High temperature stabilization of a nanostructured Cu-Y2O3 composite through microalloying with Ti

The effects of minor additions (0.2, 0.4 and 0.8 wt%) of Ti on the thermal stability of both Cu nanograins and Y2O3 particles in nanostructured Cu-5 vol%Y2O3 composite powder particles were investigated via 1 h isochronal annealing at temperatures ranging from 300 to 1000 °C. It was found that a small amount addition of 0.4 wt%Ti effectively inhibits the coarsening of the Y2O3 particles during annealing at a very high homologous temperature of 0.87Tm, where Tm is the melting point of Cu, which, in turn, stabilizes Cu nanograins and retains the hardness value of the as-milled powder sample. However, this is in clear contrast with the significant decrease in hardness of the Ti-free and 0.2 wt%Ti doped milled powder samples annealed at the same condition, resulting from the coarsening of the Y2O3 particles and growth of Cu nanograins. The energy dispersive X-ray spectrometry elemental analysis shows that the stabilizing mechanisms responsible for the improved thermal stability of the Y2O3 particles are associated with the chemical reactions between Ti, O and Y2O3.