Synergistic effects of agro-waste ash and alumina on the surface texture and tribological properties of hybrid AMCs

The increasing demand for sustainable and eco-friendly lightweight materials in surface engineering has spurred the development of hybrid aluminum matrix composites (AMCs) that incorporate agro-waste residues as natural fillers. This study investigates the synergistic effects of plantain peel ash (PPA) and alumina (Al₂O₃) on the surface, mechanical, and tribological properties of Al–Mg-Si-based hybrid AMCs. A double-step stir-casting technique was employed to fabricate AMCs with varying weight proportions of PPA (2, 4, 6, and 8 wt.%) and Al₂O₃. Lightweight composites were produced with densities ranging from 2.60 to 2.73 g/cm³, with SEM analysis confirming uniform reinforcement dispersion within the matrix. Hardness values improved significantly with increasing Al₂O₃ weight percent, while surface roughness ranged from 2.38 to 3.52 µm, showing a statistically significant variation (p < 0.005). Tribological tests revealed wear rate increase from 1.34 × 10⁻³ to 2.90 × 10⁻³ mm³/m and coefficient of friction (COF) values ranging from 0.31 to 0.48, with 8% Al₂O₃ and 2% PPA showing the best wear resistance and lowest COF. These improvements were attributed to the enhanced interfacial bonding, ceramic-hardening effects of Al₂O₃, and lubricating properties of PPA at moderate reinforcement levels. The synergy balance was obtained using 4–6% Al₂O₃ and 6–4% PPA. This study underscores the potential of combining natural agro-waste-derived PPA with synthetic Al₂O₃ to fabricate lightweight high-performance AMCs. These findings highlight the environmental and industrial significance of integrating sustainable and synthetic reinforcements to produce advanced composites with enhanced surface integrity, wear resistance, and frictional stability for diverse engineering and aesthetic applications.