Effects of Process Temperature and Reinforcement Ratio on the Properties of 7075 Aluminium-Y2O3 Rare Earth Oxide Composites Fabricated by Hot-Pressing

Abstract

In this study, composites were fabricated at 1, 5, 10 wt.% Y2O3 ratios by hot-pressing. The fabrication process was performed at two different temperatures, 450 and 500 degrees C, under an argon atmosphere for 30 min at 200 MPa pressure. The microstructure properties were investigated by SEM, EDS and XRD analyses. Furthermore, Archimedes and Vickers hardness tests were performed to determine the density, porosity and hardness properties. Electrochemical corrosion properties were determined using potentiodynamic polarization and electrochemical impedance spectroscopy tests. Microstructural analysis showed that magnesium and copper in the matrix exhibited a tendency to segregate toward the reinforcement-containing regions. Moreover, the segregation of the alloying elements provided an enhanced matrix-reinforcement interaction and formation of in-situ phases. On the other hand, the aging response of the 7075 matrix was retarded owing to magnesium and copper segregation, and the highest hardness values were obtained with 163.1 and 168.4 HV0.3 in the unreinforced samples. Electrochemical corrosion tests demonstrated that 1 wt.% Y2O3 addition improved the corrosion properties of the composites. Also, increasing Y2O3 ratio deteriorated corrosion behavior owing to increasing elemental segregation and formation of intermetallic in-situ phases. Additionally, it was revealed that 1 wt.% Y2O3 containing composite produced at 500 degrees C exhibited favorable microstructure, hardness and corrosion properties.