Microstructure, hardness and corrosion behaviour of friction-stir processed AA5083

Abstract

Purpose The purpose of this study is to refine the microstructure and improve the corrosion behaviour of aluminium alloy AA5083 by subjecting it to friction stir processing (FSP). Design/methodology/approach FSP trials are conducted as per central composite design, by varying tool rotation speed, tool traverse speed and shoulder diameter at three levels. The microstructure is examined and the hardness is measured for both the base material and the processed workpieces. The corrosion behaviour of the base material and processed workpieces is studied using potentiodynamic polarization technique for three different testing temperatures, and the corrosion current and corrosion rate are calculated. Findings The results reveal that FSP refined the grains, dispersed secondary phases, increased the hardness and improved the corrosion resistance of most of the friction stir processed specimens than the base material at all the three testing temperatures. Grain refinement and fine dispersion of ß phase improves the hardness and corrosion resistance of most of the FSPed specimens. However partial dissolution of ß phase decreases the hardness in some of the specimens. Most of the FSPed specimens displayed more positive potential than the base material at all the testing temperatures representing a higher nobility than the base material, as a result of fine dispersion of secondary phase particles in the matrix. Large pits formed on the surface of the base specimen indicating a higher corrosion rate at all three testing temperatures. The SEM image of FSPed specimens reveals the occurrence of very few pits and minimal corrosion products on the surface, which indicates lower corrosion rate. Originality/value The corrosion mechanism of the friction stir-processed AA5083 specimens is found to be a combination of activation and concentration polarization.

Corrosion and Tribological Characteristics of FSPed Aluminum Alloy AA5052

“…Also, the electrochemical corrosion potential depends on the grain size (intimately with grain boundary) and morphology and distribution of the β phase particles. Similar to the observations of the earlier research work (Vaira Vignesh et al, 2018, Ramalingam et al, 2019, Ramalingam and Ramasamy, 2017, Aravind et al, 2019, the FSPed specimens had also exhibited a non-linear relationship between corrosion potential and corrosion rate. Therefore the process window for simultaneously maximising cathodic behavior and minimising the corrosion rate would be delusive.…”

“…The corrosion rate was calculated using Equation (2) (Ramalingam et al, 2019, Vaira Vignesh et al, 2020.…”

“…The electrochemical corrosion rate for the base material and the FSPed specimens have been determined through the potentiodynamic corrosion test. The extraction of data from the Tafel region was discussed in our earlier research work (Ramalingam et al, 2019). The corrosion rate for the FSPed specimens is shown as a bar graph in Figure 3 (e).…”

Corrosion behavior of Al/TiO2/Y2O3hybrid nanocomposites manufactured using the vacuum-assisted stir casting route

“…The reinforced nanoparticles were evenly scattered throughout the matrix before the corrosion testing samples (Hayajneh et al , 2020). After subjecting the material to an immersion corrosion test in a 3.5 Wt.% NaCl solution, the damaged areas were observed as shallow pitting on FESEM pictures (Ramalingam et al , 2019). It exposes a film with a reduced crystallinity on the surface that was in a more flexible condition and was easily impacted by the NaCl solution used in the analysis.…”

A review on in-situ aluminum metal matrix composites manufactured via friction stir processing: meeting on-ground industrial applications

“…The aluminum possessing high stacking fault energy has an advantage by treating via FSP. In aluminum, the change in microstructure mainly depends on DRX and FSP being an intense plastic deformation process facilitates in attaining the same (Bajakke et al, 2019;Bajakke et al, 2020a;Ramalingam et al, 2019). In the current industrial scenario, aluminum alloys are considerably replacing steel due to their high strength-toweight ratio and corrosion resilience.…”