Microstructures and mechanical properties of in-situ TiB2/Al−xSi−0.3Mg composites

Abstract

In-situ 2 vol.% TiB2 particle reinforced Al−xSi−0.3Mg (x=7, 9, 12, 15 wt.%) composites were prepared by the salt–metal reaction, and the microstructures and mechanical properties were investigated. The results show that the TiB2 particles with a diameter of 20–80 nm and the eutectic Si with a length of 1–10 μm are the main strengthening phases in the TiB2/Al−xSi−0.3Mg composites. The TiB2 particles promote grain refinement and modify the eutectic Si from needle-like to short-rod shape. However, the strengthening effect of TiB2 particles is weakened as the Si content exceeds the eutectic composition, which can be attributed to the formation of large and irregular primary Si. The axial tensile test results and fractography observations indicate that these composites show more brittle fracture characteristics than the corresponding alloy matrixes.