Novel preparation of big bulk-nanocrystalline Cu in large quantities

The micrometer-sized Cu powder produced on commercial scale was compacted under pressure of 1.0-2.0 GPa and at room temperature,and the nanocrystalline(nc) Cu with diameter of 10 mm and thickness of 8 mm, relative density of 99.4% of the theoretical density for pure Cu (8.96 g/cm(3)), and mean grain size of 34-43 nm and microstrain of 0.16%-0.19% was obtained. The compacting process was analyzed with HUANG Pei-yun equation and the microstructure and properties of ne Cu were studied by XRD, SEM, PAS, MHV2000 mircrohardness tester and Datron 1081-type electrometer. The results show that the grain size of nc Cu samples is correlated with compacting pressure, the microhardness is 1.14-1.27 GPa which is about two times larger than that of the coarse-grained polycrystalline Cu, but the relationship between microhardness and grain size do not obey Hall-Petch equation strictly. The electrical resistivity of the specimens is 5.1 x 10(-7) Omega.m, larger than the coarse-grained Cu materials by a factor of 29, the mean lifetime of positron-annihilation is (172.8 +/- 0.8) ps. The cost of the method of fabrication for big-sized nc material is much lower than that of any others. This method has the advantages such as the lowest cost, largest output and volume as well as highest density over all other methods so far.