Microstructural evolution and investigation of mechanical properties of Al 7055 –Nano Si3N4 composites

Abstract

In this paper an attempt has been made to develop the aluminium based metal matrix composites. Al7055 were chosen as base material and hard ceramic particulate nano silicon nitride as reinforcement. The composites were fabricated by using bottom pouring stir casting technique by varying weight percentage of Si3N4 in steps of (3 wt%, 6 wt% & 9 wt%) respectively and particle size of 30, 60 and 90nm. Morphological characterization of composites was conducted by using HRFESEM. The SEM result reveals that there is homogeneous distribution between the matrix and reinforcement. EDS mapping for prepared composites were done to identify the presence of alloying elements and phase distribution. XRD analysis is conducted for validation of the structural composition. Mechanical tests like tensile, micro Vickers hardness and impact test were performed on developed composites. The ultimate tensile strength of the composites at 9 wt% and particle size of 90 nm found to be diminishing due to severe agglomeration. The hardness value increases at 9 wt% and particle size of 30 nm. The toughness of the composites increased at 30 nm reinforcement size and 6 wt% as compared to higher weight percentage developed composites. Corrosion test were conducted as per ASTM G31 by weight loss method for different samples by dipping composite samples in 50 g Hcl solution for duration of 6 h and it was found that the corrosion resistance of the composites was higher while increasing the wt% of Si3N4 as compared to base matrix..