Synthesis of Mg–Al2O3 nanocomposites by mechanical alloying

Abstract

Mg–Al2O3 nanocomposite powders, with Al2O3 particles of 50nm size, were synthesized by mechanical alloying starting from a mixture of 70vol.% pure Mg and 30vol.% Al2O3 powders. A steady-state condition was obtained on milling the powder mix for about 20h, when the crystallite size of the Mg powder was about 10nm. The structural evolution during milling was monitored using scanning electron microscopy, energy dispersive spectrometry, and X-ray diffraction methods. The results showed that a mixture of Mg, Al2O3, and MgO phases were obtained on mechanical alloying. On annealing the milled powders at 600°C for 30min, a displacement reaction occurred between the Mg and Al2O3 phases, when the formation of a mixture of pure Al and MgO phases was observed. Also, a reaction occurred between the initial Mg powder and Al formed as a result of the displacement reaction, leading to the formation of Mg17Al12, Al0.58Mg0.42, and Al3Mg2 phases. Thus, the powder annealed after milling the Mg+Al2O3 powder mix for 25h consisted of Al, MgO and Al3Mg2 phases.