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.