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

• Al matrix composites have been developed via mechanical alloying and sintering.
• Micron and submicron TiB2 particles were used as reinforcements.
• MA duration and TiB2 content were evaluated concerning microstructure/properties.
• Submicron TiB2 particles have positive effects only on the hardness values.
• Higher TiB2 content and MA duration have positive effects on wear resistances.

In this study, TiB2 particulate reinforced Al matrix composites were fabricated with the incorporation of both micron- and submicron-scale TiB2 particles by a combined method of mechanical alloying, cold pressing and pressureless sintering. Commercial TiB2 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 TiB2 particle size (40 μm and 320 nm), TiB2 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 TiB2 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 TiB2 particles. Furthermore, hardness and relative wear resistance values of the composites increased with increasing TiB2 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 TiB2 reinforced Al matrix composites contain homogeneously dispersed fine- and ultrafine-grained TiB2 particles and an amount of Al3Ti flakes.

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