DYNAMIC CONSOLIDATION OF METASTABLE NANOCRYSTALLINE POWDERS

Nanocrystalline metal powders synthesized by mechanical alloying in a ball mill resulted in micron-sized powder particles with a nanosized ( 5 to 25 nm) substructure. Conventional consolidation methods resulted in considerable coarsening of the metastable nanometer crystallites, b ut dynamic consolidation of these powders using explosive techniques p roduced fully dense monoliths while retaining the 5- to 25-nm substruc ture. Numerical modeling, used to guide the experimental phase, reveal ed that the compression wave necessary for suitable consolidation was of the order of 10 GPa for a few tenths of a microsecond. The consolid ation process is described, and the retention of the metastable nanost ructure is illustrated.