The synthesis, microstructure, hardness and thermal properties of bulk nanocrystalline Al produced by in situ consolidation with low-energy ball milling

Bulk nanocrystalline (nc) Al was produced by in situ consolidation of Al powder with low-energy ball milling at room temperature. Microstructure and thermal properties of Al subjected to ball milling were investigated by means of differential scanning calorimeter (DSC), differential thermal analyzer (DTA), transmission electron microscope (TEM), X-ray diffraction (XRD), and scanning electron microscope (SEM). As a result of long time milling, considerable energy has been stored in the powder particles which suffered a repetitive cold welding and fracture mechanism. It was found that the microhardness of Al was increased with the increasing of ball milling time. The highest microhardness (1372 MPa) was observed at room temperature in nanocrystalline Al in the experiment.