Synthesis and characterization of mechanically alloyed cerium oxide reinforced Al-4.5Mg alloy composite

Al-4.5Mg-0.5Mn alloy powders were mechanically alloyed by the addition of 1-3 wt.% cerium oxide (CeO2) nanoparticles using a planetary ball mill under a dry argon atmosphere. A milling speed of 300 rpm and ball to powder ratio of 20:1 was used for all samples. An optimum milling time of 20 h was chosen considering the morphological and structural changes in the milled powders. The composite powders were consolidated via vacuum hot pressing at 515 degrees C. Mechanical properties were evaluated by hardness and compression tests. The evolution of the structure and microstructure during the milling process was studied using X-ray diffraction and field emission scanning electron microscopy, respectively. The corrosion behavior of the samples was investigated by potentiodynamic polarization testing in a standard 3.5 % chloride salt solution and assessed in terms of pitting potential and passivation range. CeO2 reinforced mechanically alloyed Al-4.5Mg exhibited a major improvement in its hardness and compressive strength compared to the un-reinforced base alloy, i.e. 40 and 50% increment respectively. Nevertheless, the most important effect of CeO2 incorporation was observed in the pitting resistance of the alloy.