Effect of nano-size Al2O3 reinforcement on the mechanical behavior of synthesis 7075 aluminum alloy composites by mechanical alloying

Reinforcing aluminum matrix with much smaller particles, submicron or nano-sized range, is one of the key factor in producing high-performance composites, which yields improved mechanical properties. High-energy ball milling was successfully employed to synthesize nano-crystalline Al7075 alloy powders reinforced with 1, 3 and 5 vol.% Al2O3 at nano-size level. Hot pressing was employed to consolidate the green powder metallurgy products. The nano-composite powders were characterized by SEM, TEM, and XRD. Using Williamson–Hall equation, crystallite size and lattice strain of various Al7075 composite powders were estimated with broadening of XRD peaks. XRD results showed that the crystallite size of aluminum reached 42.30, 36.25 and 32.22 nm, respectively, after 20 h milling in case of Al7075/1, 3, and 5 vol.% Al2O3 nano-composite powder with uniform particle size distribution. TEM observation confirmed the nano-crystalline nature of Al7075/5 vol.% Al2O3 milled powder. Mechanical measurements showed that the hardness and ultimate tensile strength of the Al7075–nano Al2O3 tend to increase with increasing nano Al2O3 volume content at the expense of tensile ductility.

Graphical abstractTEM image of mechanically alloyed Al7075/5 vol.% Al2O3 nano-composite powder showing lattice fringes after 20 h of high-energy ball milling. The bright areas in the micrograph correspond to nano-sized reinforcement crystallites. The inset in the figure represents the selected area diffraction pattern with continuous rings, which confirms the nano-crystalline nature of the composite powder.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Nano-composite Al7075–Al2O3 was made by mechanical alloying successfully. ► Volume fraction increases, reduction in grain size and increase in lattice strain. ► Increases of Al2O3 lead to reduction in toughness thus increase tendency of fracture. ► Ultimate stress of Al7075 improved about 60.5% with incorporation of 5 vol.% Al2O3. ► Hardness of the nano composites found increased with increased filler content.