The Influence of Alumina Particle Size on Sintered Density and Hardness of Discontinuous Reinforced Aluminum Metal Matrix Composite

Abstract

Kertas kerja ini melaporkan kesan saiz partikel alumina (Al₂O₃) terhadap sifat–sifat komposit matriks logam aluminium (KML) difabrikasi melalui kaedah metalurgi serbuk. Serbuk campuran dipadatkan pada tekanan 250 MPa dan disinter pada suhu 600°C selama 5 jam. Sampel KML dihasilkan berdasarkan 10% berat Al₂O₃. Artikel ini akan membincangkan kesan saiz partikel alumina terhadap mikrostruktur, ketumpatan jasad sinter dan kekerasan komposit. Ketumpatan komposit yang telah disinter adalah dalam julat 2.78 gcm^–3 hingga 2.84 gcm^–3. Kesan saiz partikel Al₂O₃ (0.3 μm, 1.0 μm, 3.0 μm, 12.5 μm dan 25.0 μm) ke atas mikrostruktur komposit diperhatikan menggunakan Mikroskop Imbasan Elektron. Nilai kekerasan diukur menggunakan penguji mirokekerasan Vickers. Pemerhatian menunjukkan bahawa partikel penguat halus (0.3 μm) memberikan nilai kekerasan yang tertinggi (70.1 Hv). Partikel alumina yang halus akan mewujudkan penghalang terhadap kehelan yang lebih efisien di dalam komposit aluminium. Komposit yang diperkuat dengan saiz partikel yang kecil mempunyai bilangan penghalang per unit isipadu yang tinggi berbanding dengan komposit yang diperkuat dengan partikel yang bersaiz besar pada peratus berat penguat yang sama. Kata kunci: Komposit matriks logam, matriks aluminium, alumina, saiz partikel, metalurgi serbuk This paper reports the effect of alumina (Al₂O₃) particle size on the properties of aluminum metal matrix composite (MMC), fabricated via powder metallurgy route. Mixture powders were compacted at 250 MPa and sintered at 600°C for 5 hours. The MMC samples were prepared based on 10 wt% of Al₂O₃. This paper will discuss the effect of alumina particle size on microstructure, sintered density and hardness of the composite. The densities of sintered composites were in the range of 2.78 gcm^–3 to 2.84 gcm^–3. The effect of Al₂O₃ particles sizes (0.3 μm, 1.0 μm, 3.0 μm, 12.5 μm and 25.0 μm) on the microstructure of the composites were observed using Scanning Electron Microscope (SEM). The hardness value was measured using Vickers microhardness tester. It is observed that the finest reinforcement particle size (0.3 μm) gave the highest hardness value (70.1 Hv). The finer Al₂O₃ particles will provide more efficient barriers to dislocation flow in aluminum matrix. Composites reinforced with the smallest particle size have higher number of barriers per unit volume compared with composites reinforced with larger particle size at the same weight percentage. Key words: Metal matrix composite, aluminum matrix, alumina, particle size, powder metallurgy