Suppressing Al2O3 nanoparticle coarsening and Cu nanograin growth of milled nanostructured Cu-5vol.%Al2O3 composite powder particles by doping with Ti

Both the coarsening of Al2O3 nanoparticles and the growth of Cu nanograins of mechanically milled nanostructured Cu-5vol.%Al2O3 composites with, and without, trace amounts of Ti during annealing at 973 K for 1 h were investigated. It was found that doping with a small amount of Ti (e.g. 0.2 wt%) in a nanostructured Cu-5vol.%Al2O3 composite effectively suppressed the coarsening of Al2O3 nanoparticles during exposure at this temperature. Further, the Ti addition also prevented the concomitant abnormal growth of the copper grains normally caused by the coarsening of the Al2O3 nanoparticles. Energy dispersive X-ray spectroscopy analysis of the Al2O3 nanoparticles in the annealed Cu-5vol.%Al2O3-0.2wt%Ti sample suggested that the Ti atoms either diffused into the Al2O3 nanoparticles or segregated to the Cu/Al2O3 interfaces to form Ti-doped Al2O3 nanoparticles, which was more stable than Ti-free Al2O3 nanoparticles during annealing at high homologous temperatures.