Bulk nanostructured materials produced by mechanical alloying and spark plasma sintering

For about a decade we have used mechanical alloying processes to produce powder materials which were subsequently consolidated by means of spark plasma sintering. The mechanical alloying process ensured the production of nanostructured powder particles, while the application of plasma sintering was intended to achieve densification in a short time and, concurrently, to avoid excessive coarsening of the microstructures in the sintered materials. Materials produced in this way included intermetallic compounds (Co2Ti-Co3Ti, NiAl, and others), as well as different composite materials; in addition, nanostructured copper and Cu-Ni alloys were also produced. As a rule, the combination of mechanical alloying and fast sintering has yielded materials with grain sizes typically below 100 run. As a result of these refined structures, high mechanical strengths have been observed in most cases in which porosity levels were low. These features of the materials so produced are illustrated here by selected results from two nanostructured intermetallic systems (Co-Ti, NiAl) and from nanocrystalline Cu-Ni alloys.