Sinter densification of nanocrystalline composite W-Cu powder

High-energy ball milling (HEBM) was used to prepare composite W-30 w/o Cu powder consisting of well-dispersed nanometer-sized tungsten particles in a copper matrix. Densification of compacts sintered at two heating rates (7.6°C and 10°C/min), below and above the melting point of copper, was monitored. Optical and electron metallography and X-ray diffraction were utilized to characterize microstructures, to determine the tungsten and copper grain sizes, and to identify constituents in the sintered samples. A density of about 72% at the pore-free level was obtained by solid-state sintering. Tungsten and copper nanocrystals were observed to grow as temperature and time increased. The growth of nanometer-sized particles of tungsten inside the composite particles was also detected. Copper spread before reaching its melting point, filling pores between the composite powder particles. Sintering at 1.200°C for 60 min resulted in a final density of about 95% of the pore-free level, with an attendant homogeneous microstructure.