INVESTIGATING THE CHARACTERISTICS OF METAL MATRIX COMPOSITES BASED ON ALUMINIUM ALLOY REINFORCED WITH ALUMINA

Abstract

Metal Matrix Composites (MMCs) are increasingly adopted in aerospace, automotive, and marine engineering owing to their tailor-made mechanical properties. The present study investigates the mechanical characteristics of Al-Li 2050 aluminium alloy reinforced with nano alumina (Al₂O₃, particle size 13 nm) at weight percentages of 0%, 0.5%, 1.0%, and 1.5%, fabricated using the stir casting technique at a stirring speed of 500 RPM under argon atmosphere. Ball milling was employed to pre-process the nano Al₂O₃ reinforcement with pure aluminium powder into tablet form to ensure controlled and uniform dispersion into the molten matrix. A two-step homogenisation treatment (500°C/10 h + 515°C/20 h, heating rate 180°C/h, followed by air cooling) was conducted to eliminate micro-segregation and promote uniform distribution of alloying elements. The fabricated composites were evaluated for Ultimate Tensile Strength (UTS), Yield Strength, percentage elongation, Brinell Hardness Number (BHN), and density. Experimental results confirm that UTS, Yield Strength, and BHN increased progressively with increasing Al₂O₃ content, achieving maximum values of 138.04 N/mm², 104.12 N/mm², and 61.43 BHN respectively at 1.5 wt% reinforcement, representing improvements of 13.5%, 17.8%, and 13.1% over the base alloy. Percentage elongation and density decreased with increasing reinforcement, reducing from 7.8% to 5.9% and from 2.7 to 1.99 g/cm³ respectively, indicating improved stiffness at a manageable trade-off in ductility. The findings confirm that AlLi 2050/Al₂O₃ nano-composites fabricated by stir casting exhibit superior mechanical performance over the unreinforced base alloy, making them suitable for lightweight structural and aerospace applications