STUDY ON MICROHARDNESS OF BULK NANOCRYSTALLINE COPPER

Bulk nanocrystalline copper samples weighted 5 gram with average grain size d=25nm were synthesized by inert gas condensation and in situ co mpacting method. The microhardness study is carried out in this paper considering two influence factors of density and grain size. The speci mens with different densities and grain sizes were obtained through co mpacting the as-evaporated particles under pressures from P=0.5 to 2.5 GPa at room temperature and annealing the specimen as-compacted under 1 GPa at temperature fi om T=373K to 773K respectively. The results s how that the nanocrystalline copper specimens exhibit higher microhard ness than conventional coarse-grained copper, and the microhardness ri ses with the increase of compacting pressure and reaches a maximum val ue under P=2.5 GPa, which is six times as high as that of conventional copper. The specimen density also plays an important role on the micr ohardness of bulk nanocrystalline copper except for the grain size. (C ) 1997 Acta Metallurgica Inc.