Effect of Milling Time on the Synthesis of In-situ Cu-25 Vol. % WC Nanocomposite by Mechanical Alloying

This paper presents a study on the effect of milling time on the synthesis of Cu-WC nanocomposites by mechanical alloying (MA). The Cu-WC nanocomposite with a nominal composition of 25 vol.% of WC was produced in-situ via MA from elemental powders of copper (Cu), tungsten (W), and graphite (C). These powders were milled in the high-energy “Pulverisette 6” planetary ball mill according to the composition Cu-34.90 wt.% W-2.28 wt.% C. The powders were milled in the different milling times; 16 hours, 32 hours, and 48 hours at rotational speed of 600 rpm. The milling process was conducted under argon atmosphere by using a stainless steel vial and 10 mm diameter of stainless steel balls, with ball-to-powder weight ratio (BPR) 10:1. The as-milled powders were characterized by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). XRD result indicated the formation of WC after milling for 32 hours, and the peak broadening was observed at higher milling time. From SEM observations, the particle size of Cu-25 vol.% WC composites was gradually refined with increasing milling time until the homogenous microstructure was obtained at 48 hours of milling, even though there were still some unreacted W particles existed in the matrix. Increasing milling time resulted in smaller crystallite size and higher lattice strain of Cu. The overall result demonstrates that the longer milling time can be used to achieve WC reinforced copper matrix nanocomposite.