Fabrication of TiB 2 nanoparticulates-reinforced aluminum matrix composites by powder metallurgy route

Abstract

Al/TiB₂ nanocomposites were fabricated via powder metallurgy route through a primarily cold isostatic pressing of aluminum powder containing 1.5, 2.5, 3.5, 5, and 10 Vol.% of TiB₂ nanoparticles and subsequent sintering at two temperatures of 650℃ and 680℃. Density, phase analysis, microstructure, and compressive strength of the samples were then characterized. Results indicated that with increasing the content of the second phase (TiB₂), the amount of structural deteriorations like porosity and crack increases as a result of poorer distribution of ceramic nanoparticles, agglomeration, and retarded sintering. However, the compressive strength of nanocomposites tends to enhance with addition and increasing the amount of reinforcement phase (TiB₂). Improvement in the compressive strength of composites is a result of activation of strengthening mechanisms such as formation and pile-up of dislocations. The trend of the compressive strength decreases after reaching a maximum amount for Al-2.5TiB₂, in 680℃. Generally, samples with moderate amounts of TiB₂ (2.5–5 Vol.%) have shown better microstructural and mechanical characteristics due to efficient impact of strengthening mechanisms with lower negative effects of destructive factors like porosity and agglomeration.