Effect of microwave sintering on the microstructure and mechanical properties of Al-Al₂O₃-Si₃N₄ hybrid composite fabricated by powder metallurgy techniques

Abstract

In the present investigation, Si3N4 has been used in the partial replacement of SiC with Al/Al2O3 composite for the application in the automobile industries parts. A microwave sintering technique was employed for the processing of the composite. The aluminum-based composite was developed with the constant 5 wt.% of Al2O3. The weight percent of Si3N4 increased from 2.5% to 7.5%. Uniform distribution of the reinforcement particles was observed for the composition Al-5 wt.% Al2O3 − 2.5 wt.% Si3N4 composite and Al-5 wt.% Al2O3 − 5 wt.% Si3N4 composite. Optical microscope images Al-5 wt.% Al2O3 − 5 wt.% Si3N4 composite showed that the dispersion of the reinforcement (Al2O3 and Si3N4) has been done in a very fine and dense manner. Dispersion of reinforcement in a very dense manner helped in enhancing the mechanical properties of the composite. EDX pattern of Al-5 wt.% Al2O3 − 5 wt.% Si3N4 composite showed the maximum weight percentage of an element of Al, followed by Si, O, and N. Minimum porosity was found to be 0.045% for the composition Al-5 wt.% Al2O3 − 2.5 wt.% Si3N4. However, the percent porosity of the Al-5 wt.% Al2O3 − 5 wt.% Si3N4 was 0.072%. The hardness, compressive strength, and tensile strength of aluminum were improved by about 82.85%, 18.94%, and 62.60% respectively with respect to aluminum after adding 5 wt.% Al2O3 and 5 wt.% Si3N4. XRD of the Al/Al2O3/Si3N4 composite showed the presence of Al, Al2O3, Si3N4, MgAl2O4, and Al2Cu phases. Thermal expansion and corrosion behavior were also observed to identify the Al2O3 and Si3N4 addition effect in the aluminum alloy.