Influence of TiB2 particle size on the microstructure and properties of Al matrix composites prepared via mechanical alloying and pressureless sintering

Abstract

Abstract In this study, TiB 2 particulate reinforced Al matrix composites were fabricated with the incorporation of both micron- and submicron-scale TiB 2 particles by a combined method of mechanical alloying, cold pressing and pressureless sintering. Commercial TiB 2 powders with an average particle size of 40 μm were milled to 320 nm for 12 h in a high-energy ball mill. The effects of TiB 2 particle size (40 μm and 320 nm), TiB 2 content (5, 10 and 15 wt.%) and mechanical alloying duration (2, 4 and 8 h) on the microstructural and properties of the Al matrix composites were investigated. The composites reinforced with submicron TiB 2 particles exhibited higher hardness (in the vicinity of 2 GPa for 15 wt.% reinforcement) and lower relative wear resistance values compared to those reinforced with micron-scale TiB 2 particles. Furthermore, hardness and relative wear resistance values of the composites increased with increasing TiB 2 contents. Density and hardness values of the sintered samples has uncertain tendency in regard of different mechanical alloying durations. Microstructures of the micron- and submicron-scale TiB 2 reinforced Al matrix composites contain homogeneously dispersed fine- and ultrafine-grained TiB 2 particles and an amount of Al 3 Ti flakes.