Melting behavior and origin of strain in ball-milled nanocrystalline Al powders

Ball-milled aluminum powders have been investigated by differential scanning calorimetry and high resolution X-ray line profile analysis. Ball-milling was carried out for different milling times ranging from 45 min to 32 days. The milling time dependence of the average grain-size and of the density of lattice defects, mainly dislocations, were determined by the modified Williamson-Hall and Warren-Averbach procedures based on the dislocation model of mean square strain. Characteristic grain sizes of ball-milled Al-powders decreases with increasing milling time and simultaneously, the grain-size distribution becomes sharper.