The effect of Mg content on microstructure and mechanical properties of Al–xMg/5Al2O3 nanocomposite prepared by mechanical alloying

The effect of Mg content on the microstructure and mechanical properties of Al–xMg/5 wt.% Al2O3 (x = 0, 5, 10 and 20 wt.%) powder mixtures during milling was investigated. For the binary Al–Mg matrix, the predominant phase was an Al–Mg solid solution. With the increment of Mg to 20 wt.% the crystallite sizes of 20 h milled powders diminish from 47 to 21 nm and lattice strains increase from 0.45 to 0.9% caused by Mg atomic penetration into the substitutional sites of the Al lattice. At the same condition an increase in lattice parameter was observed due to solid solution formation and grain refinement. With up to 20 wt.% Mg (for 20 h milled composites) microhardness increases from 118 to 218 HV caused by the increment of the Mg concentration and dislocation density as well as the decrease of the crystallite size.

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► Steady-state situation occurred for 10 and 20 wt.% Mg after 20 h milling.
► The predominant phase after 20 h milling was an Al–Mg solid solution.
► The Mg content has remarkable effects on grain refinement process and lattice strain.
► The lattice parameter increases due to solid solution formation and grain refinement.
► The hardness increment is caused by the increase of the Mg content.