Effect of microwave sintering on the microstructure and mechanical properties of Al-Al 2 O 3 -Si 3 N 4 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.