Dispersion hardening of metals by nanoscaled ceramic powders

Nanoscaled Al2O3-powders (n-Al2O3) with a median particle diameter of 14 nm are distributed in microscaled copper powders by ball milling in a planetary mill followed by uniaxially hot pressing. The microstructures of the samples are analysed by SEM and EDX investigations and the hardness of the specimens is determined before and after heat treatments of the composites. The results on the produced Cu/n-Al2O3 composites show that the nanoparticles are largely homogeneously distributed in the matrix grains, that the matrix grains are stabilised against growth even after heat treatments close to the melting temperature of Cu, and that the hardness of the sample is largely maintained after heat treatment. The results show that mechanical alloying of metal micropowders with oxide ceramic nanopowders can produce dispersion-strengthened materials. The mechanical alloying with n-powders can be easily applied to systems which cannot be dispersion-strengthened with n-oxide ceramics by other methods, e.g. internal oxidation. The last is shown by dispersion-strengthening of magnesium with n-Al2O3.