  A complex study of aging kinetics for both coarse-grained and nanostructured
by severe plastic deformation Cu -- 2 wt% Be alloy is reported. It is shown
that aging of a coarse-grained alloy leads to continuous formation of nanosized
CuBe body centred cubic (bcc, CsCl -- type) semi-coherent particles with the
{220} Cu // {200} CuBe crystallographic orientation relationship. These
particles created significant internal stress fields and became obstacles for
dislocation glide that resulted in a change in the hardness from 95 Vickers
hardness (HV) for the solubilized alloy to 400 HV for the aged one. The severe
plastic deformation led to the formation of a single-phase nanograined
microstructure with an average grain size of 20 nm and 390 HV. It was found
that this grain size was slightly driven by grain boundary segregation. Further
aging of the nanocrystalline alloy led to the discontinuous formation of
precipitates on the former Cu grain boundaries and skipping of metastable
phases. Significant age hardening with a maximum hardness of 466 HV for the
aged nanostructured alloy was observed. Mechanical tests result revealed a
strong influence of microstructure and further aging on strength capability of
the alloy for both coarse-grained and nanostructured alloy. A good thermal
stability in the nanostructured alloy was also noticed. Theoretical
calculations of the hardness value for the CuBe phase are provided. It was
shown that Be as a light alloying elements could be used for direct change of
microstructure of severely deformed copper alloys.
