Synthesis and Characterisation of Al-Zn-Mg /3 wt. %Al2O3 Nanostructured Composite using a Pre-milled Matrix Through Mechanical Alloying

Al-Zn-Mg/3 wt-% Al2O3 nanostructured composite powder was synthesized through Mechanical Alloying (MA). At first, the 7014 alloy matrix constituents were milled in a planetary ball mill for 20 hours. Then, 3 wt.% µ-Al2O3 particles were added to the pre-milled matrix and the nanostructured composite powder was produced at different MA times to investigate the effects of MA time on the characteristics of the produced composite powders such as morphology, crystallite size, lattice strain and microhardness. The characterization results proved that synthesizing nanostructured composite powder with a low amount of micrometric reinforcements in addition to pre-milled micrometric matrix is possible. Also, synthesis of the nanostructured composite powder with the minimum crystallite size of 24 nm and the minimum mean particle size of 5 µm was confirmed. Moreover, the steady state occurred after around 20 hours milling and further milling did not affect the powder characteristics excluding crystallite size, lattice strain and microhardness. In addition, sinterability of the composite powders increased with increasing the milling time due to decreased average particle size. However, after the steady state, the sinterability did not change.