No abstract

No abstract

The current study focuses on the influence of varying wt% of nano-TiO2 particles (1%, 2% and 3%) on the microstructure, mechanical and tribological properties of AA7178 alloy matrix composite produced by stir casting method. The grain boundaries of the prepared composites were revealed using an optical microscope. The uniform distribution of nano-TiO2 particles in the alloy matrix was observed by scanning electron microscope. X-ray diffraction verified the existence of reinforced nano-TiO2 particulates in the samples, and microstructural images revealed a consistent distribution of reinforcements in the matrix. The formation of more refined grains from coarser grains was observed using electron backscatter diffraction analysis. The texture analysis revealed the presence of dominant A and A2* components with a maximum intensity of 5.137. Fractography disclosed that the reinforcements did not peel away from the alloy matrix, and the form of failure was both brittle and ductile. Abrasive wear was observed for the worn-out surface of the nanocomposites. It was observed that by increasing wt% of TiO2 nanoparticles, the mechanical and tribological properties of the alloy matrix increased compared to the base alloy. The optimum mechanical and tribological properties were obtained at 2 wt% of nano-TiO2 particulates.

The interaction of pre-strain and corrosive medium can either accelerate or decelerate material failure. In the present study, the electrochemical activity of forged preforms is assessed by the open circuit potential (OCP), potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). A powder metallurgy route was used to fabricate Al-5.6Zn-2Mg alloy with 0.8 relative density. The fabricated alloy was subjected to hot axial forging at various temperatures such as 300°C, 400°C, and 500°C under a 0.005/s strain rate. The microstructure and corrosion morphologies of sintered and forged preforms under various deformation levels and temperatures were investigated using scanning electron microscopy (SEM). After the deformation process, flow behavior, densification behavior, and electrochemical behavior are studied. Deformation behavior (true strain was linked to the local mechanical properties (hardness) and electrochemical properties (pitting potential (Epit)). The potentiodynamic polarization results showed that as the degree of deformation increased, there was a decrease in the corrosion current density and an increase in the pitting potential. Al-5.6Zn-2Mg corrosion resistance significantly improved with a degree of deformation and temperature. A mathematical model relating corrosion rate and true strain for various deformation temperatures is developed to estimate the corrosion rate for any true strain. Pitting corrosion was observed in deformed preforms as a corrosion mechanism. Because of the increased deformation degree and temperature, the corrosion morphologies showed the closing of pores.

No abstract