Corrosion study and quantitative measurement of crystallite size of high strength aluminum hybrid composite developed via friction stir processing

This present study is centered on the corrosion behaviors and structural integrity of high strength aluminum-alloy 7075-T651 hybridized with carbonaceous coconut shell ash (CSA) and α+β titanium alloy powder in ratio of 50 : 50, fabricated during friction stir processing (FSP). The study examined the base metal – AA7075-T651 as well as the friction stir processed AA7075-T651 as control experiments. The Processing parameters used were plunge depth of 0.3 mm, travel speed of 20 mm/min, the tilt angle of 3° and rotational speed of 1500 min⁻¹. The corrosion characteristics were examined with the Potentiodynamic Polarization method in 3.5 % NaCl medium while crystalline phases were studied with x-ray diffraction (XRD). Results show that fabricated aluminum hybrid composite (AHC) AA7075-T651/coconut shell ash (CSA)/titanium-alloy has the highest percentage of inhibition performance efficiency (IPE) of 84.81 % resulting to 0.76938 mm/year corrosion rate and 356.51 Ω polarization resistance, whereas inhibition performance efficiency (IPE) for friction stir processed (FSPed) AA7075-T651 was 63.99 % while the base metal – AA7075-T651 was taken as the reference point. It was also revealed that the hybridized coconut shell ash (CSA)/titanium-alloy powder on AA7075-T651 enhanced the structural integrity, producing 38.5 nm crystallite size over friction stir processing (FSP) AA7075-T651 with 41.2 nm and the base metal with 48.7 nm crystallite size.