In-situ fabrication and characterization of ultrafine structured Cu-TiC composites with high strength and high conductivity by mechanical milling

In this study, copper-based composites containing nanoscale TiC with high strength and high electrical conductivity (712 MPa and 72% IACS) were produced by a newly developed mechanical milling process. As-milled powder mixtures were investigated by X-ray diffraction (XRD) analysis. The results indicated that the lattice parameters of copper were increased with progress of milling due to the formation of solid solution of Cu (Ti, C). There was no transformation of Ti and C into TiC phase during the high energy milling process. It was found that the TiC particles were firstly formed during the sintering process. The effects of SPS parameters including sintering temperature and pressure on electrical and mechanical properties of sintered samples were systematically investigated. The heat treatment process after SPS was found to increase the electrical conductivity greatly as the proceeding reaction of Ti/C results in an extremely low Ti concentration in Cu matrix. Moreover, an obvious drop in microhardness was observed. The strength was slightly improved by the following hot pressing, while there was no obvious change in electrical conductivity. The microstructure evolution during the entire developed process was analyzed by means of Electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The formed TiC particles were homogeneously distributed in copper matrix. Furthermore, the ultrafine-grained (UFG) structure developed by the present process could maintain stable because of the Zener pinning effect caused by nanoscale TiC particles located at grain boundaries.