Effect of Milling Tools on the Microstructure and Property of Cu-Based Composites Prepared by Mechanical Alloying

Cu and Nb powders were used as starting materials to produce Cu-Nb and Cu-NbC-WC composites by mechanical alloying. X-ray diffraction, scanning electron microscopy, transmission electron microscopy observations and microhardness measurements have been used to study the effects of milling tools on the phase, microstructure and property of the composites. The results revealed that a single-phase nanocrystalline solid solution was obtained using stainless steel vials and balls (Alloy 1). Nevertheless, Cu-7 wt% Nb powders milled by tungsten carbon vials and balls exhibited an amorphous phase (Alloy 2). The as-milled powders were then vacuum hot-pressing sintered. The microstructure of sintered Alloy 1 consisted of Nb nanoparticles and Cu nanograins. Instead, Alloy 2 showed a microstructure with NbC nanoparticles and WC submicron-sized particles dispersed throughout the Cu matrix. Furthermore, Alloy 2 (similar to 322 HV) had a higher microhardness than Alloy 1 (similar to 302 HV).