Synthesis and wear properties of near eutectic Al-Si-TiB2/Al2O3 hybrid composites

Abstract

In metal matrix composites a metal/alloy is often combined with non-metallic/inter-metallic phases to produce a novel material possessing attractive engineering attributes of its own. AMCs or Aluminium matrix composites refer to the group of light weight, high performance, aluminium based material systems which are employed to meet the demand of automotive and aerospace sectors. The present study emphasises on casting of Al–11.8 wt% Si metal-matrix composites with the help of an exothermic reaction among the melt and halide salts (K2TiF6 and KBF4) to incorporate 2 and 3 wt% TiB2 in the base alloy matrix. Al2O3 particles (0.5, 1 and 2 wt%) were also mixed with these in-situ prepared composites to produce hybrid composites which were characterized using optical microscopy. Optical Emission Spectroscopy revealed some amount of silicon loss during casting. XRD analysis indicated the presence of Al2O3 and TiB2 in the cast composites. Hardness, density and dry sliding wear tests were carried out and analysed. The results of the present investigation revealed that the wear rate of the composites decreases when there is an increase in the TiB2 content but this behaviour is limited to 1 wt% reinforcement in case of Al2O3. Increasing load promoted wear rate. At higher sliding distances wear rate decreased though wear volume was more. Density values of the composites were found to increase with increasing amounts of reinforcements. Increasing Al2O3 up to 1 wt%, the hardness of the composites was found to increase. Further increase in Al2O3 to 2 wt% revealed lower hardness values of the composites due to agglomeration of the particles.