MECHANICAL-PROPERTIES OF NANOCRYSTALLINE COPPER PRODUCED BY SOLUTION-PHASE SYNTHESIS

Nanocrystalline copper powder was produced by a NaBH4 reduction of CuC l in a simple solution phase room temperature reaction, Uniaxial hot p ressing in a closed tungsten die was used to compact powder into dense specimens. Samples were analyzed by x-ray diffraction, precision dens itometry, electron microscopy, energy dispersive x-ray analysis, and s elected area diffraction. Mechanical properties of the consolidated sa mples were determined by microhardness measurements, three-point bendi ng of rectangular specimens, and compression tests. Yield strength mea sured for nanocrystalline Cu in the present work was over two times th at reported in literature for Cu with comparable grain size and over f ive times that of conventional Cu. Restricted grain growth observed in the hot-pressed samples and improved mechanical properties are attrib uted to the presence of boron. A unique method of obtaining homogeneou s in situ nanosized reinforcements to strengthen the grain boundaries in nanocrystalline materials is identified.