Synthesis behavior of nanocrystalline Al–Al 2O 3 composite during low time mechanical milling process

Abstract

In this work, four different volume fractions of Al 2O 3 (10, 20, 30 and 40 vol.%) were mixed with the fine Al powder and the powder blends were milled for 5 h. Scanning electron microscopy analysis, particle size analysis and bulk density measurements were used to investigate the morphological changes and achieving the steady state conditions. The results showed that increasing the Al 2O 3 content can provide the steady state particle size in 5 h milling process. It was found that increasing the volume fraction of Al 2O 3 leads to increasing the uniformity of Al 2O 3. Standard deviations of microhardness measurements confirmed this result. The XRD pattern and XRF investigations depicted that increasing the Al 2O 3 content causes an increase in the crystal defects, micro-strain and Fe contamination during 5 h milling process of nanocrystalline composite powders while the grain size is decreased. To investigate the effect of milling time, Al–30 vol.% Al 2O 3 (which achieved steady state during 5 h milling process) was milled for 1–4 h. The results depicted that the milling time lower than 5 h, do not achieve to steady state conditions.