Mechanical and electrical properties of mechanically alloyed nanocrystalline Cu–Nb alloys

Nanocrystalline Cu and Cu–Nb alloys were prepared by the consolidation of mechanically alloyed powder. The alloys show a microstructure with a grain size below 50 nm. The microstructure of the Cu matrix remains stable even at elevated temperatures of up to 900 °C, whereas the Nb precipitates coarsen during annealing. The mechanical strength as well as the electrical conductivity depend on the grain size of the Cu matrix, which can be influenced by the temperature of the heat treatment, i.e., a mechanical strength of about 1.6 GPa is measured for a Cu–10 at.% Nb alloy which shows an electrical conductivity of about 10% IACS (international annealing copper standard) at room temperature. The main contribution to the mechanical strength of the alloys is attributed to the grain boundary strengthening in Cu referring to the Hall–Petch relation, which is quantified. The grain boundaries are also found to influence considerably the electrical resistivity.