Ultralight Functionally Graded Hybrid Nanocomposites Based on Yttrium and Silica-Reinforced Mg10Li5Al Alloy: Thermal and Tribomechanical Properties.

Despite the amazing properties of lightweight Mg 10 Li 5 Al alloy, its use in industrial applications is highly limited due to its low mechanical properties, wear resistance, and coefficient of thermal expansion (CTE). In this context, this work aimed to improve the above properties without sacrificing the important benefit of this alloy being lightweight. Therefore, function grade composites (FGCs) were prepared based on the Mg 10 Li 5 Al alloy reinforced by yttrium (Y) and silica fume using the powder metallurgy technique. Then, the nanocomposite's microstructure, mechanical properties, artificial aging, wear resistance, and thermal expansion were examined. The results indicated that the precipitation (MgAlLi 2 ), softening (AlLi 2 ), and Mg 24 Y 5 phases were formed in high-reinforced samples during high-energy milling. Furthermore, the addition of reinforcements accelerated the decomposition from the MgAlLi 2 phase to the Al-Li phase (softening point). For the layer containing the highest reinforcement content, microhardness, strength, and Young's modulus improved up to 40, 22.8, and 41%, respectively, due to the combined effect of the high strength of silica fume and the dispersion strengthening Mg 24 Y 5 phase. Meanwhile, the same sample exhibited a remarkable improvement in wear rate and the CTE value to about 43 and 16.5%, respectively, compared to the non-reinforced alloy.