What question did this study set out to answer?

This work aims to develop a functionally graded composite of Aluminium 6061 reinforced with Alumina particles and assess its hardness and corrosion behavior.

May 15, 2026Open Access

Impact of Al2O3 particles on the hardness, metallurgical and corrosion behaviour of Al 6061–10 wt. % Al2O3 functionally graded composite

Key Points

This work aims to develop a functionally graded composite of Aluminium 6061 reinforced with Alumina particles and assess its hardness and corrosion behavior.
Created a hollow cylindrical Al 6061 alloy reinforced with 10 wt% Al2O3 using horizontal centrifugal casting.
Conducted Vickers microhardness testing and corrosion studies using H2SO4, HCl, and HNO3 over up to 216 hours.
Analyzed results using Taguchi’s SNR and ANOVA to identify factors affecting corrosion rate.
Maximum hardness of 108 HV observed at the Al2O3-rich exterior, 76% greater than the interior region.
Highest corrosion rate of 27.31 mm/yr in HCl at 72 h; lowest rate of 6.83 mm/yr in HNO3 at 216 h due to stable oxide film.
Immersion duration contributed 56.25% to corrosion rate variation according to ANOVA analysis.

Abstract

The objective of this work is to create a hollow cylindrical Aluminium (Al) 6061 alloy reinforced with 10 wt% Alumina (Al2O3) Functionally Graded Composite (Al 6061–10 wt% Al2O3 FGC) using horizontal centrifugal casting. Vickers microhardness testing revealed a maximum hardness of 108 HV at the Al2O3-rich exterior periphery, which is 76% higher than the Al2O3-depleted interior region. Optical microstructural and XRD (X-ray Diffraction) analysis confirmed the gradient distribution of Al2O3 particles. Acidic immersion corrosion studies on the Al2O3-rich region were performed using Sulphuric acid (H2SO4), Hydrochloric acid (HCl), and Nitric acid (HNO3) solutions for immersion durations up to 216 h. The highest Corrosion Rate (CR) (27.31 mm/yr) was observed in HCl at 72 h due to Chloride (Cl) ion attack and pitting, while the lowest CR (6.83 mm/yr) occurred in HNO3 at 216 h owing to stable oxide film formation. Taguchi’s Signal-to-Noise Ratio (SNR) analysis indicated immersion duration as the most significant factor, with Analysis of Variance (ANOVA) confirming its 56.25% contribution to CR variation. High Resolution Scanning Electron Microscopy (HRSEM) analysis of corroded surfaces showed microcracks, interfacial regions, and surface damage. The findings highlight that controlling immersion duration and selecting appropriate acidic media can significantly enhance the corrosion resistance of Al2O3-reinforced Al 6061 FGCs, making them suitable for chemical industry applications.

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