The microstructural basis for the mechanical properties and electrical resistivity of nanocrystalline Cu-Al2O3

The mechanical properties and electrical resistivity of nanocrystalline copper reinforced by 1 vol.% and 5 vol.% of nano-alumina particles have been measured. The composites were prepared by ball-milling and consolidated by a combination of hot extrusion and HIPing. The uniaxial tensile and compressive strengths are comparable for each composite, and an elastic, ideally plastic response is observed. Shear bands, of width a few microns, accompany plastic deformation. A number of microstructural characterisation tools were used to reveal that grain boundary strengthening and dispersion strengthening are the dominant strengthening mechanisms. Nano-indentation measurements reveal a size effect in hardness. The electrical resistivity is almost double that of pure oxygen free copper and this is mainly ascribed to the presence of dissolved iron.