Enhanced mechanical properties of in situ aluminium matrix composites reinforced by alumina nanoparticles

In situ fabrication of metal matrix composites has various advantages such as the formation of clean particle-metal interface with strong bonding. In this study, three types of metal oxides powders (commercial TiO2, commercial ZnO, and recycled Pyrex) were injected into a pure aluminium melt to fabricate in situ aluminium matrix composites. Through chemical reaction this process produces alumina nanoparticles which act as the reinforcing agent. The process steps investigated include liquid-state stir casting at 1123 K followed by a hot rolling process. SEM and FESEM microstructural characterizations, as well as EDAX analysis, were used to determine the reactions, which occurred between the molten aluminium and the metal oxides to form nano alumina particles as the reinforcement. Tensile and microhardness tests were also performed on the rolled composites, to identify the effect of metal oxide type and amount, on the mechanical properties of the produced composites. It was found that using recycled Pyrex crushed powders led to the formation of a uniform distribution and reinforcement of alumina nanoparticles, while fine-micron ZnO and especially TiO2 powders did not uniformly distribute in the melt.