The activation of deformation mechanisms for improved tensile properties in nanocrystalline aluminum

We report tensile properties and TEM observations of in situ consolidated bulk nanocrystalline Al with an average grain size of 29 nm. The nanocrystalline Al is synthesized using a combination of cryogenic and room temperature ball milling. This nanocrystalline Al exhibits extremely high tensile strength, strain hardening rate, and ductility when compared with the conventional coarse-grained commercially pure Al. The tensile strength of this bulk nc Al is at least ten times higher than that of the coarse-grained Al with a total elongation of 10%. These results demonstrate the dependence of the extraordinary tensile properties on the grain size, dislocation activities in the large nanograins, and the deformation twinning controlled by partial dislocations and stacking faults in the nanograins with relatively small grain size.