The microhardness of nanocrystalline silver

Abstract The microhardness of nanocrystalline Ag, synthesized by inert gas condensation and in-situ compaction, and the effects of both grain size and compacting pressure on the hardness were studied. The results show that the microhardnesses of all the nanocystalline Ag specimens compacted under the pressure range from 0.15 to 1.80 GPa are greater than that of polycystalline Ag. No effect of the strain within the specimens, introduced by the compaction process, on the microhardness was detected. However, the microhardness did increase with increase of pressure and density. Moreover, the influence of grain size on the microhardness was well described by a normal Hall-Petch relation in the grain size range investigated (from 17 nm to 105 nm). In the cases where its microhardness increased, being accompanied by an increase of its grain size, experimental results indicated that this deviation from Hall-Petch relation was related to densification of nanocrystalline Ag, not implying that an inverse Hall-Petch relation exists.