milling. Their microstructures dependent on milling time were investigated with the scanning electron microscopy (SEM), back-scattered electron images and X-ray diffraction (XRD). The results show that by increasing the milling time, the particle shape of Cu changes from dentritic to laminal, then to nubby and to near-spherical finally. The diffraction peak of graphite disappears after mechanical milling for 2 h. The microstrain of Cu in composite powders increases while lengthening the milling time. The grain size of Cu in composite powders is about 20 nm after milling for 3 h, which confirms that the grain can be refined effectively with this technique.