Electro-discharge consolidation applied to nanocrystalline and RSP/MA powders

Electro-discharge consolidation (EDC) was applied to consolidate nanocrystalline intermetallic powders and RSP Al alloy powders. Because EDC employs a high-voltage, high-density current pulse discharged from a capacitor bank to powders under external pressure, one can take advantage of the basic characteristics of EDC to preserve the microstructure inherent in the starting powder, remove oxide films on the prior powder particle surface to enhance the bonding, densify to the bulk and thereby improve the mechanical properties. Mechanically alloyed Nb-23 at.% Al was consolidated to a density of 99% theoretical, and the nanocrystalline state (less than 35 nm grain size) was preserved. Because of such a small grain size, the EDC consolidates exhibit a negative Hall–Petch relation. Another example is presented for RSP and MA powders of an Al alloy, in which the magnitude of ductilities exhibited by EDC bulks clearly indicates that the oxide film on the powder particle surface has been completely removed.