Microstructure characterisation and dry sliding wear behaviour of Al-Si near eutectic and hypereutectic alloys reinforced with in-situ TiB2 synthesized by stir casting route

Aluminium matrix composites (AMCs) are well known for their excellent wear resistance and low weight. In the present work, in-situ synthesis of Al-Si-TiB2 composites with near eutectic and hypereutectic compositions of Al-Si alloys has been attempted through salt-metal reaction (K2TiF6 and KBF4 halide salts) by stir casting route. The fabricated composites were subjected to microstructure analysis, XRD study, sliding wear test, hardness and density measurements. The combined effect of Si and TiB2 is the novelty of this investigation to alter the structure-property correlation as well as hardness and tribological properties. Optical Emission Spectroscopy analysis indicated some amount of Si loss during stir casting and revealed the final composition of the cast composites. Though the increase in the density of the composite was not considerable due to incorporation of TiB2 particles, there was remarkable improvement in hardness and tribological properties attributed to clear interface between the matrix and the reinforcement as a result of in-situ process of fabrication. Wear resistance was found to be improved with increasing amount of Si content with a fixed TiB2 content in the composites under a constant load. TiB2 acts as a good grain refiner and improves the wear properties of the hypereutectic Al-Si alloy composites by decreasing the brittle primary silicon particle size.