STRUCTURE AND MECHANICAL-PROPERTIES OF NANOCRYSTALLINE AG MGO COMPOSITES/

Nanocrystalline Ag/MgO composites were prepared by the ultrafine-powde r-compaction method. The structure was investigated for the first time by high-resolution electron microscopy. Nanometre-sized Ag grains and MgO grains in the composites bonded directly without any intermediate phase layer. Certain preferred orientation relationships were observe d between the Ag and MgO grains. The nanocrystalline Ag/MgO composites retained their grain size during annealing up to 873 K. Vickers micro hardness measurements were performed on the as-compacted and annealed specimens. Generation and propagation of cracks were less active in th e nanocrystalline Ag/MgO composites than in a single-phase nanocrystal line MgO. The Vickers microhardness of the nanocrystalline Ag/MgO comp osites remained up to 1073 K. Hot-pressing deformation tests showed th at the nanocrystalline Ag/MgO composites deformed plastically at 1073 K.