Evaluating the microstructural and mechanical properties of TiO2/AA7075 metal matrix nanocomposite via friction stir processing

Abstract This study investigates the effect of TiO₂ nanoparticle reinforcement based on volume ratio on the mechanical properties and microstructure of AA7075 aluminum alloy processed by friction stir processing (FSP). Samples with varying TiO₂ contents and blind hole spacings (5 mm, 7.5 mm, and 10 mm) were analyzed. Results show that optimal TiO₂ dispersion, achieved at a 5-mm spacing (Sample T1), significantly enhances hardness (96.6 HV), ultimate tensile strength (506 MPa), and ductility (9.7% elongation). Microstructural analysis reveals grain refinement and improved fracture toughness due to nanoparticle-induced crack growth suppression. However, higher TiO₂ concentrations lead to increased brittleness. The study highlights the importance of controlling nanoparticle distribution and process parameters to maximize mechanical performance, concluding that a balance between reinforcement concentration and dispersion is essential for optimizing the properties of AA7075-TiO₂ nanocomposites.